Trendy v nanotechnologiích-část 7
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NanoHorizons
BSI nanoparticles vocabulary
Reinhard Lipowsky, Max Planck Institute of Colloids and Interfaces
Allianz Group nanotechnology report
OECD
Nanostart
CREA project
Arrowhead Research
Melosh Group, Stanford
Voxtel
US Air Force Research Laboratory
University of Oregon
Evident Technologies
Electron-beam sculpting of metallic nanowires 3 Jun
Detecting biomolecules with fluorescently-labelled DNA 3 Jun
1) * Y-shaped carbon nanotubes switch on to nanoelectronics *
Researchers at the University of California, San Diego and Clemson University, US, believe they are the first to demonstrate switching in a Y-shaped carbon nanotube without the use of an external gate. The structures could have applications in transistors, logic devices and higher harmonic-frequency generation.
See http://nanotechweb.org/articles/news/4/8/11?alert=1
2) * Nano-stamping makes its mark *
Researchers at Massachussetts Institute of Technology and Virginia Commonwealth
University, US, reckon their supramolecular nanostamping printing technique could enable the mass production of nanodevices. The method uses DNA hybridization to replicate a pattern and has a resolution of less than 40 nm.
See http://nanotechweb.org/articles/news/4/6/7?alert=1
3) * 'Smoking' grass leads to nanotubes *
Researchers at Northeast Normal University in China have made multiwalled carbon nanotubes by heating grass in the presence of oxygen. The resulting tubes had diameters of

30-50 nm.
See http://nanotechweb.org/articles/news/4/6/6?alert=1
4) * Buckyballs could restrict growth of soil bacteria *
Researchers at Rice University and Georgia Institute of Technology in the US have found that the nano-C60 aggregates that may form when C60 molecules are exposed to water can have a detrimental effect on soil bacteria. Under certain conditions, the aggregates restricted the bacteria's growth and respiration rates.
See http://nanotechweb.org/articles/news/4/6/5?alert=1
5)
• Financial services provider
Allianz Group , Germany, has published a study on the opportunities and risks of nanotechnology, in conjunction with the Organization for
Economic Co-operation and Development (OECD) . "Allianz believes that it would not be appropriate to create a general exclusion of nanotech from insurance coverage," said Axel Theis, chief executive officer of Allianz Global Risks. "However, a general 'wait and see' attitude is also not an option. As a responsible insurer,
Allianz has worked with the OECD in this report to stimulate an early, active and positive response to nanotech-related risks from all parties involved."
• German nanotechnology investment business Nanostart has listed on the Frankfurt
Stock Exchange. Founded in 2003, the company provides capital to nanotech startups and also has a consulting division that advises financial sector companies on nano investments.
• A joint US/European project is seeking out the most innovative researchers in nanotechnology and human genetics. A survey of 1200 scientists, industrial researchers, editors and research programme directors will aim to track down about
60 high-flying scientists and research teams. The aim is to determine the personal and environmental factors that promote groundbreaking research. The Project on
Creative Capabilities and the Promotion of Highly Innovative Research (CREA) involves a team from the Fraunhofer Institute for Systems and Innovation Research,
Germany, Georgia Institute of Technology, US, and Sussex University, UK.
•
Arrowhead Research , US, says it has licensed intellectual property from Stanford
University , US, covering a nanotech device that controls the behaviour of adult stem cells. The company will fund additional research into the technology to the tune of
$600,000 (€ 492,095) in exchange for an exclusive licence to it. "The solution we are pursuing is to build a device that can interact with the stem cell at the micro- and nanoscale," said Nick Melosh of Stanford University. "For example, exposure to minute amounts of chemical at the appropriate time and place could be the key for guiding stem cells isolated from fat tissue to turn into cartilage or bone constructs."
• Voxtel , US, has won a two-year $750,000 contract from the US Air Force
Research Laboratory . In association with the University of Oregon and Evident
Technologies, Voxtel will develop high-speed photodetectors that consist of quantum dots embedded in conducting organic polymers.
• Konarka Technologies , US, and Solaris Nanosciences , US, are to jointly develop solar cells. The devices will combine Konarka's "light-activated power plastic" and Solaris' nanoscale metallic structures that act as "nano-antennas" for light-sensitive molecules.

•
NanoHorizons , US, has received a notice of allowance from the US Patent Office for its nanoscale photovoltaic cell design. The design incorporates vertically-aligned collector "nano-spikes" inside a layer of light-absorptive material. The company says this enables photovoltaics builders to use an optimally thick absorption layer while dramatically shortening the collection distance, and should increase solar cell efficiency and reduce fabrication costs. NanoHorizons has also launched a technology licensing programme.
•
The British Standards Institution (BSI) is to chair the International Organization for Standardization's (ISO) technical committee for nanotechnologies. The first meeting of the committee will take place in the UK later this year. The BSI has also developed a standardised vocabulary for nanoparticles, which it's dubbed the
Publicly Available Specification PAS 71:2005 Vocabulary - Nanoparticles.
• Researchers from 9 European institutions have received € 2 m ($2.44 m) from the
European Union to research active biomimetic systems. The scientists will explore the integration of two types of biomolecular nanomachine - growing filaments and stepping motors - into nano- and microsystems. Reinhard Lipowsky of the Max
Planck Institute of Colloids and Interfaces in Germany will co-ordinate the network.
The other participants are the AMOLF Institute in the Netherlands; BASF, Germany;
Curie Institute, France; European Molecular Biology Laboratory, Germany; Institute of
Molecular Biotechnology, Germany; CNRS Laboratory on Enzymology and Structural
Biochemistry, France; Politecnico of Milan, Italy; and University of Leipzig, Germany.
6)* Superconducting nanowires pulse to a new beat *
Researchers at the University of Illinois at Urbana-Champaign, US, have made a quantum interference device by coating a pair of DNA molecules with superconducting material. The resulting two-nanowire device showed unusual resistance oscillations.
See http://nanotechweb.org/articles/news/4/6/11?alert=1
7) * Nanoscale friction proves a sticking point *
Conventionally, researchers have used continuum contact mechanics to model friction and adhesion between surfaces. But it hasn't been clear how accurate the models are at an extremely small scale. Now researchers from John Hopkins University, US, have calculated that atomic-scale surface roughness is likely to alter friction by an order of magnitude.
See http://nanotechweb.org/articles/news/4/6/10?alert=1
8) * Solar cells light up with water-soluble polymer *
Researchers at Virginia Commonwealth University, US, have made bilayer heterojunction solar cells from a water-soluble thiophene polymer and a nanocrystalline titanium dioxide layer. The fabrication process was environmentally friendly because it did not require the use of organic solvents.
See http://nanotechweb.org/articles/news/4/6/9?alert=1
9) * It's about the numbers, stupid! *
Lawrence Gasman of NanoMarkets, US, gives his views on forecasting the nanoelectronics market.
See http://nanotechweb.org/articles/column/4/6/1/1
10) * Polymeric worm micelles as nano-carriers for drug delivery *
A team at the University of Pennsylvania, US, investigates flexible nanostructures.
See http://nanotechweb.org/articles/journal/4/6/3/1

11) * Mimicking biology to make a dry adhesive *
Researchers at the University of California at Santa Barbara, US, develop a flexible platform structure coated with vertical polymer nanorods.
See http://nanotechweb.org/articles/journal/4/6/4/1
12) news
<< previous article more articles
17 June 2005
• The second annual International and North Coast Nanotechnology Business
Idea Competition is now accepting submissions. The prize money is $150,000
(€124,127) while teams must pay $100 for each of their entries. Organized by Case
Western Reserve University, US, and Nano Network – a consortium based in
Northeast Ohio, US – the competition aims to encourage the commercialization of nanotechnology research. The deadline for proposals is 15 September 2005.
• Two nanoresearchers at Argonne National Laboratory , US, have won University of Chicago distinguished performance awards. Stephen Choi was praised for his work in nanofluids while Julius Jellinek was rewarded for his research into atomic and molecular clusters. Choi’s group showed that nanofluids conduct heat much faster than scientist had predicted possible at very low volume fractions of nanoparticles.
The University of Chicago operates Argonne National Laboratory for the US government Department of Energy.
• The NASA Institute for Advanced Concepts , US, has selected proposals for its
2005 Phase 1 awards. Brian Gilchrist at the University of Michigan, US, will receive one of the awards to study scalable flat-panel nanoparticle MEMS/NEMS propulsion technology for space exploration. NASA says proposals typically receive up to
$75,000 for a six-month study to find out whether the concept is viable.
•
Nano Cluster Devices , New Zealand, has released a prototype nanowire-based hydrogen sensor. The company has patented methods for making nanoparticles selfassemble into nanowires. It says the devices could have applications in predicting electrical power transformer failure, monitoring hydrogen concentrations in fuel cells, leak detection during hydrogen transport, industrial process gas monitoring and sensing hydrogen build-ups in lead acid storage batteries.
Related Links
Nanotechnology Business Idea Competition
Nano Network
Argonne National Laboratory
Stephen Choi
University of Chicago
Cluster Studies Group, Argonne
NASA Institute for Advanced Concepts
Brian Gilchrist, University of Michigan

Nano Cluster Devices
13)
14 June 2005
Researchers at Virginia Commonwealth University, US, have made bilayer heterojunction solar cells from a water-soluble thiophene polymer and a nanocrystalline titanium dioxide layer. The fabrication process was environmentally friendly because it did not require the use of organic solvents.
"Organic semiconductors have recently attracted much attention and show great promise in the ongoing effort to lower the cost of solar cells," Jim McLeskey of Virginia
Commonwealth University told nanotechweb.org
. "These materials are usually soluble in common solvents, which leads to the possibility of making large-area thin-film solar cells using inexpensive liquid-based processing techniques."
Solar cell research
Unlike other polymers used to make solar cells, sodium poly[2-(3-thienyl)-ethoxy-4butylsulphonate] (PTEBS) is water-soluble. Solutions of the polymer in water have a low viscosity, so the scientists used a doctor blade technique rather than spin coating to deposit a film of the polymer onto a titanium dioxide-coated substrate. The doctor blade technique sweeps a glass rod across the polymer film as it dries.
The presence of a nanocrystalline film of titanium dioxide helps to enhance charge separation in solar cells. To lay down the film, the team spin coated a solution of anatase titanium dioxide powder in acetic acid onto a layer of fluorinated tin oxide on a glass substrate. Then they sintered the m aterial at 500 °C for one hour. This resulted in a porous nanocrystalline network of titanium dioxide particles. The average particle size was 80 nm and the pores were more than 20 nm across
– large enough for the polymer to penetrate.
Once they had deposited the polymer coating onto the titanium dioxide layer the team dried the structure at 150 °C overnight to remove any remaining water. Then they applied a mask and a thin gold layer to act as an electrode. The resulting devices had an energy-conversion effficiency of 0.13%, an open circuit voltage of
0.81 V, a short-circuit current density of 0.35 mA/sq. cm and a fill factor of 0.4.
"Using water as a solvent has several benefits," said McLeskey. "It is an environmentally friendly, low-cost solvent that allows safe processing. In addition, using water allows the fabricator to use heat to adjust the evaporation rate. This leads to greater control over device morphology and electronic properties. The watersoluble polymer is also less sensitive to moisture and oxygen in the air."
It’s also possible to tune PTEBS' absorption spectrum by changing the pH of the aqueous solution. In water the material has an absorption band of 400 –650 nm.
Adding acid to the solution creates an absorption band of 600
–800 nm. The researchers say that this means that they could harvest a greater portion of the solar spectrum by building tandem junction cells containing PTEBS layers made using both acidic and basic solutions.

