Low-temperature luminescence and thermally stimulated luminescence of BeO: Mg single crystals

Luminescence and thermally stimulated luminescence (TL) of BeO: Mg crystals are studied at T = 6–380 K. The TL glow curves and the spectra of luminescence (1.2–6.5 eV), luminescence excitation, and reflection (3.7–20 eV) are obtained. It is found that the introduction of an isovalent magnesium impurity into BeO leads to the appearance of three new broad luminescence bands at 6.2–6.3, 4.3–4.4, and 1.9–2.6 eV. The first two are attributed to the radiative annihilation of a relaxed near-impurity (Mg) exciton, the excited state of which is formed as a result of energy transfer by free excitons. The impurity VUV and UV bands are compared with those for the intrinsic luminescence of BeO caused by the radiative annihilation of self-trapped excitons (STE) of two kinds: the band at 6.2–6.3 eV of BeO: Mg is compared with the band at 6.7 eV (STE₁) of BeO, and the band at 4.3–4.4 eV is compared with the band at 4.9 eV (STE²) of BeO. In the visible region, the luminescence spectrum is due to a superposition of intracenter transitions in an impurity complex including a magnesium ion. The manifestation of X-ray-induced luminescence bands at T = 6 K in BeO: Mg indicates their excitation during band-to-band transitions and in recombination processes. The energy characteristics of the impurity states in BeO: Mg are determined; the effect of the isovalent impurity on the fluctuation rearrangement of the BeO: Mg structure in the thermal transformation region of STE₁ → STE₂ is revealed.     

Scintillation properties of BeO single crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 2, pp. 286–291, August, 1988.     

Intrinsic luminescence in oriented BeO crystals under VUV and inner-shell excitation

Beryllium oxide (BeO) crystals were investigated by time-resolved low temperature VUV-spectroscopy at the SUPERLUMI station and BW3 beam line of HASYLAB (DESY, Hamburg). Photoluminescence spectra (3–10.5 eV), luminescence decay kinetics upon selective photoexcitation, as well as luminescence excitation (50–650 eV) and reflectivity (9–35 eV) spectra were measured and analyzed for oriented BeO crystals. It was shown that study of oriented crystals makes the traditional time-resolved spectroscopy method essentially more informative. Formation of the self-trapped exciton excited states of different multiplicity was found to sensitively depend on excitation energy and mutual orientation of the crystal's C optical axis and electric vector E of exciting polarized synchrotron radiation.     

Absorption and thermostimulated electron emission and luminescence of LiF crystals bombarded with alpha particles

The paper gives the results of measuring the absorption and thermostimulated electron emission and luminescence in the same kind of LiF crystals irradiated with X-rays and alpha particles. The different method of excitation has the consequence that the curves of the three phenomena are to a certain extent different. The possible causes of these differences are discussed.The author would like to thank K. Listoová and Z. Klímová for carefully performing the measurements.     

The effect of annealing on thermostimulated processes of coloured sodium chloride crystals

It is shown experimentally that after annealing samples of NaCl the thermoluminescence in the high-temperature maxima not only increases, which is in agreement with the results of other authors, but that simultaneously the thermoemission decreases. It follows from a discussion of the results that this effect is probably caused by the formation of a surface layer, which takes place during the evaporation of the sodium and both prevents the rise of the electrons from the crystal and the vacancies left in it by the sodium increase in the concentration of theV centres and thus the probability of luminescence.

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, NaCl - , , , , , - , , V- ( ).

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The authors thanks K. Listoová for carefully carrying out the measurements.     

Interactive process in the mechanism of thermostimulated luminescence in anion-defect α-Al2O3 crystals

A study of the role of deep traps in the specific features of the thermoluminescence (TL) of anion-defect α-Al₂O₃ single crystals is reported. The existence of deep traps is proven by direct observation of the associated TL peaks. Experimental support for the effect of deep-trap filling on the main characteristics of the main TL peak at 450 K is presented. A model involving trap interaction is proposed, which differs radically from the others described in the literature by taking into account the temperature dependence of the carrier capture probability by deep traps. This model was used to calculate the dependences on heating rate and deep-trap filling of the main parameters of the main TL peak for the crystals under study (TL yield, glow-curve shape, and sensitivity to the stored light sum), which were found to be close to those observed experimentally. Fiz. Tverd. Tela (St. Petersburg) 40, 229–234 (February 1998)     

Determination of trap parameters by simultaneous measurement of thermostimulated luminescence and thermostimulated conductivity

A method is proposed for processing of thermostimulated luminescence (TSL) curve in the presence of thermostimulated conductivity (TSC) in which no assumption is made as to the smallness of dn_c/dt (n_c is the conduction electron concentration). Results of the theory are applied to study of ZnSAg, Al and ZnSCu single crystals, in which elementary traps are revealed, and their activation energy and the value of the frequency factor determined. For ZnSCu the radiative transition recombination section is calculated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 94–101, June, 1977.     

Cathodoluminescence in ion-implanted BeO crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 218–224, August, 1989.     

Theory of thermostimulated currents in layered crystals

A mathematical model is proposed for layered crystals, based on a system of kinetic equations describing the change in charged relaxation oscillators with time. An analytical solution of this system is found and a theory constructed, which allows determination of the type and parameters of relaxation oscillators, as well as the properties of the crystals. A calculation of the thermostimulated depolarization current spectrum is confirmed by experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 68–72, January, 1991.     

Pulse measurements of thermostimulated currents in AgCl crystals

The course of thermostimulated currents in AgCl crystals was measured in a temperature region between 200 and 300K. Maxima at 240, 275 and 290K were observed on the curves obtained.