Thermal stability of UBM sputtered DLC coatings with various hydrogen contents

Thermal stability of tetrahedral amorphous carbon (ta-C) films is higher than that of hydrogenated amorphous carbon. This study investigates hydrogen content effects on thermal stability of diamond-like carbon (DLC) coatings using materials with two different hydrogen contents (H: 10.8 and 25.3  at.%) annealed in vacuum at up to 600  °C. Indentation measurements of the films showed decreased hardness of the films annealed at temperatures greater than 400  °C. Raman spectroscopy revealed D-band and G-band splitting at those temperatures for films with 25.3 at.% hydrogen content. Structural change with hydrogen effusion occurred ca. 440  °C in both hydrogen content films. Structural changes in 25.3  at.% hydrogenated films affected tribological properties, but 10.8  at.% of hydrogen content films showed only slight changes.