Structure and Mechanical Properties of Ti-Al-C and Ti-Al-Si-C Films: Experimental and First-Principles Studies

The Ti-Al-C and Ti-Al-Si-C films have been deposited on Si(100) substrates by dual DC magnetron sputtering of the Ti-Al composite, graphite, and SiC targets at various sputtering currents. The effects of the sputtering current and annealing temperature on the structural, compositional, and mechanical properties of the films have been studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and hardness measurements. The as-deposited films are amorphous and exhibit low values of the root mean square roughness (0.25-0.27 nm). The results of XRD and XPS studies and first-principles calculations confirm that the annealing at 800 degrees C leads to the formation of the crystalline Ti2AlC MAX, Al4C3, TiC2, and TiO2 phases and the amorphous Al-C-O phases, and the crystalline Ti2Si1-xAlxC MAX, Al4C3, and TiSi/TiSi2 phases and the amorphous Al-Si-C-O phases in the Ti-Al-C and Ti-Al-Si-C films, respectively. The amorphous films exhibit an increase in the hardness with an increase in the sputtering current at the graphite or SiC targets, which reaches maximum values of 19.1 and 17.8 GPa for the Ti-Al-C and Ti-Al-Si-C films, respectively. The observed changes in the hardness are explained by the evolution of chemical bonds.