Date of Award

1-1-2001

Thesis Type

PhD

Document Type

Thesis

Divisions

Faculty of Science

Department

Department of Physics

Institution

Universiti Malaya

Abstract

Cadmium Selenide multilayer thin films have been prepared using physical vapour deposition method. Alternate layers of Cadmium and Selenium are deposited on unheated glass substrates. Morphological study of the samples has been done using SEM micrographs with a magnification of 5000. The EDX analysis gives the quantitative atomic percentage content of elements present in the samples. It is found that the high Cadmium content in the samples increased the crystallinity. From XRD measurements, it is evident that many films are polycrystalline in nature with a peak corresponding to < 111 > plane orientation of the zinc blende structure. The lattice constant of the samples has been determined and it varies from 3.442 to 3.551 A and the resultant strain varies from -1.9 to 1.2 %. The size or the crystallites has been determined using full width at hair maximum' values by substituting them in Scherrer's equation. The size or the crystallites varies from 4 to 28 11111. In the optical studies, the absorption coefficients arc calculated from the refractive indices or the film. These are differentiated as a function of photon energy and the extrema, which vary between 1.71 to 2.36 eV correspond to the band gap energy of the films. The blue shift in the optical band gaps can be explained using the quantum confinement effect proposed by Brus. Using the magnitude of the shift in energy, the size of the crystallites is calculated to be between 4.4 to 22 nm, which is correlated with the crystallite size determined using x-ray diffraction studies. The transmission spectra have broadened excitonic peaks along the absorption edge. The structural and optical studies give ample evidence for the presence of nanoclusters in the multiplayer CdSe thin films.

Initial

snms

Additional Information

Thesis (PhD) -- Faculty of Science, Universiti Malaya, 2001.

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