The researchers say that the water-soluble polymer may have applications in photodetectors, light-emitting diodes, displays and sensors, as well as in solar cells.
"We are working to optimize our devices by improving our fabrication techniques," said McLeskey. "In addition, our best devices to date have been in a bilayer configuration where we deposit a layer of TiO
2
and then deposit a layer of polymer on top. We are working on building efficient bulk heterojunction devices where the TiO
2
(the electon acceptor) and the polymer (the electron donor) are deposited simultaneously."
The researchers reported their work in Applied Physics Letters .
14)
23 May 2005
LCD, plasma and OLED displays could soon have a new challenger. Motorola
Labs, the applied research arm of Motorola, has unveiled a prototype nanoemissive display (NED) based on carbon nanotubes.
"Our NED display is basically a thin, flat cathode ray tube with thousands of electron guns at each pixel," a spokesperson for
Motorola told Optics.org
. "The prototype has full colour video, high brightness, uniformity and colour purity in the ranges required for a commercial product. It shows NEDs have a promising future for use in flat panel displays."
Nanotube display
The key to the development is Motorola's ability to grow carbon nanotubes directly onto the display's glass substrate. In the past, carbon nanotubes have been pasted or printed onto a surface but the quality of the resulting display has been disappointing.
"On a back plate, only 3 mm behind each sub-pixel, we place a small structure that contains about one thousand carbon nanotubes arranged such that a properly applied voltage excites each nanotube to bombard the colour phosphors with electrons," explained the spokesperson.
With a thickness of just 3.3 millimetres, the prototype is a 5-inch diagonal section of a
42-inch 1280x720 high-definition television and has a refresh rate of 60 Hz.
Motorola estimates that a 42-inch NED running typical video would consume 75 W. In comparison, the firm says a similar LCD would consume around 180 W because it requires a 60 W backlight and matrix switching.
Motorola now plans to license the technology to panel manufacturers. "Motorola is ready to deliver this technology to manufacturers today," said the spokesperson. "We estimate that this technology can be commercialized in the very near term, depending on the aggressiveness of the licensees."
The prototype has also been given the thumbs up by display analysts. "Motorola's
NED technology is demonstrating full colour video with good response time," said
Barry Young, the CFO of DisplaySearch. "According to a detailed cost model analysis conducted by our firm, we estimate the manufactured cost for a 40-inch NED panel could be under $400."

15)
25 May 2005
Simplified and more efficient white light-emitting diodes (LEDs) could result from replacing external colour-converting phosphors with CdSe-based nanocrystals that are incorporated directly into the p-n junction.
Scientists from the Los Alamos and Sandia laboratories in New Mexico, US, have fabricated the first LEDs that use an all-inorganic, nanocrystal-based architecture.
The devices, which have CdSe nanocrystals incorporated within a GaN-based light emitting region, circumvent the inefficiencies associated with the majority of today’s
LEDs, which use phosphors to convert blue emission into yellow light.
Examples of these inefficiencies include losses associated with light capture of the phosphor, non-radiative carrier losses during the re-emission process and losses due to re-absorption of the colour-converted photons by the phosphor.
Semiconductor nanocrystals offer high quantum efficiencies and size-tunable colours.
However, LEDs based on the technology have been plagued with the difficulty of making direct electrical connections to the nanocrystals.
The solution was to sandwich the quantum dots between the GaN injection layers, explained project leader Victor Klimov from Los Alamos.
The US scientists’ devices are pin structures with an intrinsic layer containing nanocrystals with a CdSe core and a ZnS shell. A monolayer of nanocrystals was assembled onto a p-type GaN layer, before 100-400 nm of n-type GaN was grown over the top.
Standard GaN deposition methods could not be used because the high temperatures would have degraded the nanocrystals. Instead, the researchers used a new lowertemperature technique, which they call energetic neutral atom beam lithography/epitaxy (ENABLE). With this, they created films said to be as good as those produced by MOCVD.
To grow GaN with the ENABLE process, a neutral nitrogen atom beam with kinetic energies of 0.5-5.0 eV and electron-beam-evaporated gallium metal combine to form epitaxial layers on a sapphire substrate heated to less than 500 °C.
The researchers produced a variety of LEDs, including 573 nm and 619 nm emitters with nanocrystal core diameters of 3.6 nm and 5.2 nm, respectively.
The devices showed no degradation in emission performance after 72 hours of continuous operation, but their external quantum efficiencies were only 0.001-0.01%.
However, the researchers say that these low values can be improved significantly by optimizing the structure, and are not the result of their novel injection method.
16) * Nanotube bike enters Tour de France *
This year's Tour de France will see cyclists from the Phonak Team use a bike with a frame containing carbon nanotubes. Swiss manufacturer BMC claims that the frame of its "Pro
Machine" weighs less than 1 kg and has excellent stiffness and strength.
See http://nanotechweb.org/articles/news/4/7/1?alert=1

17) * On-wire lithography takes it smaller *
Current lithography techniques struggle to create gaps smaller than about 20 nm wide in nanowires, an ability that's crucial for the future development of nanoelectronic devices. But now researchers from Northwestern University, US, claim their on-wire lithography technique can produce gaps just 2.5 nm wide.
See http://nanotechweb.org/articles/news/4/6/16?alert=1
18) * Vesicles roll up for rechargeable batteries *
Researchers from the Naval Research Laboratory, Nova Research and the University of
Maryland, US, say they have made the first vesicle-based rechargeable battery. Based on a biological design, the battery could find applications in nanoscale devices such as sensors, biomolecular motors and molecular electronics.
See http://nanotechweb.org/articles/news/4/6/15?alert=1
19) * Bacteria sport nanowire hairs *
Researchers at the University of Massachusetts Amherst, US, have discovered that Geobacter species of bacteria produce conductive nanowire-like structures on one side of their cells. The team believes the bacteria could have applications in creating nanowires for nanoelectronic devices.
See http://nanotechweb.org/articles/news/4/6/14?alert=1
20) * EUV microscope explores nanoscale *
A team of US, Russian and Ukrainian scientists is using a table-top extreme ultraviolet (EUV) illumination source to create an optical microscope that can image features as small as 100 nm. Operating in reflection mode and requiring little sample preparation, the EUV microscope can rapidly characterize the topography of microelectronic circuits, lithography masks and other material surfaces.
See http://nanotechweb.org/articles/news/4/6/13?alert=1
21)
1 June 2005
Researchers at the University of California, Santa Barbara, US, have synthesized a nanostructure that can catalyze the formation of silica at low temperatures and neutral pH. To achieve this, the team copied the polysiloxane-synthesizing enzyme found in the orange puffball sponge Tethya
aurantia, which lives in seawater.
“When you remove the tissue [of the sponge] you’re left with a handful of fibreglass needles as fine as spun glass or cotton,” said Daniel Morse of the University of
California, Santa Barbara. “This primitive skeleton supports the structure of the sponge, an d we’ve discovered how this glass is made biologically.”
Morse and colleagues found that protein filaments acted as both catalysts and templates for the formation of the sponge’s silica needles. Analysis of the proteins revealed that they are members of a “super-family” of proteolytic and hydrolytic enzymes.

The researchers mimicked the naturally occurring enzyme by attaching nucleophilic and hydrogen-bonding amines to gold nanoparticles. Then they mixed the resulting two types of nanoparticles together and added tetraethoxysilane.
The structures catalysed the hydrolysis of silicon alkoxide and promoted condensation of silica and polysilsesquioxanes at 22°C. The silica had an amorphous structure and entrapped the gold nanoparticles.
The researchers believe the technique could have applications in making nanocomposites, photonic crystals and core-shell quantum dots.
What’s more, the scientists reckon they should be able to apply the same strategy to synthesize metal oxides at low-temperature. They are currently investigating functionalizing the nanoparticles with different chemical groups.
The researchers reported their work in Advanced Materials .
22)
2 June 2005
Researchers from the University of Alberta in Canada, the National Institute for
Nanotechnology, Canada, and the University of Liverpool, UK, say they have shown for the first time that a single charged atom on a silicon surface can regulate the conductivity of a molecule nearby. The finding could be useful for developing single molecule transistors.
“This concept could circumvent the limits of conventional transistor technology and permit miniaturization on a nanometric scale,” said Robert Wolkow of the University of Alberta. “Better, faster, cheaper - that’s the promise of molecular electronics. In our case, we also have a potentially powerful green technology because of its minimal power and material requirements, and the biodegradable nature of the device.”
Wolkow and colleagues discovered that the electrostatic field from a fixed-point charge (a negative silicon dangling bond) controlled the conductivity of styrenederived molecules bound to an n-type doped silicon substrate. Observations in a scanning tunnelling microscope revealed that molecules nearer the dangling bond appeared to stand out further from the silicon surface than molecules further away.
Such measurements indicate the amount of charge transport across molecules.
What’s more, since the changes in conductivity were large, the scientists were able to observe them at room temperature. Other molecular electronics experiments have had to take place at extremely low temperatures.
The team also demonstrated chemical gating of molecular conductivity by attaching
TEMPO radicals to the silicon dangling bond.
The researchers reported their work in Nature .
23)
2 June 2005
As electronic chips become faster and their feature sizes shrink, manufacturing techniques have been struggling to stay ahead of the game.

