We prepared ZnS thin films via chemical bath deposition (CBD) in an aqueous solution of ammonia (NH₃) and hydrazine (N₂H₄). The composition ratio of hydrazine used was 0%, 17%, 22%, 29%, or 50%. We investigated the effects of hydrazine and ammonia on the growth, and the structural and optical properties of ZnS in terms of surface uniformity, voids, and grain size. We found that during the growth of ZnS films, hydrazine was very effective for improving the surface morphology and layer uniformity with fast layer formation, while it had no effect on the bandgap energy, Eg.

The effect of Cu coating on the sensing properties of nano SnO2:Cu based sensors for the CH4, CH3CH2CH3 gas was studied. This work was focussed on investigating the change of sensitivity of nano SnO2:Cu based sensors for CH4, CH3CH2CH3 gas by Cu coating. Nano sized SnO2 powders were prepared by solution reduction method using stannous chloride(SnCl2·2H2O), hydrazine(N2H2) and NaOH and subsequent heat treatment. XRD patterns showed that nano SnO2 powders with rutile structure were grown with (110), (101), (211) dominant peak. The particle size of nano SnO2:Cu powders at 8 wt% Cu was about 50 nm. SnO2 particles were found to contain many pores, according to SEM analysis. The sensitivity of nano SnO2:Cu based sensors was measured for 5 ppm CH4 gas and CH3CH2CH3 gas at room temperature by comparing the resistance in air with that in target gases. The sensitivity for both CH4 and CH3CH2CH3 gases was improved by Cu coating on the nano SnO2 surface. The response time and recovery time of the SnO2:Cu gas sensors for the CH4 and CH3CH2CH3 gases were 18∼20 seconds, and 13∼15 seconds, respectively.