In-situ ellipsometry and SHG measurements of the growth of CdS layers on CdxHg1-xTe

Wark, A.W. and Berlouis, L.E.A. and Jackson, Fiona and Lochran, S. and Cruickshank, F.R. and Brevet, Pierre-Francois (1997) In-situ ellipsometry and SHG measurements of the growth of CdS layers on CdxHg1-xTe. Journal of Electroanalytical Chemistry, 435 (1-2). pp. 173-178. ISSN 0022-0728

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Abstract

In-situ measurements of ellipsometry and second harmonic generation (SHG) are carried out to examine the growth of thin CdS films on CdxHg1−xTe (CMT) from aqueous sulphide solutions. The change in the extinction coefficient (at λ = 632.8 nm) with film thickness indicates that impurities, notably β-HgS, become increasingly incorporated in the CdS layer. The low value for the refractive index (n = 1.73) on the other hand suggests that the film is porous. In this first reported monitoring by SHG of the growth of a non-centrosymmetric layer on another such layer, we have observed an increase of the SH response as the CdS layer was grown. From first principles of non-linear optics, this increase should be quadratic with the film thickness. However, the observed increase does not depart clearly from a linear increase owing to the very thin CdS films grown. Anisotropy measurements have been performed prior to the growth and after the growth of the thin film. A clear change of the pattern attributed to the CdS film is observed but the SH response does not arise solely from the CdS film.