Electronic States of NbB₂(0001), TaB₂(0001) and ZrB₂(0001) Surfaces Studied by Angle-resolved Ultraviolet Photoelectron Spectroscopy

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We have investigated the surface electronic structures of transition-metal diboride (0001) surfaces by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) 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 E_F 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. [DOI: 10.1380/ejssnt.2006.100]