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New dG
Measurement
Methods Reveal
Nanodevice
Characteristics
Faster, at Lower Cost
Jennifer Makupson
Keithley Instruments, Inc.
Ohm's Law May Not Be Relevant importantmeasurementsmadeonnanoscale Since differential conductance (dI/dV)
The demand for smaller, lower power devices,butitpresentsauniquesetofchal- is directly proportional to the density of
electronic devices is fueling nanotechnol- lenges.Fortunately,newmeasurementtech- states, it is the most direct measurement of
ogy development. Researchers are striving niques are making this type of study much this phenomenon. Such measurements can
to understand the quantum level structure easier. identifyconditionsunderwhichconductance
andbehaviorofnanoscaledevicesandhow reaches a maximum, i.e., the electron ener-
theseaffectelectricalproperties.Thismakes Applications for Differential gies(eV)wherenanoscalematerialelectrons
itpossible,forexample,toobserveorpredict Conductance Measurements arethemostactive.Thisallowsresearchers
when tunneling occurs, calculate a device's Differential conductance measurements tocharacterizethenumberofenergyoptions
densityofstates,understandconductionphe- areperformedinmanyapplicationsbutmay availabletoanelectronasitfallsintoalower
nomenon in cryogenic environments, and haveanumberofaliases.Theseinclude: energylevelbygivingupenergyorasitas-
create artificial atoms in which energy quan-