Electronic structures of the suboxide films formed on TiC(1 0 0) and ZrC(1 0 0) surfaces: Density functional theory studies

Density functional theory (DFT) calculations have been performed to elucidate the electronic structures of the TiO-like film on TiC(1 0 0) and the ZrO-like film on ZrC(1 0 0), which are assumed to be monolayers of suboxide films with (1 × 1) periodicity with respect to the substrate (1 0 0) surfaces. It was revealed that the electronic structures of both films were characterized by the existence of a band around 6 eV and a band around the Fermi level. The former and latter bands were mostly composed of O 2p and metal d orbitals, respectively, indicating the substantial ionic nature of the film. The calculated DOS well reproduced the previously obtained photoelectron spectra. From the inspection of the optimized structures, it was found that the both suboxide films have rippled structures; the metal and oxygen atoms are displaced vertically downward and upward, respectively, maintaining the (1 × 1) structures.