Thermally stimulated luminescence

Typically, nonisothermal relaxation is effectively employed in the studies of thermally stimulated luminescence (TSL), condnctivity (TSC), polarization, and depolarization. 

As it is known, I centres are the most mobile radiation-induced radiation defects in alkali halides and therefore they play an essential role in low-temperature defect annealing. It is known, in particular, from thermally-stimulated conductivity and thermally-stimulated luminescence measurements, that these centres recombine with the F and F electron centres which results in an electron release from anion vacancy. This electron participates in a number of secondary reactions, e.g., in recombination with hole (H, Vk) centres. Results of the calculations of the correlated annealing of the close pairs of I, F centres are presented in Fig. 3.11. The conclusion could be drawn that even simultaneous annealing of three kinds of pairs (Inn, 2nn and 3nn in equal concentrations) results in the step-structure of concentration decay in complete agreement with the experimental data [82]. 

The nature of the participating defects in EE from LiF has been studied by thermally stimulated luminescence (TSL) ( ). TSL peaks from LiF samples pulverized in a mortar and pestle are quite similar to the peaks from LiF irradiated with UV light, suggesting that the same defects participate in both emissions. TSL studies of MgO powders suggest that above room temperature the rate controlling process involves electron traps. phE and EE decay from MgO follow very similar kinetics, as seen in Figure 1, suggesting that phE and EE are rate limited by the concentration of the same defect. 

The calculated curves in Fig. 3.19 were obtained using a traps depth of 0.25 eV below the conduction band. (The low-current discrepancies between the model and experiment are either due to some field-effect component of the mobility or else to a non-negligible energy barrier for electron in ection.) This value is consistent with independently measured trap levels determined by thermally stimulated luminescence experiments.84 It is also corresponds well with the difference in reduction potential of Hq and Alq3, about 0.2 eV, as suggested in Figs. 3.7 and 3.8. 

The stoted energy can be released by thermal or optical stimulation. In the case of thermal stimulation the irradiated phosphor is heated to a temperature at which the energy barrier AE can be overcome thermally. The trapped electron (or hole) can escape irom the trap and recombine with the trapped hole (or electron). In the case of radiative recombination, luminescence is observed which is called thermally stimulated luminescence (TSL) (compare Sect. 3.5). Under optical stimulation the energy of an incident photon is used to overcome AE. The luminescence due to optical stimulation is called photostimulated lumine.scence (PSL). The phenomenon of stimulated luminescence from storage phosphors has been known since 1663 (Boyle). Storage phosphors have found a wide range of applications, e.g. as infrared detectors and in the field of dosimetry [3J. 

Manam J. and Das S. 2009. Determination of kinetic parameters of thermally stimulated luminescence of Cu... 

McKeever S. W. S. 1985. Thermoluminescence of Solids. Cambridge, U.K. Cambridge University Press, p. 75. McKeever S. W. S., Markey. B.G. and Lewandowski, A. C. 1993. Fundamental processes in the produchon of thermally stimulated luminescence. Nuclear Trackes and Radiation Measurements, 21(1) 57-64. Nakajima T, Murayama Y, Matazawa T. and Koyano A. 1978. Development of a new highly sensitive LiF thermoluminescent dosimeter and its applications, Nucl. Instrum. Methods 157 155—162. 

Somaiah K, Narayana MV, Brixnta- LH (1990) Thermally stimulated luminescence of LaOBnTm. Physica Stams Solidi A AppI Res 117 K81-K84... 

Other classes of luminescence have been used in analytical applications some examples are provided in Table 2. Thermally stimulated luminescence (or thermoluminescence) is the emission arising during... 

Insulatois and semiconductois exposed at a temperature To to ionizing radiation or light will often emit characteristic hght when warmed up above To- This effect is conventionally caUed thermoluminescence (TL). Some investigators prefer to call it thermally stimulated luminescence (TSL), which stresses the fact that the thermal energy supplied during warming only stimulates the emission potentially excited by the irradiation. 

The characteristic glow curve of DQ12 annealed in air at 520 K for 24 h after X-raying (30 kV, 45 mA, 1 min) at 133 K as depicted by Kriegseis et al. (1977) is comparable to thermally stimulated luminescence curves which have been obtained by other authors from natural crystalline and amorphous SiO samples as well as synthetic quartz single crystals (Medlin 1963, Schlesinger 1965, Halperin et al. 1979, Mattern 1973). 

Robock and KlosterkStter (1973) and Robock (1974) have shown that thermally stimulated luminescence of Si02 materials is extremely sensitive to surface treatment. The effect of heat treatment at 850 K on the thermally stimulated liuninescence was dependent on the gas atmosphere (air, N2, O2). 

Kovalev D, Heckler H, Averboukh B, Ben-Chorin M, Schwartzkopff M, Koch F (1998) Hole burning spectroscopy of porous silicon. Phys Rev B 57(7) 3741-3744 McKeever SWS (1984) Thermoluminescence in quartz and silica. Radiat Prot Dosim 8(l/2) 81-98 Moscovitch M, Horowitz YS (2007) Thermoluminescent materials for medical applications LiF Mg, Ti and LiFiMg, Cu, P. Radiat Meas 41 S71-S77 Pincik E, Bartos P, Jergel M, Falcony C, Bartos J, Kucera M, Kakos J (1999) The metastability of porous silicon/crystalline silicon structure. Thin Solid Films 343-344 277-280 Rivera T (2011) Synthesis and thermoluminescent characterization of ceramics materials. In Sikalidis C (ed) Advances in ceramics - synthesis and characterization, processing and specific applications. InTech, Rijeka, Croatia pp 127-164 Skryshevskii YA, Skryshevskii VA (2001) Thermally stimulated luminescence in porous silicon. J Appl Phys 89(5) 2711-2714... 

If we examine more carefully single bursts of phE, we find that in fact smaller afterbursts accompany many of the larger bursts over time scales of microsecondsThus, the signal averaging used to acquire the initial time distribution (Figure 20) forms a smooth decay curve which is really determined by the frequency and size of these multiple phE bursts, rather than any solid state or surface relaxation process, typical of thermally stimulated luminescence... 

TSL is observable in most dielectrics in polymers the sample is commonly irradiated at liquid nitrogen temperature and heated to room temperature at a rate of approximately 3" C/min. TSL emission in many commercial polymers is negligible above room temperature and the information, which can be extracted from a single TSL measurement on the molecular environment of the trapped electrons, is not as precise as from ESR. The TSL spectrum of a polymer may contain both fluorescent and phosphorescent components. TSL provides information about ageing processes and can be used as a method for early recognition of damage in polymers. Fleming [488] has reviewed thermally stimulated luminescence (TSL) for the analysis of polymers. 

Thermal surface ionisation Thermally stimulated luminescence... 

At higher trap concentration, however, the activation energy for the conductivity decreases. The traps themselves can serve as an effective hopping transport band. So the effect of traps on the charge conductivity is qualitatively similar to that caused by a high carrier concentration. It is interesting that such transition has also been observed in thermally stimulated luminescence measurements [29],... 

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