Gas-sensing performance of WS₂/WO₃ binary thin films for methane and hydrogen detection

This study presents the synthesis and characterization of WS₂/WO₃ binary thin films with varying sulphur to tungsten (S/W) molar ratios ([S]/[W] = 6 and 18 at%) for gas-sensing applications. The films were obtained by annealing sprayed layers in a sulphur atmosphere. The structural, morphological, optical, electrical and gas-sensing properties of the films were investigated. X-ray diffraction analysis revealed that the as-deposited films exhibited an amorphous nature, while annealing in a sulphur atmosphere resulted in the formation of a mixed-phase WS₂/WO₃ structure. Surface morphology studies showed changes associated with the sulphur concentration in the spray solution. Electrical characterization indicated p-type conductivity for all films, with a decrease in electrical resistivity as the sulphur-to-tungsten molar ratio increased. Gas-sensing experiments were performed to evaluate the detection of methane (CH₄) and hydrogen (H₂) gases. The pressure changes of 1.5 and 12.37 kPa were taken into account for methane gas and hydrogen gas, respectively. These pressure changes are equivalent to a concentration of 10 ppm for each gas. The WS₂/WO₃ films exhibited high sensitivity, with the highest values observed at approximately 70% for CH₄ and 85% for H₂ gases. Overall, the successful synthesis and characterization of WS₂/WO₃ binary thin films with tunable properties and superior gas-sensing performance suggest their potential for various gas-sensing applications.