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© 2003 American Institute of Physics. The authors acknowledge C.A.I. de Implantación Iónica (U.C.M.) for technical support, and especially to Rosa Cimas Cuevas for aid in sample processing, and C.A.I. de Espectroscopia (U.C.M.) for providing access to the FTIR spectrometer. This work was partially supported by the Spanish CICYT, under Contract No. TIC 01-1253., The composition, bonding configuration, hydrogen content, and paramagnetic defects of SiOxHy thin films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH4 and O-2 as precursor gases. The film composition was measured by heavy ion elastic recoil detection analysis and energy dispersive x-ray spectroscopy. Suboxide films with compositions ranging from SiO2 to SiH0.38 were obtained. Infrared spectroscopy showed the presence of different Si-O and Si-H vibration modes. The usual estimation of the oxygen to silicon ratio by the wave number of the Si-O-Si stretching band was not accurate for films far from stoichiometry. These off-stoichiometric films also showed a broader Si-O-Si stretching peak than the stoichiometric ones, indicating a higher bonding disorder. The position of the Si-O-Si bending and rocking modes did not depend on the film composition. On the other hand, the peak position of the Si-H modes were found strongly dependent on the Si environment. By single-wavelength ellipsometry at lambda=632.8 nm the refractive index n was found to range between 1.45 (SiO2) and 2.04 (SiO0.06H0.36). Electron spin resonance measurements showed that stoichiometric films presented the well known E' center (.Siequivalent toO(3)) with concentrations in the 10(16)-10(17) cm(-3) range, while for Si-rich films (x<1) the Si dangling bond center (Si-DB, .Siequivalent toSi(3)) was the only detectable defect, with concentrations in the 10(18)-10(19) cm(-3) range. In near-stoichiometric films both E-' and Si-DB centers were found., Spanish CICYT, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Society of Plant Biologists. This work was supported by a Ramón y Cajal contract from the Ministry of Science and Innovation, Spain, cofinanced by the European Social Fund (to V.F.), by a Ph.D. grant from the Government of the Republic of Panama (grant no. SENACYT-IFARHU to P.M.-P.), and by the Programa Nacional de Proyectos de Investigación Fundamental (project nos. AGL2009-08501/AGR and AGL2009-12134/AGR). We thank Drs. M.J. Rubio, A. Wünsch, and J.M. Alonso (Centro de Investigación y Tecnología Agroalimentaria de Aragón), Dr. M.J. Aranzana (Institut de Recerca i Tecnologia Agroalimentàries), Dr. G. Reighard (Clemson University), and J.L. Espada (Centro de Transferencia Agroalimentaria del Gobierno de Aragón) for providing information about the origins of peaches and on the characteristics of Calanda peaches., The surface of peach (Prunus persica 'Calrico') is covered by a dense indumentum, which may serve various protective purposes. With the aim of relating structure to function, the chemical composition, morphology, and hydrophobicity of the peach skin was assessed as a model for a pubescent plant surface. Distinct physicochemical features were observed for trichomes versus isolated cuticles. Peach cuticles were composed of 53% cutan, 27% waxes, 23% cutin, and 1% hydroxycinnamic acid derivatives (mainly ferulic and p-coumaric acids). Trichomes were covered by a thin cuticular layer containing 15% waxes and 19% cutin and were filled by polysaccharide material (63%) containing hydroxycinnamic acid derivatives and flavonoids. The surface free energy, polarity, and work of adhesion of intact and shaved peach surfaces were calculated from contact angle measurements of water, glycerol, and diiodomethane. The removal of the trichomes from the surface increased polarity from 3.8% (intact surface) to 23.6% and decreased the total surface free energy chiefly due to a decrease on its nonpolar component. The extraction of waxes and the removal of trichomes led to higher fruit dehydration rates. However, trichomes were found to have a higher water sorption capacity as compared with isolated cuticles. The results show that the peach surface is composed of two different materials that establish a polarity gradient: the trichome network, which has a higher surface free energy and a higher dispersive component, and the cuticle underneath, which has a lower surface free energy and higher surface polarity. The significance of the data concerning water-plant surface interactions is discussed within a physiological context., Ministry of Science and Innovation, Spain, European Social Fund, Government of the Republic of Panama, Programa Nacional de Proyectos de Investigación Fundamental, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2008 American Chemical Society. Acknowledgment. This work was supported by MEC through