Person: Hidalgo Alcalde, Pedro
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First Name
Pedro
Last Name
Hidalgo Alcalde
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
Ciencia de los Materiales e Ingeniería Metalúrgica
Identifiers
72 results
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Now showing 1 - 10 of 72
Item Influencia del tratamiento térmico en las intercaras y propiedades mecánicas de un laminado multicapa de aluminio(Revista de Metalurgia, 2010) Cepeda Jiménez, C. M.; Hidalgo Alcalde, Pedro; Pozuelo, M.; Ruano, O. A.; Carreño, F.The microstructure and mechanical properties in the interface region of a multilayer laminate based on high strength aluminium alloys, Al 7075 and Al 2024, have been characterized mainly by EBSD and shear tests. It is shown that the time of solution treatment during T6 thermal treatment modifies the microstructure of the constituent alloys adjacent to the interface and, as a consequence, the interfacial mechanical properties. The combination of the correct rolling processing with optimized thermal treatment leads to strong interfaces prone to delaminate, and thus, materials with outstanding mechanical properties.Item Kinetic study of the thermal quenching of the ultraviolet emission in Zn_2GeO_4 microrods(Physica status solidi-rapid research letters, 2022) Dolado Fernández, Jaime; Hidalgo Alcalde, Pedro; Méndez Martín, BianchiZn_2GeO_4 microrods obtained by thermal evaporation of a compacted powder mixture of ZnO and Ge exhibit quite intense UV luminescence at low temperatures. Herein, the luminescence properties of Zn_2GeO_4 microrods are studied for 2:1 and 1:1 ZnO:Ge ratio in the precursor mixture. In both cases, Zn2GeO4 microrods of high crystal quality produce a 355 nm emission under aforementioned bandgap excitation conditions at low temperatures. However, this emission vanishes at room temperature (RT) in the 1:1 samples while it is kept in the 2:1 ones. Herein this work, the thermal quenching of the UV luminescence is studied by means of steady and time-resolved photoluminescence techniques from 4 K up to RT for both Zn_2GeO_4 microrods. The analysis of the results leads us to conclude that although the luminescence mechanisms are the same in both cases, a higher decay rate is observed in the 1:1 in both intensity and lifetime, which explain the observed thermal quenching at RT.Item Nanostructural characterization of luminescent polyvinyl alcohol/graphene quantum dots nanocomposite films(Nanomaterials, 2023) Elumalai, Dhanumalayan; Rodríguez Fernández, Beatriz; Kovtun, Ganna; Hidalgo Alcalde, Pedro; Méndez Martín, María Bianchi; Kaleemulla, Shaik; Joshi, Girish M; Cuberes, M. TeresaThis study focuses on the fabrication of polymer nanocomposite films using polyvinyl alcohol (PVA)/graphene quantum dots (GQDs). We investigate the relationship between the structural, thermal, and nanoscale morphological properties of these films and their photoluminescent response. Although according to X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and differential thermal analysis (DTA), the incorporation of GQDs does not significantly affect the percentage crystallinity of the PVA matrix, for a range of added GQD concentrations, atomic force microscopy (AFM) showed the formation of islands with apparent crystalline morphology on the surface of the PVA/GQD films. This observation suggests that GQDs presumably act as nucleating agents for island growth. The incorporation of GQDs also led to the formation of characteristic surface pores with increased stiffness and frictional contrast, as indicated by ultrasonic force microscopy (UFM) and frictional force microscopy (FFM) data. The photoluminescence (PL) spectra of the films were found to depend both on the amount of GQDs incorporated and on the film morphology. For GQD loads >1.2%wt, a GQD-related band was observed at similar to 1650 cm(-1) in FT-IR, along with an increase in the PL band at lower energy. For a load of similar to 2%wt GQDs, the surface morphology was characterized by extended cluster aggregates with lower stiffness and friction than the surrounding matrix, and the PL signal decreased.- Project number: 158
Item Hacia una formación integral en el Programa de Doctorado en Física(2023) Domínguez-Adame Acosta, Francisco; Méndez Martín, Bianchi; Nogales Díaz, Emilio; Hidalgo Alcalde, Pedro; Quereda Bernabeu, Jorge; Baba, Yuriko Caterina; Rodriguez Fernandez, BeatrizEl principal objetivo de la propuesta es promover nuevas vías de formación de doctorandos en aspectos para los cuales rara vez se incide en los diversos Programas de Doctorado. Los resultados esperados son (i) Mejora de la metodología de formación de doctorandos por parte de los profesores del Programa de Doctorado en Física, bajo el auspicio de la Comisión Académica del Programa, con énfasis en la difusión de sus resultados científicos. (ii) Establecimiento de las bases para organizar actividades formativas transversales similares y de interés para otros Programas de Doctorado del área de Ciencias Experimentales, bajo los auspicios de la Escuela de Doctorado de la Universidad Complutense. Item Investigations of defects introduced in 4H-SiC n-type epitaxial layers by hydrogen DC plasma(Silicon Carbide and Related Materials 2003, Prts 1 and 2, 2004) Ottaviani, L.; Yakimov, E.; Hidalgo Alcalde, Pedro; Martinuzzi, S.Hydrogen is known to passivate donor and acceptor levels in SiC bulk, and also at the surface by forming bonds with Si atoms. Introduction of H atoms can then improve the electrical performance of Schottky diodes by reducing the metal-SiC interface state density. However