Residual Stress Effects on Raman Spectra of RuO2 Thin Films

Abstract

The RuO2 thin films have been deposited onto glass substrates by rf reactive magnetron sputtering at different deposition conditions, such as different substrate temperatures, different sputtering pressures and different reactive gas pressures, using a metallic target. The deposited films have been characterized by the X-ray diffraction and Raman scattering. By analysis of data of the X-ray diffraction, it has been found that all the films are subject to a compressive stress. The residual stress in these films can be released by increasing the substrate temperature. In addition, the films, which have been prepared at the oxygen partial pressure higher than 1 x 10-3 mbar and at the total pressure lower than 6 x 10-3 mbar, show a quite high residual stress because the films peeled off automatically from the substrates when they were moved out from the vacuum chamber. Three Raman models (Eg, A1g and B2g) have been observed in all the Raman spectra. These Raman spectra have shown a strong relation with the residual stress in the films. As the residual stress increases, the Raman peaks move toward to the low wavenumber comparing to the standard value. In addition, the residual stress also results in the disappearance of the A1g Raman mode. In this work, these phenomena will be discussed.