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Today’s environmental needs require the reduction of the weight of vehicles, thus reducing fuel consumption and associated emissions. For this reason, the use of light alloys is being studied, which, due to their reactivity, must be protected before use. In this work, the effectiveness of a hybrid sol-gel coating doped with various organic environmentally friendly corrosion inhibitors applied to an AA2024 lightweight aluminium alloy is evaluated. Some of the inhibitors tested are pH indicators, acting as both corrosion inhibitors and optical sensors for the surface of the alloy. Samples are subjected to a corrosion test in a simulated saline environment and characterised before and after the test. The experimental results regarding their best inhibitor performance for their potential application in the transport industry are evaluated., Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía, Comercio y Empresa (España), Depto. de Física de Materiales, Fac. de Ciencias Físicas, Instituto de Magnetismo Aplicado (IMA), TRUE, pub

© 2001 The American Physical Society. A. Mu., F. J. G. de A., and J. E. O. are supported by the Universidad del País Vasco (1/UPV/EHU/00057.240-EA-8078/2000) and the Max Planck Research Award Program. V. R. and S. R. are supported by the CNRS-ULTIMATECH program, the CRIF, and the Université de Paris 7. A. Ma. is supported by a Marie Curie Fellowship of the European Union, under Contract No. HPMF-CT-2000-00565. V. P.-D. is supported by the Comunidad Autónoma de Madrid (Project No. 07N/0042/98) and the DEFICIT (Spain) (Grant No. PB-97-1199). The experiments performed at LURE were funded by the Large Scale Facilities program of the European Union. Critical reading of the manuscript by F. J. Himpsel is acknowledged. Technical support from the Spanish-French beam line staff is gratefully acknowledged., STM images show that vicinal Au(788) surfaces are made up or a uniform array of (111)-oriented terraces of similar width (similar to3.8 nm). This uniformity makes it possible to study the electronic Structure of the resulting step superlattice by angle-resolved photoemission. We show that for this terrace array the surface state appears to be broken up into one-dimensional quantum-well levels, indicating total electron confinement within the terraces. The angular resolution allows the probability density of the terrace quantum well state to be mapped in reciprocal space, complementing nicely the wave function measured in real space by STM., Universidad del País Vasco, CNRS-ULTIMATECH, CRIF, Université de Paris 7, Marie Curie Fellowship of the European Union, Comunidad Autónoma de Madrid, DEFICIT (Spain), Max Planck Research Award Program, Large Scale Facilities program of the European Union, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1996 - Elsevier Science S.A.. International Workshop on Beam Injection Assessment of Defects in Semiconductors (BIADS 96) (4. 1996. El Escorial, España). A. Cremades thanks the Universidad Complutense for a predoctoral grant. This work has been partially supported by DGICYT Projects No. HP95-98B and PB93- 1256., GaN epitaxial layers have been investigated by cathodoluminescence (CL) in the scanning electron microscope (SEM). The most prominent feature of the spectra is a complex band at 2.2 eV, whose evolution with temperature and excitation density suggests emission mechanisms involving a deep center and donor-donor or donor-acceptor pairs. Time resolved photoluminescence (TRPL) measurements confirm the involvement of a deep center in the emission. CL images reveal that the centers responsible for this emission decorate grain boundaries. Emission bands al 2.87 eV and 1.31 eV have been also detected in the films., DGICYT (Spain), Universidad Complutense, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© Institute of Physics This research was supported by the U.S. Department of Energy under contracts No. DEAC04-94AL85000 and DE-AC02-05CH11231 and by the Spanish Ministry of Science and Innovation under Projects No. MAT2009-14578-C03-01 and No. FIS2007-64982., For the non-magnetic system of Ag films on Ru(0001), we have measured the circular dichroism of photoelectrons emitted along the surface normal, the geometry typically used in photoemission electron microscopy. Photoemission spectra were acquired from micrometer-sized regions having uniformly thick Ag films on a single, atomically flat Ru terrace. For a single Ag layer, we find a circular dichroism that exceeds 6% at the d-derived band region around 4.5 eV binding energy. The dichroism decreases as the Ag film thickness increases to three atomic layers. We discuss the origin of the circular dichroism in terms of the symmetry lowering that can occur even in normal emission., US Department of Energy, Spanish Ministry of Science and Innovation, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2002 American Institute of Physics. This work was supported by MCYT /Project MAT2000-2119)., Near-field cathodoluminescence (NFCL) has been used to characterize hydride vapor phase epitaxy grown n-GaN films. This technique can obtain high resolution luminescence images and perform local measurements of the diffusion length for minority carriers in different parts of the sample. NFCL contrast observed in round growth hillocks at the sample surface, with a diameter of less than 10 mum, is compared with that observed by conventional cathodoluminescence in scanning electron microscope (CLSEM) techniques. In particular NFCL images reveal features not detected by CLSEM which is explained by the fact that under near field conditions the signal arises from a depth of only several tens of nanometers and is then directly related to the surface hillocks. Diffusion lengths of about 0.4 and 4 mum have been found for the holes in different regions of the samples at room temperature. The order of magnitude of these minority carriers diffusion lengths is in good agreement with previous measurements performed at different GaN samples with other techniques. The NFCL contrast and the differences in the measured diffusion lengths are discussed and explained by variations in local trap concentrations., MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© EDP Sciences. International Conference on Defects - Recognition, Imaging and Physics in Semiconductors (DRIP 10). (10.2003.Batz sur Mer, FRANCE ). This work has been supported by MCYT (Project MAT 2000- 2119). R. Plugaru acknowledges MECD for the research grant SB2000-0164., The luminescence of amorphous silicon layers either implanted with Er or co-implanted with Er and O has been studied by photoluminescence (PL) and cathodoluminescence (CL) in the scanning electron microscope. Annealing in nitrogen causes the formation of oxide species and Er-Si