Analysis of illumination-time-dependent profiles of phototransferred thermoluminescence of Al2O3:C,Mg

Abstract

Time-dependent profiles of phototransferred thermoluminescence (PTTL) of Al2O3:C, Mg are presented and analysed. Whereas qualitative discussions consider theoretical predictions, mathematical analysis of the profiles is based on experimental results. The thermoluminescence glow curve of unannealed Al2O3:C, Mg measured at 1 °C/s following irradiation to 2 Gy consists of at least eight peaks. There is a prominent peak at 165 °C and 7 secondary peaks at 43, 73, 195, ~246, 284, ~336 and 374 °C respectively. These are labelled I through VIII in order of appearance. Of these, only peaks I-IV are reproduced under phototransfer. The role of various electron traps as donors was determined using pulse annealing as well as by monitoring the dependence of peak intensity on duration of illumination used in the phototransfer. In particular, this shows that the electron trap for peak III at 165 °C, the main one, is the dominant donor to the electron traps responsible for PTTL at peaks I and II. There is also evidence of deep electron traps and deep hole traps beyond 500 °C which contribute to phototransferred thermoluminescence associated with peak III. The dependence of PTTL intensity on illumination time has been analysed using sets of coupled first order linear differential equations which describe the charge transfer at the electron traps involved. Particular solutions to the family of equations set up have been applied on experimental data successfully as evident in residuals associated with each fit.