The thermally stimulated luminescence and conductivity of insulators

The insulator model used is of greater generality than in most previous treatments in that the degree of retrapping is arbitrary and the dependence upon temperature of the lifetime of free carriers is controlled by the degree of occupation of deep trapping levels. The assumptions involved in the definition of this model are discussed and expressions are presented for the temperature variation of thermally stimulated conductivity and thermoluminescence, peak position and height, and the rate of change of peak position for variation of the heating rate. In particular the dependence upon the initial excitation level is discussed. The equations are illustrated with computed curves. The emphasis is on the use of these results in the interpretation of experimental data and to this end the basic parameters have been retained wherever practicable. Previous experimental results are discussed with respect to these extensions to the theory. The temperature dependences of parameters such as the capture cross section of the traps are explicitly considered and shown to cause a systematic error of the order of ±10% in the evaluation of activation energy from heating rate variation methods.