CORE TECHNOLOGIES
Nanosys applications development platform is based on three fundamental core technologies:
1) Rational design and fabrication of high-quality inorganic semiconductor nanostructures,
2) Flexible assembly of high-performance nanostructures into devices, and
3) Precise engineering of ‘quantum’ properties.
By developing these three core technologies, Nanosys develops nanotechnology-enabled systems
addressing a wide range of applications.
Rational design and fabrication of high-quality inorganic semiconductor nanostructures
Nanosys technology allows our engineers to synthesize inorganic semiconductor nanostructures
that fall into three major categories: nanodots, nanorods and nanowires. In addition, these same
processes are capable of producing more complex shapes, such as cones, teardrops and tetrapods.
Using our proprietary computer modeling and synthetic methods, we can rationally design
inorganic semiconductor nanostructures with desired composition, size, shape, crystal structure,
doping and surface chemistry characteristics, and successfully fabricate these materials every time.
This allows us to build new functioning inorganic semiconductor nanostructures with very short
development time, making this class of nanomaterials the only one with a completely rational
fabrication cycle: from design to synthesis to modeling and back to design.
The materials fabricated at Nanosys are atomically perfect, with each particle having the same
physical, optical, chemical and electronic properties of every other particle. The following figures
exemplify the uniformity and control over the physical characteristics of the nanomaterials
fabricated at Nanosys.
Nanosys fabrication technologies are capable of synthesizing nanostructures of all of the
industrially important semiconductor materials, including all of the Group III-V, Group II-VI and
Group IV semiconductors as well as their alloys.
In addition, we are able to fabricate nanostructures from transition-metal oxide materials, providing
additional functional properties such as ferroelectric, piezoelectric, converse-piezoelectric and
thermoelectric etc. Within this large family of compositions, our technology allows us to select
materials to suit a specific application (rather than the other way around), and also allows us to
select materials to leverage the infrastructure and know-how that has been developed over the past
25 years in the semiconductor industry.
The maturity of Nanosys technology to rationally design and synthesize inorganic semiconductor
nanostructures is in stark contrast to other classes of nanomaterials, which have no available
methods for synthetic control. For example, current carbon nanotube fabrication methods yield all
different types of nanotubes in every batch, ranging from semiconducting to semi-metallic to
metallic. As such, while carbon nanotubes have generated tremendous academic interest, they will
never truly compete in the high-value applications targeted by inorganic semiconductor
nanostructures. See Competition for a more comprehensive comparison of inorganic semiconductor
nanostructures with carbon based nanostructures.
In addition to controlling the composition of these nanostructure, we can even change the
composition as they are grown, forming nano heterostructures containing nano-sized
heterojunctions. These junctions can be made atomically sharp, and defect-free; allowing the
production of complex, high-performance electronics integrated directly within a single
nanostructure. In contrast to traditional microelectronics, elements such as p-n diodes, p-i-n diodes,
LEDs, bipolar transistors, etc. can be constructed chemically from the bottom up as the
nanostructures are grown.
Many different types of nano-heterostructures are possible, including core-shell structures,
longitudinal heterostructures, bi-layer ribbons and combinations thereof. This allows for the first
time the integration of complexity on the individual nanomodule level, eliminating the need for
patterning multiple nanomaterials down to achieve functional complexity.
Finally, one of the most important aspects of the nanostructures developed at Nanosys, and one that
is in complete contrast to other nanomaterials such as carbon nanotubes, is that the surface of these
materials can be chemically treated and functionalized using standard organic and inorganic
chemistry. For instance, a silicon nanowire can be chemically modified using decades of expertise
in the field of glass-functionalization chemistry. This affords us even greater flexibility and control
in developing nano-enabled systems for different applications. In one instance, molecules such as
proteins, antibodies, DNA or even small molecules can be bound to nanowires to facilitate the
creation of novel chemical and biological sensors, while other molecular species can be bound to
the same nanowires for applications in molecular memory and logic. By controlling the surface
functionality, we can separate the functional characteristics of a nanomaterial (i.e. its electronic,
optical, physical and conductive properties) from its physical and process characteristics (i.e.
chemical compatibility, wetting characteristics, deposition process, etc). This extraordinary ability
to separate a material’s structure from its function is a profound example of the power of
nanotechnology being developed at Nanosys.
Flexible assembly of high-performance nanostructures into devices
The powerful ability to separate the functional characteristics of an inorganic semiconductor
nanomaterial from its physical and processing characteristics enables Nanosys to develop a wide
variety of processes for the controlled assembly of different nanostructures into functional
structures, composites and devices. In some cases, this assembly is as simple as incorporating the
