Time: 2:00pm - 3:00pm
Location: Dodge 450
Speaker: Prof. Teng Li, University of Maryland
Graphene, a monolayer of graphite, has rapidly emerged as a rising star of materials science and condensed-matter physics, largely due to its exceptional properties. These extraordinary properties of graphene have sparked a surge of scientific and technological interest in graphene-based electronics, driven by the desire to overcome the fast-approaching fundamental limits of silicon in 15~20 years. The promising future of graphene-based applications aside, there are still significant challenges to their realization, largely due to the difficulty of precisely controlling the graphene properties. Graphene is intrinsically non-flat and corrugates randomly. These random corrugations lead to unpredictable graphene properties, which are fatal for nanoelectronic devices.
Recent experiments suggest that, when graphene is subject to external regulation (e.g., a substrate surface), its corrugations are rather extrinsic, prevailing its intrinsic random corrugations. In this talk, we first lay out a general research framework that captures the energetics of the interplay between graphene and the external regulation, from which the equilibrium graphene morphology can be quantitatively determined. We then apply such a framework to investigate the graphene morphology regulated by engineered substrate surfaces with various patterns, such as 1-D grooves, 2-D herringbone and checkerboard. We next extend to study the graphene morphology regulated by nanowires patterned on a substrate surface. Interestingly emerging from the results is a morphological instability of graphene under certain conditions, in which graphene morphology snaps between two distinct states. Since the graphene morphology is closely tied to its electronic properties, such a morphological instability can be potentially used to enable functional components in graphene-based devices, such as nano-switches. Our research framework and case studies shed light on abundant but largely unexplored pathways to fine tune graphene properties through surface/interface morphologic regulation.