3 - Thermoluminescence analysis

Summary

Introduction

One of the prime objectives of a thermoluminescence experiment is to extract data from an experimental glow-curve, or a series of glow-curves, and to use these data to calculate values for the various parameters associated with the charge transfer process in the material under study. These parameters include the trap depths (E), the frequency factors (s), the capture cross-sections and the densities of the various traps and recombination centres taking part in the thermoluminescence emission. Of course, arriving at values for these parameters does not necessarily mean that we fully understand them, or that we are knowledgeable about the defect model with which they are associated. (Indeed, having calculated, say, E and s, there is often a temptation to ask ‘so what?’.) Nevertheless, calculations of this sort are an important step in arriving at an acceptable level of understanding of the underlying processes and a great deal of effort has been directed towards the development of a reliable method of analysis. Unfortunately, this development is proving to be less straightforward than was at first imagined.

The most popular procedure begins by selecting the rate equations appropriate to a particular model (cf. chapter 2) and continues by introducing simplifying assumptions into these equations in order to arrive at an analytical expression which describes the variation in thermoluminescence intensity with temperature, in terms of the desired parameters. From these equations even simpler expressions are produced which relate the parameters directly to the data.