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FABRICATION OF II-VI SEMICONDUCTOR THIN FILMS AND A STUDY OF STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES

Ali, Zulfiqar (2005) FABRICATION OF II-VI SEMICONDUCTOR THIN FILMS AND A STUDY OF STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES. PhD thesis, Quaid-i-Azam University, Islamabad.

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Abstract

The II-VI compound semiconductors thin films (CdS, ZnTe and ZnSe) have been prepared by different methods such as electron beam vacuum evaporation, closed space sublimation and two-sourced thermal evaporation. The choice of the deposition method was based on the quality of the films required for specific Application. The effects of deposition parameters, such as electron beam power (in case of electron beam evaporation); substrate temperature and annealing of the film, on the structural, optical and electrical properties have been studied. In spite of that the main goal is to get comparatively high electrical conductivity of the films, the optical properties of the films were also very important from the application point of view so that the improvement of the film conductivity should not associated with drastic change in the optical and structural properties of the films. In addition to that, the structure and the composition of the resulting films were of the basis of this study. The structure of the films was studied by X-ray diffraction and the composition of the resulting films was measured by electron micro probe analysis (EMPA). A model was used for the calculation of optical parameters (refractive index, absorption coefficient, film thickness and optical band gap) from the optical transmission spectra recorded by spectrophotometer. For reducing the resistively of II-VI group semiconductor thin films, doping with different materials were performed. These films have been doped with (Cu, Ag) dopant to make it p-type with different methods. Since Cu and Ag dopant in II-VI group compounds act as an accepter. The ion exchange process is a very simple, and low cost technique. In this technique the dopant has to be in the form of ion in a solution, where the pre-prepared films are to be immersed, i.e. Ag(NO3) solution in case of silver doping and Cu(NO3) solution in case of copper doping. The ion exchange parameters such as solution temperature, concentration and immersion time, and its effect on the speed of the process and further on the status of the resulting films was carefully determined and analyzed. Also the effect of post heat treatment, on the physical properties and the composition of the resulting films were studied. Ag and Cu doping of the ZnTe as well as ZnSe thin films were successfully achieved and the conductivity of the films was converted to p-type.

Item Type:Thesis (PhD)
Uncontrolled Keywords:thermal evaporation, doping, semiconductors, electron beam vacuum evaporation, closed space sublimation, two-sourced thermal evaporation
Subjects:Physical Sciences (f) > Physics(f1)
ID Code:423
Deposited By:Mr. Muhammad Asif
Deposited On:03 Aug 2006
Last Modified:04 Oct 2007 21:00

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