Now, researchers from the University of Wisconsin, Madison, US, Korea
Advanced Institute of Science and Technology, and the Paul Scherrer Institute in Switzerland have come up with a hybrid method for patterning silicon that exploits a mixture of polymers.
“We believe that self-assembling materials used in conjunction with the most advanced exposure tools may enable extension of current manufacturing practices to dimensions of 10 nm and less,” Paul Nealey of the University of Wisconsin told nanotechweb.org
.
The technique uses a blend containing a diblock copolymer and additional amounts of its two constituent homopolymers. Patterning the polymer mixture onto a chemically altered region of a silicon substrate produced very fine feature sizes.
“Diblock copolymers consist of two polymer chains connected at one end that tend to form ordered structures, including spheres, cylinders and lamellae,” said Nealey.
“Previously these self-assembling materials have been used to fabricate periodic arrays at the nanoscale. [In our work] we demonstrate that by directing the assembly of blends of block copolymers and homopolymers on chemically nanopatterned substrates, it is possible to pattern perfect, registered, non-regular shaped structures facilitated by the local redistribution of homopolymer across the patterns.”
Nealey and colleagues used a mix containing 60 wt% symmetric polystyrene-blockpoly(methyl methacrylate), 20 wt% polystyrene and 20 wt% poly(methyl methacrylate). They applied the mix to a silicon substrate coated with hydroxyterminated polystyrene that had been chemically patterned using advanced lithography and an oxygen plasma. This patterning rendered regions of the substrate hydrophilic.
The polystyrene domain of the polymer blend preferentially wet the unpatterned areas of the substrate, while the poly(methyl methacrylate) domain preferred the chemically modified regions. Annealing the polymer blend at 193°C for a week enabled it to reach a stable morphology.
“The extension of block copolymer lithography to pattern features more complex than simple periodic arrays creates opportunities for the use of these non-traditional imaging materials for the production of nanoelectronic devices,” said Nealey.
According to Nealey, there is still significant research needed to optimize blend compositions, materials and interfacial interactions, understand the fundamental physics of polymer blends in thin films, and investigate the achievable surface density of bends or other nonregular geometries. “It is also possible that the design of circuit elements could be adapted to be more amenable for manufacturing using selfassembling materials,” he said. “Single chain in mean-field simulations may, some day, allow for the prediction of the optimal block copolymer or blend to achieve device or pattern-specific selfassembled templates.”
The researchers reported their work in Science .
24)
3 June 2005

Experiments in quantum communications and computing could be about to get much easier thanks to the development of a semiconductor source of single photons at the telecoms window of 1.3 µm.
The quantumdot based device was announced at last week’s
CLEO/QELS conference in Baltimore, US. It has been developed by scientists from Toshiba Research Europe and the University of Cambridge, UK.
Quantum dots
To date, single photon sources are notoriously difficult to build and rely on either heavily attenuating a laser or exciting single atoms. The drawback is that these schemes are often complex and it can be hard to prevent multiple photons being emitted.
In contrast, Toshiba’s quantum-dot emitter reliably generates single photons on demand when excited by short optical pulses. In addition, the semiconductor approach is potentially compatible with electrical pumping and should be much easier to package and commercialize.
"In terms of suppressing multiple photon generation, we’ve achieved an order of magnitude below what you get from a laser," said Martin Ward, a member of the research team from Toshiba Research Europe. "There are other ways of generating single photons, like down-conversion, but this is the first time that strong [multiple photon] suppression from a quantum-dot type source has been demonstrated at telecom wavelengths."
In order to ensure that single photons could be isolated and directed into an optical fibre, the team had to learn how to fabricate sparsely populated fields of InAs/GaAs quantum dots, each 45 nm in diameter and 10 nm high. The dots were grown by molecular beam epitaxy on a GaAs substrate at a temperature of about 500 °C.
After fabrication, a long-wavelength dot is embedded inside a pillar microcavity consisting of two mirrors (distributed Bragg reflectors) and an optical filter is applied to block emission from any surrounding dots of a smaller size.
At the moment, the source operates at cryogenic temperatures but the Cambridge team is confident that this can be raised to more practical levels. "The results in the paper are taken at 5 K and 30 K, but the long wavelength dots should also emit at higher temperatures - we’ve seen photoluminescence up to 200 K," Ward told
Optics.org
. "We certainly don’t envisage using cryrogenic liquids to cool any future commercial devices."
25)
6 June 2005
Researchers at Rice University and Georgia Institute of Technology in the US have found that the nano-C
60
aggregates that may form when C
60
molecules are exposed to water can have a detrimental effect on soil bacteria. Under certain conditions, the aggregates restricted the bacteria’s growth and respiration rates.

“We have found that these C
60 aggregates are pretty good antibacterial materials,” said Joseph Hughes of Georgia Tech. “It may be possible to harness that for tremendously good applications, but it could also have impacts on ecosystem health.”
C
60
molecules have a solubility of less than 10 -9 mg/L in polar solvents such as water.
But the molecules can also form colloidal nano-C
60
aggregates with diameters of 5-
500 nm that have solubilities in water of up to 100 mg/L.
“We haven’t really thought of water as a vector for the movement of these types of materials,” said Hughes.
The team tested the response to nano-C
60
of two types of bacteria that are commonly found in soil - the Gram-negative Escherichia coli DH5α and Gram-positive Bacillus subtilis CB315.
The aggregates prevented growth of both types of bacteria in a minimal media at relatively low concentrations of nano-C
60
(>= 0.4 mg/L). In a rich growth media, however, bacterial growth did not stop until nano-C
60
concentrations of more than 2.5 mg/L were reached. The scientists believe this may be because the media salted the fullerenes out of solution or coated them with excess protein.
Similar C
60
concentrations also reduced bacterial respiration rates, whereas hydroxylated fullerenes (C
60
(OH)
22-24
) did not significantly affect respiration.
Hughes and colleagues also found that the aggregates contained underivatized C
60
, had an ordered crystal structure, and that their size and stability depended on the conditions under which they formed, such as the rate of water addition and the pH of the solution.
The aggregates were not stable in solutions simulating seawater or brackish waters.
But in solutions with ionic strengths of or below 0.05 I, as in most freshwater environments, an “appreciable percentage if not all” of the aggregates remained stable for 15 weeks.
Current guidelines in the US for the handling and disposal of buckyballs are based on the properties of bulk carbon black. But Hughes says that buckyballs have different properties from this bulk material and should be treated differently.
“As information becomes available, we have to be ready to modify these regulations and best pra ctices for safety,” said Hughes. “If we’re doing complementary studies that help to support this line of new materials and integrate those into human safety regulations, then the industry is going to be better off and the environment is going to be better off.”
The researchers reported their work in Environmental Science & Technology
26)
8 June 2005
Researchers at Northeast Normal University in China have made multiwalled carbon nanotubes by heating grass in the presence of oxygen. The resulting tubes had diameters of 30-50 nm.

"We think it is a novel and 'green' approach - from grass to carbon nanotubes," Enbo Wang told nanotechweb.org
. "Using renewable natural products as the carbon source and the participation of oxygen, a benign oxidation reagent, offer numerous benefits ranging from environmental safety to further exploitation of existing farm and natural produce."
Wang and colleagues took grass from a field, before drying, crumbling a nd heating it at 250 °C for one hour. Then they heated the resulting material to 600 °C for around 20 minutes in a sealed container, together with about 15 ml of oxygen.
Enbo Wang
Following cooling, the team reinjected oxygen and repeated the heat treatment. They carried out this cycle about 50 times.
The result was nanotubes about 1 µm long with outer diameters of 30-50 nm and inner diameters of 10-30 nm. The researchers estimate that the average yield for the process was roughly 15%.
"Recently it was shown that the participation of water can simplify the synthesis and purification of nanostructured carbon based on the complex chemistry in the C-H-O system," added Wang. "That inspired us to look for a new strategy for carbon nanotube fabrication directly from carbohydrates, based on the conversion from carbohydrate to pure carbon and water. This breaks through not only the limits of carbon source but also the traditional idea of obtaining active carbon atomic species and then assembling them into carbon nanotubes."
Many plants, including grass, contain vascular bundles that transport fluids throughout the organism. The bundles have a tubular structure and consist mainly of cellulose, hemicellulose and lignin. The researchers reckon that their pretreatment of the gra ss removed its protein and grease components, while the treatment at 600 °C dehydrated the cellulose and converted it into nanostructured carbon, as well as causing oxidative delignification.
The tubular structure of the carbon sources appeared to be crucial. Using the same heat treatment on carbohydrates that weren't in tubular form, such as glucose and saccharose, created only a very low number of nanotubes. But wood and hemp - both plant materials with a tubular structure - were good carbon sources for nanotube production.
"The obtained carbon nanotubes have some defects in the walls, which have potential applications in catalysis for use as catalyst supports," said Zhenhui Kang.
"We intend to explore the effects of various reaction conditions on the yields of carbon nanotubes, and we will try to find an ideal juncture of high production yields and low cost. [This work] may also provide a new route for the further development of green carbon nanostructure synthesis."
The researchers reported their work in Nanotechnology .
27)
9 June 2005
Researchers at Massachussetts Institute of Technology and Virginia
Commonwealth University, US, reckon their supramolecular nanostamping printing technique could enable the mass production of nanodevices. The

method uses DNA hybridization to replicate a pattern and has a resolution of less than 40 nm.
Initially, the scientists believe their nano-printing method might be of benefit in making DNA microarrays. Currently manufacturing these devices requires at least
400 printing steps and costs around $500 per microarray. But supramolecular nanostamping would need only three steps and could reduce the cost of each microarray to less than $50. "This would completely revolutionize diagnostics," said
Francesco Stellacci of MIT. "The more we test with microarrays, the more we know about illnesses and the more we can detect them."
To carry out the technique, the researchers created a gold master patterned with single-stranded DNA molecules. The molecules were modified with hexyl-thiol so that they bonded to the gold surface. Stellacci and colleagues immersed this master in a solution of complementary DNA (cDNA) strands that were also modified with hexylthiol attachment groups. The cDNA hybridized to the DNA strands on the master, with their attachment groups pointing away from the gold substrate. This created double-stranded DNA.
Next the team brought a second gold substrate into contact with the master. The upwards-facing thiol groups of the complementary DNA bonded to this secondary substrate. Heating the structure caused dehybridization of the DNA double strands and left the complementary DNA bonded to the secondary substrate in a replica of the master pattern.
According to the researchers, the technique transfers both spatial and chemical information at the same time. Crucially, it can also print different types of molecules at once, by using a master bonded to several types of DNA and a solution containing each of the relevant types of complementary DNA.
What's more, the researchers believe supramolecular nanostamping is the only printing method where the printed substrate can be reused as a master. This enables an exponential increase in the number of masters and potentially makes the technique suitable for mass production.
The researchers have demonstrated the technique using gold and glass substrates but reckon they could adapt it to many different substrates by using different chemical linkers. And the method could also make use of reversible molecular recognition reactions other than that of DNA, for example receptor-receptand and antibodyantigen binding.
The researchers reported their work in Nano Letters .
28)
14 June 2005
Researchers at Virginia Commonwealth University, US, have made bilayer heterojunction solar cells from a water-soluble thiophene polymer and a nanocrystalline titanium dioxide layer. The fabrication process was environmentally friendly because it did not require the use of organic solvents.