nanostructures into a polymer host-matrix and printing the nanocomposite into functional units
such as LEDs, solar cells or macroelectronic circuits. In other cases, specific phases can be
generated with the nanostructures to provide additional functionality such as highly polarized
absorption in nanocomposite optical detectors. Nanowires can also be controllably oriented and
deposited for applications such as biosensors and high-performance macroelectronics. It is even
possible to directly grow nanowires into ordered arrays for applications such as field-emission
displays and thermoelectric cooling.
For more complicated architectures, such as nano-based chemical and biological sensors or
memory or logic-circuits, it is necessary to use more sophisticated methods of assembly. For
instance, we have developed proprietary methods to align nanowires and bind them specifically to
electrode surfaces using a combination of micro-contact printing, fluidic-flow and the application
of electric fields. The figure below shows examples of single nanowires suspended between
individual electrode pairs. For even more complex devices, we can also leverage properties of
chemical self-assembly to create dense device arrays.
There are many other methods of ordered assembly that are being developed at Nanosys, including
methods that take advantage of standard top-down micro-lithographic-processes as well as novel
bottom-up chemical approaches. These techniques allow us to create ever-more increasingly
complex assemblies of nanostructures. One of the most important aspects of the flexibility provided
by these nanomaterials is that they are fully-compatible with the traditional planar semiconductor
processing currently used in the microprocessor industry. As such, as Moore’s Law winds to an end
during this decade, nanotechnology can extend the capabilities of microelectronics, not only by
reducing feature-size, but also by increasing overall functionality by adding unique characteristics
to silicon devices such as optical or sensing capabilities.
Precise engineering of ‘quantum’ properties
The inorganic semiconductor nanostructures being developed at Nanosys are characterized by
having a variety of unique physical, optical, electronic, conductive, chemical and magnetic
properties that can be precisely controlled and tuned during the fabrication of the structure. Some
unique properties arise from “quantum confinement” effect observed in nanomaterials. As an
example, light emission from bulk semiconductors such as LEDs results from exciting the
semiconductor either electrically or by shining light on it, followed by emission of a photon from
this excited state. In the case of bulk semiconductors, the energy, and therefore the wavelength, of
the emitted light are governed entirely by the composition of the semiconductor material. If,
however, the physical size of the semiconductor is reduced, so that it is much smaller than the
wavelength of light, additional energy is required to confine this excitation within the nanoscopic
semiconductor structure. As a result, the photons emitted from this nano-state are of higher energy
(i.e. bluer color) than emission from larger semiconductor structures. The result is that different
sized nanocrystals emit light of different wavelengths due to different levels of quantum
confinement. In the case of spherical nanocrystals (quantum dots), the wavelength is dependent on
the diameter of the nanocrystal. In the case of nanowires, the wavelength is dependent on the
diameter of the nanowire. The figure below illustrates how nanocrystals can be tuned to emit from
the IR to the UV by either changing their composition or size.
In another example of the “quantum confinement” effect in these nanostructures, quantum-confined
carrier conduction is dramatically improved as scattering of electrons by dopants and phonons in
semiconductor nanowires dramatically reduces. This quantum-conduction in semiconductor
nanowires results in far superior electronic performance than in bulk materials. In transistors
formed with Silicon nanowires, hole-mobility more than three times greater than comparably doped
single-crystal silicon wafers has been measured.
By controlling the composition, doping and size of these materials, we have the ability to
completely bandgap-engineer a material for each specific application, radically departing from
conventional methodology. For example, in conventional organic LEDs (OLEDs), each different
color in an OLED is formed from a different chemical composition, with its own stability,
processing characteristics, chemical compatibility, conductivity, etc. As each new color must be
developed from scratch, and device architectures are dependent on color, very complex and suboptimal configurations are required for multi-color displays. In contrast, the difference between a
red and blue nanocrystal LED is simply the size of the nanocrystals while all other material
properties remain the same. This allows our engineers to design a single material and device
architecture that can be used to produce LEDs ranging from the UV to the IR, all with identical
characteristics except for color. Such effective separation of structure and function is a truly unique
property of the nanostructures being developed at Nanosys using our proprietary fabrication and
assembly techniques.
Competition: Inorganic semiconductor nanostructures vs. carbon nanotubes
As explained in the technology section, the level of synthetic control available with inorganic
semiconductor nanostructures provides a substantial commercial benefit over other more common
nanomaterials such as carbon nanotubes. This is only one of the many characteristics that make
inorganic semiconductor nanomaterials superior to carbon-based nanomaterials for the high-value
applications that Nanosys is pursuing.

