20 Conference on Electron Devices and Materiais

THE THERMOLUMINESCENCE

DOSYMETRIC CRYSTALS OF c~-Al,0, LASER-IRRADIATED

A.N. Shwaizer * , S.V. Smirnov **

* Tomsk Polytechnic University 30 Lenin Avenue, Tomsk, 634034, Russia E-mail: shwaizer@mail.ru ** Tomsk State University of Control Systems and Radioelectronics TUCSR, 40 Lenln Avenue, Tomsk, 643050, Russia

The anion-defective crystals a-.Al,O, are perspectivenes of materials for creation of ionizing and nonionizing radiation detectors. Researches have showed that the creation in a corundum lattice of Ngh concentration of oxygen vacancies (F-centers) for giving to this material of necessary

view the most effective n is processing of crystals

We investigate that processing by YAG iaser radiating with density of power in focus center 107-108 Wt/cm2 and velocity of surface scanning at 5-10 cm/sec results to breaking layer surface to oxygen shortage [2, 3, 51. Herewith the loosen and amorphousation surface layer with changing of its coloration is occurred. Earlier it is show 121 that y - part of AI3+ ions transfers from octahedral in tetrahedral oxygen clasters. On results of the radiograph analysis 133 is following that in processable layer the new phase - y-a-A1203 is presented. From the literature it is also known that melting material consists of mixtures a n crystallites 85 % weight a-A120, and 15% weight y-a-A1203 [4], moreover 1/3 parts of A13+ ions in the structure y-a-A1203 has coordination number about 4.

The change of coordination number of Ai3+ ions is connected wil h oxygen ejection from the a-A1203 structure. It is confirmed by the study of the corundum cathodeluminescence [ 5 ] . After processing hy laser radiating the cathodeluminescence intensity of pr0cessir.g samples is considerably increased (fig. 1). Simultaneously the displacement of spectrum maximum in the long wave domain (fig. 1 ) is observed. At first, it shows the occurrence of the F-centers (distinctive band 3,8 ev) in processing high density material, at secondly - on disordering

0-7803-7274-3/02/$10.00 0 2002 IEEE

Conference on Electron Devices and Materials 21

and loosing of structure. Conducted comparative evaluation of spectrum curves (see fig. I ) shows the increase in processed corundum the concentrations of defects as F-centers by an order of magnitude.

d

I50 m

2 100 E

50

0 5 4 3 2

h v , eV

Fig. 1

For deeper studying of defect crystals a-A1203, processed by laser radiation, the study of this material by the curve thermoflashing method

' is the problem of interest. The results of thermostimulate luminescence (TSL) measurements in the temperatures from 20 up to 350°C has been received by us. Samples previously are keeped by ultraviolet light of xenon lamp at the temperature of liquid nitrogen. TSL spectrums removed by usual method with the photomultiplier FEU39A. The velocity of samples heating was 0.3 deg./s. It is tuned out that a-A1203 samples, processed by laser radiation flashes more significant light sum compare non exposition samples (fig. 2 ) . Herewith on the TSL curve of the processing corundum the temperature maximums are more clearly revealed. The calculation carried out at the method, offered in [6], gives the following values of activation energy in eV: 0,67; 0,79; 0,94, and 1,19.

The collection of received results, testifies indicative of occurrence in the investiption material of high concentrations of defects, in particular, F-centers, and reorganization of a-A1203 structure, processed by the laser radiation. The use the thermpluminescence method complements an information on phosphorescence centers, enables to define their activation energy.

22 Conference on Electron Devices and Materials

0,150 - 0,140 -

.i 0,120 - e! E 0 0,110 - iii 2 il;. 0,100 - F

0,090 -

0 . 0 5 o i : : : ; ; ; ; I . 250 300 350 400 450 500 550 600 650

Fig.2

Thus, the results of the paper show the perspectiveness of laser activation for giving the necessary dosimeter properties for corundum, with the purpose of use it as a material of ionizing radiation detectors.

REFERENCES

1. V.S. Kohov, 1.1. Milman, In News of High Schools. Physics, no.

2. A.N. Shwaizer, N.I. Radishevskaya. In Radioelectronics and Information Systems and Devices: Proceedings. Tomsk, 2000. Vol. 1 !

3. A.N. Shwaizer, S.V. Smirnov, "Radiation-thermal effects and1 processes in inorganic materials". Proceedings. Tomsk, 2000. Pp. 21 3- 215.

4. V.M. Raetski, S.A. Kutolin, "Impact of coherent radiation on the: physics-chemical properties of inorganic substances". In Reviews ori

11, 1996, pp. 145-161.

pp. 64-65.

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the Electronic Technique. Microelectronics. Vol. 1 1(161), 1973, 46 p.

5. A.N. Shwaizer, A.G. Kharchenko. In V International Conference APIE. Proceedings. Novosibirjk, 2000. Vol. 2, pp. 124-125.

6 . V.N. Vertoprakhov, E.G. Salman. "Thermostimulate currents in inorganic substances". Novosibirsk, "Science", 1979. 336 p.