project MAT2006-01259., Vanadium pentoxide (V_2O_5) nanorods and nanotips have been grown without a catalyst by a thermal deposition method using compacted V_2O_5 powder as the starting material. The tips, with diameters of about 50-100 nm, grow on the top of rods of larger size. Transmission electron microscopy shows that the obtained structures are single crystalline. The luminescence behavior of the nanostructures has been investigated by cathodoluminescence (CL) in the scanning electron microscope. CL reveals that the presence of nanostructures leads to changes in the spectral distribution of the emission. The obtained results are discussed by considering the band structure of V_2O_5., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2006 The American Physical Society. Work at Madrid was supported by MEC Project No. MAT2003-01533. Yu.A.K. acknowledges support from Generalitat Valenciana Grant No. CTESIN/2005/022. V.A.M. acknowledges support from NanoNed, a national nanotechnology programme coordinated by the Dutch Min istry of Economic Affairs, and from ISTC Grant No. 2679., We study numerically the linear optical response of a quasiparticle moving on a one-dimensional disordered lattice in the presence of a linear bias. The random site potential is assumed to be long-range correlated with a power-law spectral density S(k)similar to 1/k(alpha), alpha > 0. This type of correlation results in a phase of extended states at the band center, provided alpha is larger than a critical value alpha(c) [F. A. B. F. de Moura and M. L. Lyra, Phys. Rev. Lett. 81, 3735 (1998)]. The width of the delocalized phase can be tested by applying an external electric field: Bloch-like oscillations of a quasiparticle wave packet are governed by the two mobility edges, playing now the role of band edges [F. Dominguez-Adame , Phys. Rev. Lett. 91, 197402 (2003)]. We demonstrate that the frequency-domain counterpart of these oscillations, the so-called Wannier-Stark ladder, also arises in this system. When the phase of extended states emerges in the system, this ladder turns out to be a comb of doublets, for some range of disorder strength and bias. Linear optical absorption provides a tool to detect this level structure., MEC, Generalitat Valenciana, NanoNed, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Iberian Vacuum Meeting (5.2005.Guimaraes,Portugal). © 2008 Elsevier Ltd. All rights reserved. The authors acknowledge C.A.I de Implantación Iónica (U.C.M.), C.A.I de Espectroscopía y Espectrometría and C.A.I. de Microscopía y Citometría for technical support. This work was made possible thanks to a FPU grant of the Spanish M.E.C. This work was also supported by the Spanish M.C.Y.T., under the contract TEC 2004-1237/MIC., Hafnium oxide films were deposited on silicon by High Pressure Reactive Sputtering (HPRS) at pressures between 0.8 and 1.6 mbar. Growth, composition and morphology were investigated using Transmission Electron Microscopy (TEM), Heavy Ion Elastic Recoil Detection Analysis (HI-ERDA), Fourier Transform infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD). The growth rate was found to decrease exponentially with deposition pressure. The films showed a monoclinic polycrystalline structure, with higher grain size for intermediate pressures. All the films were slightly oxygen rich with respect to stoichiometric HfO2, which is attributed to the oxygen plasma. Additionally, it was observed the formation of an interfacial silicon oxide layer, with a minimum thickness for deposition pressures around 1.2 mbar. These results are explained by the oxidation action of the oxygen plasma and the diffusion of oxygen through the grain boundaries of the HfO2 film., FPU grant of the Spanish M.E.C., Spanish M.C.Y.T., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2007 American Chemical Society. This work has been supported by MEC (Project MAT 2003-00455). L.K. is thankful for a research grant from UCM and Grupo Santander., ZnO microspheres, with surfaces covered with nanowalls, as well as nano- and microrods, have been grown by thermal treatment of ZnS powder. The structures have been grown at temperatures in the range of 750-900 ºC in a catalyst-free process. Previous mechanical treatment of the ZnS powder by ball milling has been found to influence the morphology and size of the obtained structures. Cathodoluminescence in the scanning electron microscope has shown that spheres and elongated structures have an inhomogeneous luminescence emission., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2013 AIP Publishing LLC. This work is supported by the PRODEX programme of the Belgian Federal Science Policy Office, ESA. The authors would like to thank referee for useful discussion of the fitting algorithms., We present a comprehensive analysis of experimental results obtained for Fickian diffusion in the