Lead iodide（PbI_2） films have been prepared by the electron beam evaporation technique,and their photoconductive response to visible light was investigated under different deposition and illumination conditions.It is found that the films＇ photoconductive response speed increases and the relative sensitivity decreases with the increase of substrate temperature due to the opposite requests for photo-carrier lifetime.Further,appropriately increasing the film＇s thickness and rising substrate temperature simultaneously can effectively balance the opposite demands.Under optimized conditions of a substrate temperature of 200℃,a source-substrate distance of 30 cm and a deposition time of 10 min,the prepared films exhibit the best response properties.In addition,the response to illumination with different wavelengths was also measured,revealing that the decline of response performance with increasing wavelength is due to the lower photon energy of incident light.
Highly crystalline and transparent cadmium sulphide （CdS） films were deposited on glass substrate by electron beam evaporation technique. The structural and optical properties of the films were investigated. The X-ray diffraction analysis revealed that the CdS films have a hexagonal structure and exhibit preferred orientation along the （002） plane. Meanwhile, the crystalline quality of samples increased first and then decreased as the substrate temperature improved, which is attributed to the variation in film thickness. UV-vis spectra of CdS films indicate that the absorption edge becomes steeper and the band gap present fluctuation changes in the range of 2.389-2.448 eV as the substrate temperature increased. The photoluminescence peak of the CdS films was found to be broadened seriously and there only emerges a red emission band at 1.60 eV. The above results were analyzed and discussed.
