Thickness Dependent Structural, Optical, and Electrical Properties Of ZnSe Thin Films

In present work, nanostructured films of ZnSe are synthesized on glass substrates by using electron beam vacuum evaporation technique. To enhance the luminescence performance and electrical conductivity, the optimal film thickness are investigated for which films of thickness 250 nm and 500 nm are grown on glass substrates. Additionally, films’ crystal structures are also characterized. The XRD pattern revealed that the synthesized films exhibit preferred orientation of ZnSe (111) lattice which exhibits polycrystalline state having cubic zinc blende structure. Various structural parameters such as their crystallite sizes, strain developed in films, and their dislocation densities are also calculated. UV/VIS/NIR spectrophotometer indicates that visible transmittance decreased while the infrared transmittance switching efficiency increased as the film thickness increased from 250 nm to 500 nm. Moreover, the optical energy gaps of ZnSe films were in a range of 2.1-2.20 eV which is comparatively smaller in comparison to their bulk counterparts revealing their confinement in nano-dimensions. The study of their luminescence properties yields that the film of thickness 250 nm yield better results in blue spectral region which is also illustrated through CIE plots. The reason could be that for smaller film thickness electrons can easily jump to excited states for similar excitations owning to smaller crystallite sizes and thus showed greater luminescence. However, from the analysis of its electrical characteristics, the enhanced electrical conductivity is captured for the films having thickness of 500 nm. Therefore, the enhanced blue emission in the optimized film thickness indicates that these films can be utilized as luminescent materials.