complexes or precipitates as well a spectral changes in the visible and infrared ranges. The main CL emission takes place in the visible range while PL spectra reveal intense visible and infrared emission. CL spectra show blue-violet, or green, emission bands whose relative intensities depend on the post-implantation annealing temperature. The PL spectra show a blue-violet band with a series of lines in the violet region related to phonon assisted transitions as well as different emission bands in the range 1200-1500 nm. The influence of the annealing-induced structural changes on the observed spectra is discussed., MCYT, MECD, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2003 Elsevier Science B.V. All rights reserved. The authors want to thank V. A. Malyshev for the critical reading of the manuscript. Work in Madrid was supported by DGI-MCyT (Project MAT2000-0734) and CAM (Project 07N/0075/2001). P. Orellana would like to thank Milenio ICM P99-135-F and Cátedra Presidencial de Ciencias for financial support., We present a novel model to calculate vertical transport properties such as conductance and current in unintentionally disordered double-barrier GaAs-AlxGa1-xAs heterostructures. The source of disorder comes from interface roughness at the heterojunctions (lateral disorder) as well as spatial inhomogeneities of the Al mole fraction in the barriers (compositional disorder). Both lateral and compositional disorder break translational symmetry along the lateral direction and therefore electrons can be scattered off the growth direction. The model correctly describes channel mixing due to these elastic scattering events. In particular, for realistic degree of disorder, we have found that the effects of compositional disorder on transport properties are negligible as compared to the effects due to lateral disorder., DGI-MCyT, CAM, Milenio ICM, Cátedra Presidencial de Ciencias, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

©2010 The American Physical Society. Travel between Bayreuth and Madrid was supported by the joint program Acciones Integradas of Deutscher Akademscher Auslandsdienst (DAAD) and Ministerio de Educación y Ciencia (MEC). C.G. and C.A.M acknowledge financial support from Deutsche Forschungsgemeinschaft (DFG), and thank H.-C. Nägerl and his group for hospitality and helpful discussions. Work at Madrid was supported by MEC (Project MOSAICO). Work at Maceio was partially supported by the Brazilian research agencies Conselho Nacional de Desenvolvimento Científico e Tecnologico (CNPq) and Coordenac ión de Aperfecionamiento de Pessoal de Nível Superior (CAPES)., Bloch oscillations of Bose-Einstein condensates realize sensitive matter-wave interferometers. We investigate the dynamics and stability of bright-soliton wave packets in one-dimensional tilted optical lattices with a modulated mean-field interaction g(t). By means of a time-reversal argument, we prove the stability of Bloch oscillations of breathing solitons that would be quasistatically unstable. Floquet theory shows that these breathing solitons can be more stable against certain experimental perturbations than rigid solitons or even noninteracting wave packets., Deutscher Akademischer Auslandsdienst (DAAD), Ministerio de Educacion y Ciencia (MEC), Deutsche Forschungsgemeinschaft (DFG), MEC, Brazilian research agencies Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2003 American Institute of Physics. The authors wish to thank D. C. Look, H. Morkoc¸ and J. van Nostrand for providing the investigated material. C. D.-G. acknowledges M. E. C. D. for a postdoctoral research grant. This work has been partially supported by MCYT through Project No. MAT2000-2119., Time-resolved cathodoluminescence (TRCL) and photocurrent (PC) spectroscopies have been applied to the study of the yellow band of Si-doped GaN. Measurements carried out combining both techniques unambiguously reveal the complex nature of this broad emission and confirm that different deep defect levels are involved in the observed luminescence. Five emission bands centered at 1.89, 2.03, 2.16, 2.29, and 2.38 eV were found by steady state and time-resolved CL investigations, while PC spectra showed four transitions at about 2.01, 2.14, 2.28, and 2.43 eV. The behavior of the deep-level emissions intensity as a function of the excitation pulse width as well as their decay times were investigated by TRCL. A decay time of 245 mus was measured for the 2.29 eV emission band, while longer decay times of 315 and 340 mus were found, respectively, for the 2.16 and 2.38 eV bands, in agreement with TRCL spectra. The appearance of the 2.03, 2.16, 2.29 eV and 2.38-2.43 eV peaks both in PC and CL spectra suggests that these bands are related to deep acceptor to band transitions, as supported by the single exponential character of the corresponding decay transients., MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2004 IOP Publishing Ltd. This work is carried out in the framework of a European Marie Curie project (HPMT-CT-2001-00215). Support of MCYT (MAT2003-00455) is acknowledged., The effect of electrochemical etching of n-type GaSb in aqueous solutions of HCl and HF has been analysed. By anodization in HCl, two different morphologies of porous layers were observed depending on the current density. At low current density (0.5 mA cm_(-2)) a macroporous layer is formed with the pores following preferential directions, while at high current density (15 mA cm_(-2)) pores of sizes less than 100 nm were observed. Furthermore, a comparison between the luminescence in the porous layer and bulk GaSb is also performed. On the other hand, anodization in HF leads to an electropolishing process and no porosification is obtained., European Marie Curie project, MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1998 The American Physical Society. Work at Russia was supported by the Russian Foundation for Basic Research (Project No. 95-03-09221). Work at Madrid was supported by CICYT under Project No. MAT95-0325. V.A.M. thanks Universidad de Salamanca, where this study was started, for hospitality., We study a one-dimensional Frenkel Hamiltonian with off-diagonal disorder, focusing our attention on the physical nature of the zero-energy peak of the density of states. The character of excitonic states (localized or delocalized) is also examined in the vicinity of this peak by means of the inverse participation ratio. It is shown that the state being responsible for the peak is localized. A detailed comparison of the nearest-neighbor approach with the long-range dipole-dipole coupling is performed., Russian Foundation for Basic Research, CICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2008 Elsevier B.V. This work was partially supported by the following Projects: ESP2006-09935, Spanish ‘‘Ministerio de Educación y