Electrical Properties of Sputtered Au/Ta2O5 Cermet Thin Films

Abstract

Thin film cermets of Au/Ta2O5 were deposited by rf co-sputtering, using two different methods, on glass substrates. In the first method a single target of Ta2O5 covered partially with Au was used. The second method utilized tile sputtering of Au, in the form of a mesh placed in the plasma of an rf discharge between the Ta2O5 target and the substrate. The composition of the cermets investigated varied from 11% to 52% by weight Ta2O5. The resistivity varied from 6×10−5 to 32 Ω⋅cm with the corresponding TCR’s from +1700 to −2000 ppm/°C. Resistivities were measured in the temperature range −180-160°C. Plots of logρ vs T−1 for negative TCR films show the occurrence of three different activation energies for the conduction process: a low activation energy for T<133K, intermediate activation energy for 133K<T<∼253K, and a high activation energy for T>253K approximately. Good correlations between resistivity, TCR, activation energy, and composition are observed. Resistivity is seen to correlate well with TCR.