Oxidation of Graphene on Metals

Abstract

We use low-energy electron microscopy to investigate how graphene is removed from Ru (0001) and Ir(111) by reaction with oxygen. We find two mechanisms on Ru(0001). At short times, oxygen reacts with carbon monomers on the surrounding Ru surface, decreasing their concentration below the equilibrium value. This undersaturation causes a flux of carbon from graphene to the monomer gas. In this initial mechanism, graphene is etched at a rate that is given precisely by the same non-linear dependence on carbon monomer concentration that governs growth. Thus, during both growth and etching, carbon attaches and detaches to graphene as clusters of several carbon atoms. At later times, etching accelerates. We present evidence that this process involves intercalated oxygen, which destabilizes graphene. On Ir, this mechanism creates observable holes. It also occurs mostly quickly near wrinkles in the graphene islands, depends on the orientation of the graphene with respect to the Ir substrate, and, in contrast to the first mechanism, can increase the density of carbon monomers. We also observe that both layers of bilayer graphene islands on Ir etch together, not sequentially.

Enhanced reactivity of graphene wrinkles and their function as nanosized gas inlets for reactions under graphene

“…The formed 1D etched trenches were exactly located at the bold wrinkles. Our finding is similar to the preferential oxidation of wrinkles at graphene/Ir(111) surface reported by Starodub et al 27 Besides the 1D trenches, many etched holes were also observed inside the graphene islands. We suggest that these holes may be attributed to oxygen etching of the wrinkles with nanometer scale, which can not be clearly imaged by LEEM.…”

“…26 Upon oxidation of graphene on metals, wrinkles showed different reactivity to the surface reaction compared to the flat graphene structure. 27 In the present work, an attempt was made to perform chemical reactions at graphene/Pt(111) surfaces, and the surface processes were dynamically imaged by low energy electron microscopy (LEEM). Both graphene oxidation and CO oxidation were found to occur underneath the graphene overlayers.…”

Transforming moiré blisters into geometric graphene nano-bubbles

“…4a-c). The average size of the anti-dots shows a linear dependence with reaction time indicating that the etching process is controlled by oxidation kinetics 19,28 . STM imaging of the anti-dot, as shown in Fig.…”

“…At high temperatures and oxygen pressure, macroscopic regions of graphene can be delaminated from oxidized Ru(0001) 18,19 . O 2 molecules can diffuse through step edges and surface defects 20 and permeate between graphene and ruthenium through the hump regions of the Moiré structures.…”

Radiation-mode optical microscopy on the growth of graphene

“…These R s values were comparable to the detachment rate of C adatoms from the graphene on Ru (0.15 mm min À 1 ) at 1,070 K (ref. 44).…”