Ciencia’’; S-0505/MAT-0279, Spanish ‘‘Comunidad de Madrid’’; FP7-SEC- 2007-01, European Commission, and Contract number 14240/00/ NL/SH, European Space Agency. One of the authors VC is thankful to the Ministry of Education and Science, Spain for the financial support. The author NV is grateful to Department of Science and Technology, Govt. of India for providing the BOYSCAST fellowship. The author JRF is thankful to the Universidad Autónoma of Madrid for financial support., The II-VI compound semiconductor crystal cadmium zinc telluride (CZT) is very important in the field of room-temperature radiation detectors and medical imaging applications. In the present study, bulk CZT single crystal has been grown by (i) oscillatory Bridgman technique, (ii) from vapour phase using pyrolytic boron nitride ampoule in the Bridgman geometry, and (iii) by using a Pt tube used for the ampoule support as a cold finger. Several improvements were found in the thermal environments such as the effects of superheating and reduced growth velocity, as well as improvements in the grain size and zinc composition along the ingot. The compositional homogeneity and its current-voltage characteristic behaviour have been analysed using energy dispersive X-ray analysis and I-V method, respectively., España. Ministerio de Educación y Ciencia, Comunidad de Madrid, European Commission, European Space Agency, Department of Science and Technology, Govt. of India, Universidad Autónoma de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

©2012 Elsevier B.V. This work was supported by MICINN (Projects MAT2009-07882 and CSD2009-0013). B. Sotillo acknowledges Ministerio de Educación (Subprograma FPU) of Spain for financial support., ZnS nanowires and nanoribbons have been obtained by the vapor–solid (VS) method. The morphology depends mainly on the deposition temperature; nanowires are grown at temperatures between 300 °C and 650 °C while the growth of nanoribbons takes place at deposition temperatures in the range 650 °C–900 °C. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies show that from cubic ZnS precursor hexagonal-phase nanostructures are obtained. Cathodoluminescence (CL) and photoluminescence (PL) measurements show a dominance of the native defects related emission compared to the near band edge emission, with marked differences between nanowires and nanoribbons., MICINN (Ministerio de Ciencia e Innovación, España), Ministerio de Educación (Subprograma FPU) of Spain, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© Copyright IOP Publishing. This work was supported by Ramón y Cajal Program, MEC (Project MOSAICO), and BSCH-UCM (Project PR34/07-15916)., We present a theoretical analysis of the effects of the environment on charge transport in double-stranded synthetic poly(G)-poly(C) DNA molecules attached to two ideal leads. Coupling of the DNA to the environment results in two effects: (i) localization of carrier functions due to static disorder and (ii) phonon-induced scattering of the carriers between the localized states, resulting in hopping conductivity. A nonlinear Pauli master equation for populations of localized states is used to describe the hopping transport and calculate the electric current as a function of the applied bias. We demonstrate that, although the electronic gap in the density of states shrinks as the disorder increases, the voltage gap in the I-V characteristics becomes wider. A simple physical explanation of this effect is provided., Ministerio de Educación y Ciencia (MEC), España, Programa Ramón y Cajal (MEC), Banco Santander Central Hispano (BSCH), Universidad Complutense de Madrid (UCM), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2004 The American Physical Society. The authors thank A. Rodríguez, M. A. Martín-Delgado, and G. Sierra for discussions. This work was supported by DGI-MCyT (MAT2003-01533) and MECyD (SB2001 -0146), We consider a two-parameter one-dimensional Hamiltonian with uncorrelated diagonal disorder and nonrandom long-range intersite interaction J(mn)=J/\m-n\(mu). The model is critical at 1

(C) 1999 Elsevier Science B.V. All rights reserved. The authors thank A. Sánchez for critical reading of the manuscript. This work was supported by CAM under Project 07N/0034/98. V. A. M. thanks UCM for the support under Sabáticos Complutense as well as partial support from the Russian Foundation for Basic Research under Project 97-03-09221., We analyze the peculiarities of the motional narrowing effect in disordered one-dimensional Frenkel chains with off-diagonal disorder, induced by uncorrelated Gaussian fluctuations in the positions of the host units. A clear difference in the scaling laws with respect to the magnitude of the positional disorder and the chain size is found, as compared to those for uncorrelated diagonal disorder as well as for off-diagonal disorder modeled by uncorrelated randomness in the nearest-neighbor couplings. The origin of such a difference is discussed in detail., CAM, UCM-Sabáticos Complutenses, Russian Foundation for Basic Research, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2001 Elsevier Science B.V. All rights reserved. International Conference on Dynamical Proces Excited States of Solids (30. 2001. Villeurbanne, Francia) The authors thank E. Macía, A. Sánchez, E. Díez, R. Römer and M. Hilke for discussions. F. D-A. and A. R. were supported by DGI-MCyT (Project MAT2000-0734). V. A. M. acknowledges support from INTAS (Project No. 97-10434)., The standard one-parameter scaling theory predicts that all eigenstates in two-dimensional random lattices are weakly localized. We show that this claim fails in two-dimensional dipolar Frenkel exciton systems. The linear energy dispersion at the top of the exciton band, originating from the long-range inter-site coupling of dipolar nature, yields the same size-scaling law for the level spacing and the effective disorder seen by the exciton. This finally results in the delocalization of those eigenstates in the thermodynamic limit. Large scale numerical simulations allow us to perform a detailed multifractal analysis and to elucidate the nature of the excitonic eigenstates., DGI-MCyT, INTAS, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2007 IOP Publishing Ltd. This work has been supported by the Ministry of Education and Science of Spain under a Ramon y Cajal Contract, by the project MAT2003-09873 and by the project MEC (MAT 2003-00455)., The luminescence of porous InP prepared by electrochemical etching is investigated by cathodoluminescence (CL) in a scanning electron microscope (SEM). Anodization causes a strong reduction of CL intensity as well as a blue spectral shift. Additional blue shift and enhancement of CL intensity is observed in samples cracked in vacuum by the effect of the SEM electron beam, which is explained by the reduction of the influence of surface states on the recombination mechanism. The relationship of the CL spatial distribution with the multilayer porous structure is described., España. Ministerio de Educación y Ciencia, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1996 - Elsevier Science S.A. International Workshop on Beam Injection Assessment of Defects in Semiconductors (4. 