Investigation of structural, spectral, optical and nonlinear optical properties of nanocrystal CdS: Electrodeposition and quantum mechanical studies

Abstract

Nanocrystalline CdS semiconductor was synthesized by electrodeposition technique, and characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and FTIR spectroscopic methods. XRD analysis result showed that it is a hexagonal crystal structure. SEM micrographs showed that the CdS nanocrystal is homogeneously distributed on the surface. The roughness of the CdS thin films was measured by AFM. The presence of band in the FTIR spectrum at 558 cm-1 corresponds to the stretching of CdS. CdS nanocrystals were modeled separately and calculated in the Gaussian program. Structural, spectroscopic, and nonlinear optical (NLO) properties were investigated using the DFT/Lanl2dz and semi-empirical/pm6 level. Besides, by making energy calculations, Homo, Lumo, band gap, and total state density (TDOS) were calculated. The experimental band gap was measured at 2.40 eV, while this calculated for hexagonal and cubic structure as 2.21 and 2.01 eV with semiemprical/pm6 model, 2.44 and 2.25 eV with DFT/lanl2dz level.These results support that CdS nanostructures are crystallized in hexagonal structure. With this study, the obtaining of nano structured CdS films by electrodeposition method, their structural, optical and surface properties were experimentally examined, supported by theoretical calculations, and additionally NLO properties were investigated. It has been determined that the nanocrystals obtained are suitable material for optoelectronic applications.