Photoluminescence and Raman Study of CdS–Al2O3 Nanocomposite Films Prepared by Sol–Gel Techniques
Abstract:The optical and microstructural properties of CdS–Al2 O3 nanocomposite (CdS–Al2O3 = 20:80 to 50:50) thin films synthesized by sol–gel techniques were studied. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement. Band gaps of CdS–Al2O3 nanocomposites were found to varyin the range 3.69–2.61 eV. The sizes of the nanocrystals, estimated from the blue shift (0.2–1.2 eV) of the absorption edges and transmission electron microscopy, were found to varyin the range 2.8–7.0 nm. X-raydiffraction studies showed reflections from (111), (200), (220), and (311) planes of CdS in the cubic phase. Microstructural characterization byhigh-resolution transmission electron microscope (HRTEM) indicated well crystallinity of the nanoparticles and lattice fringes supported the cubic phase of CdS. Raman spectroscopywas carried out for CdS–Al2O3 nanocomposites, which indicated a prominent peak at ∼299 cm−1. Significant changes in the peak position and intensityof the Raman peak were observed with varying the annealing temperature (373–573 K). Photoluminescence measurements indicated a prominent broad peak at ∼ 1.81 eV due to the surface defects in the CdS nanocrystallites. The present studyrevealed Al2 O3 to be a good capping material for CdS nanoparticles.
Document Type: Research Article
Publication date: March 1, 2005
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