Mechanical properties of zinc oxide thin films grown by spray-pyrolysis

Abstract

Zinc oxide (ZnO) thin films are considered promising materials for optoelectronic applications, and characterization of their optical, electrical, and mechanical properties is essential for such purposes. In this study, thin films were deposited on glass substrates using spray-pyrolysis at 450°C, with film thicknesses ranging from 57 to 160 μm achieved by controlling the volume of the sprayed solution. ZnO thin films were characterized by XRD, where texture coefficient analysis was carried out to determine the preferential crystal growth, showing variations on (002), (100), (101) planes as the thickness of the film increases. The surface topography and grain size distribution of the films were analyzed using FE-SEM. The optical transmittance and optical bandgap of the thin films were studied by UV-Vis spectroscopy, with no significant change in the optical bandgap observed with varying thickness. Electrical properties were studied under the Van der Pauw method, obtaining conductivity values between 3.45 and 23.8 S. Finally, elastic modulus and film hardness were analyzed by instrumental indentation and calculated through the Hertz model, obtaining hardness and elastic modulus values between 4.5 – 6 GPa and 96.7 –111.5 GPa, respectively. The observed increase in hardness was attributed to the densification around the indentation zone.