Effect of Etching on Composition and Morphology of CdTe(111) Surfaces

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Abstract
Various surface treatments, including wet chemical etching, heat treatment in H2 and sputter etching with Ar ion, were applied to CdTe(111) surfaces. The induced surface layer and morphology were studied with angle-resolved X-ray photoelectron spectroscopy (ARXPS), Auger electron spectroscopy (AES) and atomic force microscopy (AFM). For wet chemical etching, both Br/methanol and KOH/methanol resulted in a Te-enriched surface, while the Te-rich layer induced by Br/methanol etching can be at least partially removed by treating with reducing etchants including hydrazine and dithionite. A hillock like morphology was the common feature of these wet-chemically etched surfaces. After hydrogen heat treatment, both Cd(111) and Te(111) surfaces were Cd-rich and a distinct difference in microscopic morphology between the Cd(111) and the Te(111) surfaces was observed. The surface morphology developed by hydrogen heat treatment can be used to identify the crystal polarity. The sputter etching caused compositional changes in the surface of CdTe(111), resulting in Te enrichment at the outermost layer but Te depletion in the subsurface region. Also, an Ar-ion-energy-dependent surface morphology was observed.