Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor-metal boundary, together with the characteristic structures at 150×nmeV possibly due to the strong electron-lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron-lattice coupling and the superconductivity in doped diamond.