Influence of composition, bonding characteristics and microstructure on the properties of AlNxOy films

Abstract

The aim of the present work is to study the influence of composition, bonding characteristics and microstructural features on the properties of aluminium oxynitride thin films, AlNxOy. The change of films’ properties will be carried out by adding oxygen and nitrogen to Al thin films, giving rise to an oxynitride film with a wide range of optical and electrical responses, tailored between metallic-like to semiconducting and insulating ones. The overall set of results suggested the formation of a nanocomposite-like material, with Al nanoparticles dispersed in an AlNxOy matrix. The conductivity of the films was found to be governed by the constrictions between the particles that can be in contact or separated by insulating layers, forming a percolation network. The particular combination of morphological and structural features induced a gradual transition from positive to negative TCR values as the atomic ratio of (N+O)/Al increases, with potential applications in electrical devices. Furthermore, flat and low reflectance profiles were observed, which suggests their application in concentrated solar power systems. Taking into account the wide range of possible applications in electrical and optical-based devices, the films were also tested in terms of their structural stability, as well as the usual resistance to chemical degradation, by immersion in typical solutions such as NaCl. Results showed that the films are very stable, even when immersed for several weeks.