Transport in tungsten-containing diamond-like films

Electron transport in tungsten-containing diamond-like films (DLF) grown by combined plasma-enhanced chemical vapour deposition and magnetron sputtering was investigated. It was shown that at room temperature for dielectric films with a metal concentration of 1 × 1016–1 × 1018/cm3, the electron conductivity is in agreement with the Pool-Frenkel model and tends to be activationless following the Shklovskii mechanism or the Fowler-Nordheim one at low temperatures. Transition into a low-resistant state was observed, as an electric field of about Ec = 1 × 105 V/cm was applied. As the field is more than the Ec the resistance depends on neither temperature nor electric field. In the strong electric and magnetic fields the non-ohmic hopping conductivity of both Mott and Shklovskii types was observed in the DLF samples with tungsten concentration as low as 1016–1018/cm3. Using the experimental data the parameters of hopping conductivity theory were evaluated. The data of low-frequency capacitance measurements in insulating DLF are also presented. Possible mechanisms of obtained results are discussed.