The effects of deep trap population on the thermoluminescence of Al 2O 3:C

Abstract

The influence of deep traps on the 450 K thermoluminescence (TL) peak of Al 2O 3:C is studied. Depending upon the sample and on the degree of deep trap filling, features such as the TL width, area and height can vary considerably. These effects are interpreted to be due to: (a) sensitivity changes introduced by competition mechanisms involving deep electron and hole traps, and (b) the multiple component nature of the 450 K TL peak. The influence of the deep traps on the TL was studied using different excitation sources (beta irradiation or UV illumination), and step annealing procedures. Optical absorption measurements were used to monitor the concentration of F- and F +-centers. The data lead to the suggestion that the competing deep traps which become unstable at ∼800– 875 K are hole traps, and that the competing deep traps which become unstable at ∼1100– 1200 K are electron traps. Both the dose response of the TL signal and the TL sensitivity are shown to be influenced by sensitization and desensitization processes caused by the filling of deep electron and hole traps, respectively. Changes in the TL peak at low doses were also shown to be connected to the degree of filling of deep traps, emphasizing the influence of deep trap concentration and dose history of each sample in determining the TL properties of the material. Implications of these results for the optically stimulated luminescence properties are also discussed.