In-situ evaluation of the anodic oxide growth on Hg1-xCdxTe (MCT) using ellipsometry and second harmonic generation

In-situ measurements of ellipsometry and second harmonic generation (SHG) w ere carried out to monitor the electrochemical growth of native anodic oxid e films an Hg1-xCdxTe (MCT). Growth of the anodic oxide was performed using two different methods viz., by linear sweep voltammetry and by applying a constant current density. The influence of scan rate and the magnitude of t he applied current density on the properties of the growing films were exam ined. From the ellipsometry data, we have shown that the measured refractiv e index value of 2.19 for the oxide Rim remains unchanged for moderate and high oxide growth rates. Only at very slow growth rates were significant in creases in the refractive index observed (n = 2.4), indicating an increase in the compactness of the layer. For film thicknesses in excess of similar to 1200 Angstrom, a non-zero value for the extinction coefficient was found , indicating the incorporation of HgTe particles within the anodic oxide fi lm. SHG rotational anisotropy measurements, performed on the MCT with and w ithout an anodic oxide film showed only the four-fold symmetry associated w ith the MCT and so confirmed that the oxide was centrosymmetric. However, a n increase in the SH intensity was observed in the presence of the oxide an d this has been attributed to multiple reflections in the thin oxide film a nd also to the increase in the chi((2)) non-linear susceptibility tensor as a result of charge accumulation at the MCT/anodic oxide interface.