DEVELOPMENT OF MODELS FOR STRUCTURAL DEFECT CHARACTERISATION OF SELECTED METALS AND SEMICONDUCTORS BASED ON SLOW POSITRON BEAM TECHNIQUE

Abstract

In this work, models were developed for calculating the S parameter (amount of positron annihilation with valence electrons in low momentum regions) and W parameter (amount of positron annihilation with core electrons in high momentum regions) of materials. Experimental results obtained from Slow Positron Beam Research work for Aluminium and Silicon obtained from the Department of Physics, University of Cape Town, South Africa, were used to test the models. The models will be useful in the study of defects in materials. Moreover, the results of this work will be useful in predicting the S and W parameters, and hence defect structural characterization of materials, in studying the behaviour' of positrons in materials, and also to study how defects in materials vary with any of the dependent parameters of the materials. The models were developed based on parameters such as energy of incident beam, thickness of the sample, illumination time that the S and W parameters depend on. The developed models contain some mathematical functions which were in very good agreement with experimental values. The correlation between the developed models and experimental values was calculated statistically using the Spearman's correlation. High correlation between 0.72 and 0.99 was obtained between the modeled and experimental values. The models obtained will be used as substitutes to actual experimental work in making accurate predictions of the vertical defect profile of any material.