Electronic states of NbB2(0001), TaB2(0001) and ZrB2(0001) surfaces studied by angle-resolved ultraviolet photoelectron spectroscopy

Abstract

We have investigated the surface electronic structures of transition-metal diboride (0001) surfaces by angle-resolved ultraviolet photoelectron spectroscopy (AR.UPS) and ab-initio calculations based on the slab model with 13 layers. In the spectra of NbB2 and TaB2, the peaks near -1 eV blow EF are derived from the π band of their surface graphitic boron layer. As compared with graphene, the dispersion curves of the π bonds are greatly modulated by the hybridization of B-π orbits with the metal d orbits. On the other hand, the similar peaks were not observed in spectra of ZrB2, of which the surface is terminated with Zr atoms. © 2006 The Surface Science Society of Japan.