Do grain boundaries assist S diffusion in polycrystalline CdS/CdTe heterojunctions?

We report on a transmission electron microscopy and energy-dispersive x-ray spectroscopy study of S diffusion in polycrystalline CdS/CdTe heterojuncti ons. We find that grain boundaries significantly assist S diffusion in the CdTe layer when the CdTe is grown without the presence of oxygen, i.e., the S diffuses more easily along the grain boundaries than in the grains. Howe ver, grain boundaries do not enhance the S diffusion in CdTe when it is gro wn in the presence of oxygen. The reason is likely to be the formation of C d-O bonds at the grain boundaries, which are resistance to the S diffusion. (C) 2001 American Institute of Physics.