Interactions between (HgCd)Te and overlayers of intermediate reactivity (Ge, Ag, and Cu).

Abstract

The interactions between Ge, Ag, and Cu and both cleaved and sputtered (HgCd)Te substrates have been investigated using synchrotron radiation, and the results have been compared with those reported in the literature when available. Each of these overlayers forms tellurides with heats of formation near that of HgTe. Consequently, the extent of the interfacial reactions is intermediate between those occurring after deposition of reactive and unreactive metals and, in the absence of a large thermodynamic driving force for a reaction, is sensitive to the stability of the surface and the propensity of the overlayer to diffuse into the semiconductor. Ag readily diffuses into cleaved substrates, confirming earlier results. In contrast, it is trapped, at least partially, in the interfacial region of sputtered surfaces because of their increased reactivity, i.e., decreased stability. This increased reactivity of the sputtered versus cleaved surface is also demonstrated for Ge and Cu, where a greater fraction of the Hg is lost upon deposition. Our results show less Hg loss from cleaved surfaces than do the results of other work, which we attribute to differences in material or surface quality. The interactions between (HgCd)Te and intermediate overlayers are seen to serve as sensitive indicators of the surface stability.