Atomic Imaging and Microanalysis of Photovoltaic Semiconductor Surfaces and Interfaces

Techniques for chemical, compositional, and structural analysis of grain boundaries and other microfeatures in polycrystalline photovoltaic semiconductors are examined. These analyses cover the spatial resolution regime from several hundred microns to single atoms. Several conventional surface analysis methods used for chemical mapping are introduced for comparison of the limitations and interpretation of data, stressing the limits of spatial resolution. The emphasis is on techniques that provide structural, chemical, and bonding information on atomic dimensions. Specifically, spectroscopic scanning tunneling microscopy (STM) is discussed in terms of providing complementary diagnostic information. Comparative examples are given for the neutralization of shallow impurities at Si grain boundaries by hydrogen, and the incorporation of oxygen at surfaces and internal defects in CuInSe₂.