Electron transport and superconductivity in transition metal-containing diamond-like films

The electron transport in W-, Mo-, and Nb-containing diamond-like films with specific resistance of 10-4 to 10-4 Ω cm is investigated. It is shown that for most dielectric films (with low metal concentration) at room temperature the electric conductivity is in agreement with the Poole-Frenkel model and trends to be activationless following Shklovskii's mechanism at low temperatures. The transition to a low-resistance state is observed as an electric field of about 5 x 105 V/cm is applied. At high metal concentrations (more than 18%) evidence of superconductivity with Tc ≤ 4 K is observed. At temperatures below Tc one or two reentrant transitions to the resistive state are revealed. The influence of the magnetic field on the superconducting and reentrant transitions is studied. Possible mechanisms for the reentrant transitions are also discussed. (orig.)