Nanoscale materials and devices, such as graphene and carbon nanotubes (CNTs), hold enormous promise for the development of new electronic devices. Graphene is particularly attractive because it is a high quality, flawless crystalline lattice of carbon, without atomic defects; it’s transparent; it has high affinity for other elements; and it forms strong yet highly flexible bonds and can handle substantial deformation.
Graphene also exhibits very high electrical conductivity and thermal conductivity. Electrons travel through it unimpeded and behave according to quantum electro-dynamic principles, with carrier mobility of ~10,000cm2/V*s at room temperature and mobility values as high as 200,000cm2/V*s on suspended samples.
As a result of these characteristics, researchers are exploring myriad applications for graphene, including high frequency transistors and single electron transistors (SETs) for use in ICs, high efficiency solar cells, flexible displays, touchscreens, printable electronics, and a wide range of chemical sensors. Researchers at IBM have already reported creating graphene-based RF transistors with high bandwidths.
Graphene and other nano materials undoubtedly offer enormous potential for innovation for the designers and manufacturers of electronic devices, but they also represent an enormous testing challenge. For example, for characterizing delicate samples, the instrumentation used must be able to source sub-microamp currents with high precision in order to limit total power dissipated in the sample. The current source must also provide a constant output so the exact value forced to the material is known with a high level of accuracy. It should also have an adjustable voltage compliance to prevent overvoltages and device damage. Ideally, it would have a bipolar output to eliminate voltage offsets and reduce noise.
When characterizing low resistance samples, these low-level sourced currents will generate low voltages, demanding the use of a nanovoltmeter with low internal noise and excellent ability to reject external AC noise.
About the author: Robert Green is a senior market development manager at Keithley Instruments, Cleveland, Ohio, which is part of the Tektronix test and measurement portfolio. During his career at Keithley, Green has been involved in the definition and introduction of a wide range of instrumentation. He holds a BS in electrical engineering from Cornell University and an MS in electrical engineering from Washington University in St. Louis, Missouri.
If you found this article to be of interest, visit the Test & Measurement Designline where you will find links to relevant technical articles, blogs, new products and news.
You can also get a weekly newsletter highlighting the latest developments in this sector - just Click Here to request this newsletter using the Manage Newsletters tab - if you aren't already a member you'll be asked to register.
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.