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Photoluminescence of MEH-PPV with ultraviolet excitation

FALEIROS, Marcelo M.; MIRANDA, Paulo Barbeitas
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
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The basic optical properties of PPV-based polymers have been extensively studied due to their potential technological applications. However, a detailed investigation of electronic processes following photoexcitation in the ultraviolet is still lacking. We report photoluminescence measurements on poly(1-methoxy-4-ethylhexyloxy-paraphenylenevinylene) - MEH-PPV in the 2.0-5.6 eV range, with excitation up to 5.6 eV. The photoluminescence spectra lineshape is independent of excitation energy. The photoluminescence efficiency is high for energies well below the absorption maximum due to near-resonant excitation of the longest conjugated segments which are responsible for the PL It decreases strongly for excitation energies in the range 2.1-2.5 eV (up to the absorption maximum) and slightly from 2.5 to 5.6 eV. The results indicate that states excited in the ultraviolet rapidly relax nonradiatively to the lowest state, from where the usual luminescence occurs. (C) 2010 Elsevier B.V. All rights reserved.

Photoluminescence in silicon/silicon oxide films produced by the Pulsed Electron Beam Ablation technique

Araya, M.; Diaz-Droguett, D. E.; Ribeiro, M.; Albertin, K. F.; Avila, J.; Fuenzalida, V. M.; Espinoza, R.; Criado, D.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
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In this work we report studies of the photoluminescence emission in samples based on Si/SiOx films deposited by the Pulsed Electron Beam Ablation (PEBA) technique. The samples were prepared at room temperature using targets with different Si/SiO2 concentrations. The samples were characterized using X-ray Absorption Edge Spectroscopy (XANES) at the Si-K edge, Raman spectroscopy, Photoluminescence (PL) and X-ray Photoelectron Spectroscopy (XPS). The concentration of a-Si and nc-Si in the film was dependent on the silicon concentration in the target. It was also observed that the PL is strongly dependent on the structural amorphous/crystalline arrangement. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.; Chilean agency CONICYT [11085026]; Chilean agency CONICYT

"Fotoluminescência excitada no ultravioleta em polímeros conjugados"; Photoluminescence excited in the ultraviolet in conjugated polymers

Faleiros, Marcelo Meira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/02/2007 PT
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Os polímeros conjugados luminescentes são materiais com grande potencial tecnológico, mas apesar de estudados desde a década de 80, algumas de suas propriedades óticas ainda não foram totalmente entendidas. Por exemplo, ainda persistem dúvidas quanto à natureza das suas excitações primárias. Nesse sentido foi feito um estudo da fotoluminescência do poli[2-metoxy-5-(2-etil-hexiloxi)-1,4-fenileno vinileno] (MEH-PPV), polímero semicondutor luminescente cujas propriedades ópticas já foram muito investigadas. Além da banda de absorção principal na região visível do espectro, ele possui três bandas no ultravioleta. O objetivo deste trabalho é investigar a fotoluminescência do MEH-PPV quando excitado na região do ultravioleta. Após fotoexcitação no ultravioleta, observou-se apenas a fotoluminescência usual no visível. A intensidade da emissão depende fortemente da energia de excitação, da temperatura e da estrutura morfológica do sistema polimérico, determinada pelo método de preparação das amostras. Os resultados indicam que os estados excitados no ultravioleta relaxam rapidamente de forma não-radiativa até os estados de menor energia, de onde então ocorre a luminescência. Entretanto, a eficiência da fotoluminescência excitada no ultravioleta é consideravelmente reduzida...

Filmes sensíveis a pressão pela técnica de fotoluminescência.; Pressure sensitive films based on photoluminescence technique.

