11 documents found, page 1 of 2
BiLaWO6: Er3+/Tm3+/Yb3+ phosphor: study of multiple fluorescence intensity rati...
Pavani, K.; Neves, A. J.; Pinto, Ricardo J. B.; Freire, Carmen S. R.; Soares, M. J.; Graça, M. P. F.; Kumar, K. Upendra; Jakka, S.K.
Práticas da História. Journal on Theory, Historiography and Uses of the Past (2...
Neves, A. J.
Práticas da História. Journal on Theory, Historiography and Uses of the Past (2...
Neves, A. J.
Role of high microwave power on growth and microstructure of thick nanocrystall...
Tang, C. J.; Fernandes, A. J. S.; Girao, A. V.; Pereira, S.; Shi, Fa-Nian; Soares, M. R.; Costa, F.; Neves, A. J.; Pinto, J. L.In this work, we study the growth habit of nanocrystalline diamond (NCD) films by exploring the very high power regime, up to 4 kW, in a 5 kW microwave plasma chemical vapour deposition (NiPCVD) reactor, through addition of a small amount of nitrogen and oxygen (0.24%) into 4% CH4, in H-2 plasma. The coupled effect of high microwave power and substrate temperature on NCD growth behaviour is systematically inves...
ZnO micro/nanocrystals grown by Laser Assisted Flow Deposition
Rodrigues, J.; Fernandes, A. J. S.; Mata, D.; Holz, T.; Carvalho, R. G.; Allah, R. Fath; Ben, T.; Gonzalez, D.; Silva, R. F.; da Cunha, A. F.Laser assisted flow deposition (LAFD) is a very high yield method based on a vapor-solid mechanism, allowing the production of ZnO crystals in a very short time. The LAFD was used in the growth of different morphologies (nanoparticles, tetrapods and microrods) of ZnO micro/nanocrystals and their microstructural characterization confirms the excellent crystallinity of the wurtzite structure. The optical properti...
ZnO nano/microstructures grown by laser assisted flow deposition
Rodrigues, J.; Peres, M.; Soares, M. R. N.; Fernandes, A. J. S.; Ferreira, N.; Ferro, M.; Neves, A. J.; Monteiro, T.; Costa, F. M.Nano/microstructures of zinc oxide (ZnO) were grown by the laser assisted flow deposition (LAFD) method. This new process has proved to be very efficient, allowing high yield ZnO deposits at high-rate applicable to large-scale substrates. Laser local heating promotes fast ZnO decomposition and recombination under a self-catalytic vapour–liquid-solid mechanism for the nucleation and growth. Three types of ZnO mo...
Rare earth co-doping nitride layers for visible light
Rodrigues, J.; Miranda, S. M. C.; Santos, N. F.; Neves, A. J.; Alves, E.; Lorenz, K.; Monteiro, T.AlN and GaN films were co-implanted with europium and praseodymium ions followed by thermal annealing treatments for the lattice recovery and ions activation. Their structural and optical properties were studied by Rutherford Backscattering Spectrometry and optical spectroscopy techniques. The evolution of the ions photoluminescence intensity with temperature was analyzed for both AlN:Eu,Pr and GaN:Eu,Pr hosts,...
Influence of neutron irradiation and annealing on the optical properties of GaN
Rodrigues, J.; Peres, M.; Soares, M. J.; Lorenz, K.; Marques, J. G.; Neves, A. J.; Monteiro, T.Epitaxial GaN layers were irradiated with fast and thermal neutrons in the Portuguese Research Reactor. Irradiation leads to a quenching of the typical GaN near band edge and yellow luminescence for samples excited with above band gap photon energy. Although structural techniques indicate a full recovery of irradiation damage for annealing at 1000 ºC, the near band edge emission is not recovered after annealing...
Morphological and optical studies of self-forming ZnO nanocolumn and nanocone a...
Peres, M.; Soares, M. J.; Neves, A. J.; Monteiro, T.; Sandana, V. E.; Teherani, F.; Rogers, D. J.ZnO nanostructures were grown by pulsed laser deposition on c-sapphire, Si (111) (n-type and p-type) and analysed using morphological and optical techniques. Under optimized growth conditions, self-forming arrays of vertically aligned nanostructures were obtained. Scanning electron microscopy studies revealed two main structures: nanocolumns and a ‘moth-eye type’ array of nanocones, which gave a graded effectiv...
Optical doping and damage formation in AIN by Eu implantation
Lorenz, K.; Alves, E.; Gloux, F.; Ruterana, P.; Peres, M.; Neves, A. J.; Monteiro, T.AlN films grown on sapphire were implanted with 300 keV Eu ions to fluences from 3×1014 to 1.4×1017 atoms/cm2 in two different geometries: “channeled” along the c-axis and “random” with a 10° angle between the ion beam and the surface normal. A detailed study of implantation damage accumulation is presented. Strong ion channeling effects are observed leading to significantly decreased damage levels for the chan...