Orientation relationship of polycrystalline Pd-doped SnO2 thin film deposits on sapphire substrates

Pd-doped SnO2 thin films of rutile structure were deposited using radio-frequency magnetron sputtering method on sapphire substrates with three different orientations: r-cut (0112), a-cut (1120), and m-cut (1010). The deposited films were characterized using transmission electron microscopy and X-ray pole figures. All the deposited films were polycrystalline but highly oriented with the interface, and also had in-plane or near-epitaxial relationships were observed for the SnO2 films grown on all three cases of sapphire substrates. In particular, (101), (101), and (001) oriented films were respectively grown on r-, a-, and m-cut sapphire substrates. The in-plane orientation relationships were determined to be [010]SnO2 || [100]Al2O3 and [101]SnO2 || [121]Al2O3 (r-cut), [101]SnO2 || [110]Al2O3 and [010]SnO2 || [001]Al2O3 (a-cut), and [100]SnO2 || [010]Al2O3 and [010]SnO2 || [001]Al2O3 (m-cut). A highly textured structure was observed for the films grown on m-cut substrate.