Middle-temperature thermally stimulated transformations of Cu–Si–O films

Abstract

This paper presents a comprehensive characterization of the structural and optical properties of the Cu–Si–O films prepared by the ion-plasma sputtering method of a combined Cu/Si target in an Ar and O₂ atmosphere before and after heat treatment at temperatures up to 600 °C. For this purpose, data from seven experimental methods were analyzed: scanning electron microscopy, X-ray photoelectron spectroscopy, dynamic secondary ion mass spectrometry, quantitative X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, and combined reflection–transmission spectroscopy. It was found that as-deposited films represent a uniform over-depth film, the main components of which are suboxides and oxides of silicon and copper with nano- and dispersed inclusions of silicon and copper. At annealing temperatures of 400–600 °C, the film gradually transforms into a heterogeneous structure composed of copper and silicon oxides, CuO and SiO₂, and inhomogeneity of composition and structure appears along the film depth. The film becomes two-layered, with a denser lower layer and a less dense upper layer depleted in silicon. Similar to substoichiometric silicon oxide (SiO_x) films, the annealed Cu–Si–O films have the best ordering at the level of short and medium range order (minimal value of the Urbach tail energy E_U) after annealing at ∼600 °C. The obtained results demonstrate the possibility of deliberately tuning the structure and physicochemical properties of Cu–Si–O films over a wide range, making them promising for applications in sensing, dielectric layers for microelectronics, and functional oxide coatings.