"Organic semiconductors have recently attracted much attention and show great promise in the ongoing effort to lower the cost of solar cells," Jim McLeskey of Virginia
Commonwealth University told nanotechweb.org
. "These materials are usually soluble in common solvents, which leads to the possibility of making large-area thin-film solar cells using inexpensive liquid-based processing techniques."
Solar cell research
Unlike other polymers used to make solar cells, sodium poly[2-
(3-thienyl)-ethoxy-4-butylsulphonate] (PTEBS) is water-soluble. Solutions of the polymer in water have a low viscosity, so the scientists used a doctor blade technique rather than spin coating to deposit a film of the polymer onto a titanium dioxidecoated substrate. The doctor blade technique sweeps a glass rod across the polymer film as it dries.
The presence of a nanocrystalline film of titanium dioxide helps to enhance charge separation in solar cells. To lay down the film, the team spin coated a solution of anatase titanium dioxide powder in acetic acid onto a layer of fluorinated tin oxide on a glass substrate. Then they sintered the material at 500 °C for one hour. This resulted in a porous nanocrystalline network of titanium dioxide particles. The average particle size was 80 nm and the pores were more than 20 nm across
– large enough for the polymer to penetrate.
Once they had deposited the polymer coating onto the titanium dioxide layer the team dried the st ructure at 150 °C overnight to remove any remaining water. Then they applied a mask and a thin gold layer to act as an electrode. The resulting devices had an energy-conversion effficiency of 0.13%, an open circuit voltage of
0.81 V, a short-circuit current density of 0.35 mA/sq. cm and a fill factor of 0.4.
"Using water as a solvent has several benefits," said McLeskey. "It is an environmentally friendly, low-cost solvent that allows safe processing. In addition, using water allows the fabricator to use heat to adjust the evaporation rate. This leads to greater control over device morphology and electronic properties. The watersoluble polymer is also less sensitive to moisture and oxygen in the air."
It’s also possible to tune PTEBS' absorption spectrum by changing the pH of the aqueous solution. In water the material has an absorption band of 400
–650 nm.
Adding acid to the solution creates an absorption band of 600 –800 nm. The researchers say that this means that they could harvest a greater portion of the solar spectrum by building tandem junction cells containing PTEBS layers made using both acidic and basic solutions.
The researchers say that the water-soluble polymer may have applications in photodetectors, light-emitting diodes, displays and sensors, as well as in solar cells.
"We are working to optimize our devices by improving our fabrication techniques," said McLeskey. "In addition, our best devices to date have been in a bilayer configuration where we deposit a layer of TiO
2
and then deposit a layer of polymer on top. We are working on building efficient bulk heterojunction devices where the TiO
2
(the electon acceptor) and the polymer (the electron donor) are deposited simultaneously."
The researchers reported their work in Applied Physics Letters .
29)

15 June 2005
Conventionally, researchers have used continuum contact mechanics to model friction and adhesion between surfaces. But it hasn't been clear how accurate the models are at an extremely small scale. Now researchers from John
Hopkins University, US, have calculated that atomic-scale surface roughness is likely to alter friction by an order of magnitude.
"Traditional models of contact approximate solids as a 'continuous media' with no internal structure, but all solids are made up of discrete atoms," Mark Robbins of
John Hopkins University told nanotechweb.org
. "Ignoring atomic structure may be a good approximation when modelling parts of macroscopic machines like cars, but what happens when the size of the parts and their contacts shrinks down to a few atomic diameters? How small is too small for continuum theory to apply? The answers to these questions are crucial to the function of man-made machines and many biological processes."
Robbins and colleague Binquan Luan say they modelled the displacements of up to
~10 7 atoms on a computer as two solids were pushed together. They compared the mechanical deformation, adhesion and friction forces to continuum calculations for a curved surface - cylinder or sphere - pushed into a flat surface. The pair varied the radius of the curve from about 100 atoms (~30 nm) to 1000 atoms.
"Knowing the exact atomic structure and how each atom moved allowed us to test the two key assumptions of continuum theory," said Robbins. "Being able to vary the placement of atoms allowed us to quantify the influence of different geometries on deviations from continuum theory."
According to the researchers, the continuum description of deformations inside solids worked surprisingly well, but the assumption that surfaces can be represented by smooth curves did not.
"Any surface made of discrete atoms has bumps of atomic dimension, and surfaces with the same average shape, but different atomic-scale structure behave very differently," said Robbins. "Surfaces formed by bending a flat crystal into a curve behaved most like the continuum models. Surfaces formed by cutting a sphere from a crystal or random, glassy material behaved quite differently."
The researchers reckon their findings have implications for avoiding unwanted adhesion and excessive friction in nanoscale devices; for varying materials at the nanometre scale to create optimal macroscopic mechanical properties; for examining the contacts between macroscopic objects, since the fractal structure of surfaces means these contacts are often extremely small; and for interpreting contact measurements such as those taken using atomic-force microscopes.
"Mechanical properties of small components are often determined by fitting contact measurements to continuum theory," said Robbins. "Our results indicate when continuum theory can be used to model such situations. They show that some quantities, like the stiffness, may be determined accurately, that others - contact area, adhesion and the yield stress where permanent deformation sets in - may be off by a factor of two, and others, like friction, may be off by more than an order of magnitude. Hopefully this will help in the creation of new tools needed to guide design of nanotechnology."
The scientists reported their work in Nature .

30)
17 June 2005
Researchers at the University of Illinois at Urbana-Champaign, US, have made a quantum interference device by coating a pair of DNA molecules with superconducting material. The resulting two-nanowire device showed unusual resistance oscillations.
“Initially, this project started as a search for the well known Little-Parks oscillations in superconducting nanodevices,” said Alexey Bezryadin. “Unexpectedly, our measurements on these two-nanowire devices revealed a strange class of periodic oscillations in resistance with applied magnetic field that were qualitatively different from the expected LittleParks effect.”
Bezryadin and colleagues made the devices by arranging two DNA molecules across a roughly 100 nm-wide trench in SiN/SiO
2
on a silicon chip. Then they sputter-coated the molecules and substrate with superconducting Mo
21
Ge
79
.
The resulting nanowires became superconducting at low temperatures, with their resistance decreasing exponentially with temperature. As is typical for nanowires, they did not exhibit zero resistance.
“In the absence of a magnetic field, these ultra-narrow wires exhibited a nonzero resistance over a broad temperature ra nge,” said Bezryadin. “At temperatures where thicker wires would already be superconducting, these DNA-templated wires remained resistive.”
When a magnetic field was present, the device showed regular oscillations of resistance with the magnetic field. To investigate the effect, the researchers tested devices with different geometries, varying the lead width and interwire spacing. This enabled them to formulate an explanation for the behaviour.
“The applied magnetic field causes a small current to flow along the trench banks, and this current then causes a large change in resistance,” explained Paul Goldbart.
“The strength of the current is controlled only by the magnetic field and the width of the banks supporting the wires.”
The researchers say their device is very sensitive to magnetic fields and, if coupled to a scanning probe microscope, can be used to detect local variations in magnetic field. “The device is also sensitive to phase gradients of the superconducting order parameter,” said Bezryadin. “Thus it may be used as a superconducting phase gradiometer.”
Now the scientists plan to produce phase variations in the device by injecting electrical currents into the electrodes, without using magnetic fields. “If successful, this approach will prove that our NQUID - nanowire quantum interference device - can be used as a phase gradiometer,” said Bezryadin. “We also plan to develop DNA self-assembly strategies and use them for fabrication of nanowire networks with complex structures.”
The researchers reported their work in Science .
31)
27 June 2005

A team of US, Russian and Ukrainian scientists is using a table-top extreme ultraviolet (EUV) illumination source to create an optical microscope that can image features as small as 100 nm. Operating in reflection mode and requiring little sample preparation, the EUV microscope can rapidly characterize the topography of microelectronic circuits, lithography masks and other material surfaces. (OPTICS EXPRESS 13 3983)
At the heart of the imaging apparatus is a pulsed EUV capillary discharge laser emitting at 46.9 nm developed by researchers at Colorado
State University, US.
"Materials have low reflectivity at this wavelength, making it a challenge to obtain images," Fernando Brizuela from Colorado
State University told Optics.org
. "[However], the brightness of the source allowed us to produce very sharp images with short exposure times." EUV team
Completing the microscopy set-up is a Schwarzschild condenser, developed by a team from Lebedev Physical
Institute, Moscow, and National Technical University, Ukraine, and a zone plate objective. The condenser focuses light from the EUV source on to the sample and the zone plate objective magnifies the reflected sample image on to a CCD detector.
Test sample
Scientists from Lawrence Berkeley National Laboratory, US, came up with a substrate-free zone plate by attaching a 200 nm nickel film to a silicon frame. The design helps to minimize attenuation of the 46.9 nm emission, which is readily absorbed by most materials.
To reduce image-degrading effects such a speckle and interference, the team shortened the laser's capillary tube length from 36 to 18 cm to give a low-coherence beam with a pulse energy of around 0.1 mJ.
The team trialled its EUV microscope by imaging a silicon test structure and patterned nickel film. Exposure time varied between 20 and 70 seconds.
"The next step is to develop a sub 100 nm resolution microscope that will fit on to a small desk," Brizuela said. "We are interested in cooperating with industrial partners to develop and commercialize the technology."
32)
29 June 2005
Researchers at the University of Massachusetts Amherst, US, have discovered that Geobacter species of bacteria produce conductive nanowire-like structures on one side of their cells. The team believes the bacteria could have applications in creating nanowires for nanoelectronic devices.

"Such long, thin conductive structures are unprecedented in biology," said Derek Lovley of the University of Massachusetts
Amherst. "This completely changes our concept of how microorganisms can handle electrons, and it also seems likely that microbial nanowires could be useful materials for the development of extremely small electronic devices."
Lovley discovered Geobacter in 1987 at the bottom of the
Potomac River in Washington DC, US. The bacteria, which are anaerobic, live in aquatic sediments and soils worldwide. The organisms respire by transferring electrons to material outside the cell, for example iron (III) oxides. This means they can be
Geobacter bacteria used to clean up groundwater contaminated with pollutants such as toxic and radioactive metals or petroleum.
The bacteria grow hair-like structures that are 35 nm wide and up to 20 µm long from one side of their cells. Lovley and colleagues tested these pili with an atomic force microscope with a conductive tip. They found that the structures were highly conductive - they believe that the pili provide an electrical connection between the cell and the surface of iron (III) oxides.
Bacteria researchers
Harvesting pili from Geobacter cultures could provide a relatively cheap and simple way of producing nanowires.
What’s more, the researchers reckon it would be possible to genetically modify the pilin structure or composition to create nanowires with different functionalities.
The scientists reported their work in Nature .
33)
29 June 2005
Researchers from the Naval Research Laboratory, Nova Research and the
University of Maryland, US, say they have made the first vesicle-based rechargeable battery. Based on a biological design, the battery could find applications in nanoscale devices such as sensors, biomolecular motors and molecular electronics.
“Power sources commensurate in size with the electronic devices are in great demand,” Alok Singh told nanotechweb.org
. “We wanted to develop a battery small enough to fit into nanoscopic devices by using environmentally benign materials and a simple and straightforward methodology.”
Singh and colleagues created their batteries by encapsulating oxidant and reductant chemicals inside separate polymerized phospholipid membranes. The resulting vesicles were around 45 nm in size. The scientists attached the vesicles to gold films using a disulphide functionalized phospholipid tether. They linked oxidant-containing cathodic vesicles to one substrate and anodic vesicles, which contained reductants,

