Electronic structure of monolayer graphite on some transition metal carbide surfaces

Abstract

It has been revealed that monolayer graphite on the (111) surfaces of transition-metal carbides differs substantially from bulk graphite in the lattice constant and the phonon dispersion, while those of monolayer graphite on the (100) surfaces are hardly modified. In this work, the electronic structure of monolayer graphite formed on TiC(111), (100), and TaC(100) surfaces has been investigated by XPS, UPS, and EELS. From the results of XPS and UPS, we have concluded that these large changes are caused not by charge transfer but mainly by orbital hybridization between the graphite overlayer and the (111) surface. This is in contrast to the case of graphite intercalation compounds. By angle-resolved EELS, in addition, we have clearly detected a two-dimensional character of the plasmons in monolayer graphite.