Nanomaterials Workshop for
High School Science Teachers
The University of Tulsa
Summer 2004
Workshop Facilitators:
Dr. Winton Cornell
Dr. Saibal Mitra
Written by:
Lindsay Jones
Deer Creek-Lamont High School
Lamont, OK.
Table of Contents
Introduction------------------------------------------------------ Page 3
Flow Chart of Techniques Used---------------------------------Page 4
RF Sputtering Technique----------------------------------------Page 5
RF Sputtering Diagram------------------------------------------Page 6
Electrochemical Deposition Technique-----------------------Page 8
Electrochemical Deposition Diagram-------------------------Page8
SEM Technique--------------------------------------------------Page 9
SEM Photos--------------------------------------------------------Page 10
SEM Ni crystal Measurements----------------------------------Page 11
Graph of Ni Deposition ------------------------------------------Page 13
X-Ray Diffraction Technique------------------------------------Page 13
X-Ray Diffraction Diagram--------------------------------------Page 14
Diagram of X-Ray Apparatus-----------------------------------Page 15
X-Ray Spectrum Plot of Nickel---------------------------------Page 17
Chemical Vapor Deposition Technique------------------------Page 18
Diagram of Chemical Vapor Apparatus------------------------Page 19
SEM Photos of Carbon Nanotubes-----------------------------Page 20
Measurement of Carbon Nanotubes--------------------------- Page 21
Conclusions-------------------------------------------------------- Page 21
References----------------------------------------------------------Page 22
2
I.
Introduction and Overview of Workshop:
This workshop was designed to allow High School science teachers to have the
opportunity to observe and use the methods and technology utilized in the field of
Nanomaterials Science. The participants attended lectures over current topics and techniques
being used in this field and then participated in using some of the nanotechnology methods in
the laboratory.
The goals of this workshop were to allow the participants follow processes and
technology utilized in making carbon nanotubes (CNT). This was accomplished by using
different techniques in the laboratory.
Both actual labs and demonstrations were used in this workshop. The procedures and
technological methods used in making the carbon nanotubes are discussed in the following
report.
3
Flowchart of Nanomaterials Workshop
Technology & Labs
I. Preparation and Analysis of Ni deposition substrate plate:
Ni Substrate Surface
Preparation Techniques
and Technology
RF Sputtering
Technique
Electrodeposition
Technique
X-Ray Diffraction
Analysis and
SEM Photo
Analysis
II. Preparation and Analysis of Carbon Nanotubes:
Carbon Nanotube
Formation
Chemical Vapor Deposition
Technique
Analysis of
Carbon Nanotubes
Atomic
Force
Microscope
Scanning
Electron
Microscope
4
A. Preparation and Analysis of Nickel Deposition on Steel Plates:
I.
RF Sputtering Technique Demonstration:
Lab Assistants: Michael Deshazer and Lauren Hutter
A. Introduction:
Sputtering, commonly known as physical vapor deposition, is a physical process
by which atoms of one material are deposited onto another material called the substrate.
It occurs when atoms of one material become ionized and move at high speed to the
surface of the other material, called the target, to “knock” individual atoms of the target
material free, allowing them to drop onto the substrate to coat it. An apparatus
commonly known as an RF Sputter is used to form substrate plates upon which to grow
materials such as carbon nanotubes.
The RF sputter derives its name form using energy waves in the radio wave spectrum
range.
This process is widely used by industry to form coated materials that are used in
various applications of materials science. Many of materials used daily have been
produced by the sputtering method. Some examples of these materials are:
semiconductors, microchips, mirrors, colored glass, and cosmetics.
B.
This is one of the methods used to deposit the nickel onto the substrate. This
process was demonstrated for the participants. The participants did not get to use this
technique because the “sputter” was not working properly during the workshop. It
allowed the participants to observe the technique and apparatus involved in this method
of deposition.
C. Technology write-up:
Each workshop participant was assigned a specific technological apparatus to
write a detailed report over. The write-up of the operation of this machine is discussed
in detail in the write-up section.
D. Basic sputtering diagram on next page.
5
E. Basic Sputtering Process Diagram: (Graphics obtained from http://icknowledge.com/ )
1. An atom collides with an energized particle to become ionized.
2. In the reactivity chamber the ions and electrons
moving toward oppositely charged plates.
