Electronic properties of boron-doped diamond on the border between the normal and the superconducting state

We report on measurements of resistivity and magnetoresistivity, Hall effect and upper critical field on normal and superconducting heavily boron-doped diamond layer produced by microwave plasma assisted chemical vapour deposition. The magnetoresistivity shows a characteristic change as a function of the boron concentration with strong evidence for a closed Fermi surface for superconducting samples. Although experimental and theoretical results favour a conventional, weak coupling electron-phonon interpretation of the superconducting mechanism, the observed dependence of the transition temperature TC on the hole concentration cannot be consistently described by the conventional theory.