A5056657768- GaN-based semiconductor devices and materials
- ZnO doping and properties
- Ga2O3 and related materials
- Semiconductor materials and devices
- Quantum Dots Synthesis And Properties
- Metal and Thin Film Mechanics
- Copper-based nanomaterials and applications
- Gas Sensing Nanomaterials and Sensors
- Semiconductor Quantum Structures and Devices
- Chalcogenide Semiconductor Thin Films
- Nanowire Synthesis and Applications
- Silicon Nanostructures and Photoluminescence
- Acoustic Wave Resonator Technologies
- Transition Metal Oxide Nanomaterials
- X-ray Diffraction in Crystallography
- Semiconductor materials and interfaces
- Phase-change materials and chalcogenides
- Perovskite Materials and Applications
- Electronic and Structural Properties of Oxides
- Catalysis and Oxidation Reactions
- Catalytic Processes in Materials Science
- Ion-surface interactions and analysis
- Luminescence Properties of Advanced Materials
- Diamond and Carbon-based Materials Research
- Crystallization and Solubility Studies
University of Aveiro
2015-2024
Complejo Hospitalario Universitario de Santiago
2021
CEA Grenoble
2018
Université Grenoble Alpes
2018
Instituto de Engenharia de Sistemas e Computadores Microsistemas e Nanotecnologias
2018
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2018
Centre National de la Recherche Scientifique
2018
Instituto Politécnico de Lisboa
2008
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...
Hybrid metal oxide nano‐ and microstructures exhibit novel properties, which make them promising candidates for a wide range of applications, including gas sensing. In this work, the characteristics hybrid ZnO‐Bi 2 O 3 ZnO‐Zn SnO 4 tetrapod (T) networks are investigated in detail. The sensing studies reveal improved performance compared to pure ZnO‐T networks. For ZnO‐T‐Bi networks, an enhancement H response is obtained, although observed p‐type behavior attributed formed junctions between...
We report hot filament thermal CVD (HFTCVD) as a new hybrid of and demonstrate its feasibility by producing high quality large area strictly monolayer graphene films on Cu substrates. Gradient in gas composition flow rate that arises due to smart placement the substrate inside Ta wound alumina tube accompanied radical formation precracking coupled with mediated physicochemical processes like diffusion, polymerization etc., led growth. further confirmed our mechanistic hypothesis depositing...
In this work, the exceptionally improved sensing capability of highly porous three-dimensional (3-D) hybrid ceramic networks toward reducing gases is demonstrated for first time. The 3-D are based on doped metal oxides (MexOy and ZnxMe1–xOy, Me = Fe, Cu, Al) alloyed zinc oxide tetrapods (ZnO-T) forming numerous junctions heterojunctions. A change in morphology samples formation different complex microstructures achieved by mixing metallic (Fe, microparticles with ZnO-T grown flame transport...
Vibrational symmetry assignments using Raman spectroscopy and density functional theory on oriented crystals also enabling orientation optimisation of thin films.
Abstract Laser-induced graphene (LIG) is as a promising material for flexible microsupercapacitors (MSCs) due to its simple and cost-effective processing. However, LIG-MSC research production has been centered on non-sustainable polymeric substrates, such polyimide. In this work, it presented cost-effective, reproducible, robust approach the preparation of LIG structures via one-step laser direct writing chromatography paper. The developed strategy relies soaking paper in 0.1 M sodium...
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...
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,...
Laser irradiation of polymeric materials has drawn great attention as a fast, simple, and cost-effective method for the formation porous graphene films that can be subsequently fabricated into low-cost flexible electronic energy-storage devices. In this work, we report systematic study laser-induced (LIG) with sheet resistances low 9.4 Ω/sq on parylene-C ultrathin membranes under CO2 infrared laser. Raman analysis proved multilayered graphenic material, ID/IG I2D/IG peak ratios 0.42 0.65,...
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...
ZnO tetrapods–C<sub>60</sub> based hybrid materials show interesting defect mediated optical and electrical responses which could be suitable for various applications.
ZnO microrods were grown by laser assisted flow deposition technique in order to study their luminescence behaviour the near band edge spectral region. Transmission electron microscopy analysis put evidence high crystallinity degree and microrod's compositional homogeneity. Photoluminescence revealed a dominant 3.31 eV emission. The correlation between this emission presence of surface states was investigated performing plasma treatments with hydrogen nitrogen. significant modifications...
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...
Here we demonstrate a single step approach for the facile reduction of graphene oxide (GO) to hydrogenated reduced (HRGO) under ambient conditions.
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...
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&lt;0.30 0.04&lt;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...