Influence of molar concentration and temperature on structural, optical, electrical and X-ray sensing properties of chemically grown nickel-bismuth-sulfide (Ni_xBi_2−xS₃) thin films

In this report, ternary semiconducting Ni_xBi_2−xS₃(x = 0.2 M and 0.5 M) thin films were synthesized in situ for the first time by a chemical bath deposition technique at different bath temperatures (60 °C, 70 °C and 80 °C). The effects of concentration and deposition temperature on the deposited films were studied by combining the results of structural, morphological, optical and electrical analyses. The growth of Ni_xBi_2−xS₃ films with good crystalline nature and interconnected grain arrangement takes place due to increasing the concentration of Ni²⁺ ions in bismuth sulfide matrix. EDS result confirmed the stoichiometry of Ni_xBi_2−xS₃ formation. Wettability test demonstrated that the surface of the film was hydrophilic in nature. The optical absorption spectra revealed that the bandgap E_g of the x = 0.5 M film deposited at 70 °C was about 1.36 eV. Current-voltage (I-V) characteristics of the x = 0.5 M film deposited at 70 °C were studied under X-ray radiation and dark condition. An X-ray detection sensitivity analysis showed that the detection sensitivity is optimum when the bias voltage applied across the film is low (~0.9 V). These findings reveal that the film with x = 0.5 M deposited at 70 °C can be used as an efficient low cost X-ray sensor.