Mechanical characterization and oxidation characteristics of magnetron sputtered titanium diboride protective coatings

Novel ultrathin protective coatings are needed in critical thin-film technologies such as hard disks and microelectronics. Titanium diboride gained attention because of many desirable properties exhibited by thick coatings. The properties and performance of ultrathin titanium diboride coatings, however, are not well understood. Mechanical properties and oxidation characteristics of ultrathin titanium diboride coatings were studied in this dissertation. Mechanical behavior such as stress and stress-temperature evolution depended on thickness, while nanoindentation suffered from increasing substrate effects in thinner coatings. As far as oxidation characteristics are concerned, a novel technique based on the x-ray reflectivity measurements was developed. Quantitative structural information, such as erosion, oxide thickness, and interface roughness, was then obtained. Significant oxidation occurred even at room temperature, leading to considerable thickening due to volumetric mismatch. Oxidation at elevated temperatures resulted in layering of the oxides at a very early stage. The oxidation studies reveal that titanium diboride is not suitable for hard-disk overcoats due to the inevitable oxidation at room temperature. These findings highlight quantitative studies of oxidation resistance of disk overcoats in seemingly very mild environments, as well as the potential of hard oxides as novel disk overcoats.