Metal-insulator transition and superconductivity in boron-doped diamond

We report on a detailed analysis of the transport properties and superconducting critical temperatures of boron-doped diamond films grown along the {100} direction. The system presents a metal-insulator transition (MIT) for a boron concentration (nB) on the order of nc~4.5×1020 cm−3, in excellent agreement with numerical calculations. The temperature dependence of the conductivity and Hall effect can be well described by variable range hopping for nBnc) present a superconducting transition at low temperature. The zero-temperature conductivity 0 deduced from fits to the data above the critical temperature (Tc) using a classical quantum interference formula scales as 0(nB/nc−1) with ~1. Large Tc values (0.4 K) have been obtained for boron concentration down to nB/nc~1.1 and Tc surprisingly mimics a (nB/nc−1)1/2 law. Those high Tc values can be explained by a slow decrease of the electron-phonon coupling parameter and a corresponding drop of the Coulomb pseudopotential µ* as nBnc. Original Publication:T. Klein, P. Achatz, J. Kacmarcik, C. Marcenat, F. Gustafsson, J. Marcus, E. Bustarret, J. Pernot, F. Omnes, Bo Sernelius, C. Persson, A. Ferreira da Silva and C. Cytermann, Metal-insulator transition and superconductivity in boron-doped diamond, 2007, Physical Review B. Condensed Matter and Materials Physics, (75), 165313.http://dx.doi.org/10.1103/PhysRevB.75.165313Copyright: American Physical Societyhttp://www.aps.org/