Variable range hopping mechanism in band-tail states of feldspars: A time-resolved IRSL study

Time-resolved infra-red stimulated luminescence (TR-IRSL) technique enables an understanding of the dynamics of trapped electrons after IR excitation in the band-tail states of feldspar. This work intends to study the underlying physical mechanism of IRSL production. TR-IRSL studies were carried out on four feldspar mineral specimens of variable chemical composition and structural state. Assuming the IR excited trapped electrons make random walks in the band-tail states and recombine by tunnelling dynamically, hopping time is derived from the OFF time data of TR-IRSL. This analysis indicates that the hopping time decreases with stimulation temperature. Using Einstein diffusion equation, hopping probability is computed and is shown to obey the equation describing variable range hopping mechanism of Mott kind. Mott's parameters (hopping length and hopping energy) are then derived. Hopping length decreases with stimulation temperature whereas hopping energy increases with temperature. The average hopping length and energy are in the range of 11–18 Å and 45–55 meV respectively and the diffusion constant is estimated to be in the range of 10−10–10−9 cm2 s−1 for all the feldspar samples.

► New way of analyzing the TR-IRSL of feldspar is presented.
► Hopping time was deduced from the TR data using random walk model.
► Variable range hopping mechanism is responsible for IRSL.
► Mott's parameters for different feldspar samples were calculated.
► Feldspar samples - characterized with order-disorder parameter and structural state.