Effect of film thickness on physical properties of RF sputtered In2S3 layers

Indium sulfide (In2S3) layers were deposited by RF magnetron sputtering process with different thickness. The effect of thickness on structural, morphological, optical and photo-conductive properties of the In2S3 layers has been studied. In2S3 layers exhibit near stoichiometric chemical composition and single tetragonal phase with (103) preferred orientation. Variation of surface morphology, Raman bands and optical transmittance of the films have been observed with the increase of film thickness. Energy band gap of the layers determined from transmittance spectra were 2.44-2.66 eV (direct) and 1.82-2.06 eV (indirect), respectively. Based on the measured optical constants (n and k), the Wemple-DiDomenico model was performed to determine values of single oscillator energy (E-0), dispersion energy (E-d), optical band gap (E-g) and high frequency dielectric constant (epsilon(infinity)). The determined beta parameter indicates In2S3 as an ionic compound. The epsilon(infinity), values agree well with that of calculated according to the Spitzer-Fan model. Photoconductivity properties of the films were analyzed relating to the rate competition among photo-generation, recombination and trapping of carriers. (C) 2015 Elsevier B.V. All rights reserved.