X-ray studies: CO2 pulsed laser annealing effects on the crystallographic properties, microstructures and crystal defects of vacuum-deposited nanocrystalline ZnSe thin films

Abstract

This work aimed to study the influence of CO₂ pulsed laser annealing power, CPLAP, on the crystallographic properties, microstructural parameters and crystal defects of ZnSe thin films. The as-deposited samples were prepared by a vacuum deposition technique at 8.2 × 10⁻⁴ Pa and were controlled to have thicknesses of 475 nm. The as-deposited samples were annealed by a CO₂ pulsed laser at powers of 10, 20 and 30 watts. The crystal structures were investigated by X-ray diffraction, which showed that the ZnSe films have nanocrystalline zincblende cubic structures. The film thickness, lattice constant and lattice interplanar distance decreased as CPLAP increased. Microstructural parameters were investigated using line profile analyses of the X-ray diffractograms. The integral breadth method was applied to estimate the pure broadening of the samples, and the Scherrer equation was employed to calculate the average crystallite size. Increasing CPLAP led to enhanced crystalline nature and microstructural properties of the films; in addition, it decreased the crystal defects of the samples. The average microstrain, the internal stresses, the dislocation density and the crystallite size per unit area decreased. Meanwhile, the interfacial energy per unit area increased. The relationship between internal stress and strain was discussed. CPLAP led to enhance the crystallinity nature of the films and to decrease the crystal imperfections, which in turn improved the quality of the film samples.