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Title: The electrodeposition of mesoporous type II-VI semiconductors
Author: Gabriel, Tim
ISNI:       0000 0001 3486 2133
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2007
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It has recently been demonstrated that lyotropic liquid crystalline mesophases of non-ionic surfactants can act as nano-scale templates for the electrochemical growth of adherent highquality metal (e.g. platinum, palladium and cobalt) and elemental semiconductor (e.g. selenium) films leading to well-defined periodic three-dimensional interconnected nanostructures. We report the synthesis of a uniform, high-quality metalloid, tellurium films and II-VI semiconductor compound films of CdTe and Zno with a hexagonal nanoarchitecture fabricated via this true liquid crystal templating route. The preparation of the nanostructured mesoporous films was carried out by cathodic electrochemical deposition of various metal semimetal species dissolved in the aqueous domain of the hexagonal lyotropic liquid crystalline phase (HI) of the non-ionic surfactants octaethyleneglycol monohexadecyl ether (C16EOs) and Brij®56. The deposition mechanism was based on cyclic voltammetry studies. The influence of experimental factors such as the deposition potential, electrolyte composition, additives, temperature were studied in order to improve the surface morphology, crystallinity and nanostructuring of the electrodeposited film. The template mixtures and films were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) and polarising optical microscopy (POM) to ascertain the presence of a regular nanostructure. The XRD and TEM data are consistent with the expected HI nanostructure. The ability to electrodeposit mesoporous nanostructured semiconductors highlights the possibility of creating a new class of materials that would exhibit unusual electronic and optical properties. We will discuss the results of finite-element electromagnetic simulations and the extent to which the film's optical properties can be understood in terms of form birefringence. Further characterisation of the films was carried out on cadmium telluride films using UV-Vis measurements taken with a metallurgical microscope. These measurements can also demonstrate that such structuring within a film produces strong birefringence, for wavelengths both above and below the semiconductor's bandgap. Preliminary results on bandstructure modification caused by the nanostructuring of these materials will also be presented.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available