Local structure analysis of heavily boron-doped diamond by soft x-ray spectroscopy

To clarify the electronic structure of metallic heavily boron (B)-doped diamonds, the discrete variational (DV)-Xα method was used to analyze the continuous X-ray absorption near edge structure (XANES) in the BK and CK regions of a 71,000-ppm B-doped diamond. The continuous XANES profiles are well reproduced by the unoccupied B2p- and C2p-DOS of the caged B-cluster models, in which an octahedron B6 cluster, a cuboctahedron B12 cluster, or an icosahedron B12 cluster is inserted into the defect space of the diamond lattice. The delocalized conduction band structure can be understood from the hybridization of the B atoms in B-clusters with the surrounding C atoms in the diamond lattice. The results indicate that the B atoms in heavily B-doped diamonds form caged B-clusters in the defect space of the diamond lattice.