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Radiation induced processes in nitrides and other wide-gap materials (2003 - 2005)
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The project was devoted to the study of the radiation induced processes in nitrides (AlN and BN) and diamonds (natural and synthetic). Due to the mutually complementary experimental methods the study was carried out successfully. Our Laboratory of Wide Band materials had equipment and expertise in studies of photoluminescence (PL) and optically stimulated luminescence (OSL) at room and low temperatures, while French scientists had unique equipment for study of thermoluminescence (TL) and X-ray irradiation sources. Both sides contributed to the studies of luminescence processes of wide gap materials using their available technique.

Aluminum nitride AlN. TL and OSL studies of AlN ceramics helped to understand better the processes of energy transfer and storage as well as reasons of the main drawback in this material – TL or OSL signal fading during storage of the irradiated sample at room temperature. Besides, AlN nanostructures were used for mutual investigation. The PL, OSL and TL measurements of these samples fulfilled in Latvia and France and their comparison with those of bulk AlN samples allow speculations on effect of object dimensions on luminescence properties.

Boron nitride BN. The mutual efforts on studies of cubic boron nitride cBN ceramic allowed proposing a mechanism of recombination luminescence induced by irradiation in this material. Besides, hexagonal BN powder and cubic BN nanostructures (nanotubes) were studied. These studies have fundamental character, they show the influence of the object size on the luminescence properties and mechanism of energy transfer.

Diamond. Profound studies of the synthetic diamonds produced by chemical vapour deposition method (CVD diamond) were fulfilled by both sides, using the combined methods of PL, OSL and TL. Several directions of CVD diamond investigation could be mentioned: 1) studies of TL and OSL properties making the material suitable for application in dosimetry; 2) studies of the effect of ambient light conditions on the TL signal optical fading; 3) study of the luminescence mechanism and energy transfer processes in CVD and natural diamonds basing on the PL and OSL excitation spectra.

Dissemination of results. Experimental results obtained during implementation of this project were published in 6 papers and presented at 6 international scientific conferences.