Controlled synthesis: There is no rational way to control the electronic properties of
carbon nanotubes. When synthesized, all different carbon nanotube types are produced at
the same time, including metallic, semi-metallic and semiconducting nanotubes. While the
fundamental physics of nanotubes is well understood (as it is for the inorganic
semiconductor nanostructures), allowing for precise modeling of what materials
characteristics would be most desirable for a particular application, there is currently no
practical way to synthesize the materials that the models suggest. The inorganic
semiconductor nanostructures being developed at Nanosys is the only class of
nanomaterials available today that allows not only the prediction of a structure based on
computer models, but also the prediction of a precise synthetic recipe that produces that
exact structure in high-purity and high-yield, with every particle identical to every other
particle.

Controllable parameters: Even if precision synthetic control was possible with carbon
nanotubes, there are only three major parameters than can be controlled: diameter, length
and chirality. Inorganic semiconductor nanocrystals have far more variables to control (as
well as methods to control them), including length, diameter, crystallinity, doping density,
heterojunction formation and most importantly composition.

Composition and complexity: Carbon nanotubes only come in one flavor - carbon.
Inorganic semiconductor nanocrystals can be fabricated from all of the industrially
important semiconductor materials, including all of the Group III-V, Group II-VI and Group
IV materials and their alloys, as well as the transition metal oxides. Furthermore, the
inorganic semiconductor nanostructures can be fabricated such that material characteristics
change controllably throughout the nanostructure to engineer additional functionality (i.e.
heterostructures) and complexity into the nanostructure.

Range of functional properties: The uniqueness of carbon nanotubes is limited to their
electronic and structural properties. In contrast, due to the large range of materials available
for inorganic semiconductor nanostructures, as well as the ability to create heterostructures,
these materials have a larger range of functional properties that can be accessed to address a
much broader range of applications than carbon nanotubes. Inorganic semiconductor
nanostructures have unique optical, electronic, thermoelectric, ferroelectric, piezoelectric
and magnetic properties, and can address virtually all areas of technology and industry.

Compatibility with traditional materials processing technologies: For the inorganic
semiconductors nanostructures, Nanosys leverages off of more than twenty five years of
processing know-how, infrastructure and equipment developed for the electronics and
semiconductor industries to address technical issues such as electrical interfacing,
composite formation, doping/processing and surface functionalization. In the case of carbon
nanotubes, every technical issue requires a new research project.

Intellectual property landscape: Because carbon nanotubes are widely available to the
research community, critical patents in materials, compositions, devices and applications
are scattered across academic institutions and industrial companies (both large and small).
In contrast, all of the important intellectual property in inorganic semiconductor
nanostructures is consolidated in one place: Nanosys, enabling the creation of a single,
industry-dominant position.
In summary, the following table highlights the major differences between carbon based
nanomaterials and inorganic semiconductor nanostructures being developed at Nanosys.