Dielectric Properties of Ta2O5 Thin Films

Abstract

Alternating current bridge, step response, and dc conduction measurements are reported on anodic oxide films on tantalum with counterelectrodes of gold and indium. The step response currents followed a t−n law, where n was from 0.9 to 1.0 depending on conditions. For a linear dielectric response, this corresponds to ε″ (ω) varying as ωn−1, i.e., as either ω−0.1 or independent of frequency, respectively. For low values of applied step voltages with specimens made in certain ways, the magnitude of the step response agreed with extrapolated bridge measurements. Deviations are discussed in terms of electronic space-charge effects. Below room temperature, ε″/T was constant as expected for a superposition of Debye losses with relaxation times determined by a thermal activation process with a flat distribution of activation energies. The slope of log J vs F1/2 plots for electronic conduction corresponded to the Schottky or Poole-Frenkel values depending on whether the Ta electrode was negative or positive.