Effect of target poisoning ratios on the fabrication of titanium oxide coatings using superimposed high power impulse and medium frequency magnetron sputtering

Abstract

Five titanium oxide coatings with different O/Ti ratios were grown by a superimposed high power impulse magnetron sputtering (HiPIMS) and medium frequency (MF) coating system utilizing a plasma emission monitoring feedback control. The peak power density of HiPIMS increased from 517.6 to 658.5 W/cm2 and the O/Ti ratio increased from 1.4 to 2.3 as the target poisoning ratio increased from 10% to 90%, whereas the deposition rate decreased with increasing target poisoning ratios. A pure TiO phase gradually transferred to a mixture phase of anatase and rutile TiO2 as the target poisoning ratio increased. The amount of anatase TiO2 increased with increasing target poisoning ratios and reached almost a pure anatase phase as the target poisoning ratio was 90%. The highest hardness of 16.4 GPa and the best corrosion resistance were found for the coating with pure TiO phase grown at 10% target poisoning ratio (TB10). The hardness decreased gradually as the structure changed from a pure TiO phase to the rutile and anatase mixed phases. A low hardness of 5.8 GPa and a poor corrosion resistance were obtained for the anatase rich TB90 due to its microstructure defects. Good adhesion and wear resistance were achieved for coatings deposited at 70% and 90% target poisoning ratios (TB70, TB90). Among these five coatings, TB70 coating exhibited a hardness of 12.6 GPa, good wear resistance, adequate adhesion, and fair corrosion resistance, which can be used as a functional coating with good protection property.