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Analysis of confinement potential fluctuation and band-gap renormalization effects on excitonic transition in GaAs/AlGaAs multiquantum wells grown on (100) and (311)A GaAs surfaces

Lourenco, S. A.; Teodoro, M. D.; Gonzalez-Borrero, P. P.; Dias, I. F. L.; Duarte, J. L.; Marega Junior, Euclydes; Salamo, G. J.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
67.947876%
The competition between confinement potential fluctuations and band-gap renormalization (BGR) in GaAs/AlxGa1-xAs quantum wells grown on [1 0 0] and [3 1 1]A GaAs substrates is evaluated. The results clearly demonstrate the coexistence of the band-tail states filling related to potential fluctuations and the band-gap renormalization caused by an increase in the density of photogenerated carriers during the photoluminescence (PL) experiments. Both phenomena have strong influence on temperature dependence of the PL-peak energy (E-PL(T)). As the photon density increases, the E-PL can shift to either higher or lower energies, depending on the sample temperature. The temperature at which the displacement changes from a blueshift to a redshift is governed by the magnitude of the potential fluctuations and by the variation of BGR with excitation density. A simple band-tail model with a Gaussian-like distribution of the density of state was used to describe the competition between the band-tail filling and the BGR effects on E-PL(T). (C) 2012 Elsevier B.V. All rights reserved.; CAPES; CAPES; CNPq; CNPq; Fundacao Araucaria; Fundacao Araucaria; FAPESP; FAPESP; FBB; FBB; National Science Foundation of the U.S.; National Science Foundation of the U.S. [DMR-0520550]

CdSe/CdTe interface band gaps and band offsets calculated using spin-orbit and self-energy corrections

Ribeiro, M., Jr.; Ferreira, Luiz Guimaraes; Fonseca, L. R. C.; Ramprasad, R.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
57.913555%
We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme [L.G. Ferreira, M. Marques, L.K. Teles, Phys. Rev. B 78 (2008) 125116] to obtain corrected band gaps and band offsets. Our calculations include the spin-orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8-1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications. (C) 2012 Elsevier B.V. All rights reserved.; Brazilian agency CAPES; Brazilian agency CAPES; FAPESP; FAPESP; CNPq; CNPq; Instituto Tecnologico de Aeronautica (FAPESP); Instituto Tecnologico de Aeronautica (FAPESP) [2006/05858-0]; Semp-Toshiba; SempToshiba

Microstructure, dielectric properties and optical band gap control on the photoluminescence behavior of Ba[Zr0.25Ti0.75]O-3 thin films

Cavalcante, L. S.; Sczancoski, J. C.; Vicente, Fábio Simões de; Frabbro, M. T.; Li, M. Siu; Varela, José Arana; Longo, Elson
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 35-46
ENG
Relevância na Pesquisa
67.818096%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Ba[Zr0.25Ti0.75]O-3 (BZT) thin films were synthesized by the complex polymerization method and heat treated at 400 A degrees C for different times and at 700 A degrees C for 2 h. These thin films were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, field emission gun-scanning electron microscopy (FEG-SEM) and atomic force microscopy (AFM), Ultraviolet-visible (UV-vis) absorption spectroscopy, electrical and photoluminescence (PL) measurements. FEG-SEM and AFM micrographs showed that the microstructure and thickness of BZT thin films can be influenced by the processing times. Dielectric constant and dielectric loss of BZT thin films heat treated at 700 A degrees C were approximately 148 and 0.08 at 1 MHz, respectively. UV-vis absorption spectra suggested the presence of intermediary energy levels (shallow and deep holes) within the band gap of BZT thin films. PL behavior was explained through the optical band gap values associated to the visible light emission components.

Electrical and optical characteristics of SnO2 thin films prepared by dip coating from aqueous colloidal suspensions

Souza, A. E. de; Monteiro, S. H.; Santilli, C. V.; Pulcinelli, S. H.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 265-270
ENG
Relevância na Pesquisa
67.74041%
Starting from aqueous colloidal suspensions, undoped and Nb5+ doped SnO2 thin films have been prepared by using the dip-coating sol gel process. X-ray diffraction results show that films are polycrystalline with crystallites of average size1-4nm. Decreasing the thickness of the films and increasing the Nb5+ concentration limits the crystallite size growth during firing. Complex impedance measurements reveal capacitive and resistive effects between adjacent crystallites or grains, characteristic of electrical potential barriers. The transfer of charge throughout these barriers determines the macroscopic electrical resistance of the layer. The analysis of the optical absorption spectra shows that the samples present more than 80% of their transmittance in the visible region and the value of the band gap energy increases with decreasing crystallite size. © 1997 Chapman & Hall.