Matos, Keth Rousbergue Maciel de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/05/2011 PT
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O presente projeto tem como objetivo contribuir para o desenvolvimento de dispositivos para monitoração de pressão dinâmica do ar. Para isso, foram produzidos filmes sensíveis a pressão baseados na detecção de concentração de oxigênio por meio de processos de emissão fotoluminescente das moléculas de Azul de Metileno (MB) e Platina Octaetilporfirina (PtOEP). Nesse sentido, foi estudado o comportamento da emissão fotoluminescente dessas moléculas em interação com o gás de oxigênio. A concentração de oxigênio (do ar) sobre superfície sensível depende da pressão dinâmica de superfície. Desta forma, monitorando a fotoluminescência dos dispositivos submetidos a diferentes concentrações de oxigênio, pode-se determinar uma relação entre a pressão pontual da superfície analisada e a intensidade de emissão fotoluminescente do filme. Os dispositivos de monitoração de pressão dinâmica são constituídos de um filme de estado sólido contendo as moléculas sensíveis. Foram utilizados como substratos hospedeiros para o Azul de Metileno e para a Octaetilporfirina de Platina, os filmes de silício poroso oxidado e Poliestireno, respectivamente. É proposto um arranjo experimental que utiliza um fluorímetro para caracterizar as amostras produzidas e uma câmara de fluxo de gases. Os dispositivos apresentaram elevada sensibilidade e evidenciaram o potencial para desenvolvimento e integração de sensores baseados no silício poroso à microeletrônica.; This project aims to contribute to the development of devices for monitoring dynamic pressure of the air. In this sense...

Photoluminescence properties of PZT 52/48 synthesized by microwave hydrothermal method using PVA with template

Teixeira, G. F.; Gasparotto, G.; Paris, E. C.; Zaghete, M. A.; Longo, Elson; Varela, José Arana
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 46-50
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Lead Titanate Zirconate (PZT) perovskite powders were synthesized by microwave hydrothermal method (M-H) at 180 degrees C for different time periods (2, 4, 8 and 12 h) with the presence of aqueous polyvinyl alcohol (PVA) solution 0.36 g L-1. The X-Ray diffraction (XRD), SE-FEG as well as the measurements of photoluminescence (PL) emission were used for monitoring the formation of a perovskite phase with random polycrystalline distortion in the structure. Emission spectra with fixed excitation wavelength of 350 nm showed higher value for the powder obtained after undergoing 8 h of treatment. A theoretical model derived from previous calculations allows us to discuss the origin of photoluminescence emission in the powders, which can be further related to the local disorder in the network of both ZrO6 and TiO6 octahedral, and dodecahedral PbO12. The new morphology initially observed from the PZT perovskite crystal growth bearing the shape of fine plates is found to be directly related to photoluminescence emission with energy lower than that present in the PZT with cube-like morphology that emits in 560 nm. (C) 2011 Elsevier B.V. All rights reserved.

The role of structural order-disorder for visible intense photoluminescence in the BaZr0.5Ti0.5O3 thin films

Anicete-Santos, M.; Cavalcante, L. S.; Orhan, E.; Paris, E. C.; Simoes, LGP; Joya, M. R.; Rosa, ILV; de Lucena, P. R.; Santos, MRMC; Santos-Junior, L. S.; Pizani, P. S.; Leite, E. R.; Varela, José Arana; Longo, Elson
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 260-266
ENG
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The nature of the intense visible room temperature photoluminescence of BaZr0.5Ti0.5O3 non-crystalline thin films is discussed in the light of experimental results and theoretical calculations. The photoluminescence measurements reveal that the emission intensity changes with the degree of disorder in the BaZr0.5Ti0.5O3 lattice. First principles quantum mechanical techniques, based on density functional theory at B3LYP level, have been employed to study the electronic structure of a crystalline model and of structurally disordered models in order to detect the influence of disorder on the electronic structure. An analysis of the electronic charge distribution reveals local polarization in the disordered structures. The relevance of the present theoretical and experimental results on the photoluminescence behavior of BZT is discussed. (C) 2005 Elsevier B.V. All rights reserved.