3. The high speed charged ions knock the
target atoms loose, allowing them to drop onto
the substance to be coated.
6
E. RF Sputtering Apparatus used at the University of Tulsa:
Magnet
Source
Vacuum Plasma
Chamber
Target
Plate
Shield
Shield
Substrate
Gas
Supply
Power
Supply
Vacuum
Pump
Substrate
Holder
Thickness
Monitor
Sputter Coat Monitor
The substrate to be coated with the Ni coating is placed on the substrate holder and when the
RF Sputtering apparatus is turned on free nickel atoms are knocked off of the target plate at the top
and are deposited on the substrate plate at the bottom.
These nickel coated plates are used for the nucleation of the carbon nanotubes when they are
formed.
7
II. Electrochemical Deposition Technique.
Lab assistant: Vanessa Russo
A. Introduction:
Electrodeposition is the process of depositing materials on a substance by using
an ionic solution through which an electric current is passed. This process has many
industrial and scientific uses and applications. It is a relatively simple process that does
not require very much high-tech equipment.
In this lab, a nickel coating was deposited on a steel plate. The nickel crystals
deposited on the steel substrate plate were used to nucleate the growth of carbon
nanotubes in a later lab. The substrate plate was then analyzed by using Scanning
Electron Microscope (SEM). Photos were taken of the substrates showing the nickel
deposition patterns on the steel substrate plate.
B.
Diagram of electrochemical deposition apparatus used at the University of Tulsa
workshop:
Monitoring
probe
Cathode
Current
Source
Potentiostat /
Galvanostat
Anode
B
C
B
A
Computer & Monitor
8
Apparatus function:
The beaker contains 3 probes: probe A conducts the current to the solution, probe B is a
reference probe to monitor the flow of the current, and the substance that is to be plated is at probe C.
The beaker contains an ionic solution of the ions that are to be deposited onto the substance attached to
probe C.
The current source sends the current to probe A and it then flows through the solution in the
beaker to probe C; this “carries” the ions in the solution the probe C and deposits them onto the
substance held by probe C.
The Potentiostat / Galvanostat measures the current rate while the process is taking place. This
data is relayed to the computer, which then is able to plot and graph the changes in the flow of the
current during the run.
C.
In this lab, a .1 M solution of nickel sulfate (NiSO4 ∙ 6 H20) was used as the solution in
the beaker. This was the source of the nickel ions that were deposited on the substrate. An average
current of 1.5 V was passed through the solution in the beaker. Different time periods of 750s, 1000s,
1500s, 200s, and 3600s for deposition were used. This allowed different amounts of nickel to be
plated on the substrates. After each substrate was formed, it was removed and dried.
The different substrates formed by this process were then analyzed by X-Ray Diffraction to
verify the composition of the materials on and in the substrate and viewed with the SEM to see the
pattern of coating on the substrate for each of the different time periods.
II.
Scanning Electron Microscope Lab
Lab Assistant: Richard Portman
A. Introduction:
The Scanning Electron Microscope uses a beam of deflected electrons from the surface
of an object to produce an image of the object. By using electrons, a much larger image can be
obtained compared to conventional light microscopes.
B. Schematic Diagram of Scanning Electron Microscope: (Diagram obtained from
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/experimental/electron.html
9
C. Sample SEM Photos of Nickel Coated Substrates formed:
10
D. Analysis of SEM photos:
The SEM photos of the nickel deposition on the steel substrate plate shows that there
was a difference in the size, quantity of material deposited, and the uniformity of the deposition
over the steel substrate plate. The deposition time rates have a direct bearing on the type of
deposition that is formed.
