1. Synthesizing and
Arranging Indium
Antimony Nanowires
Bryan McLaren
2015

2. Introduction
Indium antimony (InSb) is a III-V compound
semiconductor. Of the III-V semiconductors, they have
the smallest energy band gap, high electron mobility, large
Bohr radius as well as the lowest effective mass.
These qualities makes them attractive for use as a
transistor and as a long wavelength infrared radiation
detector.

3. Theory of Processes Used in
this Work
Electrochemical deposition is the process by which
elements in a solution can be deposited onto an template
by applying a potential difference between them. This
method is used to create the InSb nanowires in an uniform
and orderly fashion.
Dielectrophoresis is a method of arranging nanowires on a
two-terminal electrode by applying a sinusoidal voltage to
the electrode which creates an electric field in the channel
for the nanowires to align themselves with.

4. Theory
Semiconductors have an inherent activation energy (Ea) that is a
characteristic of the solid-state material.
Its conductivity (σ) as a function of temperature (T) and is also
inversely related to resistivity (ρ)
Resistivity is related to resistance such that:
where A is the cross-
sectional area and L is the length
Resistance through the wire follows Ohms law:
where V is the
applied voltage and I is the resulting current.
σ(T)=σoexp(Ea/kBT) Eq. 1
σ=1/ρ Eq. 2
ρ=AR/L Eq. 3
R=V/I Eq. 4

5. Experimentation
From raw materials and equipment to something useful

6. Initial Setup
The first action that was taken was to prepare the
template and InSb electrolyte solution.
The chemical make up of the solution was 0.15M InCl3,
0.1M SbCl3, 0.36M C6H8O7H2O, and C6H5Na3O7.
The pH of the electrolyte was adjusted to 1.8

7. The Template
The template serves as a
insolated molding for the
nanowires to grow.
It’s made of anodic aluminum
oxide (AAO) and supplied by
Synkera Technologies Inc.
To prepare it for deposition, a thin
layer of gold 150 nm thick was
thermally evaporated to one side
of the porous template.
The template had a 1cm2 surface
area, 120 μm thickness, and
pores 40 nm in diameter.
Graphic by author
120 μm
50 nm

8. Deposition
Copper tape was applied to the gold
side of the template and sealed in an
insulating polymer.
The cell comprised of three
electrodes: working electrode [Au
coated alumina template], reference
electrode, and a standard platinum
electrode
Starting the deposition process, the
solution was poured into the cell and
the template was clipped to one of the
leads and submerged into the
solution.
The potential difference was supplied
by a potentiostat at -1.5V for 1 hour.
Princeton: Potentiostat for electrochemical (synthesis)
of NCA and InSb NWs

9. Extraction
After removing the template, acetone was used to
delicately remove the insulating polymer and the template
was annealed in argon and hydrogen for an hour at 250˚
C.
5M Sodium hydroxide (NaOH) was dropped onto the
template and gently agitated to dissolve the AAO.
The remaining solution was centrifuged at 1500 rpm for 30
min and then diluted with DI water. This was repeated a
few more times to replace the NaOH with water.

10. Nanowires
Images from scanning electron microscope (SEM)

11. Dielectrophoresis Theory
By creating an electric field between two electrodes, we can
induce a dipole moment on the wires in the solution.
This creates a force and torque on the nanowire
Force from Dielectrophoresis:
Where V is the volume, εm is the permittivity of the medium, and
K(ω) is the Clausius-Mossotti factor as a function of frequency.

12. Dielectrophoresis Theory
While force can be approximated using a spherical model,
torque must be dimensionally non-uniform, a spheriod for
example.
Where a, b, and c are semi-major axes of x, y, and z
respectively and E’ is the internal electric field.
The internal electric field x-component becomes
The we get the x-component to torque:
Similarly with Ty and Tz where a is the larger semi-major axis
making Tx<0 ; Ty >0 ; Tz>0
peff= 4π/3 abc (εm −εn) E’
E’x= Eo,x/ [1+ (εm − εn)Lx/εn] Lx =
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13. Dielectrophoresis
After acquiring the nanowires,
we created two-terminal
electrodes of Indium through
thermal evaporating.
To make the channel, we used
PMMA and a needle to draw a
thin fiber across the substrate
that would later be removed
with acetone after
evaporation.
Using a function generator, a
10V peak-peak AC current
was applied and tested from
10 Hz to 150 kHz.

14. Dielectrophoresis
Images from scanning electron microscope (SEM)

15. Dielectrophoresis
Dielectrophoresis at 10 V and 150 kHz for 1
second

16. Dielectrophoresis Analysis
Of the frequencies that were
tested, the best results were
with higher frequencies.
From applying 10 V for 1s
frequencies below 100 kHz
often didn’t result in a
connection, but above 100 kHz
there would result in at least 4
nanowire connections.
At the device’s maximum, 150
kHz was very efficient at
aligning nanowire after 1
second.
Higher frequencies are expected
to be even more efficient.

