Silicon oxide (a-SiO) is one of the most used silicon-based materials in optoelectronic and microelectronic technologies. 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 carriers' transport mechanisms in a-SiO_x. Dc current-voltage characteristics are analysed by using the Pollak and Riess model of the percolation theory. A 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 reveals 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), when the frequency was varied between 10² and 10⁶ Hz. The variation of the impedance modulus with the frequency showed a capacitive behaviour: in logôZô=f(log w) plots, the slope of the linear variation was found around –1. Similar results have been obtained studying the argument variation [arg ZÎ(-75;-90⁰)].

The intensive parameters as dielectric constant and electrical conductivity have been calculated. The results 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).

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1. Structure, Composition, Morphology, and Electrical Properties of Amorphous SiOx (0<x<2) Thin Films