A5088433613- GaN-based semiconductor devices and materials
- Metal and Thin Film Mechanics
- ZnO doping and properties
- Ga2O3 and related materials
- Semiconductor materials and devices
- Semiconductor Quantum Structures and Devices
- Acoustic Wave Resonator Technologies
- Quantum Dots Synthesis And Properties
- Diamond and Carbon-based Materials Research
- Nanowire Synthesis and Applications
- Surface and Thin Film Phenomena
- Electron and X-Ray Spectroscopy Techniques
- Thermal properties of materials
- Gold and Silver Nanoparticles Synthesis and Applications
- Advanced materials and composites
- Copper-based nanomaterials and applications
- Electronic and Structural Properties of Oxides
- Plasmonic and Surface Plasmon Research
- X-ray Diffraction in Crystallography
- Environmental Sustainability and Education
- Science and Education Research
- nanoparticles nucleation surface interactions
- Thermal Radiation and Cooling Technologies
- Quantum and electron transport phenomena
- Advanced Surface Polishing Techniques
Constructing Excellence
2023
Universidade do Porto
2016-2022
University of Aveiro
2008-2017
University of Mons
2008
TARH (Portugal)
2006
University of Strathclyde
1999-2004
In-Q-Tel
2002
Strain and composition distributions within wurtzite InGaN/GaN layers are investigated by high-resolution reciprocal space mapping (RSM). We illustrate the potential of RSM to detect strain gradients independently. This information is extracted from elongation broadened lattice points (RLP) in asymmetric x-ray reflections. Three InxGa1−xN/GaN (nominal x=0.25) samples with layer thickness 60, 120, 240 nm, were grown a commercial metal-organic chemical vapor deposition reactor. The RSMs around...
A depth-resolved study of the optical and structural properties wurtzite InGaN/GaN bilayers grown by metallorganic chemical vapor deposition on sapphire substrates is reported. Depth-resolved cathodoluminescence (CL) Rutherford backscattering spectrometry (RBS) were used to gain an insight into compositional profile a 75-nm thick InGaN epilayer in direction growth. CL acquired at increasing electron energies reveals peak shift about 25 meV blue when beam energy increased from 0.5...
Using a top-down approach, we report theoretical investigation of the melting temperature at nanoscale, Tm, for different shapes "free-standing" nanostructures. To easily calculate nanoscale wide range metals and semiconductors, convenient shape parameter called αshape is defined. Considering this parameter, argue why smaller size effects are observed in high bulk materials. phase transition stress model proposed to evaluate intrinsic strain during first steps solidification. Then, effect on...
We present a rigorous analysis of the thermal conductivity bulk silicon (Si) and Si nanowires (Si NWs) which takes into account exact physical nature various acoustic optical phonon mechanisms. Following Callaway solution for Boltzmann equation, where resistive nonresistive mechanisms are discriminated, we derived formalism lattice that incidence angles. The scattering processes represented by frequency-dependent relaxation time. In addition to commonly considered three-phonon processes,...
The effect of strain on the compositional and optical properties a set epitaxial single layers InxGa1−xN was studied. Indium content measured free from effects by Rutherford backscattering spectrometry. Accurate knowledge In mole fraction, combined with x-ray diffraction measurements, allows perpendicular (εzz) to be evaluated. Optical band gaps were determined absorption spectroscopy corrected for strain. Following this approach, dependence gap in alloys x⩽0.25. Our results indicate an...
Landfill leachates result from the degradation of solid residues in sanitary landfills, thus presenting a high variability terms composition. Normally, these effluents are characterized by ammoniacal-nitrogen (N-NH₄⁺) concentrations, chemical oxygen demands and low phosphorus concentrations. The development effective treatment strategies becomes difficult, posing serious problem to environment. Phycoremediation appears be suitable alternative for landfill leachates. In this study, potential
In this work, we investigate structural and optical properties of metalorganic chemical vapor deposition grown wurtzite InxGa1−xN/GaN epitaxial layers with thicknesses that are close to the critical layer thickness (CLT) for strain relaxation. CLT structures was calculated as a function InN content, x, using energy balance model proposed by People Bean [Appl. Phys. Lett. 47, 322 (1985)]. Experimentally determined in good agreement these calculations. The occurrence discontinuous relaxation...
The structural properties of InGaN have attracted interest on account the recent widespread use material in visible light-emitting devices. A key topic has been indirect determination composition by x-ray diffraction (XRD). We examine critically several levels approximation involved this procedure. It is shown extended absorption fine structure (EXAFS) measurements that local independent composition, range InN fraction, from about 15 to 40%, corresponds blue infrared light emission material....
We report a theoretical investigation concerning the melting temperature, Tm, of ZnO and Zn nanoparticles (NPs), nanowires (NWs) nanotubes (NTs). The shapes considered here for zinc oxide low dimensional structures include spherical NPs, NWs with circular, rectangular (nanobelts) hexagonal sections NTs circular sections. A comparison between nanostructures demonstrates higher stability most size shape ranges considered. Moreover, effect on temperature is found to be quite strong: NP radius 5...
