Deposition of Au overlayers onto cleaved (Hg,Cd)Te surfaces

Abstract

The interaction of evaporated Au overlayers with ultrahigh vacuum-cleaved p-type Hg0.72Cd0.28Te(110) surfaces has been studied with ultraviolet photoelectron spectroscopy (UPS) using synchrotron radiation. For all coverages of Au, a significant out-diffusion of Te occurs so that the cation-to-anion ratio [(Hg+Cd)/Te] decreases from 1.0 for the clean surface to 0.2 for 30 Å of Au and to 0.03 for 100 Å of Au. In contrast to the behavior previously observed following Al deposition, the Hg/Cd ratio remains constant at low coverages although it decreases to ∼70% of the initial value for thicker Au layers (20–50 Å). During the initial stages of deposition, the band bending changes from the inverted state present after cleavage toward flat band or accumulation. This behavior, probably due to in-diffusion of Au, is consistent with the use of Au as an Ohmic contact with p-type material.