Microstructural characterization of chromium oxide thin films grown by remote plasma assisted pulsed laser deposition

Abstract

In this work, we investigate the use of Remote Plasma Assisted PLD for the growth of chromium oxide thin films. In an attempt to enhance oxygen incorporation in the growing layers, laser ablation takes place in an activated oxygen background that contains atomic oxygen as well as excited oxygen molecules, thereby creating growth conditions that are inaccessible by reactive PLD. All films were grown on Si (100) substrates by ablating a pure Cr2O3 target using a KrF excimer laser. The micro-structural analysis of the grown layers was achieved using Infra- Red Spectroscopy, X-Ray Diffraction, Atomic Force Microscopy and Rutherford Back- Scattering. It is found that films deposited under remote plasma conditions show a predominance of the higher oxidation states of chromium while the antiferromagnetic Cr2O3 phase is mostly present in films grown in an O2 ambient. The effect of substrate temperature on the microstructure of the films was also studied. At low substrate temperatures (<350°C), the films have an amorphous microstructure with elongated rod-like features that could indicate the formation of the CrO2 phase. With increasing temperature up to 450oC, the structure of the films reverts to a crystalline Cr2O3 phase as inferred from the appearance of the corresponding peaks in the XRD spectra and from the narrowing of the infra-red absorption bands.