We investigate interactions between Mott-Wannier (MW) and Frenkel excitons in a family of hybrid structures consisting thin organic (polyfluorene) films placed close proximity (systematically adjusted by GaN cap layer thickness) to single inorganic $[(\mathrm{Ga},\mathrm{In})\mathrm{N}∕\mathrm{Ga}\mathrm{N}]$ quantum wells (QWs). Characterization the QW using Rutherford backscattering spectrometry atomic force microscopy allows direct measurement thickness morphology layers. Time-resolved...
O turismo sustentável é um desafio crescente para regiões litorâneas, especialmente em destinos amplamente visitados como a Praia de Canasvieiras, Florianópolis – SC. presente estudo investigou relação entre educação ambiental e sustentável, analisando os impactos ambientais gerados pela atividade turística as estratégias minimizá-los. A pesquisa partiu do problema da degradação causada má gestão resíduos, saneamento inadequado comportamento dos visitantes, o que compromete qualidade praia...
Abstract InGaN is the basis of a new generation light‐emitting devices, with enormous technological potential; it currently one most intensively studied semiconductor materials. It generally accepted that compositional fluctuations resulting from phase segregation are origin high luminescence efficiency InGaN. Evidence to show nanoscale strain inhomogeneity plays fundamental role in determining spectral properties InGaN–GaN heterostructures reported. For layers above certain critical...
The aim of the present study is to synthesize new mannosylated dextran derivative that can be labeled with Tc-99m for potential use in sentinel lymph node detection (SLND). compound was designed have a molecular weight 10 kDa as backbone, mannose binding receptors and S-derivatized cysteine suitable chelator labeling [(99m)Tc(H(2)O)(3)(CO)(3)](+) precursor. Reaction allyl bromide (MW 11800) yielded intermediate allyl-dextran (1) about 40% coupling. Addition resulted cysteine, DC15 (2). final...
The presence of two, or more, x-ray diffraction (XRD) peaks from an InGaN epilayer is sometimes regarded as indicator phase segregation. Nevertheless, detailed characterization InGaN/GaN bilayer by a combination XRD and Rutherford backscattering spectrometry (RBS) shows that splitting the peak may be completely unrelated to decomposition. Wurtzite layers were grown in commercial reactor. An reciprocal space map performed on (105) plane one component partially resolved double practically...
We present the highlights of a research programme on hybrid inorganic–organic light emitters. These devices combine recent developments in III–V nitride technology (including UV emitting micro-arrays and specifically tailored quantum wells) with conjugated polymers to access entire visible spectrum. Two types are studied, those based down conversion well emission by radiative transfer non-radiative resonant energy transfer. The spectral operating characteristics described detail. Selectable...
Despite being widely used in the clinical setting for sentinel lymph node detection (SLND), (99m)Tc-based colloids (e.g., (99m)Tc-human serum albumin colloids) present a set of properties that are far from ideal. Aiming to design novel compounds with improved biological properties, we describe herein first class fully characterized (99m)Tc(CO)₃-mannosylated dextran derivatives adequate features SLND. Dextran derivatives, containing same number pendant mannose units (13) and variable (n)...
The behavior of the A1(LO) phonon mode relaxed and pseudomorphic InxGa1−xN epilayers, at surface, is investigated by Raman spectroscopy. This study involves samples, with a compositional range 0.12⩽x<0.30 0.04<x⩽0.20, respectively. measurements were performed under excitation 3.71 eV. Due to low depth penetration incident light (40 nm), major contribution scattering comes from where strain composition have been independently determined. For linear dependence frequency obtained,...
The directional dependence of AlN intrinsic complex dielectric function, the phonon lifetimes, and decay channels are investigated by means polarized infrared reflectivity measurements on several facets self-nucleated wurtzite crystal high crystalline quality. measurement technique single used have been selected with purpose to reduce, as much possible, any instrumental-based effects well scattering mechanisms due defects. experimental arrangements necessary detect well-defined...
Reflectometry using a white light source has been applied to in situ monitoring of metal organic vapour phase epitaxy InGaN alloy structures on GaN buffer layers. Both epilayers 60-350 nm thickness and InGaN/GaN multi-quantum-well (MQW) with periods order 10 were studied. The have indium mole fractions between 0.105 0.240, determined principally by the growth temperature. standard method deriving film rates from reflectance data is useful predictor epilayer thicknesses, at wavelengths 600 or...
Currently, it is understood that the carrier recombination rate in semiconductors can be modified by metals due to pure electrodynamic interactions through surface plasmons. We propose here an electrostatic mechanism for carrier-metallic nanoparticle interaction comparable effect plasmonic interactions. Arising from Coulomb attraction of electrons and holes their images metal, this produces large concentrations near metallic nanoparticles. Increased concentration results increased quantum...