Abstract
Superlattice thin films of CdSe/PbSe were successfully deposited on glass substrate using successive ionic layer adsorption reaction (SILAR) method to study their properties for possible semiconductor device applications. Cadmium (II) chloride hemi (pentahydrate), lead nitrate and sodium hydrogen selenide were the precursor for Cd2+, Pb2+ and Se2- ions sources respectively. The SILAR process involved a total cycle time of 100 seconds for a complete SILAR cycle with a total of six cycles made as one layer of CdSe used as a substrate for PbSe to form CdSe/PbSe superlattice films. The deposited thin films were subjected to thermal annealing at different temperatures of 300 K, 373 K, 423 K 473 K and 523 K and characterized for their optical, structural elemental and morphological properties using UV-Vis spectroscopy, X-ray diffraction and SEM/EDS techniques. The results of the optical properties showed that absorbance is high in the VIS region while transmittance is low in the VIS region but increased to high values in the NIR region and was significantly influenced by thermal annealing. The bandgap energies of the films were found to be 1.8 eV, 1.75 eV, 1.65 eV,1.8 eV and 1.88 eV after thermal annealing at 300 K, 373 K, 423 K, 473 K and 523 K respectively. The XRD analysis showed that the deposited thin films are polycrystalline with diffraction spectra showing an increase in intensity at an annealing temperature of 523 K and preferential lattice planes of 101, 103, 203 attributed to CdSe and 100, 200, 220 attributed to PbSe films. The EDS results indicate that the films composed of Cd, Pb, Se and other elements traceable to the substrate used. The SEM results showed that the CdSe/PbSe superlattice films contained agglomeration of nanorods and rice grain-shaped nanoparticles of different sizes and shapes that were found to increase with an increase in annealing temperature. These observed properties position the films for photodetector, solar cells, light emitting diodes, photoconductors and many other electronic and optoelectronic device applications.
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