1996. El Escorial, España). This research has been partially supported by the Cooperation Programme “Azione Integrata” between Italy and Spain and by DGICYT (Project PB 93-1256). The authors are indebted to the Japan Energy Corporation for the undoped and Cl doped samples., We have investigated deep levels in semiconducting and semi-insulating II-VI compounds, namely undoped CdTe, CdTe:Cl and CdZnTe, in order to understand their role in the compensation mechanisms. To this aim Lye have utilized both junction spectroscopy techniques and cathodoluminescence (CL) spectroscopy. As junction spectroscopy methods we have utilized deep level transient spectroscopy (DLTS), photo-induced current transient spectroscopy (PICTS) and photo-DLTS (P-DLTS). By exploiting the peculiarities of these experimental methods, joined by CL characterization, we were able to gain further insight into the revealed traps properties, such as the trap nature (donor/acceptor). We have focused our attention on the deep levels that have been suggested to be involved in the compensation process, such as centre A., DGICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© Wiley Periodicals, Inc. This work is supported by MEC (MAT 2006-01259)., starting SnO_2, powder. In-rich nanoislands were found to grow on some edges of the tubes. ZnO nanostructures doped with Sri or Eu were grown by adding SnO_2 and Eu(2)O(3) powder, respectively, to the ZnO precursor powder. All the samples have been characterized by the emissive and cathodoluminescence (CL) modes of scanning electron microscopy. CL images from SnO_2:In and In_2O_3:Sn tubes and islands show a higher emission from the Sn-rich structures related to oxygen deficiency. CL of doped ZnO enables to detect the presence of dopant in specific regions or structures. CL appears to be a useful technique to study optical and electronic properties of semiconductor Oxide nanostructures., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2008 Elsevier B.V. All rights reserved. This work was supported by MEC(ProjectMAT2006-01259)., A study of the variation of structural and optical properties of different SnO2 micro- and nanostructures grown by thermal treatments including a post-growth annealing under argon flow has been carried out. The samples have been characterized by atomic force microscopy (AFM) and cathodoluminescence (CL) in the scanning electron microscope (SEM). It has been found that a post-growth annealing under argon flow at high temperature modifies the appearance of the initial structures as well as their optical properties. In this way, micro- and nanoislands terraced features or microtubes with smooth surfaces have been obtained as a function of the crystallographic orientation of the initial structure used as a substrate. Some other effects such as the increase of the 1.94eV CL emission, related to oxygen vacancies, which involves an electrical conductivity increase, are achieved by the annealing treatment., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2009 American Institute of Physics. This work was partially supported by the following Projects: Grant Nos. MEC-ESP2006-09935, CM-S-0505/ MAT-079, and FP7-SEC-2007-01 “European Commision,” and Contract No. 14240/00/NL7SH “European Space Agency.” One of the authors, V.C., thanks MEC, Spain for financial support. N.V. is grateful to Department of Science and Technology, Government of India for providing the BOYSCAST fellowship. The author J.R.F. is thankful to the Universidad Autónoma of Madrid for the financial support., Cadmium zinc telluride, CdZnTe, bulk single crystals doped with 10^19 at./cm^3 of indium in the initial melt were grown by vertical Bridgman technique. The samples were investigated by energy dispersive spectroscopy, cathodoluminiscence (CL), and current-voltage behavior at room temperature. The results shows that Cd and Te vacancy concentration depend on the indium and zinc concentrations. CL measurements indicate a relationship between radiative centers associated to Cd and Te vacancies and resistivity values., European Commision, European Space Agency, Department of Science and Technology, Government of India, Universidad Autónoma de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2001 Elsevier Science B.V. This work was supported by DGES (Project PB96- 0639)., We report here the studies carried out in zinc diffused n-type GaSb by cathodoluminescence (CL) microscopy and by scanning tunneling spectroscopy. Samples with different diffusion profiles measured by secondary ion mass spectrometry (SIMS) were obtained. CL plan-view observations show high homogeneity in the diffused layers. Cross-sectional measurements of the Zn diffused layers were performed by current imaging tunneling spectroscopy (CITS). The junction border was revealed clearly in the CITS images and conductance spectra recorded at differents points of the layers provided information on the local surface band gaps and the conductive behaviour. The results were related to the diffusion profiles and were found to agree with diffusion models suggested previously., DGES, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license The authors acknowledge the technical support given by technician Fernando Giacomone and also the support given by the Centros de Apoyo a la Investigación, especially the XRD and Microscopie centers, of the Complutense University of Madrid, and by the Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza, Spain. Funding: This research has been funded by the Ministerio de Ciencia, Innovación y Universidades (grant number PID2021-123112OB-C21) and Agregaduría Cultural de Arabia Saudí, Spain (project code 4157592)., In this work, we have studied structural and magnetic properties of LaFeO_3 as a function of the particle size d, from bulk (d >> 1 µm) to nanoscale (d ≈ 30 nm). A large number of twins were observed for large particles that disappear for small particle sizes. This could be related to the softening of the FeO_6 distortion as particle size decreases. It was observed that the bulk sample showed spin canting that disappeared for d ~ 125 nm and can be associated with the smoothening of the orthorhombic distortion. On the other hand, for d < 60 nm, the surface/volume ratio became high and, despite the high crystallinity of the nanoparticle, a notable exchange effect bias appeared, originated by two magnetic interactions: spin glass and antiferromagnetism. This