The SEM photos were then viewed under a binocular microscope. By using the scale
in µm from the photo, a conversion was made for the metric scale ruler. The size and average
area in nm for the size of six representative large nickel particles were calculated. These
figures are shown on the table below:
Nickel Deposit Sizes Vs. Time on Steel Substrate
Measurement Formula:
Ellipse shape Area = Radius Long Axis X
Large Deposit
Photo #1
Measurement
Large
Axis
X
Radius Short Axis X π
Short
Axis
=
Square
Area
Sq. Area of actual
particle
log(sq
area)
20μm @ 750s
#1
2
X
2
=
3.1
2.0E+05
5.3
#2
2
X
1.8
=
3.1
1.9E+05
5.3
#3
1.8
X
1.5
=
2.1
1.3E+05
5.1
#4
1.6
X
1.5
=
2.8
1.8E+05
5.2
#5
1.8
X
1.2
=
1.4
8.8E+04
4.9
#6
1.8
X
1.9
15.2
2.5
1.2E+05
9.1E+05
1.5E+05
4.5E+04
5.1
6.0
5.2
Photo #2
1.5 =
Total Sq. Area=
Ave Sq. Area=
Standard Deviation=
20µm @ 1000s
#1
2.5
X
2.3
=
4.5
2.8E+05
5.5
#2
2.1
X
1.8
=
3.1
1.9E+05
5.3
#3
2.8
X
2.1
=
4.6
2.9E+05
5.5
#4
2.5
X
1.8
=
2.8
1.8E+05
5.2
#5
2.6
X
2.2
=
1.4
8.8E+04
4.9
#6
2.2
X
1.9
15.2
2.5
1.2E+05
1.1E+06
1.9E+05
8.2E+04
5.1
6.1
5.3
1.8 =
Total Sq. Area=
Ave. Sq. Area=
Standard Deviation=
11
Photo #3
20µM @ 1500s
#1
2.5
X
2.25
=
4.4
2.8E+05
5.4
#2
2.8
X
2.2
=
3.1
1.9E+05
5.3
#3
2
X
2
=
3.1
2.0E+05
5.3
#4
2
X
1.8
=
2.8
1.8E+05
5.2
#5
2.2
X
2.2
=
1.4
8.8E+04
4.9
#6
2.2
X
2.2 =
Total Sq. Area=
Ave. Sq. Area=
Standard Deviation=
1.9
15.2
2.5
1.2E+05
1.0E+06
1.7E+05
6.6E+04
5.1
6.0
5.2
1.8
=
1.8
=
1.6
=
2
=
2
=
2
=
Total Sq. Area=
Ave. Sq. Area=
Standard Deviation=
2.5
3.1
2.3
2.8
1.4
1.9
15.2
2.5
1.6E+05
1.9E+05
1.4E+05
1.8E+05
8.8E+04
1.2E+05
8.8E+05
1.5E+05
3.9E+04
5.2
5.3
5.2
5.2
4.9
5.1
5.9
5.2
Photo #4
#1
#2
#3
#4
#5
#6
20µm @ 2000s
1.8
X
1.8
X
1.8
X
2
X
2.1
X
2.2
X
Photo #5
20µm @ 3600s
#1
2.8
X
2.5
=
5.5
3.4E+05
5.5
#2
3
X
2.2
=
5.18
3.2E+05
5.5
#3
2.8
X
2.2
=
4.83
3.0E+05
5.5
#4
2.8
X
2.5
=
5.5
3.4E+05
5.5
#5
2.8
X
2.3
=
5.05
3.2E+05
5.5
#6
2.8
X
5.06
31.12
5.19
3.2E+05
1.9E+06
3.2E+05
1.7E+04
5.5
6.3
5.5
2.3 =
Total Sq. Area=
Ave. Sq. Area=
Standard Deviation=
The average size of the particles for each deposition time was then plotted in log form on a
graph (see next page). This showed that the quantity of nickel deposited increases with time at first,
but then drops within the 1000s to 2000s range. It then rapidly increases as time continues to increase.
This data shows what was seen in the photos. At 2000s time, the deposition is more even and uniform.
The particles also are more uniform in size.
12
Average Square Area of Large Particles vs. Deposition Time
3.50E+05
Average Square Area (sq. nm)
3.00E+05
2.50E+05
2.00E+05
1.50E+05
1.00E+05
5.00E+04
0.00E+00
0
500
1000
1500
2000
2500
3000
3500
4000
Deposition Time
III.
X-Ray Diffraction Analysis Lab
Lab Assistant: Dr. Winton Cornell
A. Introduction:
The X-Ray Diffraction Technique is used to determine the chemical composition of the
substances in a material. This process involves the use x-rays being “beamed” at a
crystalline object and being reflected back after they are diffracted by the planes within the
crystal. The diffraction patterns of different crystalline substances give off different spectra
which are caused by the x-ray beams that are reflected back in multiples of the whole
wavelength of the x-ray. This occurs due to the distance between the planes the atoms are
aligned upon within the crystal.
