Sensitivity of Cadmium Sulfide under the Influence of Both Substrate Temperature and Gas Operation

The importance of this research is to study the effect of changing the temperature at the same time on each of the prepared samples and during the gas sensing processes, the effects of substrate temperature T_s were investigated after precipitation by the microstructural and optical characteristics of cadmium sulfide using thermal spraying method with different temperatures of (300, 400, and 500) ºC. The structural investigations of these films were studied, showing that the increases in substrate temperature were shown cubic and hexagonal phases according to ICDD card no. (21-0929) and (43-0989). The dramatic change occurred at 500 ^oC in changing the phase from hexagonal to a cubic structure. XRD exhibits a dominant plane at (200) for different substrate temperatures. Optical transmittance, absorption coefficient, and energy gap values were calculated by UV/VIS spectrophotometer. These results showed that the band gap values decreased with increasing substrate temperature. The gas sensitivity was tested for NO₂ gas at several working temperatures from 175 ºC to 250 ºC, and various gas concentrations from 150 ppm to 200 ppm and found that the sensitivity increase with increasing both the operating temperature and gas concentration for a T_s at 500 ºC which offer also the best crystallization the best sensitivity at an operating temperature of 175 ^oC is 75% at a gas concentration of 150 ppm.