Photoluminescence at room temperature in amorphous SrTiO3 thin films obtained by chemical solution deposition

Pontes, F. M.; Longo, Elson; Leite, E. R.; Lee, EJH; Varela, José Arana; Pizani, P. S.; Campos, CEM; Lanciotti, F.; Mastelaro, V; Pinheiro, C. D.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 598-602
ENG
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Intense photoluminescence in highly disordered strontium titanate amorphous thin films prepared by the polymeric precursor method was observed at room temperature (300 K). The luminescence spectra of SrTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region. X-ray absorption near edge structure was used to probe the local atomic structure of SrTiO3 amorphous and crystalline thin films. Photoluminescence intensity in the 535 nm range was found to be correlated with the presence of non-bridging oxygen defects. A discussion is presented of the nature of this photoluminescence, which may be related to the disordered structure in SrTiO3 amorphous thin films. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Conditions giving rise to intense visible room temperature photoluminescence in SrWO4 thin films: the role of disorder

Orhan, E.; Anicete-Santos, M.; Maurera, MAMA; Pontes, F. M.; Paiva-Santos, C. O.; Souza, A. G.; Varela, José Arana; Pizani, P. S.; Longo, Elson
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 1-9
ENG
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The nature of intense visible photoluminescence at room temperature of SrWO4 (SWO) non-crystalline thin films is discussed in the light of experimental results and theoretical calculations. The SWO thin films were synthesized by the polymeric precursors method. Their structural properties have been obtained by X-ray diffraction data and the corresponding photoluminescence (PL) spectra have been measured. The UV-vis optical spectra measurements suggest the creation of localized states in the disordered structure. The photoluminescence measurements reveal that the PL changes with the degree of disorder in the SWO thin film. To understand the origin of visible PL at room temperature in disordered SWO, we performed quantum-mechanical calculations on crystalline and disordered SWO periodic models. Their electronic structures are analyzed in terms of DOS, hand dispersion and charge densities. We used DFT method with the hybrid non-local B3LYP approximation. The polarization induced by the symmetry break and the existence of localized levels favors the creation of trapped holes and electrons, giving origin to the room temperature photoluminescence phenomenon in the SWO thin films. (c) 2004 Elsevier B.V. All rights reserved.

CdMoO 4 synthesized by a microwave-assisted hydrothermal method and their photoluminescence and photocatality properties

De Moura, Ana P.; Oliveira, Larissa H.; Xavier, Camila S.; Rosa, I. L V; Li, Máximo Siu; Longo, Elson; Varela, José Arana
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 429-432
ENG
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In this work CdMoO 4 nanoparticles were obtained under hydrothermal conditions using microwave radiation (2.45 GHz) (MH) at 100°C for different times. These powders were analyzed by X-ray diffraction (XRD), Field-emisson gum scanning electron microscopy (FEG-SEM), Ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD pattern confirmed that the pure CdMoO 4 phases were obtained. FEG-SEM powders present large-scale and homogeneous particles with microspheres-like morphology. UV-vis results were employed to determine the optical band gap these materials. Also, it showed existence of photoluminescence (PL) emission in the green wavelength range of 540-546 nm. Photocatalytic activity of CdMoO 4 nanocrystals was examined by monitoring the degradation of rhodamine B dye.

Preparation and photoluminescence characteristics of In(OH) 3:xTb3+ obtained by Microwave-Assisted Hydrothermal method

Motta, F. V.; Marques, A. P A; Li, M. S.; Abreu, M. F C; Paskocimas, C. A.; Bomio, M. R D; Souza, R. P.; Varela, José Arana; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 338-342
ENG
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Crystalline terbium-doped indium hydroxide structures were prepared by a rapid and efficient Microwave-Assisted Hydrothermal (MAH) method. Nanostructures were obtained at a low temperature. FE-SEM images confirm that these samples are composed of 3D nanostructures. XRD, optical diffuse reflectance and photoluminescence (PL) measurements were used to characterize the products. Emission spectra of terbium-doped indium hydroxide (In(OH)3:xTb 3+) samples under excitation (350.7 nm) presented broad band emission referent to the indium hydroxide matrix and 5D4 → 7F6, 5D4 → 7F 5, 5D4 → 7F4, and 5D4 → 7F3 terbium transitions at 495, 550, 590 and 627 nm, respectively. Relative intensities of the Tb 3+ emissions increased as the concentration of this ion increased from 0, 1, 2, 4 and 8 mol%, of Tb3+, but the luminescence is drastically quenched for the In(OH)3 matrix. © 2012 Elsevier B.V. All rights reserved.

