In this article a multisample modification of variable angle spectroscopic ellipsometry is used to characterize ZnSe thin films prepared by molecular beam epitaxy on substrates formed by GaAs single crystals. Atomic force microscopy (AFM) is employed to characterize the morphology of the upper boundaries of these films. To interpret the ellipsometric data a relatively complicated physical model that contains a rough overlayer between the ambient and the ZnSe film and a transition layer between the GaAs substrate and the ZnSe film is employed. Several models of dispersion of the optical constants of the overlayers are examined to interpret the ellipsometric data. It is shown that the choice of overlayer dispersion model has a strong influence on determining the optical constants and dielectric function of the ZnSe films in the near-UV region. Within the visible region there are no differences between the overlayer dispersion models regarding determination of the ZnSe optical constants. The spectral dependences of the ZnSe dielectric function obtained are compared with those presented by other researchers. Further, by AFM it is shown that the upper boundaries of the ZnSe films are randomly rough and partially covered with small objects.
Influence of overlayers on determination of the optical constants of ZnSe thin films
Daniel Franta, Ivan Ohlídal, Petr Klapetek, Alberto Montaigne-Ramil, Alberta Bonanni, David Stifter, Helmut Sitter; Influence of overlayers on determination of the optical constants of ZnSe thin films. J. Appl. Phys. 15 August 2002; 92 (4): 1873–1880. https://doi.org/10.1063/1.1489068
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