Influence of air annealing on the structural, morphology and optical properties of ZnSe thin films by CW-CO 2 laser evaporation
2014
CW-CO2 laser evaporation was used to deposit ZnSe thin films onto glass microscope slides. The films prepared were annealed in air at annealing temperatures of 100, 200 and 300C. The effect of annealing temperature on the surface morphology, crystal structure and optical properties was investigated. All samples were seen to have an homogeneous surface morphology. The asdeposited and low temperature annealed ZnSe films exhibited the cubic phase. As the annealing temperature increased, a hexagonal phase developed and at 300C the ZnO phase began to appear. The average crystallite size of ZnSe films increased from 23.84 to 49.64 nm on annealing at 200C. Dislocation density, strain in the film and film thickness decreased when the annealing temperature increased up to 200C. The optical band-gap of the as-deposited film was 2.76 eV decreasing to about 2.70 eV at the 200C anneal. The introduction of the ZnO phase at 300C decreased crystallite size whereas it increased film strain. This work shows an easy and economical way to control band gap, crystallite size and film strain in ZnSe thin films by annealing in air. The lack of a pre-heated substrate and the ability to control band gap energy by annealing provides a versatile alternative source of ZnSe film deposition for potential optoelectronic applications. Copyright © 2014 VBRI press.
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