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Using a newly developed path-integral theory, we study of photoemission spectra of the nanosize boron-doped diamond systems coupled with Einstein phonons, and find the emergence of clear Fermi-edge in highly doped sample. Lightly doped boron as an acceptor, diamond becomes a p-type semiconductor with an activation energy of 0.37eV. Increasing the doped boron concentration, also considering the electron-phonon coupling, the impurity band is expanded and can overlap with the top of carbon valence band because of the small activation energy, and make the material undergo semiconductor-metal transition. Together with the broad scope of optical transparency in the IR and UV-visible range, this conductive boron-doped diamond is considered to be an attractive electrode material for spectroelectrochemical application. |