Effect of Annealing Temperature On Chemical Bath Deposited Copper Sulfide (Cu𝑥S) Thin Film for Photodetector Applications

Abstract

The transition metal chalcogenides draw huge attention in the current era because of possessing potential applications in the field of optoelectronics, photoelectric conversion, solar cells, and lithium-ion batteries. Copper sulfide (Cu𝑥S), a transition metal chalcogenide, exhibits excellent potential optical and electrical properties for optoelectronic applications. In this research work, Cu𝑥S thin film has been deposited by the chemical bath deposition method on a glass substrate. The Cu𝑥S thin films have been thermally treated by rapid thermal annealing system with a variation of temperature from 100 °C to 400 °C to improve optoelectronic properties. The XRD and Raman spectroscopy study depicts the presence of CuS, Cu1.8S, and Cu2S phases at annealing temperatures of 200 °C, 300 °C and 400 °C, respectively. The XRD pattern and Raman spectral studies have revealed an increase in crystallinity with an increase in annealing temperature. The Hall effect measurements reveal p-type nature of Cu𝑥S thin film. The carrier concentration of Cu𝑥S thin film is found to be increased from 3.50×1018 cm-3 to 2.14×1019 cm-3 and the resistivity is found to be decreased from 7.65×10-2 Ω.cm to 3.71×10-2 Ω.cm with an increase in annealing temperature from 100 °C to 400 °C, respectively. The current-voltage characteristics depict ohmic nature of Cu𝑥S thin film with Al/Cu𝑥S/glass/Al structure fabrication, ensuring a good metal-semiconductor contact with Al metal. The photocurrent of Cu𝑥S thin film is increased with an increase in annealing temperature. Thus, the Cu𝑥S thin film, annealed at 400 °C, has been considered to be a suitable candidate for the photodetector applications.