Nano-indentation mechanical characterizations of solution processed inorganic metal oxide thin films and influence of grain size

Aluminum-doped zinc oxide thin films were prepared by solution synthesis where molarity concentrations and mixing ratios for oxide and dopant sources were changed while deposition and pre- and post-deposition annealing steps remained the same. Post-deposition high-temperature annealing is known to improve conductivity and transparency but may deteriorate the mechanical characteristics of films. However, we report the successful preparation of thin films with high mechanical hardness (>11 MPa) and reduced modulus (>102 MPa) along with high electro-optical characteristics even after multiple annealing steps. Changes in grain sizes because of changes in molarity concentrations and difference of atomic radii caused mechanical characteristics of films. Both regular and inverse Hall–Petch relations were observed.