Photoinduced Schottky Barrier in Photorefractive Materials

LGEP 2010 ID = 604International audienc

Electron Paramagnetic Resonance Study of Ternary CuII Compounds with Glycine and Phenanthroline

We report electron paramagnetic resonance (EPR) measurements at 9 and 34 GHz, and room temperature (T), in powder and single crystal samples of the ternary compounds of copper nitrate or copper chloride with glycine and 1,10-phenanthroline [Cu(Gly)(phen)(H2O)]∙NO3∙1.5H2O (1) and [Cu(Gly)(phen)Cl]2∙7H2O (2). In compound 1 the copper ions are arranged in 1-D chains along one of the crystal axes connected by syn-anti carboxylate ligands, while in 2 the array is nearly 3-D and the connections involve H-bonds and stacking interactions. The angular variation of the squared g-factor and the line width were measured as a function of orientation of the magnetic field (B0) in three orthogonal crystal planes. In both compounds we observed one resonance without hyperfine structure for any magnetic field orientation which we attribute to the collapse of the hyperfine coupling and of the resonances of two chemically identical but rotated coppers in the unit cell, produced by exchange interactions. We analyze the results in terms of the structures of the compounds and of the chemical paths connecting neighbor copper ions which support the exchange interactions between neighbor spins in the lattice. Considering the collapse of the EPR signals of rotated sites in the lattices we are able to set lower  limits to the exchange interactions, which are supported by weak equatorial-apical carboxylate bridges in 1, and by paths containing hydrogen bonds and aromatic interactions in 2. Broadening due to dipole dipole couplings and hyperfine interactions are strongly reduced by these exchange couplings and their role in the EPR line width is more difficult to recognize.Fil: Santana, Ricardo C.. Universidade Federal de Goias; BrasilFil: Araújo, Anderson B. C.. Universidade Federal de Goias; BrasilFil: Carvalho, Jesiel F.. Universidade Federal de Goias; BrasilFil: Calvo, Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Física del Litoral; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Física; Argentin

