38 documents found, page 1 of 4
Combining x-ray real and reciprocal space mapping techniques to explore the epi...
Magalhaes, S.; Cabaco, J. S.; Concepcion, O.; Buca, D.; Stachowicz, M.; Oliveira, F.; Cerqueira, M. F.; Lorenz, K.; Alves, E.In the present work, the importance of determining the strain states of semiconductor compounds with high accuracy is demonstrated. For the matter in question, new software titled LAPAs, the acronym for LAttice PArameters is presented. The lattice parameters as well as the chemical composition of Al1-xInxN and Ge1-xSnx compounds grown on top of GaN- and Ge-buffered c-Al2O3 and (001) oriented Si substrates, resp...
Suitability of 3D printed pieces of nanocrystalline zirconia for dental applica...
Branco, A. C.; Silva, R.; Santos, T.; Jorge, H.; Rodrigues, A. R.; Fernandes, R.; Bandarra, S.; Barahona, I.; Matos, A. P. A.; Lorenz, K.; Polido, M.Objectives: The main goal of this work is to evaluate the suitability of nanostructured zirconia pieces obtained by robocasting additive manufacturing (AM), for dental applications. Methods: The density, crystalline structure, morphology/porosity, surface roughness, hardness, toughness, wettability and biocompatibility of the produced samples were compared with those of samples obtained by conventional subtract...
Tribological performance of the pair human teeth vs 3D printed zirconia : an in...
Branco, A. C.; Silva, R.; Jorge, H.; Santos, T.; Lorenz, K.; Polido, M.; Colaço, R.; Serro, A. P.; Figueiredo-Pina, C. G.This study aims to evaluate the tribological performance of the pair human teeth/robocasted zirconia, with a special focus on the enamel wear mechanisms. Zirconia pieces produced by robocasting (RC) and unidirectional compression (UC) were compared in terms of crystalline structure, density, porosity, hardness and toughness. Chewing simulation tests were performed against human dental cusps. The cusps wear was ...
Luminescence properties of MOCVD grown Al0.2Ga0.8N layers implanted with Tb
Rodrigues, J.; Fialho, M.; Magalhães, S.; Lorenz, K.; Alves, E.; Monteiro, T.AlxGa1-xN (x = 0.20) layers grown on (0001) sapphire substrates by metal organic chemical vapour deposition were implanted with terbium (Tb) ions at 150 keV with a fluence of 7 × 1014 Tb cm−2 at different temperatures. After thermal annealing, all layers evidenced the Tb-related 5D4-7FJ intra-4f8 transitions, demonstrating an enhancement of their intensity with increasing implantation temperature. A detailed sp...
Defect formation and optical activation of Tb implanted AlxGa1−xN films using c...
Fialho, M.; Magalhães, S.; Rodrigues, J.; Chauvat, M.P.; Ruterana, P.; Monteiro, T.; Lorenz, K.; Alves, E.AlxGa1−xN (x = 0.20, 0.50, 0.63) films grown on (0001) sapphire substrates by metal organic chemical vapor phase deposition were implanted with Tb ions at 150 keV and a fluence of 7 × 1014 Tb cm−2. The implantation was carried out with the beam aligned with the c-axis and the implantation temperature was varied from room temperature (RT) to 550 °C. Additionally, post-implantation rapid thermal annealing was per...
Composition, structure and morphology of Al1-xInxN thin films grown on Al1-yGay...
Magalhaes, S.; Watson, I. M.; Pereira, S.; Franco, N.; Tan, L. T.; Martin, R. W.; O'Donnell, K. P.; Alves, E.; Araujo, J. P.; Monteiro, T.; Lorenz, K.Four nominally Al0.85In0.15N thin films with different strains were grown simultaneously on Al1-yGayN (y = 1, 0.93, 0.87 and 0.69) templates by metal organic chemical vapour deposition. The nominal InN content of similar to 15% was chosen to achieve close lattice matching of Al1-xInxN with the templates of intermediate GaN molar fractions, a small tensile strain for growth on GaN, and compressive strain for the...
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...
Doping of Ga2O3 bulk crystals and NWs by ion implantation
Lorenz, K.; Peres, M.; Felizardo, M.; Correia, J. G.; Alves, L. C.; Alves, E.; Lopez, I.; Nogales, E.; Mendez, B.; Piqueras, J.; Barbosa, M. B.Ga2O3 bulk single crystals have been implanted with 300 keV Europium ions to fluences ranging from 1x10(13) to 4x10(15) at/cm(2). The damage build-up and Eu-incorporation was assessed by Rutherford Backscattering Spectrometry in the channeling mode (RBS/C). RBS/C results suggest that implantation causes a mixture of defect clusters and extended defects such as dislocations. Amorphisation starts at the surface f...
The influence of photon excitation and proton irradiation on the luminescence p...
Soares, M. R. N.; Soares, M. J.; Alves, L. C.; Alves, E.; Lorenz, K.; Costa, F. M.; Monteiro, T.Lanthanide doped zirconia based materials are promising phosphors for lighting applications. Transparent yttria stabilized zirconia fibres, in situ doped with Pr3+ ions, were grown by the laser floating zone method. The single crystalline doped fibres were found to be homogeneous in composition and provide an intense red luminescence at room temperature. The stability of this luminescence due to transitions bet...
Disorder induced violet/blue luminescence in rf-deposited ZnO films
Peres, M.; Magalhaes, S.; Soares, M. R.; Soares, M. J.; Rino, L.; Alves, E.; Lorenz, K.; Correia, M. R.; Lourenco, A. C.; Monteiro, T.In this work ZnO thin films were deposited on different substrates, glass, silicon (100), and MgO (100) using rf-magnetron sputtering at low temperature in order to promote a large defect density, aiming to study a possible correlation with the observed violet/blue emission band. The peak position, width and low energy band shape asymmetry of the violet/blue band was found to be dependent on the deposition temp...