Electrical conduction and dielectric relaxation of a-SiO x (0 < x < 2) thin films deposited by reactive RF magnetron sputtering

Abstract

Silicon oxide (a-SiO) is one of the most used silicon-based materials in optoelectronic and microelectronic technology. Previously, we have reported that the a-SiO x (0 < x < 2) physical properties related to the material structure show a kink point in their evolution when x varies. It was found that highly oxygenated a-SiO x thin films are inhomogeneous (silicon-rich nanoclusters embedded in oxygen-rich material). In this paper, we focus on electrical conductivity and transport mechanisms of carriers in this class of materials. DC current–voltage characteristics are analysed by using the Pollak and Reiss models of the percolation theory. Special attention is paid to the trapped charge in so called “dead ends” of the carriers' path. The current–time (for constant voltage pulses measurements) characteristics' analysis revealed the chargeability behaviour of the material. The AC measurements have also been employed to investigate the electrical character of the SiO x thin films. Both the modulus and the argument of the complex impedance have been analysed on SiO x (with x > 1) in conditions of variable frequency between 10 2 and 10 6 Hz. The variation of the impedance modulus with the frequency shows a capacitive behaviour: in Log | Z | = f (Log ω ) plots, the slope of the linear variation is around − 1. Studying the argument, the same results have been found [arg Z∊(− 75; − 90°)]. The intensive parameters, the dielectric constant and electrical conductivity, have been calculated. The result of this study revealed that a-SiO x sputtered thin films are characterised by dielectric relaxation and electrical conductivity (with a transport mechanism described by variable range hopping).