Effect of Retrapping on Thermoluminescence Peak Intensities of Small Amorphous Silicon Quantum Dots
N.G. Debeloa,b, F.B. Dejene a, V.N. Mal'nev b, T. Senbeta b, B. Mesfin b and K. Roro c
aPrivate Bag X13, Department of Physics, University of the Free State, QWA-QWA Campus, South Africa
bDepartment of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia
cR&D Core (Energy Initiatives), Council for Scientific and Industrial Research, P.O. Box 395, Pretoria, South Africa
Received: October 24, 2015; In final form: February 22, 2016
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The effect of retrapping on thermoluminescence intensity peak corresponding to each trap of small amorphous silicon quantum dots in three traps - one recombination center model is investigated. For first order kinetics, where there is no effect of retrapping, the thermoluminescence intensity clearly depends on the level of the trap beneath the edge of the conduction band. This energy difference between the edge of the conduction band and the level of the trap is called trap depth (activation energy). The shallowest trap gives the highest thermoluminescence intensity peak for first order kinetics. However, it was clearly observed that for second order and a case beyond second order kinetics, the thermoluminescence intensity peak corresponding to each trap does not depend on the trap depth. In this case, the retrapping probability coefficients are taken into account and most electrons which are detrapped from the shallow trap(s) will be retrapped to the deeper trap(s) resulting in fewer electrons taking part in the recombination process. This significantly reduces the thermoluminescence intensity peaks of the shallower trap(s). It was observed that the deepest trap, with very high concentration of electrons due to the retrapping phenomenon, gives the highest thermoluminescence intensity. In addition, the variation of concentration of electrons in each trap and the intensity of the thermoluminescence are presented. Though we considered the model of three traps and one recombination center, this phenomenon is true for any multiple traps.

DOI: 10.12693/APhysPolA.129.362
PACS numbers: 73.21.La, 73.63.Kv