Bulg. J. Phys. vol.46 no.1 (2019), pp. 037-048

Investigation of Size Dependent Thermoluminescence Emission from Amorphous Silicon Quantum Dots

B. Mesfin, T. Senbeta
Department of Physics, Addis Ababa University, Addis Ababa, Ethiopia
Abstract. We studied the size dependent thermoluminescence emission from small amorphous silicon quantum dots using the model of interactive multiple traps system (IMTS). The model consists of two active electron traps having activation energies E1 = 0.65 eV and E2 = 0.80 eV, a thermally disconnected deep trap (TDDT), and a luminescent center. For quantum dots of diameters between 3&\ndash;6 nm, numerical evaluations are carried out to generate the glow curve and determine relevant parameters such as the symmetry factor (μg) and the order of kinetics (b). It is observed that as the size of the quantum dots decrease, the intensity of the thermoluminescence signal increase, the glow peaks positions are almost independent of the size of dots, and the curves follow first-order kinetics (μg → 0.42 and b → 1). In addition, the glow curves possess two peaks corresponding to the two active electron trap levels with the intensity due to E2 being larger than that due to E1. Furthermore, numerical analysis of the same quantum dots using the two-traps-one-recombination center model (no TDDT traps) shows that, unlike that obtained using the IMTS model, the glow curves seems to obey second-order kinetics (μg → 0.52 and b → 2) and the peaks positions shift towards high temperature values with an increase in size of the dots. In addition, the numerical simulations enable us to determine how the concentration of carriers in the traps/center evolves as a function of temperature and quantum dots size.

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