to another. Then they joined these electrodes using a salt bridge consisting of filter paper impregnated with potassium chloride solution.
“We found that the content of such tethered vesicles can be reduced/oxidized by the electrode in a controlled manner,” said Singh. “Once we had incorporated fuel in one kind of vesicle and the oxidant in separate vesicles, we had all the relevant constituents of a battery.”
The cathodic vesicles contained the oxidants ferricyanide (K
3
[Fe(CN)
6
]) inside the vesicle core and benzoquinone (BQ) in the bilayer membrane. The anodic vesicles incorporated the reductants ferrocyanide (K
4
[Fe(CN)
6
]) within the vesicle and hydroquinone (H
2
Q) in the membrane. Benzoquinone is the oxidized form of H
2
Q.
The team found they could tune the charge capacities and drain rates of the batteries by altering parameters such as the concentration of BQ, H
2
Q and [Fe(CN)
6
] 3-/4. The maximum charge capacity they produced was 17.6 aC and the maximum current per vesicle pair was 0.2 aA. This gave power outputs of the order of sub-nanowatts per square centimetre. The batteries also proved to be rechargeable over three consecutive discharge-recharge cycles.
“We can power loads at the atto to femto watt level, which is probably a future challenge to the community involved in developing low-power detectors and autonomous devices,” said Singh. “We envision that these vesicle batteries can serve as a rechargeable power source for distributed autonomous systems that may be of interest to the military and medical communities.”
Now the researchers plan to design more robust vesicles and to encapsulate other redox couples to improve the efficiency of the system. “We are also looking for other collaborators to transform this capability into viable commercial products,” said Singh.
The researchers reported their work in Advanced Materials .
34)
30 June 2005
Current lithography techniques struggle to create gaps smaller than about 20 nm wide in nanowires, an ability that’s crucial for the future development of nanoelectronic devices. But now researchers from Northwestern University,
US, claim their on-wire lithography technique can produce gaps just 2.5 nm wide.
“With miniaturization happening across so many fields, our existing tools can’t control the shapes and spacing of these small structures,” said Chad Mirkin of Northwestern.
“Our method allows us to selectively introduce gaps into the wires. These gaps can be filled with molecules, making them components for building small electronic and photonic devices or chemical and biological sensors.”
Mirkin and colleagues created the gaps by making nanowires containing segments of two different materials. One component was susceptible to wet-chemical etching, while the other was resistant. To demonstrate the process, the scientists fabricated gold-silver nanowires and gold-nickel nanowires, with the gold component resisting wet-chemical etching.
To make the nanowires, the team used electrochemical deposition into porous alumina templates. Controlling the charge enabled them to tailor the length of each

segment. Then they dissolved the template and cast an aqueous suspension of the nanowires onto a glass microscope slide.
For gold-nickel nanowires, the next step was to deposit a layer of silica 50 nm thick onto the wires and remove the coated wires from the substrate. Finally, the researchers etched away the nickel segments using concentrated nitric acid. This left gold nanowire structures containing gaps corresponding to the length of the nickel segments.
The process was essentially the same for the gold-silver nanowires, but the team used a gold/titanium bilayer coating instead of silica, and etched away the silver portion of the nanowires with a solution of methanol, ammonium hydroxide and hydrogen peroxide.
In this way, the team made gold nanowires with 2.5, 5, 25, 40, 50, 70, 100, 140 and
210 nm gaps on a silica or gold/titanium backing. On average the wires were 4.5 µm long.
“With dip-pen nanolithography, we can then drop into these gaps many different molecules, depending on what function we want the structure to have,” said Mirkin.
“This really opens up the possibility of using molecules as components for a variety of nanoscale devices.”
The researchers also made disk structures from the nanowires consisting of disks of gold separated by 40 nm gaps. The team reckons they could design such structures to have unusual optical properties, giving them potential applications as plasmon waveguides.
The researchers reported their work in Science .
35)
1 July 2005
This year’s Tour de France will see cyclists from the Phonak Team use a bike with a frame containing carbon nanotubes. Swiss manufacturer BMC claims that the frame of its "Pro Machine" weighs less than 1 kg and has excellent stiffness and strength.
To create the frame, BMC used a composite technology developed by US sports equipment specialist Easton. The company's "enhanced resin system" embeds carbon fibre in a resin matrix that's reinforced with carbon nanotubes. Easton says that this improves strength and toughness in the spaces between the carbon fibres.
Nanotube bike
Easton has partnered with nanomaterials specialist Zyvex, US, which supplies functionalized nanotubes for the system. Zyvex is able to treat nanotube surfaces so that the tubes disperse more easily in other materials.
BMC claims to be the first to build a complete bicycle frame using Easton CNT-
Nanotechnology. The frame contains only one alloy part - the bottom bracket threading. As well as using the new material, BMC says it invested in moulding

technology. The structure did not require machining after manufacture, avoiding damage to the carbon fibres.
The 92nd Tour de France starts on 2 July and ends on 24 July. Riders will cover a total distance of 3607 km. US citizen Lance Armstrong is attempting to win the race for the seventh time. He has not, however, commented in public as to whether his bike contains carbon nanotubes.
36) Nanobridges create contact *
Researchers at the University at Buffalo, State University of New York, and the Electronics and Telecommunications Research Institute in Korea have created nanobridges of nickel silicide across trenches in a silicon wafer by a process of self-assembly. The technique could ultimately find a use in creating contacts for nanoelectronic devices.
See http://nanotechweb.org/articles/news/4/7/4?alert=1
37) Nanowire device suits microwave detection *
Researchers have made a nanowire device that can detect microwave radiation up to 110 GHz at room temperature. The team, from the University of Manchester, UK, VTT Information
Technology, Finland, University of Würzburg, Germany, University of Salamanca, Spain, and
Lund University, Sweden, believes the devices could have applications in detecting terahertz radiation and in plastic electronics.
See http://nanotechweb.org/articles/news/4/7/3?alert=1
38)
5 July 2005
Researchers have made a nanowire device that can detect microwave radiation up to 110 GHz at room temperature. The team, from the University of
Manchester, UK, VTT Information Technology, Finland, University of Würzburg,
Germany, University of Salamanca, Spain, and Lund University, Sweden, believes the devices could have applications in detecting terahertz radiation and in plastic electronics.
"This is the simplest diode in the world, as well as the quickest novel electronic nanodevice to date," Aimin Song of the
University of Manchester told nanotechweb.org
. "The selfswitching device (SSD) is made in only one nanolithography step and is planar: both electrodes and the active semiconductor are within a two-dimensional plane. This is in great contrast to a traditional diode, which is made using up to
10 steps and is a complex three-dimensional vertical structure."
Microwave detection
Song and colleagues made nanowire devices with intentionally broken symmetry by etching L-shaped trenches in a modulation-doped InP/InGaAs/InP quantum well wafer. This defined nanowires in between the trenches. The wires were 1.2 µm long and 60-100 nm wide.
"The device image is like two 'L's, back to back," said Song. "When connected into an array, the 'L's become 'U's. And indeed, to make such a device or a circuit based on SSDs we just need to 'write' insulating lines on a semiconductor layer."

The scientists say this simplicity significantly reduces production costs. The planar layout also makes the structure extremely suitable for detecting incoming electromagnetic radiation. What's more, the device has a threshold voltage that's tunable from zero to about 10 V.
"Therefore, it allows us to detect extremely weak signals, showing a very high sensitivity even when no external bias circuit is used," said Song. "A normal diode always has a threshold voltage, typically around 0.7 V, which is fixed and determined by the semiconductor used. If the applied signal is below the threshold, the diode will not operate at all."
A device containing 18 parallel nanowires produced roughly 75 mV of DC output for every mW of nominal input power of a 110 GHz signal. That's despite the fact that only about 0.4% of the microwave power was effectively transferred to the structure because of an impedance mismatch. And the detection sensitivity of the devices was pretty much stable over a frequency range of 100 MHz - 110 GHz.
"From the frequency dependence, it is virtually certain that the device will also operate well in the terahertz (1000 GHz) frequency regime, in which a very broad range of applications have been envisioned," said Song. "It could dramatically improve or even revolutionize technologies such as local oscillators and radar arrays for astronomy, high bandwidth and wireless networks for communication, environmental monitoring, industrial tomography for atmosphere control, drug delivery, food analysis for process technology, cancerous tissue imaging, and spectroscopy for medical applications."
The researchers reckon their SSDs could be ideal terahertz detectors, because the devices are small, ultra-sensitive, broadband, scalable and easy to couple. They could also prove useful in plastic electronics.
"The key difficulty [with today's plastic electronics technology] is that the speed of organic devices is too low, typically around or below kHz, whereas most applications need at least MHz," said Song. "Because the self-switching device has been shown to work to at least 110 GHz, the physical rule of transistor speed scaling ensures that organic self-switching devices will be able to perform at not only tens of MHz, but also most likely in the hundreds of MHz range."
39)
8 July 2005
Researchers at the University at Buffalo, State University of New York, and the
Electronics and Telecommunications Research Institute in Korea have created nanobridges of nickel silicide across trenches in a silicon wafer by a process of self-assembly. The technique could ultimately find a use in creating contacts for nanoelectronic devices.
“The first and inevitable step of nanoelectronics integration is to form contacts,”
Joondong Kim of the University of Buffalo told nanotechweb.org
. “In considering cost and simplicity, it’s desirable to be independent from the use of complex and multiple lithography steps. The contact made by the nanobridge is solid and strong with a small contact area that is the same as the diameter of the nanowire itself. Moreover, it does not require any additional steps to make contacts because the formation is spontaneous.”

Kim and colleagues formed nanobridges across trenches in a silicon wafer that were
1-
6 µm wide and 1.5 µm deep. They created a layer of silicon dioxide on the silicon substrate and then added a coating of nickel catalyst. The oxide prevented diffusion of the nickel into the silicon.
Finally, the researchers sputtered silicon onto the structure at a substrate temperature of 575°C. The sputtered silicon formed nickel silicide by a solid reaction with the nickel catalyst, in a process known as metal-induced growth. Nanobridges formed on the nickel layer but not on the sidewall of the trenches. The bridges were
30-80 nm in diameter and 210 µm long.
“Due to the unique process, it is possible to grow nanowires at relatively low temperatures without using a gastype silicon source,” said Kim. “The low processing temperature reduces potential damage to previously fabricated structures. Metalinduced growth nanowires and nanobranches may be directly adopted in CMOS processing as the temperature of 575 °C prevents the rediffusion of shallow junctions and reduces potential damage to fabricat ed structures.”
The scientists, who reported their work in Applied Physics Letters , are now looking to increase their control over the nanobridge formation.
40) * Superconducting nanowire devices could run and run *
Researchers at Delft University of Technology and Philips Research Laboratories, both in the
Netherlands, have combined semiconductor nanowires with superconducting contacts to make superconducting transistors. At temperatures below 1 K, the contacts induced superconductivity in the nanowires through the proximity effect.
See http://nanotechweb.org/articles/news/4/7/8?alert=1
41) * Oxygen boosts nanotube interaction with ammonia *
The presence of ammonia tends to have a dramatic effect on the conductivity of single-walled carbon nanotubes. It's a phenomenon that could be useful in chemical sensors but it's not fully understood. Now researchers at Temple University, the University of Pittsburgh, and Emory
University, all in the US, have studied the adsorption of ammonia molecules on single-walled carbon nanotubes and found that the presence of oxygen groups on the nanotubes can enhance ammonia uptake.
See http://nanotechweb.org/articles/news/4/7/7?alert=1
42) * Adsorption is key to doping nanocrystals *
Semiconductor nanocrystals, or quantum dots, have often proved difficult to dope. But researchers at the Naval Research Laboratory and University of Minnesota, both in the US, have discovered that the ease of doping depends on the structure of the nanocrystal. They used this information to incorporate manganese into nanocrystals of cadmium selenide (CdSe) for the first time.
See http://nanotechweb.org/articles/news/4/7/6?alert=1
43) * Superconducting nanowire devices could run and run *
Researchers at Delft University of Technology and Philips Research Laboratories, both in the
Netherlands, have combined semiconductor nanowires with superconducting contacts to make superconducting transistors. At temperatures below 1 K, the contacts induced superconductivity in the nanowires through the proximity effect.
See http://nanotechweb.org/articles/news/4/7/8?alert=1
44) * Oxygen boosts nanotube interaction with ammonia *

