Soft X-ray emission spectroscopy study of the valence electron states of α-rhombohedral boron

Abstract

High energy-resolution boron K-emission spectra of single-crystalline α-rhombohedral-boron (α-r-B) were measured with a newly developed soft X-ray emission spectroscopy (SXES) instrument attached to a conventional transmission electron microscope. The intensity profiles of the spectra, which correspond to the density of states of the valence bands with p-symmetry, were compared with those of amorphous boron (am-B), single-crystalline β-rhombohedral-boron (β-r-B) and B4C. A characteristic shoulder structure appears in the spectrum of α-r-B but not of am-B, β-r-B or B4C. This structure should be due to the inter-cluster three-center bonding states among B12 clusters in α-r-B. © 2009 IOP Publishing Ltd.