Effects of the Cd:Zn:S molar ratio and heat treatment on the optical and photoluminescence properties of nanocrystalline CdZnS thin films

• Published in: Materials science in semiconductor processing 2013-12, Vol.16 (6), p.1629-1636
• Main Authors: Abdolahzadeh Ziabari, A., Ghodsi, F.E.
• Format: Article
• Language: English
• Subjects: Annealing; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Materials synthesis; materials processing; Methods of deposition of films and coatings; film growth and epitaxy; Nanocrystalline thin film; Nanocrystals; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Photoluminescence; Physics; Scanning electron microscopy; Semiconductors; Sol–gel; Spectra; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Thin films; X-ray photoelectron spectroscopy
• ISSN: 1369-8001; 1873-4081
• DOI: 10.1016/j.mssp.2013.03.014

Nanocrystalline cadmium zinc sulfide thin films with different molar ratios were prepared by sol–gel dip-coating in a polyethyleneglycol matrix. After heat treatment in air at 250, 350 and 450°C, the thin films were characterized by studying their structural, morphological, compositional, optical (linear and nonlinear) and photoluminescence (PL) properties. According to X-ray diffraction (XRD) results, the samples are polycrystalline with a hexagonal crystal structure and an average grain size of 12–18nm. The surface morphology of the films was examined by scanning electron microscopy (SEM). The results show that the films consist of nanocrystalline grains included in clusters with uniform coverage over the substrate surface. To determine their chemical composition, X-ray photoelectron spectra (XPS) of composite films were measured. The transmittance and bandgap of the films increased with the Zn concentration and decreased with increasing annealing temperature. The refractive index of the films was measured and the related dispersion is discussed in terms of the Wemple–DiDomenico single oscillator model. The third-order nonlinear polarizability of the films was estimated using a semi-empirical relation based on the single oscillator model. The results show that the films are suitable as optical switches. PL spectra were recorded for an excitation wavelength of 210nm. The emission intensity for the films varied with the Zn ratio and the annealing temperature and the behavior of different peaks is discussed.