The presence of ammonia tends to have a dramatic effect on the conductivity of single-walled carbon nanotubes. It's a phenomenon that could be useful in chemical sensors but it's not fully understood. Now researchers at Temple University, the University of Pittsburgh, and Emory
University, all in the US, have studied the adsorption of ammonia molecules on single-walled carbon nanotubes and found that the presence of oxygen groups on the nanotubes can enhance ammonia uptake.
See http://nanotechweb.org/articles/news/4/7/7?alert=1
45) * Adsorption is key to doping nanocrystals *
Semiconductor nanocrystals, or quantum dots, have often proved difficult to dope. But researchers at the Naval Research Laboratory and University of Minnesota, both in the US, have discovered that the ease of doping depends on the structure of the nanocrystal. They used this information to incorporate manganese into nanocrystals of cadmium selenide (CdSe) for the first time.
See http://nanotechweb.org/articles/news/4/7/6?alert=1
46)
19 July 2005
Sharp has developed a blue-laser storage technology that is capable of holding twice as much data per layer (50 GB versus 25 GB) than the Blu-Ray disc format which is now entering the market.
The Japanese electronics firm will unveil a 100 GB dual-layer
"super-resolution" optical disc at a conference on optical storage and memory (ISOM/ODS 2005) which is taking place in Hawaii this week.
Super-resolution disc
Sharp claims that its super-resolution format holds up to 9 hrs of high-definition television (HDTV) footage in a dual-layer optical ROM disc. Each layer consists of a series of tiny data marks (pits and bumps) covered by thin transparent "super-resolution" film.
The film’s thermo-optic properties enable a very high resolution data read-out that actually beats the optical diffraction limit. This means that it is possible to identify data marks that are smaller than the footprint of the laser beam, leading the way to higher density storage.
Sharp’s scheme uses a blue laser beam with a diameter of around 400 nm to read data marks that are just 100 nm wide. Although the laser beam illuminates several marks simultaneously, heatinginduced differences in the film’s optical transmission allow a distinction between the pits and bumps.
According to Sharp, it has been searching for some time for suitable materials to create a film with the high optical transmission that is needed for a multiple layer disc.
It says that it has now found a metal oxide that is up to the task.
47)
4 July 2005

The ultimate goal of this research by Rong Wang’s group at The Illinois
Institute of Technology, US, is to develop a novel assay that enables in situ examination of the molecular mechanism of initial cell response to individual ligand-receptor interactions on a living cell membrane. The research will not only benefit fundamental understanding of the molecular mechanism of signal transduction cascade, but could also have great impact on the pharmaceutical industry, in fields ranging from drug design to validation.
Developing such an assay requires two tasks to be accomplished: the precise delivery of ligand molecules to identified cell membrane proteins, followed by high resolution imaging to monitor the local changes on the cell in situ . This has not been achieved with any other state-of-the-art method.
Together with Argonne National Laboratory, US, we designed experiments to harness the recent advancements in atomic
Rong Wang force microscopy (AFM) and novel bio-conjugation techniques to tackle this challenge. The paper published in Nanotechnology demonstrated the feasibility of the approach. Here we anchored proteins on an AFM tip via our newly synthesized photo-cleavable crosslinker. Irradiation served as a “remote controller” to cleave the proteins off the tip upon the photolytic reaction of the cross-linker. Due to the high lateral resolution of AFM, the proteins can be precisely delivered to a desired local region. After the proteins modified on the tip were cleaved away, the tip regained the same level of imaging resolution as a bare tip. Thus the result of protein delivery was resolved at a single molecular level.
Another advantage of the method is that the ligand-modified AFM tip can provide guidance to identify the cell membrane receptors on a living cell via force mapping.
That’s despite the complexity arising from the diverse distribution of various cellsurface proteins and phospholipids on the rough membrane surface. This makes it possible to deliver a ligand to its receptor on a living cell, and dynamically follow up the local cell response to the ligand-receptor interaction. We are currently making efforts along this line. In general, such a methodology can be applied to any cell types. By disclosing the initial molecular signal pathway associated with ligandreceptor interactions in living cells, the research should also provide a molecular basis and novel strategies for early diagnosis and treatment of many ligandassociated diseases.
47)
4 July 2005
For more than 20 years scientists have used the sharp tip of an atomic force microscope (AFM) to define nanometre scale structures and devices, in a process dubbed atomic force microscopy nanolithography. The most common method is based on applying a voltage between the AFM tip and the surface: the presence of humidity in the air induces local oxidation of the surface. The resulting thin oxide layer forms itself into a nanostructure, or can serve as a mask for subsequent selective etching of the surface.
This local oxidation by atomic force microscopy has been applied to fabricate structures on many materials. Now we have applied the same technique to thin

layers of PMMA. PMMA is particularly relevant to nanotechnology as it’s used as a resist material for electron beam lithography. The PMMA is locally exposed to a beam of electrons, changing its properties and making it solvent in a convenient developer. With AFM nanolithography, we have obtained at least the same resolution as with electron beam lithography systems, which are not as readily available as
AFM in research laboratories. What’s more, there is no need for a development process since the PMMA is directly eliminated.
Unlike other methods based on scratching the PMMA by exerting a high force with the AFM tip, in our approach we have identified a new mechanism responsible for eliminating the PMMA. As confirmed by electrical measurements, the process involves an electrochemical reaction that causes the PMMA to dissolve.
The work is of interest both from a practical point of view - combination with electron beam lithography is already demonstrated - as well as for fundamental reasons - it identifies a new mechanism of surface modification.
48) Fri
Nanomachines will depend on our knowledge of friction, heat transfer and energy dissipation at the atomic level for their very survival. Jacqueline Krim of
North Carolina State University, US, explains.
In the scramble to revolutionize the world with nanotechnology we must not ignore friction. Nano-scale devices based on moving molecular components have the potential to radically alter technologies such as energy storage, drug delivery, computing, communications and chemical manufacture. But getting these devices from the laboratory to the marketplace is far from guaranteed.
It is simply not clear if nano-scale structures can be made mechanically and chemically resistant enough to withstand the extreme conditions that can exist inside the human body, or in any of the other hostile environments where nanomachines might be expected to operate. The shearing-off or melting of even a single layer of atoms can easily spell death for a nanomachine, and this is before commercial issues such as energy efficiency or profitability are addressed (see "The future of nanotechnology" Physics World August 2004 pp25-29).
Rough ride
The chemical and mechanical stability of moving nanostructures underlie the field of nanotribology - the study of friction and wear at atomic length and time scales. Last year turned out to be a banner year for this field, with an impressive upsurge in both experimental and theoretical work. This included substantial progress in our understanding of how mechanical instabilities contribute towards overall friction levels, and pioneering experimental techniques for bridging the gap between nanoscale and macroscopic phenomena.
Centuries-old friction
Historically the study of friction has been driven by economic considerations. For example, by paying more attention to what is already known about friction and wear, developed countries could save up to 1.6% of their gross national product. The loss - which is estimated to be as much as $100 billion per year in the US alone - arises because entire mechanical systems are routinely discarded whenever only a few of

their parts are badly worn. And the energy consumed in the manufacture of a car, for example, is equivalent to that consumed in 100,000 miles of operation.
Given how little actually is known about friction, the potential
1 The basics of friction impact on the economy and society associated with an improved knowledge of tribology is nothing less than mind-boggling! But progress in this field has been slow, and the interest of physicists in tribology has waxed and waned over the centuries.
Modern tribology began some 500 years ago, when Leonardo da Vinci deduced the laws governing the motion of a rectangular block sliding over a planar surface.
Hundreds of years later, in 1699, the French physicist Guillaume Amontons published the first formal account of the classical, macroscopic friction laws. He found that the frictional force that resists the sliding motion between two interfaces is directly proportional to the perpendicular force that squeezes the surfaces together.
Moreover, the frictional force is independent of the apparent area of contact. A brick standing on its end, for example, experiences the same friction as when it is laid flat.
Charles Augustin de Coulomb later proposed a third law of macroscopic friction, which states that at ordinary sliding speeds the frictional force is independent of velocity.
These classical laws of friction hold for a remarkably wide range of materials, but they are equally remarkable in terms of how difficult it is to derive them from fundamental atomic or molecular principles. It is reminiscent of the situation in thermodynamics before statistical mechanics came to the rescue. The roughness of a surface was ruled out as a possible mechanism for most types of friction by the 1970s, and was
2 Friction at work replaced by the notion that the atoms in two materials may bond together and resist sliding as the materials are pressed into contact. Unfortunately, this "adhesive bonding" view of friction, which was promoted by Philip Bowden and David Tabor of
Cambridge University in the 1960s, does not make any predictions about the magnitude of the frictional force or the mechanism of energy dissipation that gives rise to it.
Tabor ultimately became convinced that friction in the absence of wear - the tearing off of fragments along the sliding interface - must be due to the build up of strains between the interfaces that were then released in the form of atomic vibrations called phonons. Phonons, which were first suggested as a mechanism for friction by G A
Tomlinson in 1929, are produced when the mechanical energy required to slide one surface over another is converted to sound, which is eventually transformed into heat
(figure 1). Tabor was aware of no experimental evidence that such phononic friction existed, but he was soon to be vindicated by a growing community of surface scientists.
Today, there are perhaps 100 physicists and other scientists worldwide who lead work on nanotribology (figure 2). This situation has come about largely due to the availability of new experimental and theoretical techniques in the 1970s and 1980s, which gave rise to a renaissance in experiments exploring the microscopic origins of friction. Devices such as the quartz crystal microbalance and the lateral force microscope, for example, can measure the friction due to a single contacting interface. This scenario is vastly simpler to study than that of macroscopic objects, where friction reflects the collective behaviour of a multitude of contacts.