See diagram of x-ray diffraction on the next page.
13
B. Diagram of X-Ray Diffraction:
Incident X-rays
Reflected & Refracted X-rays
θ
θ
O----------------O---------------O---------------O------------------O
B
D
d
C
C
O----------------O---------------O---------------O------------------O
Bragg’s Formula: nλ = 2d Sin θ
(λ = 1.5418 Ǻ)
This formula is used to calculate the distance between the planes within a crystal lattice. The
formation of these planes within a crystal lattice occurs at different distances within different crystals
due to the atoms making up the crystal lattice. The distances formed by the bonds between the atoms
are determined by the valence electrons orbiting the atoms.
By using a manipulated form of Bragg’s formula ( d = __ nλ ___ ) the distance between the
2 Sin θ
planes within the crystal can be calculated. Each place where the refracted x-ray reaches a whole
number multiple of λ ( 2λ, 3λ, etc.) will generate a refracted x-ray. This energy wave is then recorded
by the X-Ray Diffraction Apparatus and plotted on a graph. This gives a “unique” signature for each
different crystal material, based upon its composition.
A diagram of the X-Ray Diffraction Apparatus used in this analysis of the nickel deposits on
the steel plates are shown on the next pages.
14
C. Diagram of the X-Ray Diffraction Apparatus used at the University of Tulsa
1. External View
X-Ray Chamber
.
Viewing Windows
Computer
&
Monitor
X-ray
Detector
Module
X-Ray
Control
Furnace
Controller
2. Internal view:
X-ray Recorder
X-Ray Source
Sample
Holder
15
The sample to be tested is placed in the sample holder between the two rings. These two rings
are marked in degrees. When the apparatus is turned on, the x-rays are beamed from the source onto
the sample in the holder. They emerge from the sample after being refracted at certain positions and
are recorded by the receiver on the right. As the x-rays are being emitted, the two rings slowly rotate,
turning both the sample and the receiver. This allows the sample to rotate and lets the x-rays pass
through the sample at different angles to the crystalline layers. At each position where a whole
number multiple of the wavelength ( λ ) is refracted, an energy source is sent to the receiver which
records the refracted x-ray.
These positions are then sent to both the computer screen for real time viewing and the data
storage in the computer. It takes approximately 55 minutes to run one sample. After the sample is
run, the plots on the graph on the sample are compared to the peaks on the plots of known crystalline
substances in the data base. The X-Ray Diffraction energy graph that is plotted will show
characteristic peaks based on the refracted whole multiple wavelengths that are refracted by the
crystal. These then can be compared to known energy graphs to determine what the composition is of
the sample being x-rayed
This information allows the investigator to determine the chemical composition of the
substance that was x-rayed by comparing the peaks for certain elements in the sample with the known
data for other substances.
D. Analysis of nickel substrate plates made during the electrodeposition process described
earlier.
In the electrodeposition lab earlier, an attempt was made to deposit nickel onto a steel
plate substrate. After verifying through the SEM that something was deposited on the steel plate, an
X-Ray Diffraction was run on the steel plates to determine if the deposit was indeed nickel.
From the known data base, characteristic peaks for nickel are expected at 32.8 degrees, 45.9
degrees, and 66.5 degrees. The x-ray plot of the samples made earlier show that the 3 x-ray peaks on
the samples match those of nickel from the data base of known substances.
This confirmed that the steel substrate plate had been deposited with nickel which is to be used
to nucleate the growth of carbon nanotubes in the next lab.
The x-ray plots shown on the next page are for the five samples made by electrodeposition
earlier.
16
.
17
B. Formation of Carbon Nanotubes:
I.
Introduction:
Chemical vapor deposition is a process in which a mixture of gases reacts in a vacuum
and the presence of heat or some other energy source to undergo a series of chemical reactions
and cause a solid to be formed. This solid then precipitates out of the mixture of gasses and is
deposited on a substrate plate. The carbon nanotubes are basically a sheet of carbon atoms
(graphite) that is rolled into a tube.
Carbon nanotubes have high strength, are lightweight, have good chemical inertness,
are good heat conductors, have a large aspect (length/diameter), and have chirality dependant
electronic properties.
Industrial applications of this technique are used to make semiconductors, biomedical
structures, use in optic fibers and telecommunications, nanoelectric devices, supercapacitors,
and structural components of different substances.
