Low temperature conduction and breakdown phenomena in Au-SiOx-Au thin-film sandwich structures

Abstract

Measurements have been performed on vacuum-evaporated Au-SiO x -Au thin film sandwich structures, which have undergone an electro-forming process at room temperature. Such samples invariably show negative resistance behaviour at room temperature. As reported previously, negative resistivity was found to disappear for the second and subsequent voltage traces at temperatures below a certain critical value. This critical temperature remained constant for a particular sample, but varied between 180 and 230 K for the series of samples investigated. At temperatures below the critical value the samples exhibited log Ic ∝ Vb 1/2 current-voltage characteristics. Values of the slope of such characteristics did not support either Poole-Frenkel or Schottky conduction mechanisms at low temperatures, and a bulk barrier lowering effect at an internal high-field concentration was suggested as a probable cause of such behaviour. The temperature dependence of the device burn-out voltage (V β ) was also investigated. This showed behaviour consistent with a thermal breakdown process, thus substantiating earlier work. At voltages in excess of V β , small spherical dots of diameter ~1.5 µm were observed, and these were very similar to balls of crystalline silicon which have previously been observed in breakdown areas of SiO capacitors. Top electrode regions of bared material were similar to those observed in this laboratory on Ag-SiOx/B2O3-Ag samples.