STM INVESTIGATION OF SINGLE LAYER GRAPHITE STRUCTURES PRODUCED ON PT(111) BY HYDROCARBON DECOMPOSITION

STM has provided new insight into the nucleation, growth and nature of the graphite layer formed on Pt(111) by hydrocarbon decomposition. Annealing an ethylene covered surface to 800 K results in the formation of small (about 20-30 angstrom in diameter) graphite islands which are initially uniformly distributed over the surface. With further annealing above 1000 K, the graphite is observed to accumulate, forming a layer at the lower step edges and also forming large, regularly shaped islands on the terraces. It has been determined that hydrocarbon decomposition at elevated temperatures results in formation of a single layer of graphite on the Pt surface. It is interesting to note that in the STM images of this single layer of graphite only three of the six carbon atoms in the graphite lattice are visible. This result cannot be accounted for by the usual explanation given in terms of inequivalent carbons atoms for the bulk graphite surface. Superstructures with periodicities varying up to 22 angstrom are evident on the graphite areas and are due to a higher order commensurability of the graphite and Pt lattices at different relative rotations.