http://dspace.nbuv.gov.ua:80/handle/123456789/115093 Mon, 06 Apr 2026 02:39:39 GMT 2026-04-06T02:39:39Z http://dspace.nbuv.gov.ua:80/bitstream/id/342399/ http://dspace.nbuv.gov.ua:80/handle/123456789/115093 http://dspace.nbuv.gov.ua:80/handle/123456789/119102 Low Temperature Spectroscopy and Radiation Effects. To the anniversary of E.V. Savchenko Arakawa, I.; Räsänen, M. Sun, 01 Jan 2012 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/119102 2012-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/117436 Impurity and vacancy effects in graphene Loktev, V.M.; Pogorelov, Yu.G. A Green function analysis has been developed for quasiparticle spectrum of a 2D graphene sheet in presence of different types of substitutional disorder, including vacancies. The anomalous character of impurity effects in this system is demonstrated, compared to those in well known doped semiconductors, and explained in terms of conical singularities in the band spectrum of pure graphene. The criteria for appearance of localized states on clusters of impurity scatterers and for qualitative restructuring of band spectrum are established and a possibility for a specific metal/insulator transition at presence of vacancies is indicated. Sun, 01 Jan 2012 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/117436 2012-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/117435 Phase transitions in thermally annealed films of Alq₃ Baldacchini, G.; Chiacchiaretta, P.; Pode, R.B.; Vincenti, M.A.; Wang, Q.-M. Organic light emitting devices have been so very much improved lately that they are being widely applied for displays and lighting. Among many improving technologies, annealing processes in different atmospheres affect greatly their performance, for instance when the active material is the small molecule Alq3. In particular, a significant increase of the photoluminescence is observed in thin films of this molecule between 150 and 180 °C, before the physical destruction of the films occurs at higher temperatures. This phenomenon is attributed to a phase transition towards a novel morphological aggregation of the molecules in the film, which proved to be a much improved optical material for luminescent applications, and which seems common to other molecules as well. Sun, 01 Jan 2012 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/117435 2012-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/117434 Optical spectroscopy and microscopy of radiationinduced light-emitting point defects in lithium fluoride crystals and films Montereali, R.M.; Bonfigli, F.; Menchini, F.; Vincenti, M.A. Broad-band light-emitting radiation-induced F₂ and F₃⁺ electronic point defects, stable and laser-active at room temperature in lithium fluoride crystals and films, find applications in dosimeters, tuneable color-center lasers, broad-band miniaturized light sources and in novel radiation imaging detectors. A brief review of their photoemission properties is presented, and their peculiarities at liquid nitrogen temperature are discussed. A few experimental results about optical spectroscopy and fluorescence microscopy of these radiation-induced point defects in LiF crystals and thin films are presented to obtain information about the coloration curves, the point defects formation efficiency, the effects of the photo-bleaching processes, and so on. The control of local formation, stabilization and transformation of radiation-induced light-emitting defect centers is crucial for the development of optical active micro-components and nanostructures. Some of the advantages of low temperature measurements for novel confocal laser scanning fluorescence microscopy techniques, widely used for the spatial mapping of these point defects thorough the optical reading of their visible photoluminescence, are highlighted. Sun, 01 Jan 2012 00:00:00 GMT http://dspace.nbuv.gov.ua:80/handle/123456789/117434 2012-01-01T00:00:00Z