In 1991 the present author and colleagues, then at
Northeastern University in Boston, used a quartz crystal microbalance - a device that is so sensitive that phonons
3 Microelectromechanical friction modify its vibrational properties - to measure the friction of krypton monolayers that were sliding on a gold surface. Our results ultimately proved the existence of phononic mechanisms of friction, whereby phonons are excited in the adsorbed layers. Indeed, to the best of my knowledge, the term "nanotribology" first appeared in print in the title of the paper announcing these results (see Krim et al.
in further reading).
To stick or to slip
One of the most common types of friction at the macroscopic scale, and also one of the most frustrating, is static friction. This is the force that is needed to get an object to move in the first place, and it is almost always larger than the force that is needed to keep the object moving. Among other factors, static friction can depend on how long the two surfaces have been in contact with one another.
A closely associated phenomenon is that of "stick-slip" friction, whereby the transition from static to sliding friction leads to repetitive sticking and slipping at certain speeds.
This is the mechanism responsible for the familiar screeching noises associated with car brakes.
For monolayers sliding along atomically uniform substrates, however, there is essentially no static friction. Indeed, the friction in these systems can be up to 10 5 times less than that for macroscopic lubricants such as graphite. This raises questions about the fundamental dissipation mechanisms that are at work in systems at different scales. For example, do these mechanisms play a substantive role in wear-free friction at the macroscopic scale, or do they dominate only in simple geometries? Is a lack of a stick-slip phenomenon always associated with exceptionally low friction levels, and, if so, can the results be applied to meso-
(intermediate) and macro-scale systems? A series of new experiments is now under way to unravel these mysteries.
In 2004 Ernst Meyer and co-workers at the University of Basel used a lateral force microscope to observe the transition between stick-slip and continuous sliding for the first time. This instrument, which is common in nanotribology research, is a modification of an atomic
4 Nanotractor force microscope and consists of a sharp tip mounted on a flexible cantilever. As the tip is dragged over the surface of a sample, the cantilever is deflected by an amount that depends on the friction between the tip and the substrate.
Meyer and colleagues monitored silicon-tipped cantilevers as they slid along atomically uniform crystals of sodium chloride. By varying the normal load on the cantilever tip, the system could be made to enter (and return from) a state of ultralow dissipation with no mechanical instabilities or stick-slip behaviour. These data were modelled successfully using a Tomlinson model, in which friction is the result of mechanical instabilities that give rise to phonons. While the results support the idea that vibrational mechanisms can cause energy dissipation in a variety of geometries, they do not completely rule out other mechanical models.
For example, Alexander Filippov of the Donetsk Institute for Physics and Engineering in the Ukraine and colleagues at Tel Aviv University in Israel have developed a

mechanical model of friction at the micro-scale that is based on two rigid plates separated by elastic springs. The springs can spontaneously break and reform upon contact to represent the collective behaviour of the constituent molecules. An external "drive" force is then applied to the system, and the rate of bond rupture and formation with respect to the sliding speed determines the macroscopic response.
Filippov and co-workers found that stick-slip behaviour is present in cases where there is a co-operative rupture of bonds, and the presence of static friction depends on experimental conditions and timescales.
Their model therefore establishes a relationship between macroscopic observables and the dynamics of microscopic bonds at the sliding interface. Force measurements alone do not allow one to establish a microscopic picture of friction, but it will be essential to understand the links between macroscopic response and microscopic dynamics if we are eventually going to unravel the origins of friction.
Superlubricity has stuck
The relative structure of two surfaces that are in sliding contact with each other also has a profound influence on the phononic contributions to friction. For instance, friction is especially great when the surface atoms are equally spaced and aligned with the counterface atoms against which they are sliding. Although the vast majority of sliding interfaces do not meet these conditions, friction in such "commensurate" systems can be more than 10 10 times greater than the friction between
"incommensurate" surfaces.
The possibility that phononic friction can be exceptionally small between two atomically incommensurate surfaces has been referred to as superlubricity by some researchers. This is unfortunate, since the "resistance" does not drop to zero, as in the case of superconductivity or superfluidity, but instead simply arises from low levels of phononic friction associated with the structural incompatibility of the sliding surfaces. Even if phononic friction was to drop to zero, a very small amount of frictional energy would still be dissipated due to electronic and/or photonic excitations.
In March last year, Martin Dienwiebel and co-workers at Leiden University in the
Netherlands found evidence for "superlubricity" in graphite using a purpose-built force microscope that could measure forces as low as 15 pN (15 x 10 -12 N). The Leiden team captured a graphite flake on the end of a tungsten tip and measured the friction as it was slid along a crystalline graphite substrate (the contact area of the flake was estimated to be a mere 96 atoms). The researchers then brought the flake in and out of perfect commensurability with the graphite surface by rotating it into positions where the atoms were no longer aligned. As expected, high levels of friction were present in the commensurate positions and extremely low friction was found when the surfaces were incommensurate.
The Leiden experiment provides further evidence that Tomlinson-type mechanical vibrations are a fundamental source of macroscopic friction, and Dienwiebel and coworkers claim that such vibrations could account for the lubricity of graphite at the macroscopic scale. However, this is not the first time that nanotribologists have linked nano-scale lubricity to macroscopic friction, the tacit assumption being that extremely low friction coefficients and/or extremely high interfacial slip levels at the atomic level are in some way linked to macroscopic lubriciousness. The trouble is that the coefficients of friction measured in nanotribological experiments and in macroscopic
"tribotests" routinely differ by orders of magnitude.

To test this microscopic hypothesis, our group recently used a quartz crystal microbalance to monitor the nano-dynamical motion of molecules in organophosphate film samples in which the macroscopic friction coefficients are well known. We were astonished to discover that molecules that could flex or slide even just a little in response to the oscillatory motion of the microbalance were linked to low friction levels at the macro-scale. Put another way, exceptionally low friction at the atomic scale was not a prerequisite for the substantial reduction in macroscopic friction.
Last year Martin Muser of Johannes Gutenberg Universitat in Mainz, Germany, explored theoretically what happens when two chemically inert materials slide with respect to one another. Muser allowed the interactions between the two materials to vary, which had a great impact on overall friction levels. For example, whenever elasticity dominates at all length scales, the two solids move essentially as rigid blocks. In the absence of wear this would result in exceptionally low friction levels, which suggests that 3D crystals that form a perfectly flat 2D interface should exhibit super-low friction levels. Muser points out, however, that this "structural lubricity" is very likely to be lost in its entirety for the vast majority of everyday surfaces. The applicability of nanotribological results for meso and macro applications thus remains open to debate.
The meso-scale regime
Microelectromechanical systems (MEMS), which integrate mechanical and electronic components, are currently fuelling a billion-dollar industry. But tribological issues are holding back the development of a myriad of MEMS devices - such as rotary gears, microturbines and relay switches - that could form the building blocks for more sophisticated "on-chip" systems. Indeed, there are no commercially available MEMS devices that contain surfaces that are in sliding contact simply because MEMS are exceptionally susceptible to friction and wear. And you cannot simply add traditional lubricants such as oil because these microfabricated structures succumb rapidly to capillary forces in the presence of liquids (figure 3).
Michael Dugger and co-workers at Sandia National Laboratories in the US have recently developed on-chip MEMS friction testers capable of detecting friction forces as small as 5
μN. A MEMS friction tester typically consists of tens of contact regions, while nanotribological techniques typically involve only one. The devices therefore help to bridge the gap between nano- and macro-scale phenomena. Although this approach only works for simplified contact geometries, the surface structure and chemistry of the devices duplicate those found in more complicated systems that have been targeted for certain applications. The testers are also proving to be useful in fundamental studies of friction.
Maarten de Boer and colleagues, also at Sandia, have recently developed an on-chip
MEMS "nanotractor" that is dedicated entirely to fundamental studies of friction. This instrument, which is able to creep along a surface in nanometre steps, was designed specifically to study the validity of Amontons' law - which states that the frictional force is proportional to the weight of the moving object - at the micro- to meso-scale
(figure 4).
The nanotractor can measure both static and sliding friction coefficients, and is capable of progressive movements that mimic decreasing "weight". Boer's group, in collaboration with Bob Ashurst at the University of California at Berkeley, found that
Amontons' law holds for normal forces ranging from 50 μN to more than 1 mN. For

forces less than 50
μN, the researchers found deviations from Amontons' law indicative of the increased significance of molecular forces for very low external loads.
In addition, the Sandia team has discovered a "gross slip" phenomenon that happens before the static-friction limit had been reached. The gross sliding, which is about 100 times larger than theoretically expected, is very important in MEMS design, especially in cases where an object must be positioned with nanometre accuracy for optical applications. Work is now in progress to cast the experimental observations onto a firm theoretical footing.
The future for friction
The potential for nanotechnology to transform civilization as we know it is breathtaking, and the nanomechanical systems of the future will all require new atomic lubrication schemes to overcome the debilitating effects of friction. But in order for this impending revolution to be fully realized, we need a fundamental understanding of friction at the atomic to meso-scale.
Moreover, the tribological considerations of these systems will be an integral aspect of the system design, rather than the "after the fact" application of lubricants that is so common at the macro-scale. Finally, the dreams of a nanotechnological revolution will only be realized by training both existing and future scientists and engineers in nano-scale phenomena - an area that is largely absent, for instance, in the present curriculum. The time to start is now.
About the author
Jacqueline Krim is in the Department of Physics, North Carolina State University,
Raleigh, NC, US, e-mail jkrim@unity.ncsu.edu
This article first appeared in the February 2005 issue of Physics World .
Further reading
M Abdelmaksoud, J Bender and J Krim 2004 Bridging the gap between macro- and nanotribology: a quartz crystal microbalance study of extreme environment lubrication Phys. Rev. Lett.
92 176101
A D Corwin and M de Boer 2004 Effect of adhesion on dynamic and static friction in surface micromachining Appl. Phys. Lett.
84 2451
M Dienwiebel et al.
2004 Superlubricity of graphite Phys. Rev. Lett.
92 126101
A Filippov et al.
2004 Friction through dynamical formation and rupture of molecular bonds Phys. Rev. Lett.
92 135503
J Krim et al.
1991 Nanotribology of a Kr monolayer: a quartz crystal microbalance study of atomic-scale friction Phys. Rev. Lett.
66 181-184
M Muser 2004 Structural lubricity: role of dimension and symmetry Europhys. Lett.
66
97-103
A Socoliuc et al.
2004 Transition from stick-slip to continuous sliding in atomic friction: entering a new regime of ultralow friction Phys. Rev. Lett.
92 134301
49)
14 June 2005