Intense photoluminescence emission at room temperature in calcium copper titanate powders

Moura, F.; Simões, A. Z.; Deus, R. C.; Silva, M. R.; Varela, José Arana; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 3499-3506
ENG
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A study was undertaken about the structural and photoluminescent properties at room temperature of CaCu3Ti4O12 (CCTO) powders synthesized by a soft chemical method and heat treated between 300 and 800 °C. The decomposition of precursor powder was followed by thermogravimetric analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements. XRD analyses revealed that the powders annealed at 800 °C are becoming ordered and crystallize in the cubic structure. The most intense PL emission was obtained for the sample calcined at 700 °C, which is not highly disordered (300-500 °C) and neither completely ordered (800 °C). From the spectrum it is clearly visible that the lowest wavelength peak is placed around 480 nm and the highest wavelength peak at about 590 nm. The UV/vis absorption spectroscopy measurements showed the presence of intermediate energy levels in the band gap of structurally disordered powders. © 2012 Elsevier Ltd and Techna Group S.r.l.

Local electronic structure, optical bandgap and photoluminescence (PL) properties of Ba(Zr0.75Ti0.25)O3 powders

Cavalcante, L. S.; Batista, N. C.; Badapanda, T.; Costa, M. G S; Li, M. S.; Avansi, W.; Mastelaro, V. R.; Longo, Elson; Espinosa, J. W M; Gurgel, M. F C
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1035-1045
ENG
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Ba(Zr0.75Ti0.25)O3 (BZT-75/25) powders were synthesized by the polymeric precursor method. Samples were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) techniques. Their electronic structures were evaluated by first-principle quantum mechanical calculations based on density functional theory at the B3LYP level. Their optical properties were investigated by ultraviolet-visible (UV-Vis) spectroscopy and photoluminescence (PL) measurements at room temperature. XRD patterns and Rietveld refinement data indicate that the samples have a cubic structure. XANES spectra confirm the presence of pyramidal [TiO5] clusters and octahedral [TiO6] clusters in the disordered BZT-75/25 powders. EXAFS spectra indicate distortion of Ti-O and Ti-O-Ti bonds the first and second coordination shells, respectively. UV-Vis absorption spectra confirm the presence of different optical bandgap values and the band structure indicates an indirect bandgap for this material. The density of states demonstrates that intermediate energy levels occur between the valence band (VB) and the conduction band (CB). These electronic levels are due to the predominance of 4d orbitals of Zr atoms in relation to 3d orbitals of Ti atoms in the CB...

Organic acids and protein compounds causing the photoluminescence properties of natural rubber membranes and the quenching phenomena from Au nanoparticle incorporation

Cabrera, Flavio C.; Agostini, Deuber L. S.; Santos, Renivaldo J. dos; Guimaraes, Francisco E. G.; Guerrero, Ariel R.; Aroca, Ricardo F.; Job, Aldo E.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 1047-1052
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Processo FAPESP: 07/04952-5; Processo FAPESP: 10/03282-9; Natural rubber membranes were fabricated using latex from Hevea brasiliensis trees (clone RRIM 600) by casting, and controlling the time and temperature of thermal treatment. Three temperatures were used: 65, 80 and 120 degrees C and the corresponding annealing times of 6, 8, 10 and 12h. The centrifugation of the latex produces the constituent phases: solid rubber (F1), serum or protein components (F2) and bottom fraction (F3). The photoluminescence properties could be correlated with organic acid components of latex. Natural rubber membranes were used as the active substrate (reducing agent) for the incorporation of colloidal Au nanoparticles synthesized by in situ reduction at different times. The intensity of photoluminescence bands assigned to the natural rubber decreases with the increase in amount of nanoparticles present on the membrane surface. It can be assumed that Au nanoparticles may be formed by reduction of the Au cation reacting with functional groups that are directly related to photoluminescence properties. However, the quenching of fluorescence may be attributed to the formation of a large amount of metal nanostructures on the natural rubber surface. Copyright (c) 2014 John Wiley & Sons...

