Influence of thiourea on the synthesis and characterization of chemically deposited nano structured zinc sulphide thin films

Abstract

Nanocrystalline ZnS thin films incorporated onto glass substrates by chemical bath deposition method were investigated by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), UV-Visible Spectroscopy (UV-Vis), Photoluminescence (PL), and Raman Spectroscopy (FT-R) studies. The influence of thiourea on the structural and optical properties of ZnS films was discussed in detail. The X-ray diffraction patterns confirmed the rhombohedral structure of ZnS thin films. AFM measurements indicated the nano carpet-like surface morphology variation in film with influence of thiourea. The optical absorption studies in the wavelength range of 200-800 nm showed that the band gap energy of ZnS has decreased from 3.69-3.36 eV, as thiourea varied from 0.2-0.8 M. The PL spectra divulged a shift near band edge emission around 360 nm, when thiourea concentration was increased. The Stokes shift calculations from PL emission spectra supported the relative intensities estimated from PL energy band spectra and showed a dependable repeatability for different molar concentrations. The Zn-S complexes were identified in the Raman spectra and the Raman spectral shift for 0.6 M composition of thiourea, which was found to be appreciable for ZnS thin films. The characterization studies clearly exposed the effect of thiourea onto the chemically deposited ZnS thin films.

Moisture resistance in perovskite solar cells attributed to a water-splitting layer

“…The presence of thiourea detected through XPS suggest a second partial interpration of the increased optical band gap of the CuSCN-NP compared to bulk CuSCN as extrapolated from the Tauc plot in Fig. 1d: a previous literature report on a similar case 32 describes how the band gap of a ZnS thin films resulted to be singificantly affected by the presence of residual thiourea precursor, when a chemical bath deposition process was employed to fabricate it. Attempts to perform local structural analysis through selected area electron diffraction (SAED) during TEM imaging were unsuccessful (at both high, 200 kV, and low, 80 kV, acceleration voltages), due to instability of the particles under the electron beam during data acquisition 33 , a behavior that is compatible with the presence of beam-sensitive hydrated CuS x phases.…”

Influence of Bath Temperature and Deposition Time on Topographical and Optical Properties of Nanoparticles ZnS Thin Films Synthesized by a Chemical Bath Deposition Method

“…For ZnS thin films deposited at bath temperatures more than 70°C, the particle size and growth rate obviously increase as shown in Figures 4 and 5 for bath temperatures 75°C and 80°C, respectively, for different deposition times (20,30,40, and 50 min). At t d = 30 min, the average grain size was 187 nm and 228 nm for bath temperatures 75°C and 80°C, respectively.…”

“…The AFM micrograph of ZnS films deposited at bath temperature T b = 65°C for different times of deposition (t d = 20, 30, 40, 50 min) is shown in Figure 1. From AFM images, it is observed that unclear structures formed at lower deposition times (20,30, and 40 min) so it could not be able to measure their diameters. At t d = 50 min, small spherical ZnS-NPs appeared with the mean grain diameter of 120 nm approximately.…”

“…At higher deposition time 50 min, the particles start to aggregate and made huge grains (disappeared interval border). The average diameters, heights, and surface Journal of Nanomaterials roughness of ZnS thin films deposited at bath temperature 70°C for different deposition times (20,30,40, and 50 min) were showed in Table 1. Figure 3 illustrates graphic curves for changes of average diameters (d), heights (h), and roughness (Ra) in term of deposition time for synthesized ZnS thin films at bath temperature 70°C.…”

“…Zinc sulfide nanoparticles (ZnS-NPs) with wide bandgap (3.5-3.8 eV) have recently received intensive attention to be used in many applications [1] such as antimicrobial activity [2,3], electroluminescence devices, photonic devices [4], field emission devices [5], sensors [6,7], and applications in infrared windows [8] and lasers [9,10]. A variety of physical and chemical methods have been used to synthesize ZnS-NPs such as thermal evaporation [11], sputtering [12], spray pyrolysis [13], chemical vapor deposition [14], molecular beam epitaxy [15], pulsed laser deposition [16], microwave [17,18], wet chemistry processes [19,20], sonochemical thiourea [(NH 2 ) 2 CS] (S 2ion source) in an alkaline solution containing a zinc sulfate (ZnSO 4 ) (Zn 2+ ion source) and ammonia as a complexing agent which allow controlling Zn 2+ concentration. The deposition process is based on the slow release of Zn 2+ and S 2ions into the solution, which then condense on an ion-by-ion basis on the substrate that is properly mounted in a reaction solution.…”