Synthesis and characterization of sol-gel derived cu doped zno films

Well-crystallized Cu doped (1,3 and 5 mol%) ZnO films were deposited on quartz substrates by sol-gel technique. The optical, microstructural and photoluminescence properties of the films were studied. It was found that the band gaps (3.38 eV) of the films did not vary up to 5% Cu doping in ZnO. The preferred orientation along (002) was observed for all the films and the degree of orientation decreased with increasing the molar percentage of Cu in ZnO. Atomic force microscopy (AFM) measurements were performed to study the surface morphology of 1,3 and 5% Cu doped ZnO thin films; the surface roughness of 1 mol% Cu doped ZnO film was smaller (∼6 nm) than those of 3 and 5 mol% Cu doped ZnO films (∼15-20 nm). The photoluminescence spectra of the films showed six peaks at 3.11, 3.03, 2.75, 2.68, 2.65 and 2.27 eV. One peak (3.11 eV) was due to excitonic transition and the other five peaks were due to defect related transitions. The excitonic peak intensity of Cu doped ZnO increased with increasing copper concentration.