exchange bias interaction was originated by the formation of a "magnetic core-shell": the broken bonds at the surface atoms give place to a spin glass behavior, whereas the inner atoms maintain the antiferromagnetic G-type order. The LaFeO_3 bulk material was synthesized by the ceramic method, whereas the LaFeO_3 nanoparticles were synthesized by the sol-gel method; the particle size was varied by annealing the samples at different temperatures. The physical properties of the materials have been investigated by XRD, HRTEM, TGA, and AC and DC magnetometry., Ministerio de Ciencia e Innovación (MICINN), Agregaduría Cultural de Arabia Saudí, España, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2007 The American Physical Society. The authors thank E. Maciá, A. Rodríguez, and P. A. Orellana for helpful discussions. This work was supported by MEC Project MOSAICO. A.V.M. acknowledges financial support from MEC through the Ramón y Cajal program., The underlying band structure of the uniform DNA suggests the allowance of interband optical transitions. We consider such transitions in the uniform synthetic DNA, such as the poly(G)-poly(C) DNA, within a simple tight-binding model with a minimum set of parameters. We demonstrate that the helical conformation of the DNA strands results in unusual interband optical transitions all of which appear to be indirect in k space although the system has a direct band gap energy structure. Simple relationships of the optical gap and absorption linewidth to tight-binding model parameters are found. We study also the effect of disorder in base levels (relevant for the wet form of the DNA) on interband optical transitions., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2004 IOP Publishing Ltd. International Workshop on Beam Injection Assessment of Microstructures in Semconductors ( 7. 2003. Lille, Francia). This work was supported by MCYT (ProjectMAT2000-2119). RP thanks MCYT for a research grant from the NATO scientific programme., Polycrystalline samples of titanium oxide were prepared by thermal sintering, in argon and air atmospheres at temperatures ranging from 1100 to 1500 degreesC, from powders of anatase and rutile phases. The samples sintered in argon were further treated in oxygen at the temperature of 800 degreesC for intervals of time up to 8 h. The luminescence emission of the initial powders was situated in the green region, with the peak at 580 nm. The sintering treatment in argon leads to a decrease of the luminescence intensity that appears as a broad band peaked at 550 nm in the case of anatase and as a band peaked at 450 nm in the case of the rutile phase. The sintering treatment in air causes the quenching of the emission in the visible region. In both cases, a sharp and intense emission appears in the infrared region at 800 nm for rutile and 820 nm for the anatase phase. The blue emission is sensitive to the treatment in oxygen atmosphere which causes mainly an intensity increase of the band at 450 nm. The treatment in oxygen results in the reconstruction of the polycrystalline sample surface as hexagonal shape protrusions and large terraces., MCYT, NATO scientific programme, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© Springer Science+Business Media B.V. 2011. This work has been supported by Spanish Ministry of Science MICINN (under CONSOLIDER CSD 2009-00013 and MAT 2009-0788 projects) and BSCH-UCM (Group 910146)., Silicon-doped gallium oxide nanowires have been synthesized by thermal methods using either a mixture of gallium oxide and silicon powders or metallic gallium with silicon powder as precursor materials. The growth mechanism has been found to be a vapour-liquid-solid (VLS) or vapour-solid (VS) process, respectively, depending on the precursor used. In the former case, silicon oxide droplets at the end of the nanowires have been observed. Their possible role during the growth of the nanostructures is discussed. Structural and morphological characterization of the doped nanowires has been performed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show a high crystalline quality and a uniform distribution of silicon along the nanowires. Room temperature cathodoluminescence (CL) in the SEM shows that slight variations in the composed UV-blue emission band appear due to the influence of Si impurities in the oxygen vacancy defect structure., Spanish Ministry of Science MICINN, BSCH-UCM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

This research has been partially supported by the Cooperation Programme ‘‘Azione Integrata’’ between Italy and Spain and by DGICYT (Project PB 93-1256). The authors are indebted to the Japan Energy Corporation for Corporation for the undoped and doped samples., We have investigated the electrical and optical properties of the deep levels responsible for the 1.4-1.5 eV luminescence band usually observed in II-VI compounds. We compared the energy levels found by cathodoluminescence and junction spectroscopy methods for semi-insulating (CdTe:Cl and Cd_(0.8)Zn_(0.2)Te) and semiconducting samples (undoped CdTe). The techniques utilized were deep level transient spectroscopy (DLTS) on semiconducting samples and photoinduced current transient spectroscopy and photo-DLTS on high resistivity materials. These last two techniques are complementary and allow the determination of the trap character (donor/acceptor). Three acceptor levels are seen in the electrical transient data at E(upsilon)+0.12, 0.14, and 0.16 eV with hole capture cross sections of 2x10^(-16), 1x10(-16), and 4X10^(-17) cm(2), respectively. The lowest level is seen only in Cl doped material corroborating the literature optical and electron spin resonance identification of a level at E_(upsilon)+0.12 eV as being a V_Cd+Cl_Te, donor-acceptor pair center. All three levels may be present in the 1.4 eV luminescence band., DGICYT (Spain), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1995 American- Institute of Physics. F. D.-A. acknowledges support from UCM through project PR161/93-4811. A. S. acknowledges partial support from C.I.C. y T. (Spain) through project PB92-0248 and by the European Union Human Capital and Mobility Programme through contract ERBCHRXCT930413., We study resonant tunneling in B-S-doped diodes grown by Si-molecular beam epitaxy. A Thomas-Fermi approach is used to obtain the conduction-band modulation. Using a scalar Hamiltonian within the effective-mass approximation. we demonstrate that the occurrence of negative differential resistance (NDR) only involves conduction-band states, whereas interband tunneling effects seem to be negligible. Our theoretical results are in very good agreement with recent experimental observations of NDR in this type of diode. 0 1995 American Institute of Physics., UCM, C.I.C. y T. (Spain), European Union Human Capital and Mobility Programme, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1994 IOP Publishing Ltd, A relativistic equation is derived for a slowly varying potential by suitably approximating the one-dimensional Dirac equation. This equation is shown to be akin to the Schrodinger equation with an effective potential and effective eigenvalues. An iterative procedure for solving this equation is indicated. As an application, the relativistic treatment of the Mathieu potential on the basis of this equation is considered and results are compared with those obtained by solving the exact one-dimensional Dirac equation. These results are likely to take adequate account of the relativistic impacts on electrons near Fermi levels in metals., Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

