Influence Of Air Annealing On The Structural, Morphology And Optical Properties Of ZnSe Thin Films By CW-CO2 Laser Evaporation
Wuttichai Phae-ngam, Suebtarkul Suchat, Taswal Kumpeerapun and Voravit Kosalathip
Keywords: ZnSe; thin film; laser evaporation; CO2 laser; air annealing.
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 300°C. 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 as-deposited and low temperature annealed ZnSe films exhibited the cubic phase. As the annealing temperature increased, a hexagonal phase developed and at 300°C the ZnO phase began to appear. The average crystallite size of ZnSe films increased from 23.84 nm to 49.64 nm on annealing at 200°C. Dislocation density, strain in the film and film thickness decreased when the annealing temperature increased up to 200°C. The optical band-gap of the as-deposited film was 2.76 eV decreasing to about 2.70 eV at the 200°C anneal. The introduction of the ZnO phase at 300°C decreased crystallite size and 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.