This document discusses challenges in testing nanoscale materials and devices. As materials are reduced to nanoscale sizes, their energy bands separate into discrete levels and their properties change. Sensitive electrical measurements are needed to understand these new materials and devices. Techniques discussed include using nano-manipulators to make direct electrical contacts, measuring density of states from impedance measurements, and using source-measure instruments capable of high sensitivity. Electrical considerations for nanoscale measurements include using appropriate measurement topologies and accounting for effects of small size like lower voltage withstand.

1. begin
A g r e at e r m e a s u r e o f c o n f i d e n c e
Introduction 2 | Nanotech Testing Challenges 2 | Electrical Measurement Considerations 5 | Electrical Noise 6 | Source-Measure Instruments 7
Pulsing Technologies 8 | Avoiding Self-Heating Problems 9 | Application Example: Graphene 10 | Summary 12 | Glossary 13 | Selector Guide 16 | For More Information 17

2. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Nanotech Testing Challenges Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
The nature of nanotech materials requires some As a substance is reduced to nanoscopic dimensions, Summary.......................................................... 12
novel testing techniques. Because these materials both the bandgap and the distance between
Introduction are built at the atomic or molecular level, quantum adjacent energy levels within the material’s electron
Glossary............................................................ 13
Selector Guide................................................ 16
Nanotechnology has the potential to improve mechanics come into play. As a result of small energy bands are altered. These changes, along For More Information.....................................17
our quality of life in diverse ways, such as faster particle sizes, the atoms and molecules of these with a particle’s nanoscopic size with respect to the
electronics, huge memory/storage capacities new materials may bond differently than they material’s mean free path (the average distance an
for PCs, cheaper energy through more efficient might otherwise in bulk substances. There may be electron travels between scattering events), directly Want to Explore Further?
energy conversion, and improved security new electronic structures, crystalline shapes, and affect the electrical resistance of a nanoparticle.
through the development of nanoscale bio- More generally, a material’s bandgap directly Featured Resources
material behavior. Nanoparticles with these new
and chemical-detection systems. influences whether a particle is a conductor, an • Standards Will Help
properties can be used individually or as building Ensure Order in Nano-
blocks for bulk material. Although the discovery of insulator, or a semiconductor. These influential Enabled Industries
bulk properties remains important, measurements electronic properties allow, for example, a carbon
also need to uncover the characteristics unique to nanotube (CNT) to be used to create a transistor
nanoscale structures. switch.2 One way to do this is by connecting a
semiconducting CNT between two electrodes that • Discover Today’s
With nanoelectronic materials, sensitive electrical Particle size and structure have a major influence function as a drain and source. A third electrode (the Solutions for
measurement tools are essential. They provide on the measurement techniques used to investigate gate) is placed directly under the entire length of the Tomorrow’s Nano
the data needed to understand the electrical a material. The material’s chemical and electrical carbon nanotube channel. For a semiconducting Characterization
properties of new materials fully and the electrical characteristics change as particle sizes are reduced CNT, the introduction of an electric field through the Challenges
performance of new nanoelectronic devices and to nanometer dimensions. This even applies to channel (via the insulated gate placed in proximity
components. Instrument sensitivity must be much biological materials. Therefore, most of these to the CNT channel) can be used to change the CNT
higher because electrical currents are much lower materials require chemical and electrical testing to from its semiconducting state to its insulating state
and many nanoscale materials exhibit significantly characterize them for practical product applications. by increasing the gate voltage. Decreasing the gate
improved properties, such as conductivity. The For many of them, the actual quantity being voltage will transition the device into a conducting Additional Resources
magnitude of measured currents may be in the measured is a low level current or voltage that was state. This conduction mechanism is analogous to • The Emerging Challenges of
femtoamp range and resistances as low as micro- translated from another physical quantity.1 Direct the operation of a silicon MOSFET transistor switch, Nanotechnology Testing
ohms. Therefore, measurement techniques and electrical measurements are possible on many which is created by doping silicon with either an • Climbing the Commercialization Hill
instruments must minimize noise and other sources substances with the probing instruments and nano- electron acceptor or donor to alter the material’s
of error that might interfere with the signal. manipulators now available. electronic conductivity in specific localities.
Ask Us Your Application Or Product Question.
2
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

3. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Nanotech Testing Challenges (continued) Electrical Measurement Considerations....5
Electrical Noise.................................................6
For macroscopic particles, electrons take on Because the density of states can be used to predict Source-Measure Instruments. ......................7
.
discrete quanta of energy that lie within energy the electrical behavior of materials, it is also possible Pulsing Technologies......................................8
bands, with each band consisting of many energy to use electrical impedance measurements to derive Avoiding Self-Heating Problems.................9 .
levels that electrons can share through their density of states information. The density of states Application Example: Graphene................ 10
thermal energies. For a conducting material, is found by plotting differential conductance vs. Summary.......................................................... 12
electrons can be thermally excited into the applied voltage. Differential conductance is simply Glossary............................................................ 13
conduction band (i.e., electrons are present in (di/dv). When this conductance is plotted against Selector Guide................................................ 16
the valence as well as in the conduction band). voltage, the graph indicates the material’s density For More Information.....................................17
For an insulator (bandgap > thermal energy of of states. Highly conductive materials possess an
the electron), enormous energy is required for abundance of free energy levels in the conduction
an electron to transition from the valence to Figure 1. As material is reduced from band, i.e., greater density of states (more individual
the conduction band separated by the material macroscopic dimensions to nanoscopic size, allowed energy levels per unit energy). Insulating
its continuous energy bands (a) separate into
bandgap. If a suitable amount of energy is absorbed discrete energy levels within the band (b) and materials have an electronic structure with a dearth
(> bandgap), then electrons can jump bands. the bandgap increases. of occupied energy levels in the conduction band.
Because density of states corresponds to the density
As a particle’s size is reduced to nanoscopic Characterizing the density of states is a fundamental of these energy levels, a plot of conduction vs.
dimensions, the allowable energies within the activity in nanoscopic material research. Density of voltage provides a direct measure of the electronic
continuous bands separate into discrete levels states (3D dimensionality) as a function of energy density of states at each energy level (voltage across
(because there are far fewer atoms in the mix). This can be expressed as: the device).
occurs when the separation between energy levels
approaches the thermal energy of the electrons One approach to this technique is to use a nano-
(Figure 1). With fewer energy levels within the This represents the number of electron states per manipulator that makes low resistance contacts
specific energy band, the density of states of the unit volume per unit energy at energy E, where: to the nanoparticle. Such an arrangement
material changes. allows charge transport and density of states
m = the effective mass of the particle,
measurements. This works well into the conduction
The density of states is a measure of the number h = Planck’s constant, and region thanks to the low resistance direct
of energy options available to an electron as it falls E = the energy (electron orbital location) in connections of the nano-probes on the material
into a lower energy level by giving up energy or as electron volts. (particle) being tested.
it ascends to a higher energy level after absorbing
energy. A corollary is that if the density of states is Although the result is independent of volume
known, the size of the particle can be deduced. (can be applied to any size particle), this equation
is of limited value if the particle size/structure is
unknown. However, other ways are available to
determine the density of states experimentally, from
which the particle size can be found.
Ask Us Your Application Or Product Question.
3
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

4. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Nanotech Testing Challenges (continued) Electrical Measurement Considerations....5
Photos courtesy of Zyvex Corporation Electrical Noise.................................................6
The nano-manipulator and its probes, along Source-Measure Instruments. ......................7
.
with a source-measure unit (SMU), are used to Pulsing Technologies......................................8
apply a current or voltage stimulus directly to the Avoiding Self-Heating Problems.................9 .
nanoparticle and measure its corresponding voltage Application Example: Graphene................ 10
or current response (Figure 2). The advantage Summary.......................................................... 12
of electrical source-measure testing is rooted in Glossary............................................................ 13
the fact that a specific SMU measurement mode Selector Guide................................................ 16
(source current/measure voltage or vice versa) can For More Information.....................................17
be chosen based on the relative impedance of the
material or device under test (DUT). Furthermore, Want to Explore Further?
the measurement mode can change dynamically Featured Resources
as the impedance changes, such as occurs in CNTs • Give Your Microscope a
acting as semiconductor switches. This allows a Hand: Characterization of
much wider dynamic range of voltage and current Nano Structures
stimuli and measurements, thereby optimizing Kleindiek Nanotechnik
parametric test precision and accuracy. SMU voltage Figure 2. Nano-manipulator probing of nanoscale structures: Microscopic view of low impedance probe
and current sensitivity can be as good as 1 microvolt contact to a CNT for direct electrical measurements. Photo of a nano-manipulator head assembly. • Electrical Character-
and 100 atto-amps. ization of Carbon
Nanotube Transistors
Electrical measurements on nanoscopic materials Particle self-assembly can be accomplished measurements through the volume as well as over (CNT FETs) with the
place stringent requirements on the instrumentation. from silicon to silicon, where conventional the surface, using appropriately placed macroscopic Model 4200-SCS
In order to measure conductivity, impedance, photolithographic techniques are used to make test pads formed on the material surface. For
or other electrical properties, and relate those electrical connection pads for probing. Particles thatconductive materials, separate pads for source and
measurements to the density of states, a galvanic are long enough to straddle such pads (for example, measure can be deposited to create a Kelvin (4-wire) Additional Resources
connection must be made to the nanoscopic DUT.3 carbon nanowires) can be connected to the pads connection.4 This type of circuit eliminates test lead • Nanoscale Device and Material Electrical
This represents one of the major hurdles to be through externally generated electrostatic fields. resistance from the measurement and improves Measurements
overcome in the field of nanotechnology testing. accuracy. In any case, a quantum well (nano-film) • Advanced Particle Beam Methods For
Although the properties of quantum wells, wires, Nano-characterization And Analysis
There are only a few tools available and few device can be tested like any other bulk material.
and dots differ, it’s possible that information about • Optimizing Low Current Measurements
constructs that facilitate connections of this type. with the Model 4200-SCS Semiconductor
a particular material in the form of a quantum dot Bioimpedance Bioelectricity Basics, Wiley 2003.
1
can be inferred by examining the same material Applied Physics Letters, Single and Multiwalled Carbon Nanotube Field Effect Characterization System
2
fashioned as a quantum wire or well (nano-film). Transistors, volume 17, number 73, October 26, 1998, IBM Research Division. • I-V Measurements of Nanoscale Wires
Nano-films are particularly easy to measure because I-V Measurements of Nanoscale Wires and Tubes with the Model 4200-SCS and Zyvex
3 and Tubes with the Model 4200-SCS and
S100 Nanomanipulator, Application Note #2481, Keithley Instruments, 2004. Zyvex S100 Nanomanipulator
only one dimension is small. Such a film might
• Tips for Electrical Characterization of
be deposited on a conductive substrate, allowing Four-Probe Note #2475,and Hall Voltage Measurements with the Model 4200-SCS,
Resistivity
4
Application Keithley Instruments, 2004. Carbon Nanotubes and Low Power
Nanoscale Devices
4
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

5. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Electrical Measurement Considerations Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
Electrical measurements on passive devices (any n Nanoscopic particles will not hold off as much The switching speed of a source-measure test Summary.......................................................... 12
device that is not a source of energy) are made by voltage from adjacent devices as a conventional circuit may be limited by the instrumentation used Glossary............................................................ 13
following a simple procedure: stimulate the sample electronic component or material (such as a to follow the state of the device. This is especially Selector Guide................................................ 16
in some way and measure its response to the transistor). This is because smaller devices true if a non-optimal measurement topology is For More Information.....................................17
stimulus. This method also works for devices that can be and are placed closer together. Smaller used to observe the device. The two possible
have both passive and active properties with linear devices also have less mass and may be affected topologies are source current/measure voltage or
or non-linear transfer functions. With appropriate by the forces associated with large fields. In source voltage/measure current. Want to Explore Further?
techniques, a source-measure algorithm can be addition, internal electric fields associated with
When considering the measurement of low imped- Featured Resources
useful for characterizing sources of energy. nanoscopic particles can be very high, requiring
ance (<1000 ohms) devices, the source current/ • Measurement Needs in
careful attention to applied voltages.
For nanoscopic particles, this general method measure voltage technique will generally yield Nano-Architectonics
takes the form of source-measure testing to n Given that nanoscopic devices are so small, the best results. Current sources are stable when
quantify impedance, conductance, and resistance, they typically have lower parasitic (stray) applied to lower impedances, and a good signal-to- Dr. Kang Wang
Director of the Center on Functional
which reveal critical material properties. This test inductance and capacitance. This is especially noise ratio can be achieved without great difficulty. Engineered Nano Architectonics
methodology is useful even if the end application is useful when they are used in an electronic This allows for accurate low voltage response University of California, Los Angeles
not an electronic circuit. circuit, enabling faster switching speeds and measurements.
• Improving Low
lower power consumption than comparable Current Measurements
Several considerations are important in the When measuring high impedance (>10,000 ohms)
macroscopic devices. However, this also means on Nanoelectronic and
characterization of nanoscopic particles: devices, the source voltage/measure current
that instrumentation for characterizing their I-V Molecular Electronic
n Nanoscopic
technique is best. Stable voltage sources to drive Devices
particles will not support the curves must measure low currents while tracking
high impedances are easily constructed. When
magnitude of currents that macroscopic device the short reaction time.
a well-designed voltage source is placed across a
can carry (unless they are superconducting).
Because nanoscopic test applications often high impedance, it will quickly charge the stray
This means that when a device is interrogated,
require low current sourcing and measurement, capacitance of the DUT and test cables and rapidly Additional Resources
the magnitude of a current stimulus must be
appropriate instrument selection and use is critical settle to its final output value. The small current • Electrical Measurements on
carefully controlled.
for accurate electrical characterization. In addition response of the DUT can be accurately measured Nanoscale Materials
to being highly sensitive, the instrumentation must with an appropriate ammeter. • Four-Probe Resistivity and Hall Voltage
have a short response time (sometimes referred to Measurements with the Model 4200-SCS
as high bandwidth), which is related to a DUT’s low • Guide to Measuring New Materials
capacitance and ability to change state rapidly at and Devices
low currents.
Ask Us Your Application Or Product Question.
5
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

6. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Electrical Noise Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
Summary.......................................................... 12
Glossary............................................................ 13
Selector Guide................................................ 16
For More Information.....................................17
Measurement topology also has an impact on
electrical noise, which is the ultimate limitation
on measurement sensitivity and accuracy. For low
impedance voltage measurements with a current Want to Explore Further?
source, the measurement circuits will be sensitive to Featured Resources
DUT voltage noise and impedance. For macroscopic • Electronic Properties of
devices, such as a resistor, the Johnson noise voltage Zinc-Blende Wurtzite
at room temperature (270K) is expressed as: Biphasic Gallium Nitride
Vn = √(4kTBR)
Nanowires and NanoFETs
(a) (b) Dr. Virginia Ayers
Head, The Electronic and Biological
Nanostructures Laboratory
where k = Boltzmann’s constant Figure 3. (a) Circuit model for the source voltage/measure current technique; (b) Modified Michigan State University
model illustrating the noise gain (op-amp noise “gained up”) when the DUT impedance is low
T = Absolute temperature of the source compared to the measurement impedance.
in degrees Kelvin • Making Ultra-Low Current
B = Noise bandwidth in Hertz The Johnson current noise of a resistor at 270K is: the correct measurement topology is chosen. Measurements with the
For example, consider a source voltage/measure Low-Noise Model 4200-SCS
R = Resistance of the source in ohms
current topology. An operational amplifier is used
which can be further simplified to: in many current measurement (ammeter) circuits,
as shown in Figure 3.
indicating that the noise goes down as DUT resis-
tance increases. To minimize noise gain, the ammeter circuit must
This equation shows that as DUT resistance (R) operate at a low gain with respect to its non-inverting Additional Resources
For all particle sizes, in addition to Johnson
decreases, the Johnson voltage noise generated by input terminal. • Low Level Measurements Handbook
noise, there could be a noise gain associated with
the DUT also decreases. Conversely, high impedance the measurement topology chosen. Noise gain
devices stimulated with a voltage source are limited is a parasitic amplification of the noise of the
by current measurement noise. measurement system that is not present when
Ask Us Your Application Or Product Question.
6
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

7. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Source-Measure Instruments Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
A commercial DC source-measure unit (SMU) is a When using the compliance function, an SMU will Summary.......................................................... 12
convenient test tool for many nanoscopic material satisfy the source value unless the user’s compliance Glossary............................................................ 13
and device measurements. SMUs change measure- value is exceeded. For example, when an SMU is Selector Guide................................................ 16
ment topology automatically (that is, they can rapidly configured to source voltage with a preset current For More Information.....................................17
switch between sourcing voltage/measuring current compliance, if that compliance value is exceeded, the
and sourcing current/measuring voltage). This SMU automatically starts acting as a constant current
makes it easier to minimize measurement noise source. Its output level then will be the compliance Want to Explore Further?
while maximizing measurement speed and accuracy. current value. Alternately, if the SMU is set to source
current with a compliance voltage, it will automati- Featured Resources
Some nanoparticles can change state with the • Test System is Key to
cally switch to sourcing voltage (the compliance
application of an external field. When investigating Practical Applications
voltage) if the DUT impedance and the current it
such materials, an SMU can be configured to source of Nanotechnology
draws begin to drive the voltage higher than the
voltage and measure current for a nanoparticle in its
compliance value.
high impedance state. When the material is in its low
impedance state, more accurate results are achieved Although a nanoscopic device, such as a CNT switch, • In-situ Correlation of
by sourcing current and measuring voltage. can change states rapidly, the change in instrument Mechanical Properties,
Furthermore, the SMU has a current compliance state is not instantaneous. Depending on the SMU Deformation Behavior,
function that can automatically limit the DC current model, the switching time can range from 100 and Electrical
Characteristics of
level to prevent damage to the material or device nanoseconds to 100 microseconds. Although such Materials Using
under test (DUT). Similarly, there is a voltage switching speeds are not fast enough to track a Conductive
compliance function when voltage is being sourced. nanoparticle as it changes state, the time is short Nanoindentation
enough to allow accurate measurements of both Ryan Major
states while limiting DUT power dissipation to R&D Project Manager
Hysitron, Inc.
acceptable levels.
Additional Resources
• Model 4200-SCS Semiconductor
Characterization System
• Series 2600A System SourceMeter®
Instruments
Ask Us Your Application Or Product Question.
7
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

8. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Pulsing Techniques Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
Choosing the correct measurement topology to Low power pulsing techniques may offer a partial Summary.......................................................... 12
improve measurement speed and minimize noise solution to this problem and are available in some Glossary............................................................ 13
may still be insufficient to the test needs for some SMU designs. The idea is to use a much higher test Selector Guide................................................ 16
nanoscopic materials. For example, it appears current or test voltage and apply this large stimulus For More Information.....................................17
that some CNTs can switch 1000 times faster than for a short sourcing cycle. The larger stimulus will
conventional CMOS transistor switches. This is lower the sourcing noise (by improving the signal-
too fast for the nano-amp ranges of commercial to-noise ratio) and improve the rise or settle time Want to Explore Further?
picoammeters. Demanding devices like these may for a voltage pulse or current pulse, respectively.
require other techniques to improve the speed of Quieter sources require less filtering and permit a Featured Resources
impedance measurements. shorter sourcing cycle time (narrower pulse width). • Low-Level Pulsed
A larger source stimulus also increases the response Electrical Characteri-
zation with the Model
current or voltage so that higher instrument ranges 6221/2182A Combination
can be used, further minimizing the effects of
noise. Because there is less noise, the measurement
acquisition time (integration period) can be
shortened, allowing for faster measurements.
• Ultra-Fast I-V Applications
for the Model 4225-PMU
Ultra-Fast I-V Module
Additional Resources
• Pulse Testing for Nanoscale Devices
• Keithley Pulse Solutions
DC offsets due to thermal voltages and meter Performing a 2-point delta measurement cancels An optional third measurement point can help
offsets can give significant errors in the mea- offset error. The measured delta voltage gives cancel moving offsets.
sured voltage. correct voltage response to the current pulse.
Ask Us Your Application Or Product Question.
8
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

9. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Avoiding Self-Heating Problems Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
A possible source of error in nano research is The following equation illustrates how duty cycle Summary.......................................................... 12
self-heating due to excessive electrical current and measurement time in pulse mode affect DUT Glossary............................................................ 13
through the DUT. Such currents may even lead power dissipation. To calculate power dissipation Selector Guide................................................ 16
to catastrophic failure of the sample. Therefore, in pulse mode, multiply the apparent power For More Information.....................................17
instrumentation must automatically limit source dissipation (V·I) by the test stimulus time and
current during device testing. Programmable divide by the test repetition rate:
P = P × Tt / Tr
current and voltage compliance circuits are Want to Explore Further?
standard features of most SMU-based test
systems with pulsed current capabilities and may p a Featured Resources
be required to avoid self-heating of some low
resistance structures. • How to Avoid
where: Pp = Pulse power dissipation Self-Heating Effects on
When an elevated test current is required, it must Pa = Apparent power (i.e., V·I) Nanoscale Devices
be short enough so that it does not introduce Tt = Test time
enough energy to heat the DUT to destructive T = Test repetition rate
r
temperatures. (Nanoscopic devices tolerate very
little heat, so the total energy dissipated in them Pulse mode is also useful for density of state Jonathan Tucker
must be maintained at low levels.) In addition, measurements using a low impedance connection, Senior Marketer, Nanotechnology
care must be taken that the magnitude of the test such as through a nano-manipulator. Pulsing allows Keithley Instruments, Inc.
current is low enough that the DUT’s nanoscopic measurements at I/V locations that were previously
channel does not become saturated. (For instance, uncharacterizable due to particle self-heating.
a current channel that’s 1.5 nanometers in diameter
severely limits the number of electrons that can
pass through it per unit of time.) Some nanoscopic
devices can support only a few hundred nano-amps
of current in their conductive state. Thus, a device’s
saturation current may define the maximum test
current, even in pulsed applications.
Ask Us Your Application Or Product Question.
9
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

10. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Graphene: The Semiconductor Industry’s
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Replacement for Silicon? Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Nanovoltmeter Vxx = Longitudinal
Application Example: Graphene................ 10
Graphene, the single-atom-thick crystal of carbon, Researchers characterizing graphene and V xx
Voltage
Summary.......................................................... 12
Vxx
has outstanding electrical conductivity. It also has graphene-based materials use Hall effect V = Transversal Voltage,
xy I
= R xx
Glossary............................................................ 13
extremely strong, yet flexible bonds. Its hardness is measurements and study longitudinal Hall Voltage with
applied B
Selector Guide................................................ 16
greater than the hardness of diamond. Until relatively resistance to assess carrier mobility and look For More Information.....................................17
recently, physicists did not believe that a solid crystal for evidence of the quantum Hall effect,
just a single atom thick could exist. Professors whereby longitudinal resistivity decreases to Vxy Graphene
Novoselov and Geim proved otherwise with the near 0Ω-cm. These measurements require Nanovoltmeter
discovery of graphene in 2004; for their achievement, very low current, precision sourcing, on
they won the 2010 Nobel Prize in Physics. the order of nano-amps. However, the
most important aspect of tight control over
For the semiconductor industry, the exciting
sourcing is ensuring that excessive power
thing about graphene is that electrons travel DC Current Source
does not develop across the graphene sample
through it unimpeded, and these electrons behave
in order to avoid destroying it. Furthermore, Configuration for simultaneous measurement of
according to quantum electrodynamic principles.
at nano-amp source current levels, the Hall effect voltage and longitudinal resistance of a
Carrier mobilities through graphene are on the
resulting voltages developed across the graphene sample in a Hall bar configuration.
order of 10,000cm 2/V-s at room temperature,
sample are extremely small, on the order
and mobility values as high as 200,000 cm2/V-s
of ten to hundreds of nanovolts. These type of nanovolt-level measurements require special
on suspended samples of graphene have been
instrumentation with sufficient resolution and
reported. Graphene’s high mobility has
extremely high sensitivity.
already led to the development of very
high frequency (100GHz and higher) RF In nanovolt-level measurements, thermoelectric
transistors. Unfortunately, graphene does voltages and noise sources can significantly impact
not have a natural bandgap, so many measurement accuracy, so it’s important to employ
researchers are investigating methods techniques designed to minimize these effects.
to create one so graphene’s high speed For example, using a current source that allows
properties and nano scale size could reversing the polarity of its signal can eliminate
replace silicon in next-generation FETs measurement errors due to thermal voltage
for digital circuitry, thereby extending the offsets. Furthermore, a current source that can
life of Moore’s Law. output low duty cycle, narrow pulses will minimize
measurement errors due to resistivity changes
resulting from self-heating of the graphene sample.
A graphene single electron transistor (SET). Ask Us Your Application Or Product Question.
10
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

11. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Source-Measure Instruments. ......................7
.
Graphene: The Semiconductor Industry’s Replacement for Silicon? (continued) Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
Thus, using a current source and nanovoltmeter For graphene or a graphene-based material to Summary.......................................................... 12
combination that can synchronize sourcing and replace silicon, it must have a bandgap so that a Glossary............................................................ 13
measurement simplifies the elimination of the ther- FET channel can be turned on and off. A precision Selector Guide................................................ 16
mal offsets and the of averaging out noise signals. SourceMeter® instrument is needed to modulate For More Information.....................................17
the substrate or “gate” voltage to characterize
the sample’s performance across a range of gate
voltages. Again, a low level current source and a
nanovoltmeter are required to provide low power,
Want to Explore Further?
low level measurements. σxy (4e2ih)
Featured Resources
ρ (kΩ) xx
• Take Advantage of
Keithley’s Expertise
V +7/2
with Measurements
+5/2 on Graphene
10
+3/2
Hall Voltage
4K
VXY 14T +1/2
Graphene
–1/2
SiO2 Longitudinal 5
–3/2 Additional Resources
Silicon Voltage • Delta Mode Online Demo
Vgate –5/2
VXX • Achieving Accurate and Reliable
Resistance Measurements in Low
–7/2 Power and Low Voltage Applications
Configuration of a measurement system for 0
-2 0 2 4
assessing the bandgap in graphene and n (1012 cm-2)
graphene-based structures.
Plot of Hall voltage and longitudinal voltage across a magnetic field of varying intensity.
Note how the Hall Voltage is constant at specific points of magnetic field intensity;
at those points, the longitudinal voltage drops to near 0, indicating extremely high
conductivity. This demonstrates that graphene exhibits the quantum Hall effect.
Plot courtesy of Neto, Novoselov, Geim, et, al. The Electronic Properties of Graphene. Jan. 2009
Ask Us Your Application Or Product Question.
11
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

12. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Summary Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
The electronic structure of nanoscopic particles is It can be found through direct electrical measure- Summary.......................................................... 12
a reflection of the atomic electron energies and the ments of differential conductance. Thus, the Glossary............................................................ 13
distribution of orbitals for both molecularly shared density of states can predict a material’s electrical Selector Guide................................................ 16
and free electrons. This kind of information can be impedance and vice versa. For More Information.....................................17
used to describe how such materials will interact
However, there is a right way and a wrong way
in the presence of energy and other materials. The
to interrogate a nanoscopic material electrically,
density of states in a material is directly related to Want to Explore Further?
depending on its impedance. For a low impedance
its electronic structure and is useful in predicting
material, the source current/measure voltage Featured Resources
or manipulating its properties.
method will result in the least electrical noise and
• Characterizing
allow the most accurate response measurement Nanoscale Devices
with the widest bandwidth. For a high impedance with Differential
material, the source voltage/measure current Conductance
method is more appropriate for similar reasons. At Measurements
times, the appropriate measurement mode must be
used in unison with yet another voltage or current
source to activate or stimulate the device.
Additional Resources
• Model 4200 Semiconductor
Characterization Test System Product Intro
• Model 4200-SCS Semiconductor
Characterization System
Ask Us Your Application Or Product Question.
12
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

13. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Glossary Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Absolute Accuracy. A measure of the closeness of Carbon Nanotube. A tube-shaped nanodevice formed Dielectric Absorption. The effect of residual charge Faraday Cup. A Faraday cup (sometimes called a Faraday
agreement of an instrument reading compared to that from a sheet of single-layer carbon atoms that has novel storage after a previously charged capacitor has been cage or icepail) is an enclosure made of sheet metal or
Application Example: Graphene................ 10
of a primary standard having absolute traceability electrical and tensile properties. These fibers may discharged momentarily. mesh. It consists of two electrodes, one inside the other, Summary.......................................................... 12
to a standard sanctioned by a recognized standards exhibit electrical conductivity as high as copper, thermal separated by an insulator. While the inner electrode is Glossary............................................................ 13
organization. Accuracy is often separated into gain and conductivity as high as diamond, strength 100 times Digital Multimeter (DMM). An electronic instrument connected to the electrometer, the outer electrode is
offset terms. See also Relative Accuracy. greater than steel at one-sixth of steel’s weight, and high that measures voltage, current, resistance, or other connected to ground. When a charged object is placed Selector Guide................................................ 16
strain to failure. They can be superconducting, insulating, electrical parameters by converting the analog signal to inside the inner electrode, all the charge will flow into For More Information.....................................17
A/D (Analog-to-Digital) Converter. A circuit used to semiconducting, or conducting (metallic). Non-carbon digital information and display. The typical five-function the measurement instrument. The electric field inside a
convert an analog input signal into digital information. All nanotubes, often called nanowires, are often created from DMM measures DC volts, DC amps, AC volts, AC amps, closed, empty conductor is zero, so the cup shields the
digital meters use an A/D converter to convert the input boron nitride or silicon. and resistance. object placed inside it from any atmospheric or stray
signal into digital information. electric fields. This allows measuring the charge on the
Channel (switching). One of several signal paths on a Drift. A gradual change of a reading with no change in input object accurately.
Analog Output. An output that is directly proportional to switching card. For scanner or multiplexer cards, the signal or operating conditions.
the input signal. channel is used as a switched input in measuring circuits, Feedback Picoammeter. A sensitive ammeter that uses an
or as a switched output in sourcing circuits. For switch Dry Circuit Testing. The process of measuring a device operational amplifier feedback configuration to convert
Assembler. A molecular manufacturing device that can cards, each channel’s signals paths are independent of while keeping the voltage across the device below a an input current into voltage for measurement.
be used to guide chemical reactions by positioning other channels. For matrix cards, a channel is established certain level (e.g., <20mV) in order to prevent disturbance
molecules. An assembler can be programmed to build by the actuation of a relay at a row and column crosspoint. of oxidation or other degradation of the device being Floating. The condition where a common-mode voltage exists
virtually any molecular structure or device from simpler measured. between an earth ground and the instrument or circuit of
chemical building blocks. Coaxial Cable. A cable formed from two or more coaxial interest. (Circuit low is not tied to earth potential.)
cylindrical conductors insulated from each other. The Electrochemical Effect. A phenomenon whereby currents
Auto-Ranging. The ability of an instrument to outermost conductor is often earth grounded. are generated by galvanic battery action caused by Four-Point Probe. The four-point collinear probe
automatically switch among ranges to determine the contamination and humidity. resistivity measurement technique involves bringing four
range offering the highest resolution. The ranges are Common-Mode Rejection Ratio (CMRR). The ability equally spaced probes in contact with the material of
usually in decade steps. of an instrument to reject interference from a common Electrometer. A highly refined DC multimeter. In unknown resistance. The array is placed in the center of
voltage at its input terminals with respect to ground. comparison with a digital multimeter, an electrometer the material. A known current is passed through the two
Auto-Ranging Time. For instruments with auto-ranging Usually expressed in decibels at a given frequency. is characterized by higher input resistance and greater outside probes and the voltage is sensed at the two inside
capability, the time interval between application of a current sensitivity. It can also have functions not generally probes. The resistivity is calculated as follows:
step input signal and its display, including the time for Common-Mode Current. The current that flows available on DMMs (e.g., measuring electric charge, π V
r = ____ × × t × k
__
determining and changing to the correct range. between the input low terminal and chassis ground of an sourcing voltage). ln2 I
instrument.
Bandwidth. The range of frequencies that can be EMF. Electromotive force or voltage. EMF is generally where: V = the measured voltage in volts, I = the source
conducted or amplified within certain limits. Bandwidth Common-Mode Voltage. A voltage between input low used in context of a voltage difference caused by current in amps, t = the wafer thickness in centimeters,
is usually specified by the –3dB (half-power) points. and earth ground of an instrument. electromagnetic, electrochemical, or thermal effects. and k = a correction factor based on the ratio of the
probe to wafer diameter and on the ratio of wafer
Bias Voltage. A voltage applied to a circuit or device to Contact Resistance. The resistance in ohms between the Electrostatic Coupling. A phenomenon whereby a current thickness to probe separation.
establish a reference level or operating point of the device contacts of a relay or connector when the contacts are is generated by a varying or moving voltage source near a
during testing. closed or in contact. conductor. Four-Terminal Resistance Measurement. A
measurement where two leads are used to supply a
Capacitance. In a capacitor or system of conductors and Contamination. Generally used to describe the unwanted Error. The deviation (difference or ratio) of a measurement current to the unknown, and two different leads are used
dielectrics, that property which permits the storage of material that adversely affects the physical, chemical, or from its true value. True values are by their nature to sense the voltage drop across the resistance. The four-
electrically separated charges when potential differences electrical properties of a semiconductor or insulator. indeterminate. See also Random Error and terminal configuration provides maximum benefits when
exist between the conductors. Capacitance is related to Systematic Error. measuring low resistances.
the charge and voltage as follows: C = Q/V, where C is the D/A (Digital-to-Analog) Converter. A circuit used to
capacitance in farads, Q is the charge in coulombs, and V convert digital information into an analog signal. D/A Fall Time. The time required for a signal to change from
is the voltage in volts. converters are used in many instruments to provide an a large percentage (usually 90%) to a small percentage
isolated analog output. (usually 10%) of its peak-to-peak value. See also Rise Time.
Ask Us Your Application Or Product Question.
13
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

14. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Source-Measure Instruments. ......................7
.
Glossary continued Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Fullerene. Refers to C60, an approximately spherical, Input Resistance. The resistive component of input Molecular Manipulator. A device combining a proximal- Offset Current. A current generated by a circuit
hollow, carbon molecule containing 60 carbon atoms impedance. probe mechanism for atomically precise positioning with even though no signals are applied. Offset currents
Application Example: Graphene................ 10
arranged in interlocking hexagons and pentagons, a molecule binding site on the tip; can serve as the basis are generated by triboelectric, piezoelectric, or Summary.......................................................... 12
reminiscent of the geodesic dome created by Insulation Resistance. The ohmic resistance of for building complex structures by positional synthesis. electrochemical effects present in the circuit. Glossary............................................................ 13
architect R. Buckminster Fuller. Sometimes called insulation. Insulation resistance degrades quickly as
“buckminsterfullerene” or “buckyball.” humidity increases. Molecular Manufacturing. Manufacturing using Overload Protection. A circuit that protects the Selector Guide................................................ 16
molecular machinery, giving molecule-by-molecule instrument from excessive current or voltage at the input For More Information.....................................17
Ground Loop. A situation resulting when two or more Johnson Noise. The noise in a resistor caused by the control of products and by-products via positional terminals.
instruments are connected to different points on the thermal motion of charge carriers. It has a white noise chemical synthesis.
ground bus and to earth or power line ground. Ground spectrum and is determined by the temperature, Picoammeter. An ammeter optimized for the precise
loops can develop undesired offset voltages or noise. bandwidth, and resistance value. Molecular Nanotechnology. Thorough, inexpensive measurement of small currents. Generally, a feedback
control of the structure of matter based on molecule- ammeter.
Guarding. A technique that reduces leakage errors Leakage Current. Error current that flows (leaks) through by-molecule control of products and by-products; the
and decreases response time. Guarding consists of a insulation resistance when a voltage is applied. Even high products and processes of molecular manufacturing, Piezoelectric Effect. A term used to describe currents
conductor driven by a low impedance source surrounding resistance paths between low current conductors and including molecular machinery. generated when mechanical stress is applied to certain
the lead of a high impedance signal. The guard voltage is nearby voltage sources can generate significant leakage types of insulators.
kept at or near the potential of the signal voltage. currents. MOSFET. A metal oxide field effect transistor. A unipolar
device characterized by extremely high input resistance. Precision. Refers to the freedom of uncertainty in the
Hall Effect. The measurement of the transverse voltage Long-Term Accuracy. The limit that errors will not exceed measurement. It is often applied in the context of
across a conductor when placed in a magnetic field. With during a 90-day or ­onger time period. It is expressed as a
l Nano-. A prefix meaning one billionth (1/1,000,000,000). repeatability or reproducibility and should not be used in
this measurement, it is possible to determine the type, percentage of reading (or sourced value) plus a number of place of accuracy. See also Uncertainty.
concentration, and mobility of carriers in silicon. counts over a specified temperature range. Nanoelectronics. Electronics on a nanometer scale.
Includes both molecular electronics and nanoscale Quantum Dot. A nanoscale object (usually a semiconductor
High Impedance Terminal. A terminal where the Maximum Allowable Input. The maximum DC plus devices that resemble current semiconductor devices. island) that can confine a single electron (or a few) and in
source resistance times the expected stray current (for peak AC value (voltage or current) that can be applied which the electrons occupy discrete energy states, just as
example, 1µA) exceeds the required voltage measurement between the high and low input measuring terminals Nanotechnology. Fabrication of devices with atomic or they would in an atom. Quantum dots have been called
sensitivity. without damaging the instrument. molecular scale precision. Devices with minimum feature “artificial atoms.”
sizes less than 100 nanometers (nm) are considered
Input Bias Current. The current that flows at the MEMS. Microelectromechanical systems. Describes systems products of nanotechnology. A nanometer [one-billionth Random Error. The mean of a large number of
instrument input due to internal instrument circuitry and that can respond to a stimulus or create physical forces of a meter (10 –9m)] is the unit of length generally most measurements influenced by random error matches the
bias voltage. (sensors and actuators) and that have dimensions on the appropriate for describing the size of single molecules. true value. See also Systematic Error.
micrometer scale. They are typically manufactured using
Input Impedance. The shunt resistance and capacitance the same lithographic techniques used to make silicon- Nanovoltmeter. A voltmeter optimized to provide Range. A continuous band of signal values that can be
(or inductance) as measured at the input terminals, not based ICs. nanovolt sensitivity (generally uses low thermoelectric measured or sourced. In bipolar instruments, range
including effects of input bias or offset currents. EMF connectors, offset compensation, etc.). includes positive and negative values.
Micro-ohmmeter. An ohmmeter that is optimized for low
Input Offset Current. The difference between the two resistance measurements. The typical micro-ohmmeter Noise. Any unwanted signal imposed on a desired signal. Reading. The displayed number that represents the
currents that must be supplied to the input measuring uses the four-terminal measurement method and has characteristic of the input signal.
terminals of a differential instrument to reduce the output special features for optimum low level measurement Normal-Mode Rejection Ratio (NMRR). The ability
indication to zero (with zero input voltage and offset accuracy. of an instrument to reject interference across its input Reading Rate. The rate at which the reading number is
voltage). Sometimes informally used to refer to input bias terminals. Usually expressed in decibels at a specific updated. The reading rate is the reciprocal of the time
current. Molecular Electronics. Any system with atomically frequency such as that of the AC power line. between readings.
precise electronic devices of nanometer dimensions,
Input Offset Voltage. The voltage that must be applied especially if made of discrete molecular parts, rather than Normal-Mode Voltage. A voltage applied between the Relative Accuracy. The accuracy of a measuring
directly between the input measuring terminals, with the continuous materials found in today’s semiconductor high and low input terminals of an instrument. instrument in reference to a secondary standard. See also
bias current supplied by a resistance path, to reduce the devices. Absolute Accuracy.
output indication to zero.
Ask Us Your Application Or Product Question.
14
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

15. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
Source-Measure Instruments. ......................7
.
Glossary continued Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Repeatability. The closeness of agreement between Shunt Capacitance Loading. The effect on a Source Resistance. The resistive component of source Transfer Accuracy. A comparison of two nearly equal
successive measurements carried out under the same measurement of the capacitance across the input impedance. See also Thevenin Equivalent Circuit. measurements over a limited temperature range and
Application Example: Graphene................ 10
conditions. terminals, such as from cables or fixtures. Shunt time period. It is expressed in ppm. See also Relative Summary.......................................................... 12
capacitance increases both rise time and settling time. Spintronics. Electronics that take advantage of the spin of ­Accuracy, Short-Term Accuracy. Glossary............................................................ 13
Reproducibility. The closeness of agreement between an electron in some way, rather than just its charge.
measurements of the same quantity carried out with a Short-Term Accuracy. The limit that errors will not exceed Triboelectric Effect. A phenomenon whereby currents Selector Guide................................................ 16
stated change in conditions. during a short, specified time period (such as 24 hours) Standard Cell. An electrochemical cell used as a voltage are generated by charges created by friction between a For More Information.....................................17
of continuous operation. Unless specified, no zeroing or reference in laboratories. conductor and an insulator.
Resolution. The smallest portion of the input (or output) adjustment of any kind are permitted. It is expressed as
signal that can be measured (or sourced) and displayed. percentage of reading (or sourced value) plus a number of Superconductor. A conductor that has zero resistance. Trigger. An external stimulus that initiates one or more
counts over a specified temperature range. Such materials usually become superconducting only at instrument functions. Trigger stimuli include: an input
Response Time. For a measuring instrument, the time very low temperatures. signal, the front panel, an external trigger pulse, and
between application of a step input signal and the Single Electron Transistor. A switching device that uses IEEE-488 bus X, talk, and GET triggers.
indication of its magnitude within a rated accuracy. For controlled electron tunneling to amplify current. An SET Switch Card. A type of card with independent and isolated
a sourcing instrument, the time between a programmed is made from two tunnel junctions that share a common relays for switching inputs and outputs on each channel. Two-Terminal Resistance Measurement. A
change and the availability of the value at its output electrode. A tunnel junction consists of two pieces of measurement where the source current and sense voltage
terminals. Also known as Settling Time. metal separated by a very thin (~1nm) insulator. The only Switching Mainframe. A switching instrument that are applied through the same set of test leads.
way for electrons in one of the metal electrodes to travel connects signals among sourcing and measuring
Rise Time. The time required for a signal to change to the other electrode is to tunnel through the insulator. instruments and devices under test. A mainframe is Uncertainty. An estimate of the possible error in a
from a small percentage (usually 10%) to a large Tunneling is a discrete process, so the electric charge that also referred to as a scanner, multiplexer, matrix, or measurement; in other words, the estimated possible
percentage (usually 90%) of its peak-to-peak amplitude. flows through the tunnel junction flows in multiples of e, programmable switch. deviation from its actual value.
See also Fall Time. the charge of a single electron.
Systematic Error. The mean of a large number of van der Pauw Measurement. A measurement technique
Sensitivity. The smallest quantity that can be Source Impedance. The combination of resistance and measurements influenced by systematic error deviates used to measure the resistivity of arbitrarily shaped
measured and displayed. capacitive or inductive reactance the source presents to from the true value. See also Random Error. samples.
the input terminals of a measuring instrument.
Settling Time. For a measuring instrument, the time Temperature Coefficient. A measure of the change in Voltage Burden. The voltage drop across the input
between application of a step input signal and the Source-Measure Unit (SMU). An electronic instrument reading (or sourced value) with a change in temperature. It terminals of an ammeter.
indication of its magnitude within a rated accuracy. For that sources and measures DC voltage and current. is expressed as a percentage of reading (or sourced value),
a sourcing instrument, the time between a programmed Generally, SMUs have two modes of operation: source plus a number of counts per degree change in temperature. Voltage Coefficient. The change in resistance value
change and the availability of the value at its output voltage and measure current, or source current and with applied voltage. Usually expressed in percent/V
terminals. Also known as Response Time. measure voltage. Also known as source-monitor unit or Temperature Coefficient of Resistance. The change or in ppm/V.
stimulus-measurement unit. of resistance of a material or device per degree of
Shielding. A metal enclosure around the circuit being temperature change, usually expressed in ppm/°C. Warm-up Time. The time required after power is applied
measured, or a metal sleeve surrounding the wire SourceMeter. A SourceMeter® instrument is very similar to an instrument to achieve rated accuracy at reference
conductors (coax or triax cable) to lessen interference, to the source-measure unit in many ways, including its Thermoelectric EMFs. Voltages resulting from temperature conditions.
interaction, or leakage. The shield is usually grounded or ability to source and measure both current and voltage differences within a measuring circuit or when conductors
connected to input LO. and to perform sweeps. In addition, a SourceMeter of dissimilar materials are joined together. Zero Offset. The reading that occurs when the input
instrument can display the measurements directly in terminals of a measuring instrument are shorted
Shunt Ammeter. A type of ammeter that measures current resistance, as well as voltage and current. It is designed for Thevenin Equivalent Circuit. A circuit used to simplify (voltmeter) or open-circuited (ammeter).
by converting the input current into a voltage by means general-purpose, high speed production test applications. analysis of complex, two-terminal linear networks. The
of shunt resistance. Shunt ammeters have higher voltage It can also be used as a source for moderate to low level Thevenin equivalent voltage is the open-circuit voltage
burden and lower sensitivity than do feedback ammeters. measurements and for research applications. and the Thevenin equivalent resistance equals the open-
circuit voltage divided by the short-circuit current.
Ask Us Your Application Or Product Question.
15
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

