Direct evidence for grain-boundary depletion in polycrystalline CdTe from nanoscale-resolved measurements

We use scanning probe microscopy-based methods for direct characterization of a single grain boundary and a single grain surface in solar cell-quality CdTe, deposited by closed-space vapor transport. We find that scanning capacitance microscopy can serve to study polycrystalline electronic materials, notwithstanding the strong topographical variations. In this way, we find a barrier for hole transport across grain boundaries, a conclusion supported by the much more topography-sensitive scanning kelvin probe microscopy, with some variation in barrier height between different boundaries. (C) 2003 American Institute of Physics.