Nonlinear light-induced absorption In Bi2OeO5 photorefractive crystals

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIGCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESWe report on the light-induced absorption in undoped photorefractive Bi2TeO5 (BTeO) crystal. The so-called "two-center" model is shown to adequately describe the present material behavior. We demonstrate that nonlinear light-induced absorption occurs for high light intensities. The theoretical model allowed us to find out some material parameters from experimental data. We also investigate the effect of intensity and wavelength on the light-induced absorption.We report on the light-induced absorption in undoped photorefractive Bi2TeO5 (BTeO) crystal. The so-called "two-center" model is shown to adequately describe the present material behavior. We demonstrate that nonlinear light-induced absorption occurs for high light intensities. The theoretical model allowed us to find out some material parameters from experimental data. We also investigate the effect of intensity and wavelength on the light-induced absorption.311126772680FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIGCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIGCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESSem informaçãoSem informaçãoSem informaçãoSem informaçãoFrejlich, J., (2006) Photorefractive Materials: Fundamental Concepts, Holographic Recording, and Materials Characterization, , Wiley-InterscienceFöldvári, I., Denz, C., Péter Á., Petter, J., Visinka, F., Bismuth tellurite - A new material for holographic memory (2000) Opt. Commun., 177, pp. 105-109Berger, G., Denz, C., Földvári, I., Peter Á., Non-volatile volume holograms in bismuth tellurite crystals (2003) J. Opt. A Pure Appl. Opt., 5, pp. S444-S447De Oliveira, I., Carvalho, J.F., Fabris, Z.V., Frejlich, J., Holographic recording and characterization of photorefractive Bi2TeO5 crystals at 633 nm wavelength light (2014) J. Appl. Phys., 115, p. 163514Holtmann, L., Buse, K., Kuper, G., Groll, A., Hesse, H., Krätzig, E., Photoconductivity and light-induced absorption in KNbO3:Fe (1991) Appl. Phys. A, 53, pp. 81-86Mosquera, L., De Oliveira, I., Frejlich, J., Hernandes, A.C., Lanfredi, S., Carvalho, J.F., Dark conductivity, photoconductivity and light-induced absorption in photorefractive sillenite crystals (2001) J. Appl. Phys., 90, pp. 2635-2641Marinova, V., Lin, S.H., Sainov, V., Gospodinov, M., Hsu, K.Y., Light-induced properties of Ru-doped Bi12TiO20 crystals (2003) J. Opt. A Pure Appl. Opt., 5, pp. S500-S506Herth, P., Granzow, T., Schaniel, D., Woike Th., Imlau, M., Kratzig, E., Evidence for light-induced hole polarons in LiNbO3 (2005) Phys. Rev. Lett., 95, p. 067404Marinova, V., Ahmad, I., Goovaerts, E., Photo-induced absorption study of carrier dynamics in Ru-doped Bi12SiO20 crystals after nanosecond laser pulse excitation (2010) J. Appl. Phys., 107, p. 113106Luedtke, F., Buse, K., Sturman, B., Hidden reservoir of photoactive electrons in LiNbO3 crystals (2012) Phys. Rev. Lett., 109, p. 026603Evans, D.R., Shuymelyuk, A., Cook, G., Odoulov, S., Secondary photorefractive centers in Sn2P2S6:Sb crystals (2011) Opt. Lett., 36, pp. 454-456Buse, K., Light-induced charge transport processes in photorefractive crystals I: Models and experimental methods (1997) Appl. Phys. B, 64, pp. 273-291Brost, G.A., Motes, R.A., Rotgé, J.R., Intensity-dependent absorption and photorefractive effects in barium titanate (1988) J. Opt. Soc. Am. B, 5, pp. 1879-1885Kwak, C.H., Park, S.Y., Lee, E.-H., Intensity-dependent two-wave mixing at large modulation depth in photorefractive BaTiO3 crystal (1995) Opt. Commun., 115, pp. 315-322Shumelyuk, A., Wesner, M., Imlau, M., Odoulov, S., Wave mixing in nominally undoped Sn2P2S6 at high light intensities (2009) Appl. Phys. B, 95, pp. 497-503De Oliveira, I., Frejlich, J., Light intensity-dependent Debye screening length in undoped photorefractive titanosillenite crystals (2012) J. Appl. Phys., 112, p. 113523De Oliveira, I., Carvalho, J.F., Frejlich, J., Resonance running hologram velocity nonlinearity dependence upon light intensity in photorefractive crystals (2013) Appl. Phys. Lett., 102, p. 251913Carvalho, J.F., Fabris, Z.V., De Oliveira, I., Frejlich, J., Crystal growth of Bi2TeO5 by a double crucible Czochralski method (2014) J. Cryst. Growth, 401, pp. 795-797We acknowledge the financial support from Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Fundacao de Amparo a Pesquisa do Estado de Goias (FAPEG), Conselho Nacional de Desenvolvimento Cientfico e Tecnologico (CNPq), Coordenacao de Aperfeicoamento de Pessoal de Ensino Superior (CAPES), and Fundo de Apoio ao Ensino, Pesquisa e Extensao da Universidade Estadual de Campinas (FAEPEX)

Electrical and photoelectrical properties of Bi2TeO5 single crystals

We report on optical and electrical measurements contributing for a better characterization of the relevant properties of undoped Bi2TeO5. Optical absorption, dark conductivity, photoconductivity and photovoltaic effect measurements were carried out for different crystallographic directions at room temperature. The position of photoactive centers in the Band Gap were determined and the optical Bandgap was calculated. The components of dark conductivity tensor were determined94398402CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE GOIÁS - FAPEGFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão temnão temnão temnão te

Photoconductivity and photoconversion at a photorefractive thin crystal plate

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPEG - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE GOIÁSWe report on the photoconductivity and the photoelectric conversion measured on a thin photorefractive sillenite crystal plate, between transparent electrodes, in the longitudinal configuration where the current is measured along the same direction of the light beam through the sample. Its behavior is based on the already reported light-induced Schottky effect. The wavelength for optimal photoconductivity is determined. A specific parameter is formulated here for quantitatively determining the photoelectric conversion efficiency of the sandwiched material. (C) 2016 Elsevier B.V. All rights reserved.We report on the photoconductivity and the photoelectric conversion measured on a thin photorefractive sillenite crystal plate, between transparent electrodes, in the longitudinal configuration where the current is measured along the same direction of the light beam through the sample. Its behavior is based on the already reported light-induced Schottky effect. The wavelength for optimal photoconductivity is determined. A specific parameter is formulated here for quantitatively determining the photoelectric conversion efficiency of the sandwiched material.55160163CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPEG - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE GOIÁSCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPEG - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE GOIÁSSem informaçãoSem informaçãoSem informaçãoSem informaçãoWe acknowledge partial financial support from the Conselho de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Fundo de Apoio ao Ensino, Pesquisa e Extensão (FAEPEX/UNICAMP), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG) all from Brazil

Phenomenological characterization of photoactive centers in Bi12TiO20 crystals

We report optical and electrical measurements contributing for a better characterization of the relevant photoactive center levels in undoped photorefractive Bi12TiO20 (BTO) crystals grown in Brazil..