16. previous home next
Which Keithley nanotechnology solution is best for your
sourcing or measurement application?
Keithley instrumentation is being used in a growing list of Want seamless control over current pulse Studying highly resistive nanowires? Trying to characterize high Want low current measurements
without the high price tag?
sourcing and measurement? resistance nanomaterials?
nanotechnology research and production test settings. The The Model 6430 Sub-Femtoamp Remote
With <200μV burden voltage, the cost-effective
When linked together, the Model 6221 AC+DC Current Source SourceMeter® instrument's low noise and drift The Model 6517B Electrometer/High
applications shown here are only a sampling of the nanotech- and Model 2182A Nanovoltmeter are designed to operate like performance make it ideal. It measures Resistance Meter's built-in 1kV source, Model 6485 Picoammeter ensures accurate low
current measurements, even in circuits with very low
a single instrument to make high currents with 400aA (400×10-18A) sensitivity. 200TΩ input resistance, and low current
nology test and measurement tasks for which our instruments speed pulse mode measurements. sensitivity make it an ideal solution. source voltages. The Model 6487 Picoammeter/
Voltage Source adds a 500V bias source for high
and systems are suitable. If your tests require sourcing or resistance and resistivity measurements.
measuring low level signals, Keithley instrumentation can help
you perform them more accurately and cost-effectively.
Polymer Nanofibers/ Semiconductor Carbon Nanotubes Single Electron Carbon Nanotube Synthesized Molecular
Nanobatteries Nanophotonics Nanosensors & Arrays Thermal Transport
Nanowires Nanowires and Graphene Devices/Transistors Field Effect Transistors Electronics/Wires
High R/Low I, 1MΩ to 1014Ω Low Power, R <10MΩ, Pulse Low Power, R < 100kΩ Low I, Low V Low I, Pulse Low I, Low Power Low I, Pulse Low I, Low Power Low I, Low V Low I, Low Power, Pulse
Want multiple channels of sourcing Need to characterize mobility, Need tighter control over your pulses? Troubled by overheating problems? Testing lots of devices?
and measurement? carrier density, and device speed?
The Series 3400 Pulse/Pattern Generators can output The Model 4225-PMU option for the Model 4200-SCS performs Series 2600A System SourceMeter® instruments let you make
The fully integrated Model 4200 Semiconductor The Model 4210-CVU Option takes the voltage pulses with widths as short as 3ns with indepen- pulsed I-V testing on a variety of devices for many different purposes, precision DC, pulse, and low frequency AC source-measure tests
Characterization System brings together all three guesswork out of obtaining valid capacitance- dently adjustable rise and fall times as short as 2ns. including preventing device self-heating by using narrow pulses and/or quickly, easily, and economically. They offer virtually unlimited
core measurement types, DC-IV, AC impedence and voltage (C-V) measurements quickly and low duty cycle pulses rather than DC signals. flexibility to scale the system’s channel count up or down to match
transient I-V, in one easy-to-operate package. It's easily, with intuitive point-and-click setup, changing application needs.
used in many phases of nano research, development, complete cabling, and built-in element models.
characterization, and production. Looking for just a single channel?
Each Series 2400 SourceMeter instrument is a complete,
single-channel DC parametric tester. Choose from a variety of
ranges and functions to suit specific application needs. The Model
2430 can be programmed to produce individual pulses or pulse
trains up to 5ms wide.
Ask Us Your Application Or Product Question.
16
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

17. previous home next
Introduction. .....................................................2
.
Nanotech Testing Challenges.......................2
Electrical Measurement Considerations....5
Electrical Noise.................................................6
For More Information Source-Measure Instruments. ......................7
.
Pulsing Technologies......................................8
Avoiding Self-Heating Problems.................9 .
Application Example: Graphene................ 10
Nanotechnology Measurement Handbook: Other Sources of Information on Summary.......................................................... 12
A Guide to Electrical Measurements for Nano- Nanotechnology Glossary............................................................ 13
science Application is one of the resources TryNano.org is a resource for students, their Selector Guide................................................ 16
Keithley offers to help you learn how to test parents, their teachers and their school counselors. For More Information.....................................17
nanoscale materials and devices more effectively. It was created jointly by IEEE, IBM, and the New
It offers practical assistance in making precision York Hall of Science for the benefit of the public.
low level DC and pulse measurements on TryNano.org is an initiative led by the IEEE
nanomaterials and devices. This 130+-page Nanotechnology Council and the IEEE Educational
handbook is useful both as a reference and as Activities Board with funding from the IEEE New
an aid to understanding low level phenomena Initiatives Committee.
observed in the lab. It provides an overview of the
theoretical and practical considerations involved
in measuring low currents, high resistances,
low voltages, and low resistances. Click here
to request a downloadable copy of the
handbook (Adobe Reader required).
Some of the materials used in this e-handbook are reproduced from the first edition of Keithley’s
Nanotechnology Measurement Handbook, © Copyright 2007 Keithley Instruments, Inc.
Ask Us Your Application Or Product Question.
17
E n s u r i n g t h e Ac c u r ac y o f N an o sca l e E l ect r ica l M eas u r ements A g r e at e r m e a s u r e o f c o n f i d e n c e

18. previous home
Contact us by phone, fax, mail, or email:
Keithley Corporate Headquarters Consult with a Keithley applications engineer and learn how
Keithley Instruments, Inc. to get the most from your Keithley products.
28775 Aurora Road WORLDWIDE HEADQUARTERS EUROPE
Cleveland, Ohio 44139
Within the USA: 1-888-534-8453 Germany: (+49) 89 849 307 40
Phone: 440-248-0400 Outside the USA: + 1-440-248-0400 Great Britain: (+44) 118 929 7500
Toll-free: 800-552-1115
Email: applications@keithley.com
Fax: 440-248-6168
Additional contact information at www.keithley.com ASIA
info@keithley.com
China: (+86) 10 8447 5556
Japan: (+81) 3 5733 7555
Korea: (+82) 2 574 7778
Taiwan: (+886) 3 572 9077
Specifications are subject to change without notice.
All Keithley trademarks and trade names are the property of Keithley Instruments, Inc.
All other trademarks and trade names are the property of their respective companies.
A g r e at e r m e a s u r e o f c o n f i d e n c e
KEITHLEY INSTRUMENTS, INC. ■ 28775 AURORA RD. ■ CLEVELAND, OH 44139-1891 ■ 440-248-0400 ■ Fax: 440-248-6168 ■ 1-888-KEITHLEY ■ www.keithley.com
BELGIUM CHINA FRANCE GERMANY INDIA ITALY JAPAN
Sint-Pieters-Leeuw Beijing Saint-Aubin Germering Bangalore Peschiera Borromeo (Mi) Tokyo
Ph: 02-3630040 Ph: 86-10-8447-5556 Ph: 01-64532020 Ph: 089-84930740 Ph: 080-26771071, -72, -73 Ph: 02-5538421 Ph: 81-3-5733-7555
Fax: 02-3630064 Fax: 86-10-8225-5018 Fax: 01-60117726 Fax: 089-84930734 Fax: 080-26771076 Fax: 02-55384228 Fax: 81-3-5733-7556
info@keithley.nl china@keithley.com info@keithley.fr info@keithley.de support_india@keithley.com info@keithley.it info.jp@keithley.com
www.keithley.nl www.keithley.com.cn www.keithley.fr www.keithley.de www.keithley.com www.keithley.it www.keithley.jp
KOREA MALAYSIA NETHERLANDS SINGAPORE SWITZERLAND TAIWAN UNITED KINGDOM
Seoul Penang Gorinchem Singapore Zürich Hsinchu Theale
Ph: 82-2-574-7778 Ph: 60-4-643-9679 Ph: 0183-635333 Ph: 65-6747-9077 Ph: 044-8219444 Ph: 886-3-572-9077 Ph: 0118-9297500
Fax: 82-2-574-7838 Fax: 60-4-643-3794 Fax: 0183-630821 Fax: 65-6747-2991 Fax: 044-8203081 Fax: 886-3-572-9031 Fax: 0118-9297519
keithley@keithley.co.kr sea@keithley.com info@keithley.nl sea@keithley.com info@keithley.ch info_tw@keithley.com info@keithley.co.uk
www.keithley.co.kr www.keithley.com www.keithley.nl www.keithley.com www.keithley.ch www.keithley.com.tw www.keithley.co.uk
© Copyright 2011 Keithley Instruments, Inc. Printed in the U.S.A. No. 3114 02.15.11