Characterizations of ZnO thin films deposited onto langasite substrates by r.f. magnetron sputtering

We investigated in this study structural and nanomechanical properties of zinc oxide (ZnO) thin films deposited onto langasite substrates at 200°C through r.f. magnetron sputtering with an r.f. power at 200 W in an O2/Ar gas mixture for different deposition time at 1, 2, and 3 h. Surface morphologies and crystalline structural characteristics were examined using x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The deposited film featured a polycrystalline nature, with (100), (002), and (101) peaks of hexagonal ZnO at 31.75°, 34.35°, and 36.31°. As the deposition time increased, the ZnO film became predominantly oriented along the c-axis (002) and the surface roughness decreased. Through Berkovich nanoindentation following a continuous stiffness measurement (CSM) technique, the hardness and Young’s modulus of the ZnO thin films increased as the deposition time increased, with the best results being obtained for the deposition time of 3 h.