Optical and microstructural characterization of CdS–ZnO nanocomposite thin films prepared by sol–gel technique

Abstract

CdS–ZnO nanocomposite thin films were prepared using the sol–gel technique. Highly confined nanoparticles of CdS (radius 1.8–4.7 nm) were obtained with ZnO as the matrix. The molar ratio of CdS and ZnO was varied within the range 20:80 to 60:40. The influence of the annealing temperature (373–573 K) on the particle size was studied from the blue shift (0.1–0.7 eV) of the absorption edge and transmission electron microscopy. The microstructural characterization by high resolution transmission electron microscopy indicated well-resolved crystalline nanoparticles. Photoluminescence studies indicated three surface related peaks at 2.33, 2.19 and 1.89 eV for all the CdS–ZnO nanocomposites. The optical band gap (Eg) determined without preassuming the nature of the optical transition varied in the range 2.52–3.16 eV with variation of the annealing temperature, showing excellent carrier confinement of the CdS nanoparticles within the wide band gap ZnO matrix. This study indicated ZnO to be a good capping material for CdS nanoparticles.

The effect of substrate temperature on the optical properties of polycrystalline Sb2O3 thin films

“…As the films were deposited at a higher temperature, the crystallites began to move and tended to agglomerate easily. As a result, the band gap of crystallites decreases with increasing substrate temperature [31]. Also, the shift observed at absorption edge toward lower photon energies for thin films deposited on heated substrates could be attributed to the increase in crystallite size and change in the stoichiometry due to loss of oxygen, resulting in the formation of shallow acceptor levels in the forbidden band of Sb 2 O 3 thin films.…”

Characterisation, phase stability and surface chemical properties of photocatalytic active Zr and Y co-doped anatase TiO2 nanoparticles

“…The position of the band gap shown in Table 1 is determined using the procedure described by Panda and co-workers [56]. A slight decrease of the band gap is seen for low and intermediate concentrations whereas at the highest doping concentrations an up-shift of the band gap of approximately 0.1 eV occurs (Fig.…”

The Kinetics of the Coordination Transformation for Preparation of Nanosized CdS in a PVA Film

“…When the PVA -Cd(II) complex film deposited at the bottom of the crucible was immersed in the S 22 The concentration of residual S 22 decreased and the amount of S 22 consumed increased rapidly at first and then went gradually to an extreme value. This result coincides with general rule of diffusion-that is, the diffusion rate is very fast at the beginning and then slows down.…”

“…[13] Because the synthetic method, surface electronic structure, size, and distribution of nanosized semiconductors are strongly related to their preparation method and process, it is of great interest to prepare CdS nanosized crystals with controllable size and distribution, microstructure, and surface appearance. [14 -17] A variety of large-band-gap inorganic materials such as glass, [18] silica, [19] zeolite, [20] chloride salt, [21] ZnO, [22] and organic polymers [23] are employed as the protective matrix for nanosized semiconductors, among which polymers containing polar groups have been used not only to improve the stability but also to passivate the quantum dots. [24 -26] Significant enhancement of photoluminescent (PL) efficiency in CdS nanocrystals has been observed when embedded in some conductive polymers, indicating improved electronic passivation of surface bonds.…”