benchmark ternary liquid mixture of 1,2,3,4-tetrahydronaphthalene, isobutylbenzene, and dodecane (nC(12)) with equal mass fractions. Isothermal diffusion coefficients have been measured by two independent experimental methods: by Taylor dispersion technique, and by a counter flow cell fitted with an optical interferometry device. The experimental diffusion matrices have been critically analyzed regarding the Onsager reciprocal relations, for which we introduce a matrix asymmetry index S-2 that is independent of the frame of reference and the component order., PRODEX programme of the Belgian Federal Science Policy Office, ESA, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 American Institute of Physics. This work has been supported by MEC (Project MAT2003-00455), Sintering CdSe powder under argon flow at temperatures in the range 800-900 degreesC produces the formation of needles on the sample surface. Bundles of parallel needles of a diameter of about 50 nm give rise to a domain-like appearance in the sample. In addition, rods and needles with a wide range of dimensions up to several microns appear distributed in the surface. The influence of ball milling of the starting powder on the formation of the needles is investigated. Cathodoluminescence in the scanning electron microscope has been used to characterize the sintered samples., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2001 American Institute of Physics. This work was supported by DGES ~Project No. PB96-0639!, the Russian R&D program ‘‘Nanostructures’’ (Grant No. 97-2016), and RFBR under Grant No. 98-02-17350., Synthetic opals-composed of 250 nm amorphous silica spheres closed packed in a face centered cubic structure-have been infilled with silicon, platinum, and with Si and different Pt contents. The luminescent properties of these composites have been investigated by cathodoluminescence (CL) microscopy and spectroscopy. CL emission is influenced by the material used to infill the pores of the opal matrix. CL spectra of all the samples investigated show two well-known bands, associated with the defect structure of the silica spheres, centered at about 1.9 and 2.7 eV, respectively. Emission in the 2.15-2.45 eV range, particularly intense in opal-based composites with a high Pt content, is tentatively associated with SiO2 defects involving silicon clusters. A CL band peaked at about 3.4 eV as well as a band in the 1.50-1.75 eV range, whose peak position seems to be affected by the Pt content of the samples, are associated with the presence of Si nanocrystals. The behavior of these emissions suggests that both are related to defect states at the interface between Si nanocrystals and SiO2 forming the opal spheres., DGES, Russian R&D program ‘‘Nanostructures’’, RFBR, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2000 American Institute of Physics. The authors thank R. Brito for helpful comments. Work at Madrid was supported by CAM under Project No. 07N/ 0034/98. V.A.M. thanks UCM for the support under Saba´ticos Complutense., We present results of numerical simulations of optical absorption line shape of Frenkel excitons in two-dimensional disordered lattices. Disorder is generated by Gaussian randomness in the molecular positions. The intersite interaction is considered to be of dipole origin, including coupling to far neighbors. Results of simulations are compared with those obtained in the frame of the nearest-neighbor approximation, showing remarkable differences in the absorption line shape. The motional narrowing effect is found to be essentially different from that previously reported for the case of diagonal disorder as well as for that produced by randomness in nearest-neighbor hopping integrals., CAM, UCM-Sabáticos Complutenses, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2007 American Institute of Physics. This work has been supported by MEC through project MAT2006-01259., V_2O_5 nanostructures have been grown on 4H-SiC and Si substrates by a thermal deposition method without a catalyst. High aspect ratio nanowires with rectangular cross sections were grown on 4H-SiC. High-resolution transmission electron microscopy observations and cathodoluminescence (CL) spectroscopy measurements reveal the high crystal quality of the grown nanowires. Deposition on Si substrates leads to the growth of V_2O_5 platelets or rod-shaped crystals ending in arrays of parallel sharp nanotips with apex radius in the 50 nm range. A CL emission band observed centered at about 1.70 eV in spectra from these nanostructures is tentatively attributed to defect centers involving oxygen vacancies., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 1996 American Institute of Physics One of the authors (P.S.D.) would like to thank CSIR (India) for the award of a senior research fellowship. U.P. gratefully acknowledges MEC (Spain) for the