Electronic Structure of Clean and H-adsorbed HfC(111) Surface.

Abstract

The electronic structure of a clean and H-adsorbed HfC(111) surface have been studied by angle-resolved photoemission spectroscopy and Discrete-Variational Xα molecular orbital calculation. A sharp peak in normal-emission spectra of the clean surface is observed at just below the Fermi level, and the peak is ascribed to the emission from a surface state composed of 5d orbitals of surface Hf atoms. Hydrogen adsorbs dissociatively on the HfC(111) surface forming a (1×1) overlayer at the saturation coverage. H-induced bands are observed at 6-7 eV and around the Fermi level. The calculation for the Hf13C13H3 cluster shows that these bands should be ascribed to a H 1s-Hf 5d bonding state and an extrinsic surface state composed of Hf 5d orbitals formed through the modification of the surface potential by H-adsorption, respectively.