Mechanical properties of single-phase Al1-xInxN films across the compositional range (0 ≤ x ≤ 0.7) grown by radio-frequency magnetron sputtering

Aluminum indium nitride (Al_1-xIn_xN) films across the compositional range (0 ≤ x ≤ 0.7) were grown on silicon substrate by radio-frequency magnetron sputtering. The In composition was tuned by varying the number of In blocks (n_In) covered on the Al target. We further investigated the dependence of structures, morphologies and mechanical properties on In composition x. It has been found that the as-grown Al_1-xIn_xN films are pure hexagonal phase without phase separation and the (0 0 2) orientation gradually enhances with increasing n_In. While n_In is more than 3, the preferred orientation of Al_1-xIn_xN films would change from (1 0 1) to (0 0 2) plane. Compared with pure AlN film, the Al_1-xIn_xN films exhibit flatter and smoother surface morphology. In addition, the increased n_In leads to a decrease of root-mean-squared (RMS) surface roughness and grain size. All ternary Al_1-xIn_xN films exhibit better mechanical properties than pure AlN film. The hardness and modulus of as-grown Al_1-xIn_xN films tend to decrease when the In composition × is larger than 0.3. The phenomenon can be attributed to the lower density of dislocation and weaker bond energy in Al_1-xIn_xN alloys.