Paul welander cryogenic rf characterization of sc materials at slac with cu...
Final Presentation
1. Studying Electronic Properties of
Low Dimensional Nanomaterials
Robert Schurz
Faculty Mentor: Irma Kuljanishvili, Ph.D.
Department of Physics
Saint Louis University
SURE 2015 1
2. Motivation
• Two dimensional nanomaterials such as tubes, wires,
and thin few-atomic layer films have generated
considerable interest among the scientific community
• They possess great advantages in light-weight, structural
control and flexibility, diversity of fabrication approaches
• Wide range of potential applications, such as in
nanoelectronics, optoelectronics, membranes, energy
storage and conversion, catalysis, sensing,
biotechnology, etc.
SURE 2015 2
3. Graphene
• Atomic-scale hexagonal lattice of
carbon atoms
• Two dimensional material (very
thin)
• Very good conductor
• 200 times stronger than steel by
weight
• Applications to electronics
(transistors, detectors)
• Has exceptional electrical,
mechanical, thermal and optical
properties
SURE 2015 3
http://onlinelibrary.wiley.com/doi/10.1002/adma.201401857/full
http://www.nanowerk.com/spotlight/spotid=34184.php
4. Molybdenum Disulfide
• Has a similar crystal hexagonal
structure to graphene with
individual layers stacked on top of
each other to form a bulk
• These layers are held together by
van der Waals forces
• Possible to obtain single to few-
layer crystal flakes using the
mechanical exfoliation method
• A monolayer of MoS2 is much
stronger than the bulk crystal
• MoS2 is a semiconducting material,
unlike Graphene which is semi-
metal, or otherwise called zero gap
semiconductor
SURE 2015 4
5. Research Outcomes
• Built a measurement system to give I-V plots of various
nanomaterials
• Designed a method of four-wire measurement
• Built BNC breakout box
• Tested uniquely lab-grown nanomaterials such as
graphene, carbon nanotubes (CNTs), and molybdenum
disulfide
• Learned how to program in LabVIEW and analyze with
OriginLab
• Learned how to use TTPX probe station
• Wrote SOP for the TTPX probe station and LabVIEW
setup
SURE 2015 5
6. Kelvin (Four-Wire) Measurement
• One of the most common techniques of characterizing
nanostructures
• Uses four wires to obtain I-V data that can then be
plotted to determine the resistance
• The Device Under Test (DUT) is supplied with current
(Source) and the voltage drop (Sense) is measured
across
SURE 2015 6
7. Resistivity of Semiconductor Samples
• Resistivity is related to the impurity
content of a sample
• Use four point probe with equal spacing
between probes
• A current is passed through the outer
probes and induces a voltage in the
inner voltage probes
• Calculate sheet resistivity:
• Multiply by thickness of sample to find
bulk resistivity:
• Wafer thickness must be less than half
the probe spacing (t<s/2)
SURE 2015 7
8. Equipment Setup
SURE 2015 8
• Configure Keithley Electrometer and Current Source
with Lakeshore TTPX Probe Station
• Use method of four-wire measurement
• Write LabVIEW program to sweep a current and
measure voltage
10. BNC Breakout Box
SURE 2015 10
• Convert triax to coax connection (guard and ground are
shorted)
• Split each signal into two (High and Low) BNC cables
HI
LO
IN
IN
HI
Current Source
LO
Electrometer
HI LO
18. CNT Sample on Silicon
-1.5µ -500.0n 500.0n 1.5µ-1.0µ 0.0 1.0µ
-0.004
-0.002
0.000
0.002
0.004
Left Two Pads
VOLT2
Current
Intercept = -7.93478E-5, Slope = 4282.36144
-1.5µ -500.0n 500.0n 1.5µ-1.0µ 0.0 1.0µ
-0.005
0.000
0.005
Center Pads
VOLT2
Current
Intercept = -1.07061E-4, Slope = 5032.55506
-1.5µ -500.0n 500.0n 1.5µ-1.0µ 0.0 1.0µ
-0.002
0.000
0.002
Right Two Pads
VOLT2
Current
Intercept = -9.50295E-5, Slope = 2245.37834
SURE 2015 18
19. Future Studies
• Measure other materials such as graphene ribbon and
molybdenum disulfide
• Determine I-V behavior at different temperatures ranging
from 3 K to 600 K
• Configure triax configuration with cable guarding for test
setup
• Design program to trigger continuous sweep back and
forth to help characterize material via hysteresis
• Purchase/program equipment to perform a voltage
sweep
• Determine the effect of optical excitation on our samples
so their optical sensitivity can be determined
SURE 2015 19
20. Acknowledgements
This study was made possible by the generous funding of
the Summer Undergraduate Research Experience (SURE).
The author would especially like to thank Dr. Kuljanishvili
and her research team including Dr. Roy Dong, Riley
Wang, and Jiaqi Li for their contribution towards this
research project.
SURE 2015 20
21. References
• Ganatra, R & Zhang, Q (2014). Few-Layer MoS2: A Promising Layered
Semiconductor. ACS Nano 8 (5), 4074-4099.
• Feng, J.; Qian, X.; Huang, C.-W.; Li, J (2012). Strain-Engineered Artificial
Atom as a Broad-Spectrum Solar Energy Funnel. Nat. Photonics 6, 866–
872.
• Novoselov, K. S.; Jiang, D.; Schedin, F.; Booth, T. J.; Khotkevich, V. V.;
Morozov, S. V.; Geim, A. K (2005). Two-Dimensional Atomic Crystals. Proc.
Natl. Acad. Sci. U.S.A. 102, 10451–10453
• Hsu, W., Chang, B., Zhu, Y., Han, W., Terrones, H., Terrones, M.,… Grobert,
N. (2000). Journal of the American Chemical Society 122 (41), 10155-
10158.
• User’s Manual: TTPX Probe Station (2012). Lake Shore Cryotronics.
http://www.lakeshore.com/products/Cryogenic-Probe-Stations/Model-TTPX-
Cryogenic-Probe-Station/pages/Downloads.aspx
• Zhuang, X., Mai, Y., Wu, D., Zhang, F., & Feng, X. Two-Dimensional Soft
Nanomaterials: A Fascinating World of Materials. Advanced Materials 27
(3), 403-427.
SURE 2015 21
22. Studying Electronic Properties of
Low Dimensional Nanomaterials
Robert Schurz
Faculty Mentor: Irma Kuljanishvili, Ph.D.
Department of Physics
Saint Louis University
SURE 2015 22
24. Chemical Vapor Deposition (CVD) Method
• Synthesis of MoS2: SiO2 as a substrate, MoO3 and S powders used
as reactants
• The reactants are delivered on the substrate and the whole is
heated to 650 Celsius degrees in the presence of N2
• The size of the sample is larger than obtained with the exfoliation
technique
Low dimensional nanomaterials exhibit enhanced properties of bulk (3D) semiconductor material
Fabricate their properties such as band structure, magnetism, conductivity, and superconductivity
Sample at 294.784 Kelvin, Lakeshore Resistance for 290K: 79.8687Ohms, Lakeshore Resistance for 300K: 77.8662 Ohms
Shows that our equipment is working properly.