17. Gathering Data
Before testing, the InSb
electrodes were annealed again
to improve the nanowires’
contact to the electrodes.
We first tested the I-V trend at
room temperature using an
Agilent system to verify that there
were no shorts in the electrode
template.
Then the sample was mounted in
a vacuum chamber where it was
cooled with liquid nitrogen to 77
Kelvin. I-V data was recorded at
every 5 K interval up to 400 K.
Agilent B1500A for electron transport
measurements

18. I-V Samples
-1.0 -0.5 0.0 0.5 1.0
-2.0x10
-7
-1.0x10
-7
0.0
1.0x10
-7
2.0x10
-7
3.0x10
-7
I
V
80 K
% (3,@LG)
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
6.40332E-16
Pearson's r 0.99806
Adj. R-Square 0.99596
Value Standard Error
A80K_C Intercept -2.43469E-7 5.16532E-9
A80K_C Slope 5.30067E-7 6.75335E-9
-1.0 -0.5 0.0 0.5 1.0
-6.0x10
-7
-4.0x10
-7
-2.0x10
-7
0.0
2.0x10
-7
4.0x10
-7
6.0x10
-7
8.0x10
-7
1.0x10
-6
C
B
160 K
-1.0 -0.5 0.0 0.5 1.0
-6.0x10
-6
-4.0x10
-6
-2.0x10
-6
0.0
2.0x10
-6
4.0x10
-6
6.0x10
-6
I
V
240 K
% (3,@LG)
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
6.16616E-14
Pearson's r 0.99852
Adj. R-Square 0.99691
Value Standard Error
A240K_C Intercept -1.14343E-6 5.06876E-8
A240K_C Slope 5.95616E-6 6.6271E-8
-1.0 -0.5 0.0 0.5 1.0
-6.0x10
-5
-4.0x10
-5
-2.0x10
-5
0.0
2.0x10
-5
4.0x10
-5
I
V
320K
% (3,@LG)
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
8.21948E-12
Pearson's r 0.99715
Adj. R-Square 0.99407
Value Standard Error
?$OP:A=1 Intercept -7.48282E-6 5.85216E-7
?$OP:A=1 Slope 4.95552E-5 7.65136E-7

19. Temperature Dependent
Resistance
100 150 200 250 300
0.0
2.0x10
5
4.0x10
5
6.0x10
5
8.0x10
5
1.0x10
6
1.2x10
6
1.4x10
6
1.6x10
6
1.8x10
6
2.0x10
6
R()
T (K)
R Vs. T

20. Log of Conductivity vs
Temperature
0.002 0.004 0.006 0.008 0.010 0.012 0.014
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
ln()
1/T
Ea
= 0.067351 eV
Equation y = a + b*x
Weight No Weighting
Residual Sum
of Squares
1.24704
Pearson's r -0.97146
Adj. R-Square 0.94166
Value Standard Error
I Intercept 11.59207 0.18385
I Slope -781.57591 36.72458
ln(σ)

21. Analysis
To find the activation energy(Ea) which is characteristic of
the InSb structure, we first need to determine the I-V
characteristics at a large range of temperatures.
Using Ohm’s law R=V/I we can calculate R as a function
of temperature.
Knowing the dimensions of the nanowire, we can find its
conductivity σ=AR/L
Here, we use the radius of the nanowire (50 nm) and the
length (5 μm)

22. Activation Energy
From Eq. 1 σ=exp[Ea/kBT] (assuming σ0 is insignificant at
the nano scale) then we can get the equation:
By plotting log(σ) vs 1/T, we can get the slope (Ea/kB) and
multiplying this value by the Boltzmann constant, we get a
value for the activation energy or the energy band-gap.
The value that was calculated was .067 eV whereas the
accepted value for bulk InSb is 1.7 eV. We attribute this to
the differences in work function between the nanowire and
the InSb electrodes.

23. Drawbacks
DEP arrangement cannot be used for making a field effect
transistor (FET) because for DEP the electrodes must be
deposited prior to the nanowires whereas for an effective
3 terminal electrode with a back gate, the nanowires must
be deposited before the electrodes so that there is direct
contact between the nanowire and dielectric.
This limits our ability to test for other qualities using a FET
such as the Fermi energy, carrier mobility, and electron
count.
Photolithography more controlled method of creating
electrodes that is more commonly used.

24. Conclusion
Electrochemical deposition is a method that
must be very carefully executed because the
materials are very delicate and many
problems will arise if not preformed tediously.
Dielectrophoresis is an effective and easy
way to align nanowires given you have a
function generator that can provide at least
100 kHz at 10 V.