(CdZnS): Sn film deposition for optical, morphological, and structural studies

Quaternary semiconductor (CdZnS):Sn films with five different molar percentages of tin (1–5% Sn) are capped with thioglycerol and methanol (TGM) in the ratio 1:1 grown on glass substrate for 60 min deposition time at 70 ºC by using chemical bath deposition (CBD) technique. The thickness of the film varies from 430 to 576 nm measured by gravimetric weight difference method. The films have been characterized using ultraviolet (UV) spectrophotometer, scanning electron microscope (SEM), photoluminescence (PL), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray diffraction (XRD). The optical absorption and transmission spectra of the films over the wavelength range of 400–1200 nm were recorded, and band-to-band absorption edges were obtained between 470 and 510 nm indicated blue shifting. The transmittance of the film decreases with higher concentrations of Sn. Energy band gap varies from 2.41 to 2.8 eV and the Bohr radius of particles changes from 2.25 to 2.39 nm for different concentrations of Sn. Scanning electron micrograph revealed the formation of loosely packed and large-grained size (4–6 µm) of cabbage-like structure of films. Energy-Dispersive X-ray Spectrometry (EDX) spectra confirmed the existence of the desired elements and the formation of (ZnCdS): Sn, respectively. Photoluminescence spectroscopic results observed the peaks at wavelengths of 424 nm, 500 nm, and 575 nm with decreasing intensities. The development of defect states in the band gap of Sn-doped ZnCdS thin films is observed by the decreased intensity of emission peaks. FTIR showed the structural and molecular arrangements of functional groups. The films are polycrystalline with orientation (110) plane of cubic structure that is exposed in structural analysis using X-ray diffraction. The intensity of XRD changed with change in Sn concentrations, and the major diffraction peaks shift towards higher diffraction angles.