Soft X-ray core-level photoemission study of boron sites in heavily boron-doped diamond films

We have performed high-resolution soft x-ray B 1s core-level photoemission spectroscopy of heavily boron-doped diamond films in order to study the chemical sites of doped-boron atoms and their relation to the superconducting transition temperature (T _c). We find that B 1s core-level spectra exhibit several fine structures and three bulk components can be resolved from photon energy dependent studies and spectral fittings. These results indicate existence of several chemical environments of doped-boron atoms. One of the bulk components having the lowest binding energy can be assigned to a signal from substitutionally doped-boron atoms. Comparisons of bulk components with T _c suggest spectroscopic evidence for the importance of substitutionally doped-boron atoms for effective carrier and superconductivity.