Fast Detection of Precipitates and Oxides on CdZnTe Surfaces by Spectroscopic Ellipsometry

We study the surface chemistry of Cd0.96Zn0.04Te(211)B by X-ray photoelectron spectroscopy and ellipsometry. We obtain first the dielectric functions of amorphous Te and Cd on Cd0.96Zn0.04Te(211)B by in␣situ ellipsometry after growing thin films of each material by molecular beam epitaxy. We then study their oxidation in air and show that Cd oxidizes primarily as a hydroxide whereas Te is present as TeO2. In neither case is the oxidation of the films complete, as a substantial amount of either metallic Te or Cd remains even after several days of oxidation. We subsequently exploit an electroless chemical etchant based on Ce4+ to produce Te-rich Cd0.96Zn0.04Te(211)B surfaces which oxidize very little in air. Another etchant containing KCN reduces the amount of α-Te substantially. Finally, we construct a tentative optical model for the Cd0.96Zn0.04Te(211)B surface that yields the abundance of amorphous Te on the surface.