Thermal and plasma processing of graphene and h-BN
Speaker: Michael Neumann, Stanford University
Series: Topical Seminars
Location: Engineering Quadrangle J401
Date/Time: Wednesday, September 5, 2012, 4:00 p.m. - 5:00 p.m.
First, I will discuss hexagonal boron nitride (h-BN) films, which have attracted considerable interest as substrates for graphene. We studied the presence of organic contaminants introduced by standard lithography and substrate transfer processing on exfoliated h-BN films. Organic contaminants add a large broad luminescence peak to the Raman spectrum of the h-BN flake. This signal persists through typical furnace annealing recipes (argon/hydrogen). A recipe that successfully removes such contaminants and results in clean h-BN flakes involves treatment in argon/oxygen at 500 C.
In a second experiment, we studied layer-selective reactions of remote hydrogen plasma with graphene deposited on silicon oxide. We observed strong monolayer-selectivity for reactions with plasma species that lead to isotropic hole formation in the basal plane of monolayers and etching from the sheet edges. For few-layer graphene and HOPG, we observed qualitatively different effects of hydrogen plasma, with hexagonal etch pits that indicate that etching is highly anisotropic for multilayer graphene.