An anomalous diffusion barrier case: The Hg_{1- x}Cd_xTe/Yb/Ag junction

Synchrotron radiation photoemission measurements of Hg_1-xCd_xTe/Ag junctions both with and without thin Yb interlayers show that the Yb layer acts to reduce Ag indiffusion at all interlayer thicknesses investigated, although three different types of behavior are observed depending on the layer thickness and morphology. We characterized the Yb layer morphology by means of the photoemission of adsorbed xenon technique. Thin (3–6 A) Yb interlayers are only partially effective, with substantial Ag indiffusion still evident. We associate this behavior with a two-dimensional island morphology of the interlayer. Thick (10–15 A) Yb interlayers are highly effective in reducing Ag indiffusion, due to the presence of a continuous reacted Yb layer and of a Yb-rich metallic phase with high alloying enthalpy for Ag. Intermediate thickness (8 A) Yb interlayers, effectively reduce Ag indiffusion at low Ag coverages (<20 A), only to fail catastrophically upon further Ag deposition.