Electrical, optical, and microstructural properties of sol-gel derived HfZnO thin films

HfxZn1-xO thin films are deposited on glass substrates by the sol-gel method. The incorporation of Hf increases the crystallinity of the as-deposited films. The bandgap increases with the Hf content but reduces after thermal annealing because of the relaxation of built-in stress, atomic rearrangement, and precipitation of HfO2. The resistivity of ZnO decreases as the annealing temperature increases owing to the improvement of crystallinity and the reduction of defect densities. On the contrary, the resistivity of HfZnO thin films increases with the annealing temperature owing to the precipitation of HfO2 and reduction of oxygen vacancies. The incorporation of Hf in the films improves the Zn-O bonding state, and thermal annealing enhances metal-oxygen bonding. ? 2014 Elsevier B.V. All rights reserved.