Compositional dependence of the strain-free optical band gap in InxGa1 - xN layers

Pereira, S.; Correia, M.R.; Monteiro, T.; Pereira, E.; Alves, E.; Sequeira, A.D.; Franco, N.
Fonte: AIP Publicador: AIP
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
68.02977%
The effect of strain on the compositional and optical properties of a set of epitaxial single layers of InxGa12xN was studied. Indium content was measured free from the effects of strain by Rutherford backscattering spectrometry. Accurate knowledge of the In mole fraction, combined with x-ray diffraction measurements, allows perpendicular strain (e zz) to be evaluated. Optical band gaps were determined by absorption spectroscopy and corrected for strain. Following this approach, the strain free dependence of the optical band gap in InxGa12xN alloys was determined for x<0.25. Our results indicate an ‘‘anomalous,’’ linear, dependence of the energy gap on the In content, at room temperature: Eg(x)53.39– 3.57x eV. Extension of this behavior to higher concentrations is discussed on the basis of reported results

Time resolved spectroscopy of mid-band-gap emissions in Si-doped GaN

Seitz, R.; Gaspar, C.; Monteiro, T.; Pereira, E.; Leroux, M.; Beaumont, B.; Gibart, P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
68.02977%
Silicon is until now the most promising dopant for n-type GaN. Besides the near-band-gap emission centred at 3.461 eV, which becomes broader with increasing Si concentration also transitions at lower energies are observed. These emissions decrease strongly when the silicon concentration increases. While the near-band-gap emission is due to fast transitions (with decays shorter than 10 μs) the lower energy emissions have longer components whose behaviour is discussed. © 1998 Elsevier Science B.V. All rights reserved.

Síntese e fotosensibilização de nanotubos de titanatos

Bem, Vanessa Rodrigues
Fonte: Instituto Politécnico de Lisboa Publicador: Instituto Politécnico de Lisboa
Tipo: Dissertação de Mestrado
Publicado em /12/2011 POR
Relevância na Pesquisa
67.797954%
Nesta tese é descrita a preparação de nanotubos de titanatos (TNT) via síntese hidrotérmica alcalina, usando uma nova metodologia que evita a utilização de TiO2 cristalino como precursor. Foi estudada a influência da substituição sódio/protão na estrutura, morfologia e propriedades ópticas dos materiais preparados. Os resultados mostraram que a substituição Na+ → H+ resulta numa redução na distância intercamadas dos TNTs, tendo sido medidos valores entre 1.13±0.03 nm e 0.70±0.02 nm para aquele parâmetro. O comportamento óptico dos TNTs foi estudado na região UV-vis, estimando-se um hiato óptico de energia 3.27±0.03 eV para a amostra com maior teor de sódio enquanto que para a amostra protonada foi determinado um valor de 2.81±0.02 eV. Estes valores mostram que a troca iónica Na+ → H+ teve influência no desvio da banda de absorção dos TNTs para a região do visível próximo. A actividade fotocatalítica dos TNTs na degradação do corante rodamina 6G (R6G) foi posteriormente estudada. Verificou-se que, apesar de a amostra com maior teor de sódio ter sido a que exibiu maior capacidade para adsorver o R6G, foi a amostra protonada que apresentou a actividade catalítica mais elevada na fotodegradação deste corante. Numa segunda fase...

