Effect of carbon content on thermal stability of Ti–Cx–Ny thin films

Abstract

A series of Ti–Cx–Ny thin films with solid-solution and nanocomposite structures were deposited at 500 °C by reactive, unbalanced, direct-current magnetron sputtering. These films were subsequently vacuum annealed at 600, 700, 800, 900, and 1000 °C for 1 h. The effect of C content on the thermal stability of Ti–Cx–Ny thin films was investigated by way of studying the nanostructure and mechanical behaviors of pre- and postannealed samples using x-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, and microindentation measurements. The result indicated that C content played a great role in the nanostructure of Ti–Cx–Ny thin films. A small amount of C fully dissolved in the TiN lattice and produced SS Ti(N,C) thin films. Nanocomposite nanocrystalline (nc)-Ti(N,C)/amorphous-(C, CNx) thin films were followed to be formed with the incorporation of more C. On the other hand, the addition of C had a positive effect on the structural stability of Ti–Cx–Ny thin films. This effect was further enhanced after the formation of a nanocomposite structure. However, neither C content nor film structure had an effect on the thermal stability of mechanical behaviors. Both microhardness and residual stress were successively decreased with temperature and did not show any temperature retardation. The decrease in hardness values was found to be attributed to a decrease of residual compressive stress because of defect annihilation and an increase in nc size.