Intrinsic low energy bombardment of titanium chromium oxide thin films prepared by reactive sputtering

Titanium chromium oxide thin films were deposited by a DC reactive magnetron sputtering from separate Ti and Cr metallic targets in a reactive atmosphere. A constant current density JTi =150 A m−2 was used to sputter the titanium target, whereas the current density on the chromium target was systematically changed from JCr=0–200 A m−2. X-Ray diffraction, electron probe microanalysis and atomic force microscopy were used to investigate the effect of an increasing current density of the chromium target on the structural, compositional and morphological parameters of the coatings. A continuous evolution of the TixCr1−xOy composition was observed (x=1–0.34 and y=2–1.7), whereas an amorphisation of the material and a maximum of the surface roughness was obtained for JCr=50–100 A m−2. In the same way, energy distribution of the neutral and ionic species impinging on the surface of the growing film were determined by energy-resolved mass spectrometry. Mean energies and the relative fluxes of positive and negative ions were determined from their energy distributions. The behaviour of these species was also affected by the chromium current density especially between JCr=50 and 100 A m−2. Similarities in the changes of the thin films properties and the characteristics of ionic species are discussed, so as to establish some relationships between the plasma parameters and the deposited films.