ANODIC SULFIDE FILMS ON HGTE AND CD0.24HG0.76TE STUDIED BY IN-SITU ELLIPSOMETRY

The growth of anodic sulfide films on HgTe and CdxHg1-xTe (CMT) from a queous sulfide solution is examined using in-situ ellipsometry. The do minating feature at low overpotentials for the HgTe is the dissolution of the substrate whereas for CMT it is the CdS him formation. The HgS film that eventually forms on the HgTe substrate at higher overpotent ials maintains the ccp [111] orientation of the substrate and can be r egarded as epitaxial. Electrochemical passivation of the CMT and HgTe surfaces is attributed to a change in the HgS surface him structure fr om ccp to hcp, triggered by the electric held across the him. The curr ent oscillations that follow the passivation peak are due to the compe ting reactions of electrochemical formation and chemical dissolution o f the beta-HgS layer. Films grown to potentials beyond the passivation potential on the HgTe surface lose the epitaxial characteristic and s maller crystallites result, with mixed hcp and ccp orientation for the HgS, as observed from XRD measurements.