A Study on the Evolution of Structural and Optical Properties in the Thermally Evaporated Ag2Te Thin Films

• Published in: Journal of the Institution of Engineers (India): Series D 2023-06, Vol.104 (1), p.27-36
• Main Authors: Gupta, Shubhendra, Gupta, Mukesh Kumar, Sharma, Dinesh C., Chowrasia, Mukesh Kr, Banerjee, M. K.
• Format: Article
• Language: English
• Subjects: Absorptivity; Current voltage characteristics; Energy gap; Engineering; Evaporation; Evaporators; Evolution; Film thickness; Glass substrates; Intermetallic compounds; Optical properties; Original Contribution; Photomicrographs; Photovoltaic cells; Scanning electron microscopy; Silver compounds; Solar cells; Tellurides; Thin films; X-ray diffraction
• ISSN: 2250-2122; 2250-2130
• DOI: 10.1007/s40033-022-00363-9

Thermal evaporation technique was employed to prepare silver telluride (Ag 2 Te) thin films of thickness ranging from 25 to 150 nm. Ag 2 Te thin films were deposited within a resistive heating thermal evaporator under a pressure of less than 10 −5  mbar. The deposition temperature was maintained at 1275 K. Ultra clean glass substrate was used for preparation of thin films. Structural evolution was observed by X-ray diffraction study, whereas scanning electron microscopy (SEM) was used for microstructural study. UV spectroscopy was carried out for optical property characterisation. It was revealed by XRD study that the silver telluride thin films assumed complete crystallinity beyond the film thickness of 100 nm. Films of lower thickness were found to be amorphous. From the XRD and SEM results it appeared that thermally deposited Ag 2 Te thin films underwent partial decomposition under the presently used synthesis parameters. Moreover, a smooth surface of the thin films was discerned in SEM photomicrographs. The experiments with UV–visible spectrometer demonstrated that the band gap of the thermally evaporated Ag 2 Te thin films lay within 1.4–1.7 eV. High absorption coefficient in UV region had confirmed that the Ag 2 Te thin films exhibited direct band transition. Moreover, it was observed that the variation in thickness of thermally evaporated Ag 2 Te thin films gave rise to appreciable change in optical band gap. I–V characteristics study suggested that silver telluride thin films were able to be highly conducting in presence of light; therefore, this material could be a potential candidate for solar cell application.