2. Articole
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Item THE STRUCTURE OF HIGH-TEMPERATURE BLUE LUMINESCENCE CENTERS IN ZINC SELENIDE AND MECHANISMS OF THIS LUMINESCENCE(Springer Nature, 1998) Ivanova, G.N.; Kasiyan, V.A.; Nedeoglo, Dmitrii; Nedeoglo, Natalia; Simashkevich, A.V.The characteristic features of temperature quenching of the intensity of the edge luminescence bands of n-ZnSe crystals annealed in different media (vacuum, Zn, Se) are investigated a wide temperature range. A change in the mechanisms of high-temperature exciton luminescence in the short-wavelength region of the spectrum (443 nm) with increase in temperature of the crystal is observed. It is shown that the nature of temperature quenching of the long-wavelength edge luminescence band (458 nm) is evidence of dissociation of associative luminescence centers with increase in the sample temperature.Item INTERACTION OF INTRINSIC DEFECTS WITH IMPURITIES IN AL DOPED ZnSn SINGLE CRYSTALS(American Institute of Physics, 2007) Ivanova, G.N.; Nedeoglo, Dmitrii; Nedeoglo, Natalia; Sirkeli, VadimWe report on the results of a complex study of electrical (77−300 K) and luminescence (10−300 K) properties of 𝑛-ZnSe single crystals annealed in a Zn melt containing Al impurity at concentrations ranging from 0.1 to 80 at. %. It was established that Al atoms form donor centers only at a low impurity concentration (≤0.5 at. %). The increase of the amount of Al atoms in the crystal results in the formation of (VZnAlZn) associative acceptor centers leading to the self-compensation of the shallow Al donor impurity. This process is accompanied by the emergence and development of a self-activated luminescence band associated with the (VZnAlZn) acceptor centers. We show that further increase of the Al content in the melt (≥10 at. %) leads to the dissociation of the acceptor complexes and to a recurrent donor doping effect. The photoluminescence spectra of such crystals are dominated by activated luminescence via the (CuZnVSeCu𝑖) and (CuZnAlZn) associative centers.Item SHALLOW DONOR STATES INDUCED IN ZNSE:AU SINGLE CRYSTALS BY LATTICE DEFORMATION(American Institute of Physics, 2008) Nedeoglo, Natalia; Nedeoglo, Dmitrii; Laiho, R.; Sirkeli, Vadim; Lähderanta, E.Photoluminescence (PL) spectra are investigated in n-ZnSe single crystals at different temperatures from 4.4 to 300 K immediately after doping with Au from melt of Se+Au or Zn+Au and after storage of the doped samples for 4 years in the dark under normal room conditions. Due to the formation of Aui interstitial donors in the n-ZnSe:Se:Au crystals with time, the origin of the near band edge PL changes from acceptor-bound to donor-bound excitons. Taking into account the results of PL characterization, we proposed that the Aui donors are generated by displacement of Au ions from regular lattice sites to interstitial sites with the help of lattice deformation forces. Transport measurements show dramatic increase in the electrical conductivity and the free electron concentration after storage of the n-ZnSe:Zn:Au crystals, thus confirming the proposed model.Item SIMULATION ET MODELISATION DE LA VARIATION DE LA MOBILITE DE HALL DES PHOTOELECTRONS EN FONCTION DE LA TEMPERATURE DANS LES CRISTAUX DE n-ZnSe :Zn IRRADIES AVEC DES ELECTRONS ENERGETIQUES(Université Mentouri, 2007) Djouadi, D.; Boughiden, B.; Chelouche, A.; Nedeoglo, DmitriiDans l’intervalle de températures [77..300 K] a été mesurée la mobilité de Hall des électrons d’équilibre et des photoélectrons dans les cristaux de n-ZnSe :Zn irradiés avec un faisceau d’électrons d’énergie E=1,3 MeV et dont la dose d’irradiation varie entre 2,73 1016 et 5.19 1017 électrons/cm2 . Le comportement de la mobilité des photoélectrons s’explique parfaitement dans le cadre d’un modèle à deux-barrières d’un semiconducteur inhomogène représentant une matrice faiblement ohmique contenant des inclusions fortement ohmiques (clusters). En se basant sur les théories de Shik et de Petrossiyan , une expression approximative de la mobilité de Hall a été obtenue. Il a été montré que ce modèle fonctionne parfaitement pour les petites doses d’irradiation. Lorsque la dose dépasse une certaine valeur critique ( D= 2.98 1017 électrons /cm2) le modèle considéré passe au modèle du potentiel à relief aléatoire.Item GROWTH TECHNOLOGY FOR ZnSe SINGLE CRYSTALS WITH LOW DISLOCATION DENSITY(2008) Colibaba, Gleb; Nedeoglo, DmitriiThe influence of the growth temperature, undercooling, growth rate as well as growth chamber construction and furnace temperature profile on the structural perfection of the crystals grown by both physical and chemical vapors transport has been investigated. The conditions for growing of crystals free from subgrain boundaries and twins are suggested. The etch pits are not observed in the basic volume (up to 4 сm3) of grown crystals. It is shown, that PL spectra of as-grown ZnSe crystals consist of the edge radiation only. The resistivity of ZnSe crystals annealed in a Zn melt is higher than 108 Ohmcm, whereas the electrical conductivity of ZnSe:I crystals grown by chemical vapor transport and annealed in a Zn melt is 10 (Ohm⋅cm)-1 at room temperature.Item PHOTOLUMINESCENCE OF n-ZnSe SINGLE CRYSTALS DOPED WITH IODINE BY VAPOUR PHASE DIFFUSION(2006) Avdonin, A.N.; Nedeoglo, Dmitrii; Nedeoglo, Natalia; Sirkeli, Vadim; Ivanova, G.N.Photoluminescence spectra of n-ZnSe single crystals doped with iodine are investigated in the temperature range from 83 to 300 K. It is shown that the edge PL band is formed by overlapping of the PL lines attributed to ISe donor-bound ecxitons (I2I) and VZn acceptorbound excitons (D1I). A model of radiation mechanisms, which explain the redistribution of the edge and long-wave PL bands intensities with increasing doping level of the samples, is proposed.Item IMPURITY DISTRIBUTION IN n-ZnSe CRYSTALS DOPED WITH Au(2005) Nedeoglo, Dmitrii; Nedeoglo, Natalia; Sirkeli, VadimHall effect, electric conductivity and mobility of charge carriers in n-ZnSe single crystals doped with Au are investigated in the temperature range from 77 to 300 K. Impurity distribution in the crystals was studied by a method of “layer-by-layer” etching of a sample surface. The model, which explains this distribution by a simultaneous diffusion of Zn and Au atoms during a long-term high-temperature annealing of as-grown crystals in Zn + Au melt, is proposed.