Interface morphology of CdS thin films grown on cadmium stannate and glasssubstrates studied by grazing incidence x-ray scattering

The semiconductor CdS is widely used as a window material in many photovolt aic applications. The interface between CdS and the front collector transpa rent conducting material plays a pivotal role in the solar cells; a physica l understanding and control of the interface morphology are needed in order to improve the device performance. Cadmium stannate has recently been reco gnized as an important transparent conducting material in light of its supe rior physical properties over the conventional transparent conducting oxide s. Physical understanding of the interface between CdS and cadmium stannate is therefore pf great practical interest. For this study, the grazing inci dence x-ray scattering (GIXS) technique has been demonstrated very useful f or the nondestructive characterization of the interface morphology in a var iety of layered structures, thus, it is well suited for this task. In the p resent work, various thin films of CdS deposited on cadmium stannate are in vestigated by the GIXS technique using synchrotron radiation. Also, similar measurements were made with CdS films deposited on glass substrates for co mparison. Variations of surface and interfacial roughness as well as latera l correlation lengths of interface height fluctuations as functions of film thickness and processing conditions are investigated. (C) 1999 American Va cuum Society. [S0734-2101(99)08005-7].