Ammonia gas sensing property of nanocrystalline Cu2S thin films

Nanocrystalline semiconducting thin films of copper sulphide (Cu2S) were deposited by novel chemical route using aqueous solution of 0.1 M copper chloride, 0.05 M thiourea, complexing agent 10% aqueous ammonia (NH3) and hydrazine hydrate. The characterization and gas sensitivity of as deposited Cu2S thin film sensor have been investigated. The as deposited Cu2S thin films were observed to be very sensitive for NH3 gas at room temperature. Upon exposure of NH3 gas the Cu2S sensors lead to decrease in resistance which is attributed due to inter-conversion of Cu(I) and Cu(II) charge states. The response to ammonia gas by Cu2S thin film is detected at 200 to 500 ppm concentration in air. The maximum sensitivity (19.78%) for ammonia gas by Cu2S sensor was found at 500 ppm gas concentration. The quick response (~60 s) and fast recovery (~90 s) are the main features of these sensors. The effects of gas concentrations on the gas sensing performance of the Cu2S sensor have been studied and discussed