Mechanical characterization of zinc oxide thin films on glass substrates by nanoindentation

Microstructures and mechanical properties of zinc oxide (ZnO) thin films deposited onto glass substrates by rf magnetron sputtering were studied. Surface morphologies and crystalline structural characteristics were examined using atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. Mechanical properties were measured by nanoindentation. The crystalline structures of ZnO thin films were well ordered with high c-axis (002) orientations. The surface morphologies of ZnO thin films were smooth and grains grew and distributed uniformly. A single pop-in in the load-displacement curve was clearly observed at a specific depth (7-10nm) of the thin film. The hardness and Young's modulus of ZnO thin films were ranged from 8.2 to 10.4GPa and 105 to 120GPa, respectively.