postdoctoral fellowship. This work was partially supported by the Universidad Autonoma de Madrid, Spain, through a visiting scientist fellowship and by DGICYT Project Nos. PB93-1256 and ESP95-014, Passivation of point and extended defects in GaSb has been observed as a result of hydrogenated amorphous silicon (a-Si:H) treatment by the glow discharge technique. Cathodoluminescence (CL) images recorded at various depths in the samples clearly show passivation of defects on the surface as well as in the bulk region. The passivation of various recombination centers in the bulk is attributed to the formation of hydrogen-impurity complexes by diffusion of hydrogen ions from the plasma a-Si:H acts as a protective cap layer and prevents surface degradation which is usually encountered by bare exposure to hydrogen plasma. An enhancement in luminescence intensity up to 20 times is seen due to the passivation of nonradiative recombination centers. The passivation efficiency is found to improve with an increase in a-Si:H deposition temperature. The relative passivation efficiency of donors and acceptors by hydrogen in undoped and Te-compensated p-GaSb has been evaluated by CL and by the temperature dependence of photoluminescence intensities. Most notably, effective passivation of minority dopants in tellurium compensated p-GaSb is evidenced for the first time., Universidad Autonoma de Madrid, Spain, DGICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2003 American Institute of Physics. The authors gratefully acknowledge Dr. M. N. Blanco and Dr. E. Redondo for the fruitful collaboration with them in recent years. They also wish to express their deep gratitude to Dr. B. Selle, Dr. I Sieber, Dr. W. Bohne, Dr. J. Röhrich, Dr. Kliefoth, Dr. W. Füssel, and in general, to the people of the Hahn-Meitner Institut in Berlin, for a long friendship and fruitful collaboration. Thanks are also due to Professor F. López and Professor D. Bravo (Materials Department, Autónoma University of Madrid) for ESR measurements. Last, but no least, technical assistance received from the people of the ion implantation facility (CAI—Implantación Iónica) of the Complutense University of Madrid (P. Fernández and R. Cimas) is greatly acknowledge. The financial support of this work was partially done by the Spanish National Office for Science and Technology under Grant Nos. TIC 98-0740 and TIC 2001-1253., We present in this article a comprehensive study of rapid thermal annealing (RTA) effects on the physical properties of SiNx:H thin films deposited by the electron cyclotron resonance plasma method. Films of different as-deposited compositions (defined in this article as the nitrogen to silicon ratio, x=N/Si) were analyzed: from Si-rich (x=0.97) to N-rich (x=1.6) films. The evolution of the composition, bonding configuration, and paramagnetic defects with the annealing temperature are explained by means of different network bond reactions that take place depending on the as-deposited film composition. All the analyzed films release hydrogen, while Si-rich and near-stoichiometric (x=1.43) ones also lose nitrogen upon annealing. These films were used to make Al/SiNx:H/semiconductor devices with Si, In0.53Ga0.47As, and InP. After RTA treatments, the electrical properties of the three different SiNx:H/semiconductor interfaces can be explained, noting the microstructural modifications that SiNx:H experiences upon annealing., Spanish National Office for Science and Technology, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 Acta Materialia Inc. Published by Elsevier Ltd.. This work was supported by MICINN (Projects MAT-2009-07882 and CSD-2009-00013) and by UCMBSCH (Group 910146). JB acknowledges financial support from Universidad Complutense de Madrid., Microrods and hierarchical structures of indium-zinc-oxide (IZO) with different compositions were grown by thermal treatments of mixtures of InN and ZnO powders. In long rods, an increase in Zn content along the growth axis is revealed by energy dispersive spectroscopy. The structures obtained range from Zn-doped indium oxide with a few atomic per cent of Zn, to IZO compounds of the type Zn_kIn_2O_k+3. X-ray photoelectron spectroscopy measurements with spatial resolution show that IZO microstructures degenerate at room temperature, with carrier concentration of the order of 10^20 cm^-3. Electron accumulation has been found for undoped (1 0 0) and (1 1 1) surfaces, whereas depletion of carriers at the surface is observed in IZO samples. The Fermi level position correlates with the Zn concentration at the surface which, taking into account the surface dependence of the ionization potentials, work functions and band gaps, could lead to tunable material properties for device applications. Cathodoluminescence emission intensity is enhanced by the presence of Zn, which induces spectral