it is necessary to verify if H-related complexes are formed or not, creating trap centers and corresponding deep levels. In this work, the electrical characteristics of defects introduced near the surface of n-type 4H-SiC epitaxial layers by DC hydrogen plasma were investigated. C-V technique revealed a donor-nature defect located deeper than the projected range of W ions, emitting electrons at temperatures > 300 K. Two deep levels were detected by DLTS measurements after high implantation energies, while the defect concentration decreases and only one defect is detected after lower implantation energies. The activation energies are similar to the double defect RD1/2, associated to the vacancy pair V-C-V-Si. Cathodoluminescence spectra showed the existence of a peculiar luminescence peak related to H introduction, which intensity increases with plasma energy.Item Scanning tunneling spectroscopy study of erbium doped GaSb crystals(Journal of Applied Physics, 1999) Hidalgo Alcalde, Pedro; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Plaza, J. L.; Dieguez, E.Er doped GaSb single crystals have been studied by scanning tunneling spectroscopy (STS) and cathodoluminescence (CL) in a combined scanning electron microscope-scanning tunnelling microscope system. The surface band gap in doped samples has been found to be about 0.5 eV while in undoped crystals the gap is close to the bulk value. Inhomogeneities in the local electronic properties of the doped crystals are studied by a correlation of the CL images and STS data.Item Electrical and compositional properties on Bridgman-grown Gd-doped GaSb substrates(Materials Science and Engineering B-Solid State Materials for Advanced Technology, 2001) Plaza, J. L.; Hidalgo Alcalde, Pedro; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Castaño, J. L.In this work pure and Gd-doped GaSb ingots with different dopant concentrations were grown by the Bridgman Method. The compositional and electrical analysis carried out on these materials have shown the dependence of these results on the initial dopant concentration. The analysis have revealed the presence of inclusions which have been identified as Gd-Sb precipitates. The doped material was found to be p-type with a maximum value of the carrier density at the central region of the ingots. It has been also demonstrated that the Gd enhances the A band emission reducing the band-gap emission.Item Compositional and structural analysis of Nd-doped GaSb bulk crystals grown by the vertical Bridgman technique(Journal of Crystal Growth, 2002) Plaza, J. L:; Hidalgo Alcalde, Pedro; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Dieguez, E.Nd-doped GaSb bulk crystals with three different dopant concentrations have been grown by the vertical Bridgman technique. The axial segregation has been characterised by obtaining the effective segregation coefficient. Differences in the value of this coefficient show its dopant concentration dependence. Resistivity, carrier density and mobility have also been obtained showing the p-type nature of this material. Structural and compositional properties have been studied revealing some inclusions with high Nd concentration in the highest Nd-doped ingot.Item Cathodoluminescence of rare earth implanted Ga_2O_3 and GeO_2 nanostructures(Nanotechnology, 2011) Nogales Díaz, Emilio; Hidalgo Alcalde, Pedro; Lorenz, K.; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Alves, E.Rare earth (RE) doped gallium oxide and germanium oxide micro- and nanostructures, mostly nanowires, have been obtained and their morphological and optical properties have been characterized. Undoped oxide micro- and nanostructures were grown by a thermal evaporation method and were subsequently doped with gadolinium or europium ions by ion implantation. No significant changes in the morphologies of the nanostructures were observed after ion implantation and thermal annealing. The luminescence emission properties have been studied with cathodoluminescence (CL) in a scanning electron microscope (SEM). Both β-Ga_2O_3 and GeO_2 structures implanted with Eu show the characteristic red luminescence peak centered at around 610 nm, due to the 5ˆD0–7ˆF_2Euˆ3+ intraionic transition. Sharpening of the luminescence peaks after thermal annealing is observed in Eu implanted β-Ga_2O_3, which is assigned to the lattice recovery. Gd3+ as-implanted samples do not show rare earth related luminescence. After annealing, optical activation of Gdˆ3+ is obtained in both matrices and a sharp ultraviolet peak centered at around 315 nm, associated with the Gdˆ3+ 6P_7/2–8ˆS_7/2 intraionic transition, is observed. The influence of the Gd ion implantation and the annealing temperature on the gallium oxide broad intrinsic defect band has been analyzed.Item Study of GaSb junction devices by cathodoluminescence and scanning tunneling spectroscopy(Optical Microstructural Characterization of Semiconductors, 2000) Hidalgo Alcalde, Pedro; Méndez Martín, Bianchi; Piqueras de Noriega, Javier; Dutta, P: S.GaSb p-n junctions formed by Zn diffusion in Te-doped n-GaSb single crystalline wafers have been characterized by cathodoluminescence (CL) microscopy and by scanning tunneling spectroscopy. CL plane-view observations of the Zn diffused side enable to study the homogeneity of the diffusion treatment. Spectra recorded by current imaging tunneling spectroscopy (CITS) in the n and p sides of the junction, clearly show the respective conductive behaviour and provide information on the local surface band gaps. Results are related to the diffusion profile measured by secondary ion mass spectrometry (SIMS).