Effects of temperature on the resistivity of vacuum deposited Cu-MgF2 cermet thin films: an investigation of conduction mechanism

Abstract

Cermet thin films of Cu-MgF2 were deposited onto glass substrates using a conventional resistive heating co-evaporation technique. Films of starting compositions 40, 60 and 80 vol % Cu and average thicknesses 60, 145 and 285 nm were deposited at elevated substrate temperatures between 300 and 393 K in a vacuum of 1.33 × 10−3 Pa. Room temperature D.C. resistivity measurements were performed at atmospheric pressure from which activation energies and TCRs for the cermet films were determined. It was observed that the resistivity (ρ) data fitted into the ln ρ ∝ 1/T relationship. The activation energies were found to decrease with increase in film thickness and increase in metallic content of the cermet films whilst the TCRs were all negative. From the trends in both activation energies and TCRs it was concluded that the predominant conduction mechanism was tunnelling of thermally activated charge carriers.