Influência do ambiente químico na fotoluminescência de oxi-nitreto de titânio dopado com érbio; Influence of the chemical environment on the photoluminescence of Er-doped TiNxOy thin films

Diego Leonardo Silva Scoca
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/12/2013 PT
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Neste trabalho foi investigada a influência do ambiente químico na fotoluminescência de filmes finos de Oxi-nitreto de titânio dopados com érbio (TiNxOy : Er). Os filmes finos foram crescidos utilizando a técnica de Deposição por Feixe de Íons (IBD ¿ Ion Beam Deposition) e, a fim de modificar o ambiente químico ao qual os íons de Er3+ estão submetidos para controlar as características da fotoluminescência dos íons de érbio, foi realizado tratamento térmico sequencial sob atmosfera de oxigênio, durante 30 minutos em cada uma das seguintes temperaturas: 250°C, 500°C, 750°C e 1000°C. A investigação do estado atômico e da concentração relativa de cada elemento presente nos filmes foi analisada através da técnica de XPS, para as amostras antes (AD) de passarem pelo tratamento térmico e após todos os tratamentos serem realizados (TA). A estrutura cristalina dos filmes foi investigada por Difração de Raio-X à Baixo Ângulo (1°) antes (AD) e após (TA) o tratamento térmico, enquanto que, através de espectroscopia Raman, foi acompanhada cada etapa (temperatura) do tratamento térmico, possibilitando a identificação de duas fases distintas do TiO2, onde a 750°C foram detectados modos vibracionais referentes a fase anatásio e...

Structural and optical properties of Er implanted AlN thin films: green and infrared photoluminescence at room temperature

Soares, M.J.; Leitão, J.P.; Silva, M.I.N. da; González, J.C.; Matinaga, F.M.; Lorenz, K.; Alves, E.; Peres, M.; Monteiro, T.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
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In this work erbium ions were implanted into AlN films grown on sapphire with fluence range: (0.5-2) × 1015 at/cm-2, ion energy range: 150-350 keV and tilt angle: 0°, 10°, 20°, 30°. The optical and structural properties of the films are studied by means of photoluminescence and Raman spectroscopy in combination with Rutherford backscattering/channeling (RBS/C) measurements. The photoluminescence spectra of the Er3+ were recorded in the visible and infrared region between 9 and 300 K after thermal annealing treatments of the samples. The emission spectrum of the AlN:Er films consists of two series of green lines centered at 538 and 558 nm with typical Er3+ emission in the infrared at 1.54 μm. The green lines have been identified as Er3+ transitions from the 2H11/2 and 4S3/2 levels to the 4I15/2 ground state. Different erbium centers in the matrix are suggested by the change of infrared photoluminescence relative intensity of some of the emission lines when different excitation wavelengths are used. The relative abundances of these centers can be varied by using different implantation parameters. The Raman and RBS/C measurements show good crystalline quality for all the studied films.; PTDC/CTM/100756/2008; SFRH/BD/45774/2008; Portuguese Agency GRICES; Brazilian Agency CAPES the Grant 172/07

Micro-photoluminescence spectroscopy on heavily-doped layers of silicon solar cells

Nguyen, Hieu T.; Yan, Di; Wang, Fan; Zheng, Peiting; Han, Young; Macdonald, Daniel
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
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We report and explain the photoluminescence spectra emitted from silicon solar cells with heavily-doped layers at the surface. A micro-photoluminescence spectroscopy system is employed to investigate the total spectrum emitted from both the heavily-doped layer and the silicon substrate with micron-scale spatial resolution. The two regions of the device give rise to separate photoluminescence peaks, due to band-gap narrowing effects in the highly-doped layer. Two key parameters, the absorption depth of the excitation wavelength, and the sample temperature, are shown to be critical to reveal the separate signatures from the two regions. Finally, this technique is applied to locally diffused and laser-doped regions on silicon solar cell pre-cursors, demonstrating the potential value of this micron-scale technique in studying and optimizing locally doped regions.; This work has been supported by the Australian Research Council (ARC) and the Australian Renew-able Energy Agency (ARENA) through research grant RND009.

