  X-ray absorption (XAS) and emission (XES) spectroscopy near B-K and C-K edges
have been performed on metallic (~1at%B, B-diamond) and semiconducting
(~0.1at%B and N, BN-diamond) doped-diamond films. Both B-K XAS and XES spectra
shows metallic partial density of state (PDOS) with the Fermi energy of 185.3
eV, and there is no apparent boron-concentration dependence in contrast to the
different electric property. In C-K XAS spectrum of B-diamond, the impurity
state ascribed to boron is clearly observed near the Fermi level. The Fermi
energy is found to be almost same with the top of the valence band of non-doped
diamond, E_V, 283.9 eV. C-K XAS of BN-diamond shows both the B-induced shallow
level and N-induced deep-and-broad levels as the in-gap states, in which the
shallow level is in good agreement with the activation energy (E_a=0.37 eV)
estimated from the temperature dependence of the conductivity, namely the
change in C-2p PDOS of impurity-induced metallization is directly observed. The
electric property of this diamond is mainly ascribed to the electronic
structure of C-2p near the Fermi level. The observed XES spectra are compared
with the DVX-alpha cluster calculation. The DVX-alpha result supports the
strong hybridization between B-2p and C-2p observed in XAS and XES spectra, and
suggests that the small amount of borons (<1at%) in diamond occupy the
substitutional site rather than interstitial site.
