"Varactors, Tweezers and Spin – finding new applications for graphene in unexpected places"

Steven J. Koester, Professor, ECE, University of Minnesota

May 16th (Wednesday), 3:00pm
Elings Hall, Rm 1605

Graphene, a single sheet of sp2-bonded carbon has numerous remarkable properties including extremely high mobility, tremendous mechanical strength and a linear-dispersion, zero-gap band structure. Despite its unsuitability for conventional field-effect transistors, graphene is being commercialized for a range of other applications including displays, optoelectronics and sensors. Now, after a decade of intense research and tens of thousands of papers published on graphene, it would seem that the field might be reaching saturation, with no new potential applications on the horizon.

In this talk, I will show that just the opposite is happening, and that many new uses of graphene are still emerging, and these are made all the more surprising because they arise from graphene’s already well-known properties. In the first application, we have utilized the quantum capacitance in graphene create variable capacitors (varactors) that can be utilized as wireless sensing elements as well as tuning elements in transparent electronics. These varactors can have capacitance tuning ratios as high as 1.8-to-1, and can be used to realize wireless chemical sensors and flexible tuning elements. Secondly, it has long been known that graphene has extremely long spin lifetime, owing to its low spin-orbit interaction. However, functional devices that utilize these spintronic properties have proved elusive. Recently, we have shown that the spintronic properties of graphene can be used to realize ultra-low-energy neural networks and also have tremendous potential to create magnetic sensors with unprecedented spatial accuracy and signal-to-noise ratio. Finally, we have recently shown that the atomically-thin edges graphene can form ultra-sharp “tweezers” for trapping nanoparticles and biomolecules such as DNA that can operate at extremely low voltages (< 1 V), making them suitable for integration with on-chip electronic readout circuits.

About Steven J. Koester:

photo of steven koesterDr. Koester received his Ph.D. in 1995 from the University of California, Santa Barbara. From 1997 to 2010 he was a research staff member at the IBM T. J. Watson Research Center and performed research on a wide variety of electronic and optoelectronic devices, with an emphasis on those utilizing the Si/SiGe material system. From 2006-2010 he served as manager of Exploratory Technology at IBM Research where his team investigated advanced devices and integration concepts for use in future generations of microprocessor technology. Since 2010, he has been a Professor of Electrical & Computer Engineering at the University of Minnesota where his research focuses on novel electronic, photonic and spintronic device concepts. Dr. Koester has authored or co-authored over 200 technical publications and conference presentations, 7 volumes, 4 book chapters, and holds 67 United States patents. He is an associate editor for IEEE Electron Device Letters, and a Fellow of the IEEE.

Hosted by: Professor Kaustav Banerjee