Nanoelectronics is getting ready for the marketplace. Magnetic random access memory (MRAM) chips already ship in small quantities. Organic light-emitting diode (OLED) displays are in prototype. Carbon nanotube interconnects won’t generate much revenue until we reach the 45 nm node - but for pilot plants that could be just a couple of years away.
Now is the time for start-ups and corporate nanoelectronics R&D programmes to stop talking about how cool the technology is, forget the hackneyed quips about the next big thing being very, very small and come up with some re al business plans. That’s the scary part. Understanding value chains, building business models ... it’s all a very inexact science. Mistakes can cost millions. As an industry analyst covering the photonics sector during the rise and fall of the telecoms industry, I am convinced that the critical input to business plans for products based on novel technologies is realistic market forecasting. During the optical boom, I saw firms swarming with brilliant minds talk themselves into believing that the markets they were chasing were worth billions of dollars. They built business models based on this assumption, and then they crashed and burned.
Had they built those business models around the truth - that their addressable markets were actually worth hundreds or even tens of millions of dollars - many of these firms would be with us now. Let’s hope that those working with today’s hot nanoelectronics technologies can avoid this kind of hubris. All they need to do is answer a few simple questions: Where will those cool nano-enabled features really matter to customers? How much will they matter? Can these features be used to create entirely new species of product? And how are the answers to all these questions likely to change over time?
Answering these questions is the first step in coming up with a useful market forecast. Typically it will reveal the hard truth that the addressable markets for a new nano-enabled electronics or semiconductor product will be niche-like. MRAM chips, for example, are inexpensive enough to serve as replacements for battery backed-up static random access memory (SRAM) or to replace both an SRAM and Flash chip where both are used together. Yet they are likely to remain too expensive to attack the mainstream Flash and RAM markets for some time to come.
It’s also important to get timeframes right. On the demand side, for example, some of the advances in high-speed processing using carbon nanotubes or molecular nanostructures have been impressive, but they will not be needed for a few more years. On the supply side, OLEDs promise displays for mobile phones and personal digital assistants (PDAs) that consume only small amounts of power yet provide high quality video. If this promise can be kept then it will instantly solve the most difficult problem that mobile computing and communications faces - having the power to support the features required without running down the battery in a short amount of time. But it is still just a promise - today OLEDs use about the same amount of power as alternative technologies.
None of this should be taken to imply that the first high-tech giants to be born in the
21st century will not be nanoelectronics firms. Perhaps some spintronics company will strike it rich with a low-cost quantum computing platform and launch an entirely novel direction for computing. Someone might come up with a nano-enabled fuel cell or battery with the performance capable of solving the mobile power problem mentioned above. Indeed, while there is always a danger that some nanotech firms will follow the same overoptimistic path to ruin as many of the photonics firms before

them, I also sense that others are underestimating just how revolutionary some of this stuff really is and how big it could be in terms of revenues.
As a result, caught between the overoptimistic and the overpessimistic, forecasting of nanotech markets can be frustrating. Only this week, I was told by one well-informed industry insider that my projections for field emission displays were preposterously high and by another equally well-informed industry insider that they were unconscionably low.
Forecasting of nanoenabled products is a business that doesn’t get you much love.
But it’s a necessary one.
About the author
Lawrence Gasman is the co-founder and principal analyst with NanoMarkets LC. He has 25 years of experience in forecasting high-technology markets of all kinds and has recently participated in projects involving advanced memory devices, field emission displays, carbon nanotube electronics, printable electronics, interconnects and nanophotonics. Lawrence is on the editorial board of the Foresight Nanotech
Institute and is currently working on a book on the commercialization of nanotechnology that will be published by Artech House in 2006.
50) * Nanocell targets cancer *
Researchers at Massachusetts Institute of Technology and the Whitehead Institute for
Biomedical Research, both in the US, have engineered a nanocell that uses two different strategies to attack cancer. The cell contains an anti-angiogenesis agent, which destroys tumour blood vessels, and a chemotherapy drug that acts against the cancer cell itself.
See http://nanotechweb.org/articles/news/4/7/13?alert=1
51) * Atomic crystals go 2D *
A standard technique for producing two-dimensional crystals just one atomic layer thick has been developed by physicists in the UK and Russia. The crystals, which are essentially gigantic 2D molecules, were created by Andre Geim and co-workers at Manchester
University and the Institute for Microelectronics Technology in Chernogolovka.
See http://nanotechweb.org/articles/news/4/7/12?alert=1
52) * New look for hydrogen storage *
A new technique for storing hydrogen has been proposed by scientists in Canada and
Germany. The method, which involves storing the gas between layers of graphite just nanometres deep, could help in the quest for practical hydrogen-storage devices for fuel cells.
See http://nanotechweb.org/articles/news/4/7/11?alert=1
53) * Stressed-out microstructures form botanical-style patterns *
Researchers at the Chinese Academy of Sciences have used stress engineering to assemble regular patterns on the surface of spherical and conical core/shell microstructures. The technique, which produced patterns similar to those found in plants, could find a use in the mass-production of mesoscale structures over a large area.
See http://nanotechweb.org/articles/news/4/8/4?alert=1
54) * Purity pays off for nanotubes *
Physicists in the US have developed a new method for making electronic circuits with carbon nanotubes. The technique involves dipping semiconductor chips into a purified solution of

nanotubes, rather than the conventional method of growing the nanotubes directly onto the chips. The resulting devices are much better than those produced by other approaches.
See http://nanotechweb.org/articles/news/4/8/3?alert=1
55) * Nanotube laser treatment could destroy tumours *
Researchers at the University of Stanford, US, have used single-walled carbon nanotubes and a laser to selectively destroy cancer cells. The modified nanotubes entered cancer cells and were heated by a near-infrared light beam, killing the cells.
See http://nanotechweb.org/articles/news/4/8/2?alert=1
56) * Nanovalve has light response *
Researchers at the Biomade Technology Foundation and the University of Groningen, both in the Netherlands, have made a molecular valve that opens and closes in response to light. The nanovalve could have applications in controllable drug delivery or nanofluidic and microfluidic devices.
See http://nanotechweb.org/articles/news/4/8/1?alert=1
57) * Contacting single molecules *
The field of molecular electronics has so far developed relatively slowly, hindered by a number of obstacles. But now researchers at the Weizmann Institute of Science, Israel, have come up with a method for contacting single molecules more reliably.
See http://nanotechweb.org/articles/news/4/8/9?alert=1
58) * Attractive carbon nanotubes lower percolation threshold *
Scientists from the Paul Pascal Research Centre, France, have discovered a phenomenon that could cut the cost of making conductive composites. The team found that by increasing the attraction between carbon nanotubes in solution they could decrease the percolation threshold
- the concentration of nanotubes at which the tubes form a connected network. This means they could make a conductive composite using fewer nanotubes.
See http://nanotechweb.org/articles/news/4/8/8?alert=1
59) * Carbon nanotubes sort themselves out *
Researchers at the US National Institute of Standards and Technology, Kyung Hee
University, Korea, the University of Kentucky, US, and Michigan Technological University,
US, have come up with a technique that could sort carbon nanotubes according to their length.
Applying a shear stress to a suspension of multiwalled carbon nanotubes caused shorter tubes to move towards the walls while longer tubes headed for the middle of the container.
See http://nanotechweb.org/articles/news/4/8/7?alert=1
60) * For nanoparticles, just add salt *
Physicists in the US have developed a simple way to make nano-sized particles with potentially useful magnetic properties. J Ping Liu and colleagues at the University of Texas at
Arlington added ordinary table salt to particles of iron-platinum and then heated them to produce nanoparticles that could be used as building blocks for magnetic recording media and in biomedical applications.
See http://nanotechweb.org/articles/news/4/8/6/1
61)

11 August 2005
In two recent papers in Nanotechnology journal, HP Labs authors Phil Kuekes,
Warren Robinett, Gadiel Seroussi and Stan Williams explain in detail a defecttolerant interface to HP's crossbar architecture.
"We have invented a completely new way of designing an electronic interconnect for nano-scale circuits using coding theory, which is commonly used in today's digital cell phone systems and in deep-space probes," said Williams, HP senior fellow and director of Quantum Science Research at HP Labs. "By using a cross-bar architecture and adding 50 percent more wires as an 'insurance policy,' we believe it will be possible to fabricate nano-electronic circuits with nearly perfect yields even though the probability of broken components will be high."
As sizes of electronic features get down to a few nanometres, it will become either physically impossible - or economically unfeasible - to produce absolutely perfect circuits.
The coding approach was advanced by Seroussi, director of information theory research at HP Labs. "Coding theory has been used in computer storage and communication for many years," Seroussi said. "Here, we apply it to the fabrication of a hardware circuit."
"It's like giving a distinctive name to a restaurant host to be sure you hear your party called above the noise of the crowd," said Kuekes, a senior computer architect, explaining how coding theory works. "Instead of 'the Jones party', you might put yourself down as 'the John Paul Jones party'. That way, when the host calls your name, you'll hear it even if every word doesn't come through clearly."
Williams said the HP Labs group has created working devices in the laboratory at the
30 nanometre half-pitch scale - about a third the size of today's chips.
63)
11 August 2005
Work in the nanochemistry group at University College Dublin and CRANN
(Centre for Research on Adaptive Nanostructures and Nanodevices) at Trinity
College Dublin aims to use the information contained within biological molecules to 'program' nanoparticle assembly in solution and organization at patterned surfaces.
The programmed assembly and organization of nanoparticles, using strategies inspired by nature, is important because this 'bottom-up' approach can be used to assemble nanoscale devices that have potential applications in next-generation information, communication and healthcare technologies.
One potential application of our work is the assembly of nanoscale electronic wires and switches that can process information more quickly but cost less to make.
Another is the creation of smart capsules that can deliver drugs to specific sites within the body.
Our research currently focuses on the electrical characterization of nanoscale devices similar to those whose DNA-templated assembly we reported in
Nanotechnology . In the future we will focus on the organization and integration of such nanoscale devices on conventionally patterned silicon wafer substrates.

About the author
Donald Fitzmaurice is Professor of Nanochemistry at University College Dublin,
Ireland. He has over one hundred and fifty publications and patents to his name and was recently elected a member of the Royal Irish Academy.
Fitzmaurice is also the founder of NTera Ltd, a company that specializes in electronic paper. During a recent secondment to the business as chief technology officer, he focused on raising the funds necessary to grow the company and on building a world-class technology team.
He recently joined Draper Fischer Jurvetson, a venture capital fund with a particular focus on nanotechnology, as a venture partner.
64) * Carbon-nanotube fabric measures up *
Researchers at the University of Texas at Dallas, US, and Commonwealth Scientific and
Industrial Research Organization (CSIRO) Textile and Fibre Technology, Australia have drawn multiwalled carbon nanotubes into transparent sheets that are 5 cm wide and 1 m long.
An array of the sheets had a higher strength-per-unit weight than high-strength steel.
See http://nanotechweb.org/articles/news/4/8/13?alert=1
65) * Nanotubes make perfect diodes *
A physicist has made the best ever p-n junction diode from a carbon nanotube. The currentvoltage characteristics of the device exhibit an "ideality factor" of one, which is the maximum possible value for any diode. The new diode could have applications in electronics, sensors and photovoltaics.
See http://nanotechweb.org/articles/news/4/8/14?alert=1
66) * Carbon nanotubes mimic gecko foot-hairs *
Geckos have an impressive capacity to walk upside down on almost any surface, using just the attractive forces created by their feet to hold on. With this in mind, scientists have attempted to copy the structure of gecko feet to create strongly adhesive materials. The latest version, developed at the University of Akron and Rensselaer Polytechnic Institute, US, uses multiwalled carbon nanotubes attached to a polymer backing.
See http://nanotechweb.org/articles/news/4/8/12?alert=1