Transcript Research poster 36 x 48

Matlab-based Nanoscale Device Characterization
Paul R. Haugen and Hassan Raza
Nanoscale Devices and Systems Lab, University of Iowa
www.engineering.uiowa.edu/~hraza
Device characterization is an
extremely important aspect of any
laboratory at any scale. As electronic
devices are fabricated, whether it be
using new materials, designs, or
processes, accurate characterization
of these devices is essential. In the
interest of consistency, automation of
the characterization process is
essential. These devices are essential
in areas of nanoelectronics,
spintronics and energy harvesting
technologies.
In this context, the interfacings of
laboratory characterization
instruments with computers can be a
difficult and resource intensive task.
In this project, we present a package
of automated software solutions to
this problem for select laboratory
instruments. It is intended to
implement the capability to interface
these instruments with a computer
using Matlab and allow for automated
characterization of both two and three
terminal electronic devices. The data
these applications generate can also
be used to create plots that can be
saved for later analysis.
This software provides an effective
and cost-efficient alternative to
automating nanodevice
characterization in an academic or
industrial research laboratory.
CONTACT
Hassan Raza, Assistant Professor
Nanoscale Devices and Systems Lab
University of Iowa
[email protected]
http://www.engineering.uiowa.edu/~hraza/
Poster Design & Printing by Genigraphics® - 800.790.4001
INTRODUCTION
Consider a Carbon Nanotube transistor, Graphene
transistor or a metal-oxide-silicon devices as shown
below.
Carbon Nanotube Transistor
Metal
Graphene Transistor
Oxide
Usage
When the user starts the program, a number of
choices are presented in a graphical user interface,
each representing the capabilities of the software.
Two terminal IV and CV and three terminal, three
instrument output and transfer characteristics can be
chosen. After selecting the application that is
required, a graphical interface is displayed allowing
the user to input the parameters necessary for their
test. These can be the GPIB address of the
instruments in use, starting or ending values of a
voltage sweep, the increment or "step size" of the
sweep, or any delay that the user would like to
introduce for stabilization or other purposes. The
application loops through the array of voltage points
defined by the starting, ending, and step voltage
values. The measured values are stored in an array
and plotted against the array of voltage points
created by the user. Should the user choose, these
arrays along with a jpg image of the plot can be
stored in a file.
RESULTS
With this combination of characterization and interfacing
equipment, basic as well as advanced device
characterization can be performed. For example, we
show the three-terminal transfer characteristics of a
Carbon Nanotube transistor, where the current through the
carbon nanotube is modulated as a function of the back
gate voltage as well as top gate voltage. The device
performance shows that the top gate has a much better
control on the ON/OFF characteristics of the device
compared to the back gate voltage. Such insight in the
device performance is not possible without the
automated characterization software described here.
1.E-05
CNT Transistor Characterization
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Drain Current (A)
ABSTRACT
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S=120mV/dec
1.E-08
1.E-09
S=350mV/dec
1.E-10
1.E-11
Back Gate Measurement
Front Gate - Forward
1.E-12
Front Gate - Back
1.E-13
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Silicon
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0
1
2
3
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Front / Back Gate Voltage (V)
To enable electrical characterization of these
nanodevices, one needs a fully automated setup.
In this manner, two- or three-terminal IV characterization
can be done with the Keithley 236 SMUs. Capacitance vs
Voltage can also be measured using the Keithley 590. For
the AC characterization, one may use lock-in amplifier
technique (SRS SR830) and spectrum analyzer (SRS
SR780).
METHODS AND MATERIALS
In this project, we use Matlab software to implement
the device characterization automation. Matlab’s
ability to easily manipulate the data produced and
overall flexibility made it our choice. The interfacing
technology used with this software is GPIB, which
stands for General Purpose Interface Bus. GPIB is
an interfacing technology developed by HewlittPackard in the 1960's. It has a fairly high transfer
rate (8mb/s), and a reliable and simple transfer
protocol. We use Prologix USB-GPIB adapter to
make the system usable by even a Laptop for overall
mobility. The instruments that were used in this
automation were three Keithley 236 IV meters, and
one Keithley 590 CV meter. A DS360 Function
Generator and SR830 Lock-in Amplifier from
Stanford Research Systems were also used for
conductance testing.
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CONCLUSIONS
Graphical User
Interface
In conclusion, this software provides that capability to
perform reliable and accurate device characterization in
laboratories with this equipment available. Compared to
other options in automated device characterization, it is
also the most affordable. The software required to run
this application is about 10% of the cost of other typical
automation software, and the costs of the interfacing
hardware are under $500. There are many avenues for
improvement in this software, and constant revisions and
upgrades are being made, but even in its present form,
this software presents the most practical way to automate
device characterization in a laboratory environment.