Fabrication and Characterization of Nano-Semiconductor/Tetrahedral Semiconductor Heterostructures

Abstract

Abstract

In this work, nano-crystallite CdSe thin films were deposited by thermal evaporation technique from CdSe nano-powders on glass substrates. The structural features of the deposited films have been characterized by using optical transmission measurements, The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The X-ray line profile analysis revealed that the CdSe films are nano-crystallite and have a wurtzite (hexagonal) structure. These nano-crsytallite CdSe films are preferentially oriented along the (002) plane with a c-axis perpendicular to the substrate surface. The crystallite size for these films lies in the range 16 - 36 nm as measured from X-ray line broadening. It has been found that the variation of film thickness has a great influence on the microstructural parameters, such as micro-strain, the stacking-fault probabilities, dislocation densities as well as the crystallite size. In this respect, the micro-strain, dislocation density and stacking fault probabilities demonstrate a decrease by increasing the film thickness. The refractive indices (n) and absorption coefficients ( of the investigated films were obtained from transmission spectra. Here, the Sellmeier dispersion relationship quite agrees with the estimated values of n over a spectral range of 200 nm to 2500 nm. Various optical parameters of the investigated nano-crystallite CdSe films have been interpreted in the frame of Wemple-DiDomenico single oscillator model. Such evaluated parameters provide valuable physical insights; such as, the relationship between the ionicity of the CdSe films and microstructural parameters.