The static stress needed to depin a 2D edge dislocation, the lower dynamic stress needed to keep it moving, its velocity, and displacement vector profile are calculated from first principles. We use a simplified discrete model whose far field distortion tensor decays algebraically with distance as in the usual elasticity. Dislocation depinning in the strongly overdamped case (including the effect of fluctuations) is analytically described. N parallel edge dislocations whose average interdislocation distance divided by the Burgers vector of a single dislocation is L≫1 can depin a given one if N=O(L). Then a limiting dislocation density can be defined and calculated in simple cases., Depto. de Análisis Matemático y Matemática Aplicada, Fac. de Ciencias Matemáticas, TRUE, pub

© 2004 IOP Publishing Ltd. This work was carried out in the framework of a European network project (HPRN-CT-2001-00199). Partial support of MCYT (MAT2000-2119) is acknowledged. International Workshop on Beam Injection Assessment of Microstructures in Semiconductors, (BIAMS 2003) (7. 2003. Lille, Francia), The luminescence of GaSb and AlGaSb layers grown on GaAs substrates by metal organic vapour phase epitaxy has been studied by means of cathodoluminescence (CL) rising a scanning electron microscope. CL plane-view analysis reveals a distribution of defects, as misfit dislocations, in some of the structures. The luminescence bands observed in the GaSb layers are related to near band edge recombination and to an excess of Ga. In the case of AlGaSb/GaSb heterostructure emission bands related to the ternary compound and to donor-acceptor recombination are detected. In addition, with the aid of a scanning tunnelling microscope (STM), local electronic properties, such as conductance and surface energy gap, were studied in sample cross-sections. The results obtained from imaging and spectroscopy modes of STM enabled us to image the single AlGaSb layer., European network project, MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Institute of Physics. This work was supported by MCINN (MAT2009-07882, CSD2009-00013) and UCM-BSCH (Group 910146)., Fe dopedZnO nanowires,nanorods, and urchin-like nanostructures have been grown using an evaporation-deposition method with compacted mixtures of ZnS and Fe_2O_3 powders, with different Fe contents as precursors. Treatments at 950 °C under argon flow lead to the growth of irondopednanowires,nanorods, and other nanostructures on the surface of the compacted sample. The incorporation of iron into the nanostructures has been investigated via energy dispersive spectroscopy as well as by cathodoluminescence in a scanning electron microscope and photoluminescence in an optical microscope. The iron content in the structures is limited to the range of 0.5–0.7 at.% and does not depend on the content in the precursor. Bright and dark field imaging and twist contour analysis via transmission electron microscopy support the possibility of a dislocation driven growth of the nanowires., MICINN (Ministerio de Ciencia e Innovación, España), UCM-BSCH (Group), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Physical Society. We thank D. Guery-Odelin, R. Parentani, and C.Westbrook for valuable discussions. Support from MINECO (Spain) through grant FIS2010-21372 and from Comunidad de Madrid through grant MICROSERES-CM (S2009/TIC-1476) is also acknowledged., The violation of a classical Cauchy-Schwarz (CS) inequality is identified as an unequivocal signature of spontaneous Hawking radiation in sonic black holes. This violation can be particularly large near the peaks in the radiation spectrum emitted from a resonant boson structure forming a sonic horizon. As a function of the frequency-dependent Hawking radiation intensity, we analyze the degree of CS violation and the maximum violation temperature for a double barrier structure separating two regions of subsonic and supersonic condensate flow. We also consider the case where the resonant sonic horizon is produced by a space-dependent contact interaction. In some cases, CS violation can be observed by direct atom counting in a time-of-flight experiment. We show that near the conventional zero-frequency peak, the decisive CS violation cannot occur., Comunidad de Madrid, Ministerio de Economía y Competitividad (MINECO), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2003 IOP Publishing Ltd. This work has been supported by MCYT (Project MAT 2000-2119). RP acknowledges MECD for the research grant SB2000-0164., Nanocrystalline silicon films, with an average nanocrystal size of about 10 nm, obtained by boron implantation of amorphous silicon layers, have been studied by remote-beam-induced current (REBIC) in a scanning tunnelling microscope (STM) and by current imaging tunnelling spectroscopy. STM images reveal a cell structure with cell sizes of about 200 nm. STM-REBIC images display space-charge regions associated with the cell boundaries. The STM-REBIC contrast has been found to depend on the implantation dose and the thermal treatment given to the sample. The results show the capability of STM-REBIC to image electrically active regions in nanocrystalline silicon films with a resolution of up to 10 nm., MCYT, MECD, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2014 American Chemical Society. The authors thank Irina Snigireva and Armando Vicente Solé for their assistance with the SEM measurements and data processing using PyMca, respectively. We thank Peter Cloetens and Sylvain Labouréfor their help and the ESRF for the beam time allocated. This work has been partially supported by the NANOWIRING Marie Curie ITN (EU project no. PITN-GA- 2010 -265073) and by MINECO (Projects MAT 2012-31959 and Consolider Ingenio CSD 2009-00013)., Crossed nanowire structures are the basis for high-density integration of a variety of nanodevices. Owing to the critical role of nanowires intersections in creating hybrid architectures, it has become a challenge to investigate the local structure in crossing points in metal oxide nanowires. Thus, if