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

Abstract

We report on a transmission electron microscopy and energy-dispersive x-ray spectroscopy study of S diffusion in polycrystalline CdS/CdTe heterojunctions. 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. However, grain boundaries do not enhance the S diffusion in CdTe when it is grown in the presence of oxygen. The reason is likely to be the formation of Cd–O bonds at the grain boundaries, which are resistance to the S diffusion.