Repositório Comunidade: CDF_FCTCDF_FCThttps://hdl.handle.net/1822/18952024-03-29T04:43:49Z2024-03-29T04:43:49ZFerroelectric orthorhombic ZrO2 thin films achieved through nanosecond laser annealingCrema, Anna P. S.Istrate, Marian C.Silva, AlexandreLenzi, VenieroDomingues, LeonardoHill, Megan O.Teodorescu, Valentin S.Ghica, CorneliuGomes, Maria J. M.Pereira, MarioMarques, L.MacManus-Driscoll, Judith L.Silva, Jose P. B.https://hdl.handle.net/1822/857092023-12-22T12:21:46Z2023-07-26T09:10:34ZTítulo: Ferroelectric orthorhombic ZrO2 thin films achieved through nanosecond laser annealing
Autor: Crema, Anna P. S.; Istrate, Marian C.; Silva, Alexandre; Lenzi, Veniero; Domingues, Leonardo; Hill, Megan O.; Teodorescu, Valentin S.; Ghica, Corneliu; Gomes, Maria J. M.; Pereira, Mario; Marques, L.; MacManus-Driscoll, Judith L.; Silva, Jose P. B.
Resumo: A new approach for the stabilization of the ferroelectric orthorhombic ZrO2 films is demonstrated through nanosecond laser annealing (NLA) of as-deposited Si/SiOx/W(14 nm)/ZrO2(8 nm)/W(22 nm), grown by ion beam sputtering at low temperatures. The NLA process optimization is guided by COMSOL multiphysics simulations. The films annealed under the optimized conditions reveal the presence of the orthorhombic phase, as confirmed by X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Macroscopic polarization-electric field hysteresis loops show ferroelectric behavior, with saturation polarization of 12.8 mu C cm(-2), remnant polarization of 12.7 mu C cm(-2) and coercive field of 1.2 MV cm(-1). The films exhibit a wake-up effect that is attributed to the migration of point defects, such as oxygen vacancies, and/or a transition from nonferroelectric (monoclinic and tetragonal phase) to the ferroelectric orthorhombic phase. The capacitors demonstrate a stable polarization with an endurance of 6.0 x 10(5) cycles, demonstrating the potential of the NLA process for the fabrication of ferroelectric memory devices with high polarization, low coercive field, and high cycling stability.
<b>Tipo</b>: article2023-07-26T09:10:34ZElectronic transport through a biphenyl system as a function of torsion angle with a complex absorbing potential to model the self-energy in a scattering approachMoreira, A. C. L.de Melo, C. P.Marques, L.https://hdl.handle.net/1822/857042023-07-26T08:55:10ZTítulo: Electronic transport through a biphenyl system as a function of torsion angle with a complex absorbing potential to model the self-energy in a scattering approach
Autor: Moreira, A. C. L.; de Melo, C. P.; Marques, L.
Resumo: In this work, we present a self-energy model based on the complex absorbing potential (CAP) method to calculate the transmission function through an extended molecule using scattering theory. Once the CAP mimics an infinite environment at the ends of a finite system, it can be used as a model for self-energy with a low computational cost. Moreover, the matrixes required for the transport calculation can be obtained from an ab initio calculation of some extended molecules in a single step using an adjustable model, thus taking into account changes in the electronic structure of the system. This approach was applied to study electron transport across a biphenyl molecular system for different torsion angles under an external applied electric field. The results obtained are in good agreement with the available theoretical and experimental results in the literature and provide an efficient approach, with a low computational cost method, for the interpretation of electrical transport at the molecular level.
<b>Tipo</b>: articleAnalytical tool for optimization of position sensors based on eddy currents effectFaria, Andreia Raquel SampaioMarques, L.Vale, LuisFerreira, CarlosAlves, FilipeCabral, Jorgehttps://hdl.handle.net/1822/852172023-07-25T15:03:52Z2023-06-27T09:44:28ZTítulo: Analytical tool for optimization of position sensors based on eddy currents effect
Autor: Faria, Andreia Raquel Sampaio; Marques, L.; Vale, Luis; Ferreira, Carlos; Alves, Filipe; Cabral, Jorge
Resumo: This paper proposes an open-source tool for a fast and precise calculation of the inductance of planar coils in the presence of conductive targets. This tool, based on Grover equations, is versatile to any coil and target geometries. The performance of this tool has been validated by comparing the analytical results with experimental data and Finite Element Model (FEM) simulations. When compared with the experimental measurements, the developed analytical model and the FEM simulation retrieved similar results, with differences below 4%. The proposed tool, in addition to requiring less computing resources, is significantly faster than FEM simulations. This shows the effectiveness of the proposed approach for the analytical calculation of the inductance of planar coils in the presence of conductive plates. It combines accuracy, versatility, speed, and no need for high computational resources.
<b>Tipo</b>: article2023-06-27T09:44:28ZTwo-dimensional fluid approach to the dc magnetron dischargeCostin, CMarques, L.Popa, G.Gousset, G.https://hdl.handle.net/1822/842572023-05-04T12:01:31Z2023-05-04T08:13:45ZTítulo: Two-dimensional fluid approach to the dc magnetron discharge
Autor: Costin, C; Marques, L.; Popa, G.; Gousset, G.
Resumo: A two-dimensional (r, z) time-dependent fluid model was developed and used to describe a dc planar magnetron discharge with cylindrical symmetry. The transport description of the charged species uses the corresponding first three moments of the Boltzmann equation: continuity, momentum transfer and mean energy transfer (the last one only for electrons), coupled with the Poisson equation. An original method is proposed to treat the transport equations. Electron and ion momentum transport equations are reduced to the classical drift-diffusion expression for the fluxes since the presence of the magnetic field is introduced as an additional part in the electron flux, while for ions an effective electric field was considered. Thus, both continuity and mean energy transfer equations are solved in a classical manner. Numerical simulations were performed considering argon as a buffer gas, with a neutral pressure varying between 5 and 30 mTorr, for different voltages applied on the cathode. Results obtained for densities of the charged particle, fluxes and plasma potential are in good agreement with those obtained in previous studies.
<b>Tipo</b>: article2023-05-04T08:13:45ZFELINE: Finite element solver for hydrodynamic lubrication problems using the inexact Newton methodSilva, AlexandreLenzi, VenieroCavaleiro, AlbanoCarvalho, SandraMarques, L.https://hdl.handle.net/1822/784302022-11-29T22:47:14Z2022-06-20T15:02:33ZTítulo: FELINE: Finite element solver for hydrodynamic lubrication problems using the inexact Newton method
Autor: Silva, Alexandre; Lenzi, Veniero; Cavaleiro, Albano; Carvalho, Sandra; Marques, L.
Resumo: In this work we present FELINE, a C++ solver of the Reynolds equation for treating hydrodynamic lubrication problems. To correctly describe cavitation regions, FELINE implements the inexact Newton iteration (INE) algorithm within a finite element method (FEM) framework. The solver was tested and validated against known cases in literature and industrially relevant cases of dimpled textures. Furthermore, we provide a benchmark for a complex dimpled texture case to evaluate the performance and robustness of the implementation. FELINE performs very fast when compared with existing implementations and shows a great degree of stability, while providing physically correct solutions thanks to the INE algorithm.
<b>Tipo</b>: article2022-06-20T15:02:33Z