Ferromagnetic nanoclusters formed by Mn implantation in GaAs

Ferromagnetic clusters were incorporated into GaAs samples by Mn implantation and subsequent annealing. The composition and structural properties of the Mn-based nanoclusters formed at the surface and buried into the GaAs sample were analyzed by x-ray and microscopic techniques. Our measurements indicate the presence of buried MnAs nanoclusters with a structural phase transition around 40 °C, in accord with the first-order magneto-structural phase transition of bulk MnAs. We discuss the structural behavior of these nanoclusters during their formation and phase transition, which is an important point for technological applications. © 2005 American Institute of Physics.

On the nucleation of GaP/GaAs and the effect of buried stress fields

We have recently shown that spatial ordering for epitaxially grown InP dots can be obtained using the periodic stress field of compositional modulation on the InGaP buffer layer. The aim of this present work is to study the growth of films of GaP by Chemical Beam Epitaxy (CBE), with in-situ monitoring by Reflection High Energy Electron Diffraction (RHEED), on layers of unstressed and stressed GaAs. Complementary, we have studied the role of a buried InP dot array on GaP nucleation in order to obtain three-dimensional structures. In both cases, the topographical characteristics of the samples were investigated by Atomic Force Microscopy (AFM) in non-contact mode. Thus vertically-coupled quantum dots of different materials have been obtained keeping the in-place spatial ordering originated from the composition modulation. © 2006 Materials Research Society.

Biomechanical effect of one session of low-level laser on the bone-titanium implant interface

Low-level laser (LLL) has been used on peri-implant tissues for accelerating bone formation. However, the effect of one session of LLL in the strength of bone-implant interface during early healing process remains unclear. The present study aims to evaluate the removal torque of titanium implants irradiated with LLL during surgical preparation of implant bed, in comparison to non-irradiation. Sixty-four Wistar rats were used. Half of the animals were included in LLL group, while the other half remained as control. All animals had the tibia prepared with a 2 mm drill, and a titanium implant (2.2 × 4 mm) was inserted. Animals from LLL group were irradiated with laser (gallium aluminum arsenide), with a wavelength of 808 nm, a measured power output of 50 mW, to emit radiation in collimated beams (0.4 cm2), for 1 min and 23 s, and an energy density of 11 J/cm2. Two applications (22 J/cm 2) were performed immediately after bed preparation for implant installation. Flaps were sutured, and animals from both groups were sacrificed 7, 15, 30, and 45 days after implant installation, when load necessary for removing implant from bone was evaluated by using a torquimeter. In both groups, torque values tended to increase overtime; and at 30 and 45 days periods, values were statistically higher for LLL group in comparison to control (ANOVA test, p < 0.0001). Thus, it could be suggested that a single session of irradiation with LLL was beneficial to improve bone-implant interface strength, contributing to the osseointegration process. © 2012 Springer-Verlag London Ltd.

Interface formation of nanostructured heterojunction SnO 2:Eu/GaAs and electronic transport properties

Thin films of tin dioxide (SnO2) are deposited by the sol-gel-dip-coating technique, along with GaAs layers, deposited by the resistive evaporation technique. The as-built heterojunction has potential application in optoelectronic devices, combining the emission from the rare-earth doped transparent oxide (Eu3+-doped SnO2 presents very efficient red emission) with a high mobility semiconductor. The advantage of this structure is the possibility of separation of the rare-earth emission centers from the electron scattering, leading to a strongly indicated combination for electroluminescence. Electrical characterization of the heterojunction SnO2:Eu/GaAs shows a significant conductivity increase when compared to the conductivity of the individual films, and the monochromatic light irradiation (266 nm) at low temperature of the heterojunction GaAs/SnO2:Eu leads to intense conductivity increase. Scanning electron microscopy (SEM) of the heterojunction cross section shows high adherence and good morphological quality of the interfaces substrate/SnO2 and SnO2/GaAs, even though the atomic force microscopy (AFM) image of the GaAs surface shows disordered particles, which increases with sample thickness. On the other hand, the good morphology of the SnO2:Eu surface, shown by AFM, assures the good electrical performance of the heterojunction. The observed improvement on the electrical transport properties is probably related to the formation of short conduction channels at the semiconductors interface, which may exhibit two-dimensional electron gas (2DEG) behavior. © 2012 Elsevier B.V. All rights reserved.

Low-level laser therapy in pediatric bell's palsy: Case report in a three-year-old child

Objectives: The objective of this study was to apply low-level laser therapy (LLLT) to accelerate the recovery process of a child patient with Bell's palsy (BP). Design: This was a prospective study. Subject: The subject was a three-year-old boy with a sudden onset of facial asymmetry due to an unknown cause. Materials and methods: The low-level laser source used was a gallium aluminum arsenide semiconductor diode laser device (660 nm and 780 nm). No steroids or other medications were given to the child. The laser beam with a 0.04-cm2 spot area, and an aperture with approximately 1-mm diameter, was applied in a continuous emission mode in direct contact with the facial area. The duration of a laser session was between 15 and 30 minutes, depending on the chosen points and the area being treated. Light was applied 10 seconds per point on a maximum number of 80 points, when the entire affected (right) side of the face was irradiated, based on the small laser beam spot size. According to the acupuncture literature, this treatment could also be carried out using 10-20 Chinese acupuncture points, located unilaterally on the face. In this case study, more points were used because the entire affected side of the face (a large area) was irradiated instead of using acupuncture points. Outcome measures: The House-Brackmann grading system was used to monitor the evolution of facial nerve motor function. Photographs were taken after every session, always using the same camera and the same magnitude. The three-year-old boy recovered completely from BP after 11 sessions of LLLT. There were 4 sessions a week for the first 2 weeks, and the total treatment time was 3 weeks. Results: The result of this study was the improvement of facial movement and facial symmetry, with complete reestablishment to normality. Conclusions: LLLT may be an alternative to speed up facial normality in pediatric BP. © Copyright 2013, Mary Ann Liebert, Inc. 2013.

Matrizes semicondutoras GaAs e Sn'X IND. 2' dopado com terras-raras Ce ou Eu: investigação do transporte elétrico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação da técnica de evaporação resistiva para a deposição de filmes finos de GaAs e compostos de GaAs com óxidos e cloretos de Er ou Yb

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Reação histológica de exposições pulpares em dentes de ratos à aplicação do laser de baixa intensidade somente ou em associação ao capeamento com hidróxido de cálcio

Pós-graduação em Odontologia - FOAR

Ação de biomateriais e laser de baixa intensidade na reparação tecidual óssea: estudo histológico em ratos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos da radiação laser Arseneto de Gálio e Alumínio (780nm) no periodonto de sustentação de ratos diabéticos durante movimentação ortodôntica: analises radiográfica e histológica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos da membrana amniótica homógena associada ao laser arseneto de gálio-alumínio (λ=660) na reparação de mucosite oral em ratos tratados com 5-fluoruracila: análise histológica e imunohistoquímica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cálculos de estrutura eletrônica de materiais mediante combinação linear de orbitais atômicos

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Efeito do laser de baixa intensidade na polpa e nos tecidos apicais e periapicais em dentes de macaco

Pós-graduação em Odontologia - FOAR

Efeitos da terapia fotodinâmica na expressão dos genes SAP5, LIP9 e PLB2 em Candida albicans

Pós-graduação em Biopatologia Bucal - ICT

Photo-Induced Conductivity of Heterojunction GaAs/Rare-Earth Doped SnO2

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)