intentionally grown crossed nanowires are well-patterned, an ideal model to the role of impurities in the coupling formation, structural modifications, and atomic site configuration based on crossed Ga_2O_3/SnO_2 nanowires. Our experiment opens new avenues for further local structure studies with both nanometer resolution and elemental sensitivity., Unión Europea. FP7, Marie Curie ITN (EU), Ministerio de Economía y Competitividad (MINECO), Consolider Ingenio, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Chemical Society. This work was supported byMEC (MAT2006-01259, MAT2009-07782, CSD 2009-00013) and BSCH-UCM (Group 910146), In_2O_3 nanorods have been grown by a catalyst free evaporation-deposition method. Transmission electron microscopy (TEM) investigations reveal that the rods contain tubular cavities, herein referred to as "nanopipes", along the total length of the nanorods. The nanopipe diameters are constant along the nanorod axis and appear to be independent of the nanorod thickness. In most of the investigated In_2O_3 nanorods, these nanopipes are centered within the nanorod. An average nanopipe diameter of (18.5 +/- 0.7) nm has been determined from the TEM observations. Extended thermal treatments lead to nanorods with more complex morphologies, roughened interfaces, and formation of voids. The possibility that the nanopipes are related with a growth mechanism involving a dislocation along the growth axis is discussed., MEC, BSCH-UCM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1999 The American Physical Society. This work was financed by DGES (Spain) (Grants No. PB-97-0031 and No. PB-97-1199). We thank the staff of ESRF for experimental support and X. Torrelles, F. Flores, E. Tosatti, and S. Modesti for fruitful discussions. A. M. thanks Eusko Jaurlaritza for financial support., The structure of the low-temperature 3 X 3 surface phase of Pb/Ge(111) has been determined by surface x-ray diffraction experiments. Analysis of the data reveals that the Pb layer exhibits a vertical corrugation of similar to 0.4 Angstrom, affecting also the two top Ge layers. Significant distortions are found down to the third Ge layer. This structural model supports that the 3 X 3 ground state can be best described as a cooperative distortion stabilized by a gain in electronic energy. [S0031-9007(99)08749-9]., DGES (Spain), Eusko Jaurlaritza, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© American Physical Society, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1993 American Institute of Physics. This work has been supported by DGICYT (Project PB-1017). Thanks are due to Dr. E. Wolfgang for drawing our attention to the CL cross sectional measurements., Cathodoluminescence (CL) in the scanning electron microscope has been used to study the upper surface and cross-sectional samples of chemical vapor deposited diamond films. The CL emission is mainly localized at the grain boundaries of the columnar grains. The concentration of dislocation related radiative centers is higher in boundaries parallel to the growth axis than in boundaries parallel to the sample surface. The opposite occurs with the concentration of centers related to the presence of nitrogen., DGICYT (Spain), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

A novel analysis of homogeneous nucleation of dislocations in sheared two-dimensionalcrystals described by periodized-discrete-elasticity models is presented. When the crystal issheared beyond a critical strain F = Fc, the strained dislocation-free state becomes unstable via a subcritical pitchfork bifurcation. Selecting a fixed final applied strain Ff >Fc, different simultaneously stable stationary configurations containing two or four edge dislocations may be reached by setting F = Ff t/tr during different time intervals tr. At a characteristic time after tr, one or two dipoles are nucleated, split, and the resulting two edge dislocations move in opposite directions to the sample boundary. Numerical continuation shows how configurations with different numbers of edge dislocation pairs emerge as bifurcations from the dislocation-free state., Spanish Ministry of Education, Depto. de Análisis Matemático y Matemática Aplicada, Fac. de Ciencias Matemáticas, TRUE, pub

©2015 American Physical Society. Artículo firmado por 11 autores. This work was supported by the French Agence Nationale de la Recherche (ANR) under Contract SurMott, No. NT-09-618999, and by Spanish Ministerio de Economía y Competitividad, Project No. MAT2014-59966-R. W. S. and D. G. T. contributed equally to this work., Dynamical phase transitions are a challenge to identify experimentally and describe theoretically. Here, we study a new reconstruction of Sn on silicon and observe a reversible transition where the surface unit cell divides its area by a factor of 4 at 250 °C. This phase transition is explained by the 24-fold degeneracy of the ground state and a novel diffusive mechanism, where four Sn atoms arranged in a snakelike cluster wiggle at the surface exploring collectively the different quantum mechanical ground states., French Agence Nationale de la Recherche (ANR), Ministerio de Economía y Competitividad, Spain, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1996 Published by Elsevier B.V. The author thanks E. Maciá, A. Sánchez and V. Malyshev for helpful comments. This work is supported by CICYT through project MAT95-0325., We consider exciton optical absorption in quasiperiodic lattices, focusing our attention on the Fibonacci case as a typical example. The absorption spectrum is evaluated by solving numerically the equation of motion of the Frenkel-exciton problem on the lattice, in which on-site energies take on two values according to the Fibonacci sequence. We find that the quasiperiodic order causes the occurrence of well-defined characteristic features in the absorption spectra. We also develop an analytical method that relates satellite lines with the Fourier pattern of the lattice. Our predictions can be used to determine experimentally the long-range quasiperiodic order from optical measurements., Comisión Interministerial de Ciencia y Tecnología (CICYT), España, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2001 American Institute of Physics. This work was supported by MCYT (Project No. MAT2000-2119) and the Russian R&D program ‘‘Nanostructures’’ (Grant No. 97-2016)., Synthetic opals infilled with silicon (opal-Si) and with Si and Pt (opal-Pt-Si) have been irradiated in a scanning electron microscope under high excitation conditions. Electron irradiation-induced changes in the morphology and luminescent defect structure of both types of nanocomposites were assessed by scanning electron microscopy and by cathodoluminescence (CL) microscopy and spectroscopy. Irradiation causes strong morphological changes