RECONSTRUCTION, MORPHOLOGY, AND STOICHIOMETRY OF CDTE(001) AND CD0.96ZN0.04TE(001) SURFACES

The (001) surfaces of commercial, ''MBE-ready'' CdTe and Cd0.96Zn0.04T e substrates were studied by high resolution low energy electron diffr action (SPA-LEED) and Auger electron spectroscopy (AES) with respect t o reconstructions, morphologies and stoichiometries. Contrary to the c ommonly used surface preparation by growth of additional buffer layers , contamination-free and structurally long-range ordered surfaces were achieved by Ar+-sputtering and subsequent annealing at 260-350 degree s C. For CdTe, a mixed c(2 x 2)+(2 x 1) reconstruction with average te rraces of up to at least 1000 Angstrom width, separated by double laye r steps of (3.3 +/- 0.1) Angstrom height, are deduced. The c(2 x 2) do mains have a size of similar to 65 Angstrom x 300 Angstrom. No facetti ng was detected. For the Cd0.96Zn0.04Te surface, Zn enrichment occurs at temperatures > 300 degrees C, leading to various different surface reconstructions. Depending on annealing conditions and on the number o f sputter-annealing cycles performed, (3 x 1), (2 x 1) and c(2 x 2) re constructions, an increase of the step density and a formation of (011 ) facets were observed. Different mechanisms for the variation of the surface Zn concentration and of the surface reconstructions are discus sed. (C) 1997 Elsevier Science B.V.