Photoluminescence of a Plasmonic Molecule

Huang, Da; Byers, Chad P.; Wang, Lin-Yung; Hoggard, Anneli; Hoener, Ben; Chang, Wei-Shun; Landes, Christy F.; Link, Stephan
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Journal article; Text; post-print
ENG
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Photoluminescent Au nanoparticles are appealing for biosensing and bioimaging applications because of their non-photobleaching and non-photoblinking emission. The mechanism of one-photon photoluminescence from plasmonic nanostructures is still heavily debated though. Here, we report on the one-photon photoluminescence of strongly coupled 50 nm Au nanosphere dimers, the simplest plasmonic molecule. We observe emission from coupled plasmonic modes as revealed by single-particle photoluminescence spectra in comparison to correlated dark-field scattering spectroscopy. The photoluminescence quantum yield of the dimers is found to be surprisingly similar to the constituent monomers, suggesting that the increased local electric field of the dimer plays a minor role, in contradiction to several proposed mechanisms. Aided by electromagnetic simulations of scattering and absorption spectra, we conclude that our data are instead consistent with a multistep mechanism that involves the emission due to radiative decay of surface plasmons generated from excited electron–hole pairs following interband absorption.

Impact of carrier profile and rear-side reflection on photoluminescence spectra in Planar Crystalline Silicon Wafers at different temperatures

Nguyen, Hieu T.; Rougieux, Fiacre E.; Baker-Finch, Simeon C.; Macdonald, Daniel
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
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The increasing use of spectral photoluminescence as an advanced and accurate diagnostic tool motivates a comprehensive assessment of the effects of some important optical and electrical properties on the photoluminescence spectra from crystalline silicon wafers. In this paper, we present both modeling results and measurements to elucidate the effects of the internal reflectance at the planar wafer surfaces, as well as the carrier profile varying across the sample thickness due to an increased rear-surface recombination velocity, as a function of temperature. These results suggest that the accuracy of existing spectral PL techniques may be improved by using higher temperatures due to the increased effect of the carrier profile at higher temperatures. They also show that changes in the photoluminescence spectrum shape caused by the addition of a rear-side specular reflector offset those caused by changes in the carrier profile due to increased rear surface recombination, and therefore, considerable care needs to be taken when changing the rear-side optics. Finally, the possible impact of variations in the rear-side reflectance on the band–band absorption coefficient and radiative recombination coefficient, which have previously been determined using the spectral photoluminescence technique...

Hafnium-related photoluminescence in single crystal silicon

Sachdeva, R; Istratov, A A; Shan, Wei; Deenapanray, Prakash; Weber, E R
Fonte: Materials Research Society Publicador: Materials Research Society
Tipo: Conference paper
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A new photoluminescence (PL) band in the energy range of 700 meV to 950 meV associated with hafnium implanted in silicon is reported. A shift in the position of photoluminescence peaks observed on the samples implanted with two different isotopes of Hf confirms the Hf-related origin of the observed photoluminescence band. Activation of the Hf-optical centers requires a 1000°C anneal step. The intensity of the PL lines depends on the cooling conditions. The spectrum consists of five peaks in the rapidly quenched sample as opposed to twenty one in the slowly cooled sample. Temperature dependent PL measurements and hydrostatic pressure measurements were performed to identify their nature.

The effect of ion dose and annealing ambient on room temperature photoluminescence from Si nanocrystals in SiO2

Cheylan, S; Manson, Neil; Elliman, Robert
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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Photoluminescence from Si implanted silica is studied as a function of ion dose and annealing ambient. The photoluminescence emission intensity from samples as-implanted and after annealing at 1000°C in Ar is shown to exhibit a distinct maximum as a func