Effect of vacuum annealing and substrate temperature on structural and optical properties of ZnIn2Se4thin films

El-Nahass M. ; Attia A. ; Salem G.F ; Ali H. ; Ismail M. 


Abstract


Zinc indium selenide (ZnIn 2 Se 4 ) thin films were prepared by the thermal evaporation technique with high deposition rate. The effect of thermal annealing in vacuum on the crystallinity of the as-deposited films was studied at different temperatures (523, 573 and 623 K). The effect of substrate temperature (623 K) for different thickness values (173, 250, 335 and 346 nm) on the optical parameters of ZnIn 2 Se 4 was also studied. The structural studies showed nanocrystalline nature of the room temperature (3001 < ) deposited films with crystallite size of about a few nanometers. The crystallite size increased up to 31 nm with increasing the annealing temperature in vacuum. From the reflection and transmission data, the refractive index n and the extinction coefficient k were estimated for Znln 2 Se 4 thin films and they were found to be independent of film thickness. Analysis of the absorption coefficient data of the as-deposited films revealed the existence of allowed direct and indirect transitions with optical energy gaps of 221 eV and 171 eV, respectively. These values decreased with increasing annealing temperature. At substrate temperature of 623 K, the direct band gap increased to 241 eV whereas the value of indirect band gap remained nearly unchanged. The dispersion analysis showed that the values of the oscillator energy E0, dispersion energy Ed, dielectric constant at infinite frequency E, and lattice dielectric constant EL were changed appreciably under the effect of annealing and substrate temperature. The covalent nature of structure was studied as a function of the annealing and substrate temperature using an empirical relation for the dispersion energy Ed. Generalized Miller's rule and linear refractive index were used to estimate the nonlinear susceptibility and nonlinear refractive index of the thin films. © 2013 Elsevier BY. All rights reserved.


Other data

Keywords ZnIn2Se4 films/ X-ray diffraction/ Annealing Substrate temperature/ Optical properties
Issue Date 1-Jan-2013
Journal Physica B: Condensed Matter 
URI http://api.elsevier.com/content/abstract/scopus_id/84886945740
http://research.asu.edu.eg/123456789/558
DOI 10.1016/j.physb.2013.05.012


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