Preparation and mechanical properties of aluminum-doped zinc oxide transparent conducting films

Aluminum-doped zinc oxide transparent conducting films were deposited in this study by magnetron sputtering under different sputtering powers and substrate temperatures. At low sputtering powers and substrate temperatures, the deposited films were constructed by spherical grains. With increasing power and temperature, the grains became facet with an obvious (002) preferred orientation. The crystallinity and grain size of the films increased as well, and consequently the electrical resistivity decreased. By nanoindentation tests, the hardness of the deposited films was measured and found to increase from 8 to 10 GPa with higher sputtering power and substrate temperature because of higher densification and crystallinity. During nanoindentation and nanoscratch tests, interface delamination occurred between the films and substrates, and the interface adhesion energy was accordingly obtained. From the measurement of nanoscratch tests, the adhesion energy was found to be improved from 0.49 to 0.86 or 0.79 J/m2, respectively, with higher sputtering power or substrate temperature because of the deeper penetration, higher densification and easier interface reaction of the deposited films.