Correlation between the structural, morphological, optical, nanomechanical, and tribological properties of ZnO films by USPT with their photocatalytic activities

The present work focused on studying the nanomechanical properties of ZnO thin films deposited on glass substrates using the ultrasonic spray pyrolysis technique. Structural and morphological properties are related to processing conditions, which affect mechanical, optical, and photocatalytic properties. To produce the ZnO films, three different molarities of spraying solution have been used which are 0.05 M; 0.075; and 0.10. The increase in the concentration of the spray solution led to an improvement in the crystal structure with the average crystallite size increasing from 28 nm to 35 nm. Morphological investigations revealed that the spherical nanoparticles with various size distributions. The rough surface topology emerged as a result of increasing solution molarity. Optical band gap values of the films decreased from 3.29 to 3.27 eV. Photocatalytic efficiency reached 93 % for ZnO film produced at higher solution molarity. Improved hardness values were determined for all films. Scratch tests showed better adhesion behavior for ZnO film at low solution molarity. Results indicate that solution molarity is an important parameter of the physical and photocatalytic properties of ZnO films as well as mechanical behaviors.