Role of Fe doping in tuning the band gap of TiO2 for photo-oxidation induced cytotoxicity paradigm

George, Saji; Pokhrel, Suman; Ji, Zhaoxia; Henderson, Bryana L.; Xia, Tian; Li, LinJiang; Zink, Jeffrey I.; Nel, André E.; Mädler, Lutz
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
58.24897%
UV-Light induced electron-hole (e−/h+) pair generation and free radical production in TiO2 based nanoparticles is a major conceptual paradigm for biological injury. However, to date, this hypothesis has been difficult to experimentally verify due to the high energy of UV light that is intrinsically highly toxic to biological systems. Here, a versatile flame spray pyrolysis (FSP) synthetic process has been exploited to synthesize a library of iron doped (0–10 at wt%) TiO2 nanoparticles. These particles have been tested for photoactivation-mediated cytotoxicity using near-visible light exposure. The reduction in TiO2 band gap energy with incremental levels of Fe loading maintained the nanoparticle crystalline structure in spite of homogeneous Fe distribution (demonstrated by XRD, HRTEM, SAED, EFTEM, and EELS). Photochemical studies showed that band gap energy was reciprocally tuned proportional to the Fe content. The photo-oxidation capability of Fe-doped TiO2 was found to increase during near-visible light exposure. Use of a macrophage cell line to evaluate cytotoxic and ROS production showed increased oxidant injury and cell death in parallel with a decrease in band gap energy. These findings demonstrate the importance of band gap energy in the phototoxic response of the cell to TiO2 nanoparticles and reflect the potential of this material to generate adverse effects in humans and the environment during high intensity light exposure.

Aluminum doping tunes band gap energy level as well as oxidative stress-mediated cytotoxicity of ZnO nanoparticles in MCF-7 cells

Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws; Majeed Khan, M.A.; Ahamed, Maqusood
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 08/09/2015 EN
Relevância na Pesquisa
67.87766%
We investigated whether Aluminum (Al) doping tunes band gap energy level as well as selective cytotoxicity of ZnO nanoparticles in human breast cancer cells (MCF-7). Pure and Al-doped ZnO nanoparticles were prepared by a simple sol-gel method. Characterization study confirmed the formation of single phase of AlxZn1-xO nanocrystals with the size range of 33–55 nm. Al-doping increased the band gap energy of ZnO nanoparticles (from 3.51 eV for pure to 3.87 eV for Al-doped ZnO). Al-doping also enhanced the cytotoxicity and oxidative stress response of ZnO nanoparticles in MCF-7 cells. The IC50 for undoped ZnO nanoparticles was 44 μg/ml while for the Al-doped ZnO counterparts was 31 μg/ml. Up-regulation of apoptotic genes (e.g. p53, bax/bcl2 ratio, caspase-3 & caspase-9) along with loss of mitochondrial membrane potential suggested that Al-doped ZnO nanoparticles induced apoptosis in MCF-7 cells through mitochondrial pathway. Importantly, Al-doping did not change the benign nature of ZnO nanoparticles towards normal cells suggesting that Al-doping improves the selective cytotoxicity of ZnO nanoparticles toward MCF-7 cells without affecting the normal cells. Our results indicated a novel approach through which the inherent selective cytotoxicity of ZnO nanoparticles against cancer cells can be further improved.

CdSe/CdTe interface band gaps and band offsets calculated using spin-orbit and self-energy corrections

Ribeiro, M., Jr.; Ferreira, L. G.; Fonseca, L. R. C.; Ramprasad, R.
Fonte: Elsevier; Amsterdam Publicador: Elsevier; Amsterdam
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
57.913555%
We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme [L.G. Ferreira, M. Marques, L.K. Teles, Phys. Rev. B 78 (2008) 125116] to obtain corrected band gaps and band offsets. Our calculations include the spin-orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8-1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications. (C) 2012 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Gamma-induced modification on optical band gap of CR-39 SSNTD

Zaki,M. F.
Fonte: Sociedade Brasileira de Física Publicador: Sociedade Brasileira de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
Relevância na Pesquisa
68.10829%
Effect of gamma irradiation on optical absorption of nuclear track detectors like CR-39 was studied in different absorbed doses using ultraviolet-visible (UV-VIS) spectroscopy. The existence of the peaks, their shifting and broadening as a result of gamma irradiation has been discussed. The width of the tail of localized states in the band gap (Eu) was evaluated using the Urbach edge method. Finally the indirect and direct band gap in pristine and gamma irradiated CR-39 have been determined. The values of indirectly band gap have been found to be lower than the corresponding values of direct band gap. A decrease in the optical energy gap with increasing the gamma absorbed dose can be discussed on the basis of gamma-irradiation-induced defects in the CR-39. The correlation between optical band gap and the number of carbon atoms in a cluster with modified Tauc's equation has been discussed in case of CR-39.

Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius

Lacomba-Perales, R.; Ruiz-Fuertes, J.; Errandonea, D.; Martinez-Garcia, D.; Segura, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/07/2008
Relevância na Pesquisa
67.93963%
We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.; Comment: 16 pages, 3 figures, 1 table

Calculation of The Band Gap Energy and Study of Cross Luminescence in Alkaline-Earth Dihalide Crystals

Aguado, Andres; Ayuela, Andres; Lopez, Jose M.; Alonso, Julio A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
68.156235%
The band gap energy as well as the possibility of cross luminescence processes in alkaline-earth dihalide crystals have been calculated using the ab initio Perturbed-Ion (PI) model. The gap is calculated in several ways: as a difference between one-electron energy eigenvalues and as a difference between total energies of appropriate electronic states of the crystal, both at the HF level and with inclusion of Coulomb correlation effects. In order to study the possibility of ocurrence of cross luminescence in these materials, the energy difference between the valence band and the upmost core band for some representative crystals has been calculated. Both calculated band gap energies and cross luminescence predictions compare very well with the available experimental results.; Comment: LaTeX file containing 8 pages plus 1 postscript figure. Final version accepted for publication in The Journal of the Physical Society of Japan. It contains a more complete list of references, as well as a more detailed comparison with previous theoretical investigations on the subject

Measurement of spontaneous emission from a two-dimensional photonic band gap defined microcavity at near-infrared wavelengths

Lee, R. K.; Painter, O. J.; D'Urso, B.; Scherer, A.; Yariv, A.
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 15/03/1999
Relevância na Pesquisa
57.947876%
An active, photonic band gap-based microcavity emitter in the near infrared is demonstrated. We present direct measurement of the spontaneous emission power and spectrum from a microcavity formed using a two-dimensional photonic band gap structure in a half wavelength thick slab waveguide. The appearance of cavity resonance peaks in the spectrum correspond to the photonic band gap energy. For detuned band gaps, no resonances are observed. For devices with correctly tuned band gaps, a two-time enhancement of the extraction efficiency was demonstrated compared to detuned band gaps and unpatterned material.

Dynamics of Electromagnetic Systems for Energy Harvesting and Filtering

Owens, Benjamin Andrew Michael
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2014
Relevância na Pesquisa
58.133013%

The focus of this dissertation is on the dynamics of electromagnetic systems for energy harvesting and filtering applications. The inclusion of magnets into systems generates nonlinearity due to the nature of electromagnetic interactions. In this work, magnetic nonlinearity manifests in tip interactions for cantilever beams, coupling effects for electromagnetic transduction, and bistable potential wells for a two beam system. These electromagnetic interactions are used to add non-contact coupling effects for the creation of bistable oscillators or arrays of coupled beams for energy filtering.

Nonlinearity at the tip of cantilever beams acts to change the dynamic and static behavior of the system. In this dissertation, these interactions are analyzed both with and without the nonlinear tip interactions. A linear analysis of the system without the tip interaction first provides insight into the shifting frequencies of the first four natural oscillation modes when considering a rigid body tip mass with rotational inertia and a center of mass that is offset from the tip of the beam. Then, the characterization of the nonlinearities in the beam stiffness and magnetic interaction provide insight into the static and dynamic behavior of the beam. The analytical and numerical investigations...

Band-gap Engineering and Defect Modes in Photonic Crystals with Rotated Hexagonal Holes

Matthews, Aaron; Mingaleev, Sergei F; Kivshar, Yuri
Fonte: Interperiodica Publicador: Interperiodica
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
67.9778%
We study the band-gap structure of two-dimensional photonic crystals created by a triangular lattice of rotated hexagonal holes and explore the effects of the reduced symmetry in the unit-cell geometry on the value of the absolute band gap and the frequencies of localized defect modes. We reveal that a maximum absolute band gap for this structure is achieved for an intermediate rotation angle of the holes. This angle depends on the radius of the holes and the refractive index of the background material. We also study the properties of the defect modes created by missing holes and discuss the mode tunability in such structures.

Reduction of Band-Gap Energy in GaNAs and AlGaNAs Synthesized by N+ Implantation

Shan, Wei; Yu, Kin Man; Walukiewicz, W; Ager, J W; Haller, E E; Ridgway, Mark C
Fonte: American Institute of Physics (AIP) Publicador: American Institute of Physics (AIP)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
67.87766%
The optical properties of nitrogen implanted GaAs and AlGaAs were investigated. The change in band-gap energy in the implanted region was analyzed using photomodulation spectroscopy. Results showed that by increasing N+ implantation dosage, the fundamental band-gap energy decreases.

One-dimensional Periodic Structures with Complete Spectral Gap

Shadrivov, Ilya; Sukhorukov, Andrey; Kivshar, Yuri
Fonte: SPIE - The International Society for Optical Engineering Publicador: SPIE - The International Society for Optical Engineering
Tipo: Conference paper
Relevância na Pesquisa
58.051616%
Artificial structures with periodically modulated index of refraction such as photonic crystals offer novel ways of controlling light propagation due to the existence of a range of forbidden frequencies corresponding to a photonic bandgap. We discuss physical phenomena which do not allow for the existence of complete electromagnetic band gaps in dielectric structures with variation of the refractive index in one spatial dimension. We also demonstrate that the limitations imposed on one-dimensional dielectric structures can be removed by using the so-called left-handed materials, and that such a structure can posses a full photonic band gap.

Study of Structure and Spectral Characteristics of the Zinc(II) and Copper(II) Complexes With 5,5-Dimethyl-2-(2-(3-nitrophenyl) hydrazono)cyclohexane-1,3-dione and Their Effects on Optical Properties and the Developing of the Energy Band Gap and Investigation of Antibacterial Activity

Turan,Nevin; Gündüz,Bayram; Körkoca,Hanifi; Adigüzel,Ragip; Çolak,Naki; Buldurun,Kenan
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
68.17129%
A new chelating ligand, 5,5-dimethyl-2-(2-(3-nitrophenyl) hydrazono)cyclohexane-1,3-dione (L), and four transition metal complexes were synthesized. The ligand and its complexes were characterized by IR, ¹H and 13C-NMR spectra, elemental analyses, magnetic susceptibility, mass spectra, UV-Vis. and thermogravimetry-differential thermal analysis (TGA-DTA). The metal complexes showed different geometric structures. Antibacterial tests of the ligand and complexes were also done. The Zn(II) complexes showed antibacterial activity against Staphylococcus aureus ATCC-25923 at middle level. The optical properties of the ligand and its complexes were extensively investigated by optical measurements. The average transmittance value of the ligand was the highest value, while the average transmittance value of the [CuL2(NO3)2]·6H2Ocomplex was the lowest value. The optical band gap of the ligand, [(Zn)2L(OH)4]·2DMF, [ZnL(NO3)2(H2O)2]·5H2O, [CuL2(OAc)]·OAc·3.5H2O and [CuL2(NO3)2]·6H2O complexes were calculated and 3.121 eV, 2.180 eV, 1.551 eV, 2.489 eV and 1.556 eV values were found, respectively. The complexes decreased the optical band gap of the ligand. The optical band gap value of the [ZnL(NO3)2(H2O)2]·5H2O complex is the lowest value. The optical band gap value of the ligand is the highest value. The complexes decrease the angle of incidence of the ligand...

Structural characterization, optical response, and corrosion resistance of bismuth coatings

Alfonso,José E; Olaya,Jhon J; Ortiz,María F
Fonte: Universidad Simón Bolívar; ; Publicador: Universidad Simón Bolívar; ;
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
67.517954%
We present the results obtained from the deposition of nanostructure bismuth coatings through DC pulsed unbalanced magnetron sputtering. The Bi coatings were deposited simultaneously on common glass, silicon, and Ti6AL4V substrates in order to evaluate the optical properties, morphology, and microstructure as a function of the pulsed frequency deposition, and to establish the relationship between these properties and corrosion resistance. The microstructure was evaluated via X-ray diffraction (XRD), and the morphology of the coatings was evaluated through scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties were characterized through absorbance and transmittance spectra. The XRD analysis indicated that the coatings are polycrystalline. The SEM micrographs showed that the coatings are grown as droplets form. AFM revealed roughness values from 20.0 to 28.8 nm. Finally, from the optical measurements, it was possible to establish the band-gap energy of the Bi coatings.