In-depth multi-technique characterization of chromium–silicon mixed oxides produced by reactive ion beam mixing of the Cr/Si interface

Abstract

The great interest of mixed metal–silicon oxides lies in their suitability, among other applications, as optical coatings with an adjustable refractive index. In this paper we investigate a new method to obtain chromium and silicon mixed oxides. Using as starting point a metallic chromium film deposited on a silicon substrate by magnetron sputtering, we induce the formation of mixed oxides using reactive ion beam mixing by bombarding the Cr/Si interface with oxygen. We have varied the ion fluence (between 5 × 10¹⁶ and 1 × 10¹⁸ ions cm⁻²) at a fixed implantation energy of 80 keV in order to modify the final composition of the coating. The composition profiles have been obtained with Rutherford backscattering spectroscopy (RBS), by changing the He energy from 3.035 up to 3.105 MeV, and with elastic recoil detection analysis using a time of flight configuration (ERDA-ToF). Results have been compared with those obtained from secondary ion mass spectrometry (SIMS) depth profiles and Monte Carlo TRIDYN simulations. Concentration depth profiles (CDP) have been also measured using X-ray photoelectron spectroscopy (XPS) and simultaneous Ar⁺ bombardment, as well as angle-resolved X-ray photoelectron spectroscopy (ARXPS). All the obtained depth profiles agree remarkably well with cross-section transmission electron microscopy (TEM) observations made on the sample implanted at the highest fluence.