SURFACE RECONSTRUCTIONS OF (001) CDTE AND THEIR ROLE IN THE DYNAMICS OF EVAPORATION AND MOLECULAR-BEAM EPITAXY GROWTH

We present studies of the surface reconstruction and chemical analysis of the uppermost atomic layer of thick and thin (001) CdTe layers grown on (001) CdTe and ZnTe by (MBE). Techniques include reflection high energy electron diffraction and x-ray photoelectron spectroscopy (WS). All the surfaces obtained in the temperature range used (220-300 degrees C) in MBE are Cd covered with about 50% of undimerized Cd atoms; the peak of the Cd surface is clearly identified by XPS on thin CdTe layers. The surfaces can be (2x1), c(2x2) or (2x1)+c(2X2) reconstructed. Heating these surfaces above 300 degrees C leads to a (2X1) Te-stabilized surface. A reversible transition occurs between this last surface and the mixed (2x1)+c(2X2) structure: thermal cycling between these two reconstructed surfaces induces the evaporation of half a monolayer per cycle. Tentative models to account for the results are presented and correlation between these results and the properties of the MBE layers is discussed.