We have used UHV STM to study the quantum size effect gap and the effects of edge electronic structure on graphene quantum dots (GQDs) and nanoribbons [1]. GQDs on H-Si(100) exhibit the expected size-dependent gap with the exception of those with predominantly zigzag edges, which are metallic. STM spectroscopy elucidates the predicted zigzag metallic edge state, which has a characteristic decay length of 1nm. Monolayer graphene deposited in UHV on cleaved GaAs(110) and InAs(110) substrates exhibits an electronic semitransparency effect in which the substrate electronic structure can be observed ‘through’ the graphene. This effect is observed when the equilibrium graphene-substrate spacing is reduced by about 0.06nm. We have also studied the grain boundaries in graphene monolayers that have been grown on copper and then transferred to silicon dioxide or mica substrates. STM images show graphene misorientation angles of approximately 7°, 23°, and 30° at the grain boundaries. Standing wave patterns with a decay length on the order of 1 nm were observed adjacent to the grain boundaries and depend on the structure of the boundary. Spectroscopy across the boundaries showed enhanced conduction in empty states on the grain boundaries.
Biographical Sketch Joseph W. Lyding Joe Lyding is a Professor in the Department of Electrical and Computer Engineering at the University of Illinois in Urbana-Champaign. Joseph W. Lyding received his B.S. (1976), M.S. (1978) and Ph.D. (1983) degrees in Electrical Engineering from Northwestern University. In 1984 he joined the University of Illinois in Urbana-Champaign as an Assistant Professor in the Department of Electrical and Computer Engineering to work with John Bardeen and colleagues on the 1D charge-density wave problem. In 1986 Professor Lyding developed the first STM at Illinois and was promoted to Associate Professor in 1988 and Professor in 1993. Professor Lyding’s research interests include carbon nanotechnology, nanofabrication on semiconductor surfaces, hot-carrier degradation in CMOS devices and development of scanned probe technology. He has over 150 publications and has presented about 100 invited talks. His invention, with Karl Hess, of deuterium processing to reduce hot-carrier degradation effects in CMOS technology has led to a patent portfolio that has now been licensed to major chip producers. He is a Fellow of the American Physical Society, a Fellow of the American Vacuum Society, a Fellow of the Institute of Electrical and Electronic Engineers, was selected as a Finalist for the Feynman Prize in Nanotechnology and has been selected as a UIUC University Scholar.