A. Chemical Vapor Deposition Lab:
Lab Assistant: Zhijng Zhang --- “Peter”
The process of making the carbon nanotubes was a Chemical Vapor Deposition
process. In this process, gasses are subjected to heat in a vacuum and a plasma of ions is
formed. The ions then react with different gasses forming some different products. When
Hydrogen and Methane are used in this process, the Hydrogen atoms are “stripped" off of the
Methane molecule and the free state carbon atoms are precipitated down onto the nickelplated substrate below.
The chemical reaction for this process is:
H2 + CH4  CH3 + H+ + e
CH3 + H+ + e  2H+
2H+
+ 2e + CH2
+ 2e + CH2  CH2 + H2 .......
This process is repeated until all of the Hydrogen atoms have been removed
from the Methane gas and the Carbon precipitates down onto the nickel-plated substrate.
The nickel acts as a nucleation site for the carbon to aggregate and form carbon nanotubes.
18
Plasma Enhanced Chemical Vapor Deposition Apparatus used at the University of Tulsa:
Magnetron
Water
Cooler
Current regulator
1
2
Microwave
Control &
Focus
3
Plasma
Chamber
Pressure
Sensor
Vacuum
Pump
Air Convector
For Sample
Chamber
Power
Supply
Substrate
Holder
Gas
Source
Controller for
Gases & Flow
Rate
19
B. Analysis of Carbon Nanotubes:
The carbon nanotubes formed by this process were first observed with the SEM
microscope. Photos of the carbon nanotubes are shown below:
20
C. By using the measurement technique used to measure the sizes of the nickel crystals
formed by the electrodeposition process, an attempt was made to get a measurement of
the size of some of the carbon nanotubes. The chart below shows the radius and diameter
measurements obtained for some of the nanotubes formed during this process:
Size Measurements of Carbon Nanotubes
Sample run time
750 sec.
#1
#2
#3
#4
#5
Sample run time
1500 sec.
#1
#2
#3
#4
#5
Particle Radius in nm
Diameter in nm
61 nm
45.8 nm
67 nm
61 nm
55 nm
122 nm
91.5 nm
134 nm
122 nm
110 nm
213.5 nm
549 nm
543 nm
488 nm
457.5 nm
427 nm
1098 nm
1086 nm
976 nm
915 nm
D. Conclusions:
This workshop allowed hands on experience with current technology used in the
field of Nanotechnology Science. The participants performed several labs that involved
processes using procedures in forming carbon nanotubes. This goal was successfully
achieved.
Several new uses and applications of nanotechnology were presented during the
lectures. The participants gained a vast amount of the uses of nanotechnology and the
processes involved in this field of science.
It allowed the participants to observe some of the current technology that has been
discussed in the literature and shown in the media.
21
References
Atomic Force Microscope:
http://www.stolaf.edu/depts/physics/afm/diagram.htm
http://stm2.nrl.navy.mil/how-afm/how-afm.html
http://www. physics.ucsb.edu/~hhansma/afm-acs_news.htm
Carbon Nanotubes:
http://physics.wm.edu/physicsnew/undergrad/2000/will_mcbride.pdf
http://www.phy.mtu.edu/nue/tcvd_cnt_alt.htmc
http://data.engin.umich.edu/nmedseds/kc135/nanotubes/Y2K.main.htm
Deposition Processes:
http://chiserv.ac.nctu.edu.tw/~htchiu/cvd/home/html
http://www.iljinnanotech.co.kr/en/materials/r4-3.htm
http://ww.azom.com/details.asp?articleID=1552
Electrodeposition:
http://journal.kcsnet.or.kr/publi/bul/bu01n9/994.pdf
http:// www.nrel.gov/ncpv/adfs/ieee26pa.pdi
RF Sputtering:
http://www.gencoa.com/tach/index.html
http://www.soleras.com/magntrn/enhance.htm
http://icknowledge.com/
X-Ray Diffraction:
http://research.ibm.com/journal/rd/444.jordansweet.htm
http://cem.msu.edu/~kanatzid/chem913xtl.html
http:www.nanotechweb.org./articles/news/1/7/25/
Scanning Electron Microscope:
http://www.nano.unr.edu/key topics/technology/sem_intro.asp
http://mse.iastate/edu/microscopy/path2.html
22