in the ordered structure of the matrix and quenching of the nanocrystals-related CL emission in the opal-Si samples. On the contrary, such effects are not observed in the opal-Pt-Si nanocomposites. In both types of samples, electron irradiation induces the appearance of a CL band centered at 2.95 eV, attributed to complex centers involving oxygen vacancies in the silica spheres forming the matrix., MCYT, Russian R&D program ‘‘Nanostructures’’, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© Elsevier Science B.V. All rights reserved. This work was supported by the DGI-MCyT (Project MAT2000-0734). A. V. M. and F. D. A. acknowledge support from CAM (Project 07N/0075/2001). V. A. M. acknowledges support from MECyD (Project SAB2000-0103) as well as through a NATO Fellowship., We present a theoretical analysis of low-temperature quenching of one-dimensional Frenkel excitons that are localized by moderate on-site (diagonal) uncorrelated disorder. Exciton diffusion is considered as an incoherent hopping over localization segments and is probed by the exciton fluorescence quenching at point traps. The rate equation is used to calculate the temperature dependence of the exciton quenching. The activation temperature of the diffusion is found to be of the order of the width of the exciton absorption band. We demonstrate that the intra-segment scattering is extremely important for the exciton diffusion. We discuss also experimental data on the fast exciton-exciton annihilation in linear molecular aggregates at low temperatures., DGI-MCyT, CAM, MECyD, NATO, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

©2016 American Physical Society. This paper has been financially supported through of the Spanish Ministry of Economy and Competitiveness (MINECO), MAT2015-66888-C3-3-R. We thank “CAI Difracción de rayos-X” of Universidad Complutense de Madrid for the x-ray diffractometry measurements and Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) for the use of some of its facilities. We also thank BM25-SpLine, the Spanish CRG at ESRF for providing beam time., In this paper we analyze the structure of Fe-Ga layers with a Ga content of ∼30 at.% deposited by the sputtering technique under two different regimes. We also studied the correlation between the structure and magnetic behavior of the samples. Keeping the Ar pressure fixed, we modified the flow regime from ballistic to diffusive by increasing the distance between the target and the substrate. X-ray diffraction measurements have shown a lower structural quality when growing in the diffusive flow. We investigated the impact of the growth regime by means of x-ray absorption fine structure (XAFS) measurements and obtained signs of its influence on the local atomic order. Full multiple scattering and finite difference calculations based on XAFS measurements point to a more relevant presence of a disordered A2 phase and of orthorhombic Ga clusters on the Fe-Ga alloy deposited under a diffusive regime; however, in the ballistic sample, a higher presence of D0_3/B2 phases is evidenced. Structural characteristics, from local to long range, seem to determine the magnetic behavior of the layers. Whereas a clear in-plane magnetic anisotropy is observed in the film deposited under ballistic flow, the diffusive sample is magnetically isotropic. Therefore, our experimental results provide evidence of a correlation between flow regime and structural properties and its impact on the magnetic behavior of a rather unexplored compositional region of Fe-Ga compounds., Ministerio de Economía y Competitividad (MINECO), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1996 American Institute of Physics. This work was supported by DGICYT (Projects No. PB93-1256 and MAT 95-1184E). C.D.G. acknowledges MEC for a FPI research grant., Cathodoluminescence (CL) of YBa_2Cu_3O_(7-x) single crystals has been investigated in the scanning electron microscope, Some regions of the crystals, generally related to steps or other growth features, show enhanced CL Intensity. Spectra show the presence of two emission bands centered at about 2.85 and 2.3-2.4 eV, respectively. In the regions of higher CL intensity, the 2.3 eV band, which has been attributed to defects in the oxygen sublattice, shows a higher relative intensity. (C) 1996 Americans Institute of Physics., DGICYT, MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1994 The American Physical Society. It is with great pleasure that we thank collaboration and illuminating conversations with Enrique Maciá. A.S. is also thankful to Alan Bishop for warm hospital ityat Los Alamos National Laboratory where this paper was written in part. Work at Leganes is supported by the Direccion General de Investigacion Cientifica y Tecnica (Spain) through project PB92-0248, and by the European Union Human Capital and Mobility Programme through Contract No. ERBCHRXCT930413. Work at Madrid is supported by Universidad Complutense through Project No. PR161/93-4811., We study how the in8uence of structural correlations in disordered systems manifests itself in experimentally measurable magnitudes, focusing on dc conductance of semiconductor superlattices with general potential pro6les. We show that the existence of bands of extended states in these structures gives rise to very noticeable peaks in the 6nite-temperature dc conductance as the chem ical potential is moved through the bands or as the temperature is increased from zero. On the basis of these results we discuss how dc conductance measurements can provide information on the location and width of the bands of extended states. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization eKects of disorder., Direccion General de Investigacion Cientifica y Tecnica (Spain), Universidad Complutense, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2006 Elsevier B.V. All rights reserved. This work has been carried out in the frame of the Fifth Framework European Programme for research, HPRNCT 2001-00199 project. Support from MCYT through projects, MAT 2003-09873, ESP 2004-0041-E and MAT2003-00455 is also acknowledged., Dilute Te-doped GaSb alloys have been prepared by the vertical feeding method (VFM) using both casting and feeding configurations. The structural and optical properties of the samples were characterized by etching, X-ray diffraction and cathodoluminescence in the scanning electron microscope. The obtained results confirm the variation of the segregation coefficient k observed in previous VFM Te-doped GaSb experiments. The increase of k and the grain structure refinement are attributed to the increase of the interface velocity. The feeding configuration of the VFM seems to be the most appropriate one to control segregation and grain size for Te-doped GaSb alloys., MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub