Referencia principal do MROX
1. Multiple reflection optimization package for X-ray diffraction
Abstract New software titled Multiple Reflection optimization package for X-ray diffraction (MROX) to simulate and fit multiple reflections simultaneously, as well as single reflections, is presented. The simulation employs the recursive solution of the dynamical theory of X-ray diffraction to derive the deformation profile as a function of depth, ε⊥. It is applied to argon ions implanted 650 nm thick aluminium gallium nitride layers grown on c-sapphire substrates.The implantation is performed on five different pieces of the as-grown sample normal to the sample surface with increasing energies between 25 keV and 250 keV. The individual as-grown pieces reveal very good crystalline quality ... More...
S. Magalhães, J. S. Cabaço, J. P. Araújo, E. Alves
Publicações usando o MROX - XRD
10. MROX 2.0: a software tool to explore quantum heterostructures by combining X-ray reflectivity and diffraction
Synopsis New software for the simulation and fitting of X-ray reflectivity measurements is developed. The software uses the same layout as the published MROX for X-ray diffraction allowing users a faster learning curve. It is exemplified on samples with increasing layering complexity: from 1 to 10 Si/Ge periods grown Si templates and (001) substrates and one complex ZnO/Zn1-xMgxO superlattice grown on m-ZnO substrate. More...
S. Magalhães, C. Cachim, P. D. Correia, F. Oliveira, F. Cerqueira, J. M. Sajkowski, M. Stachowicz
9. Confronting Vegard's rule in Ge1-xSnx epilayers: from fundamentals to the effect of defects
Abstract Comprehensive and systematic study challenging the application of Vegard's rule to germanium tin solid solutions grown on germanium buffer layers and 100 silicon substrates is presented. The binary's lattice parameters, composition and respective uncertainties are determined through x-ray diffraction via reciprocal space mapping technique employing newly developed software. The tin content is confirmed by Rutherford backscattering spectrometry and energy dispersive x-ray spectroscopy. The statistical agreement between the tin contents derived by the different structural characterization techniques suggests the binary to follow generically the Vegard's rule in the range of low Sn molar fractions (less than 5%). More...
S. Magalhães, M. Dias, B. Nunes, F. Oliveira, M. F. Cerqueira and E. Alves
8. Structural analysis of the ZnO/MgO superlattices on a-polar ZnO substrates grown by MBE
Abstract The analysis of heteroepitaxially grown ZnO/MgO superlattices on a-oriented ZnO substrates was described. The influence of unalike natural crystalline structures of ZnO and MgO on the interface’s abruptness and retaining wurtzite crystallinity was studied. Wurtzite structure was found to be retained in the MgO thin barriers up to 1.5 nm, but creation of nonuniform biaxial strains and some interdiffusion of Mg from barriers to ZnO QW’s seemed to be inevitable. More...
M. Stachowicz, A. Wierzbicka, J. M. Sajkowski, M. A. Pietrzyk, P. Dłużewski, E. Dynowska, J. Dyczewski, K. Morawiec, S. B. Kryvyi, S. Magalhães, E. Alves, A. Kozanecki
7. Simulating the effect of Ar+ energy implantation on the strain propagation in AlGaN
Abstract In this work high quality AlGaN layers, grown by MOCVD (Metal Organic Chemical Vapour Deposition), on a commercial c-sapphire substrate, were implanted at a fluence of 1×1014 Ar+.cm-2. Implantation was performed for energies between 25 to 250 keV to explore the strain field created with increasing penetration of the implanted ions. Perpendicular to the sample surface deformation was determined through simulations of the 2θ-ω scans of the allowed (0002), (0004) and (0006) AlGaN reflections. According to the simulations, the peak attributed to the implanted region is well defined using a small number of layers with specific thickness, deformation, and static Debye-Waller factors. More...
J. S. Cabaço, D. Nd. Faye, J. P. Araújo, E. Alves, S. Magalhães
6. Crystal mosaicity determined by a novel layer de-convolution Williamson-Hall method
Abstract The application of conventional Williamson–Hall (WH) plot analysis to crystals often results in broadening not proportional to the scattering length vector. Several reasons may influence the broadening such as composition or strain heterogeneities, wafer curvature, dislocation anisotropy and other defects. In this work, linearization of WH plots is achieved given the assumption that the total crystal size may be deconvoluted into a finite number of layers, each with a constant thickness, strain and mosaic spread. A novel linearization algorithm, the layer deconvolution WH (LdCWH) method, employs a finite number of pseudo-Voigt (PV) functions for each measurement. More...
S. Magalhães, J. S. Cabaço, R. Mateus, D. Nd. Faye, D. R. Pereira, M. Peres, K. Lorenz, C. Díaz-Guerra, J. P. Araújo, E. Alves
5. Quantitative x-ray diffraction analysis of bimodal damage distributions in Tm implanted Al0.15Ga0.85N
Abstract In this work radial symmetric x-ray diffraction scans of Al0.15Ga0.85N thin films implanted with Tm ions were measured to determine the lattice deformation and crystal quality as functions of depth. The alloys were implanted with 300 keV Tm with 10° off-set to the sample normal to avoid channelling, with fluences varying between 1013 Tm cm−2 and 5 × 1015 Tm cm−2. Simulations of the radial 2θ–ω scans were performed under the frame of the dynamical theory of x-ray diffraction assuming Gaussian distributions of the lattice strain induced by implantation defects. More...
S. Magalhães, M. Fialho, M. Peres, K. Lorenz and E. Alves
4. RBS/C, XRR, and XRD Studies of Damage Buildup in Er‐Implanted ZnO
Abstract Accumulation and transformation of defects formed in bulk ZnO crystals at room temperature upon 300 keV Er ions bombardment have been thoroughly examined using complementary techniques: Rutherford Backscattering Spectrometry in ion Channeling mode (RBS/C), X‐Ray Reflectivity (XRR), and X‐Ray Diffraction (XRD). Evaluation of RBS/C spectra has been performed using Monte Carlo (MC) simulations (McChasy software). Two defect types have been indicated: point defects (randomly displaced atoms, RDA) and extended ones (edge dislocations, DIS). More...
P. Jozwik, S. Magalhães, R. Ratajczak, C. Mieszczynski, M. Sequeira, A. Turos, R. Böttger, R. Heller, K. Lorenz, E. Alves
3. Defect formation and optical activation of Tb implanted AlxGa1− xN films using channeled implantation at different temperatures
Abstract 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 performed at 1200 °C during 120 s. The impact of implantation temperature on the damage accumulation is investigated. Rutherford backscattering spectrometry/channeling (RBS/C) measurements show that two damage regions are forming and the damage is not decreasing monotonically with the increase of implantation temperature. More...
M. Fialho, S. Magalhaes, J. Rodrigues, M. P. Chauvat, P. Ruterana, T. Monteiro, K. Lorenz, E. Alves
2. Teses de Mestrado
1. Pedro Mendes Measuring strain caused by ion implantation in GaN
Supervisores K. Lorenz (IST) e S. Magalhães (IST)
2. João Cabaço Effect of Ar implantation Energy and Angle on the reflection pattern of nitrides
Supervisores J. P. Araújo Lorenz (FCUP) e S. Magalhães (IST)
Publicações usando o MROX - XRR
3. MROX 2.0: a software tool to explore quantum heterostructures by combining X-ray reflectivity and diffraction
Synopsis New software for the simulation and fitting of the specular X-ray reflectivity (XRR) measurements is developed. The novel software employs the recursive formalism of the dynamical theory of X-ray scattering and constitutes an extension of the Multiple Reflection Optimization package for X-ray diffraction (MROX). The software is used to determine the layer thicknesses, mass densities and roughness’s of quantum heterostructures of two sets of samples: 5 Si/Ge bi-layers with 1, 2, 3, 4 and 10 periods grown on Si buffer layers and (001) Si substrates, and a 50 period ZnO/Zn1-xMgxO layers grown on a m-ZnO substrate. For the case of the group IV elemental semiconductors, an increase in the interfaces roughness’s with increasing number of periods is found. ... More...
S. Magalhães, C. Cachim, P. D. Correia, F. Oliveira, F. Cerqueira, J. M. Sajkowski, M. Stachowicz
2. A Molybdenum Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates
Abstract Molybdenum oxide thin films were deposited on stiff and flexible substrates by reactive DC magnetron sputtering. Two sets of samples were prepared. The first with different O2/Ar flow rate ratios and the second, fixing the oxygen content, with different time of deposition. As the O2/Ar flow rate ratio varies from 0 up to 0.56, a threshold was found, ranging from crystalline to amorphous nature, and from a nontransparent appearance with metallic-like electrical conductivity to transparent and dielectric behaviour. ... More...
A. Marciel, M. Graça, A. Bastos, L. Pereira, J. S. Kumar, J. Borges, F. Vaz, M. Peres, S. Magalhães, K. Lorenz, R. Silva
1. Ar+ irradiation of magnetic tunnel junction multilayers: Impact on the magnetic and electrical properties
Abstract The impact of 400 keV Ar+ irradiation on the magnetic and electrical properties of in-plane magnetized magnetic tunnel junction (MTJ) stacks was investigated by ferromagnetic resonance, vibrating sample magnetometry and current-in-plane tunneling techniques. The ion fluences ranged from 1012 cm- 2 to 5 × 1015cm- 2. Below 1014cm- 2, the anisotropy of the Ta-capped FeCoB free layer was weakly modulated, following a decrease in the saturation magnetization. The tunnel magnetoresistance (TMR), along with the exchange-bias and the interlayer exchange coupling... More...
B. M. S. Teixeira, A. A. Timopheev, N. Caçoilo, L. Cuchet, J. Mondaud, J. Childress, S. Magalhães, E. Alves, N. A. Sobolev