Novel depth profiling in Cds-CdTe thin films

As the material structures of CdS-CdTe heterojunction solar cells have a significant effect on cell efficiency, there is a requirement to investigate new methods for thin film, structural, depth profiling. In an attempt to characterise structural details such as stress, stoichiometry and texture, we have developed a novel method of depth profiling, This is based upon a chemical etch bevel followed by spatially resolved Xray diffraction and Rutherford backscattering spectrometry. We show that the method provides a depth resolution of better than 0.1 mu m. We have used this method to examine CdTe thin films ( similar to 1.8 mu m) produced by electrodeposition supported upon CdS ( < 0.1 mu m). We present the results of these studies and use the method to investigate the: effect upon the structures of a type conversion anneal. The data is compared to previous studies using different depth profiling methods. The results indicate the formation of an spatially limited, intermixed CdTe(1-x)Sx layer and the conversion of the whole CdS film into a CdS(1-x)Tex layer. The structural characteristics are correlated to optical and electrical properties of the films. (C) 2000 Elsevier Science S.A. All rights reserved.