changes and broadening of the emission band compared with undoped material. The results are discussed in terms of the charge neutrality level and the band structure of the material., MICINN, UCM-BSCH, Universidad Complutense de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2007 IOP Publishing Ltd. This work was supported by MEC (Project MAT 2003-00455)., Sintering of a ZnO-SnO_2 mixture under argon flow leads to the growth of microrods on the sample surface, which are formed by oriented stacks of nanoplates. Energy dispersive spectroscopy and cathodoluminescence ( CL) in the scanning electron microscope show that the stacks of nanoplates consist of Sn doped ZnO. The stacks of nanoplates have well defined orientations relative to the growth axis of the rod. The formation of the nanoplates, which is not observed when undoped ZnO is used in the same process, is attributed to the stresses generated by the presence of Sn atoms in the rods., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2009 American Institute of Physics. This work was supported by MEC (Project No. MAT2006-01259)., Al doped ZnO arrays of nanoplates and of ordered nanoneedles have been grown by a thermal evaporation-deposition method. The nanoplates, which have mainly triangular shape. Interpenetrating triangles and crossing of the triangles with other planar arrangements form a structure consisting of arrays of microboxes. The influence of Al on the luminescence of the nanostructures has been studied by cathodoluminescence (CL) in the scanning electron microscope. Intense CL emission from the internal faces of the microboxes is related to the presence of deep level defects., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2005 IOP Publishing Ltd. This work was supported by MCYT (Project MAT2003-00455), by CAM(ProjectMAT/0630/2004) and by EU project HPMT-CT-2001-00215. JG acknowledges the Marie Curie fellowship in the framework of this project (Grant HPMT-GH-01-0021503)., Sintering of ZnO pressed powder under Ar flow at temperatures between 1250 and 1300 degrees C leads to the formation of elongated microstructures and nanostructures, with different morphologies, on the sample surface. Rods and needles with cross-sectional dimensions ranging from tens of nanometres to several tens of microns and up to hundreds of microns in length are obtained. In an advanced stage of growth, nanoneedles are frequently arranged in bundles, forming the walls of tubes with different cross-sectional dimensions. In addition, microcombs and microfeathers consisting of well oriented nanoneedles are observed. Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to characterize the structures grown. The formation of the elongated structures causes spectral changes, in particular an enhancement of the green-orange luminescence. High CL emission from the internal surface of the tubes has been observed., MCYT, CAM, EU, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2005 American Institute of Physics. This work is supported by MCYT (Project No. MAT 2003-00455), Sintering SnO_2 under argon flow at temperatures in the range of 1350-1500 degreesC causes the formation of wires, rods, and tubes on the sample surface. At high temperatures of the mentioned range, microwires with lengths of hundreds of microns are formed. At lower temperatures the formation of micro- and nanorods as well as micro- and nanotubes takes place. The influence of ball milling of the starting powder on the formation of tubes is investigated. The local cathodoluminescence measurements show a different defect structure in the tubes than in the sample background., MCYT (Spain), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2002 IOP Publishing Ltd. The authors thank M Vittori Antisari for useful discussions and suggestions and E Escudero for the measurements of the oxygen content. This work has been partially supported by MCYT (MAT2000-2119) and CICYT (MAT98-1306E)., The structural and luminescent properties of nanocrystalline silicon produced by high-energy ball milling of Si single crystals have been investigated using transmission electron microscopy (TEM), x-ray diffraction (XRD) and cathodoluminescence (CL) in a scanning electron microscope. XRD measurements show that the average size of the nanocrystals in the milled samples is about 30 nm but TEM reveals a wide range of size distribution including crystallites with the dimension of few nanometres. Ball milling causes the appearance of a visible luminescence band at 1.61 eV, attributed to the presence of nanocrystals, and a near-infrared band peaked at about 0.79 eV which is suggested to be related to the high density of extended defects formed during the mechanical treatment. These bands, attributed to processes in Si, are not observed in the cathodoluminescent spectra of untreated and ball-milled SiO2 powder., MCYT, CICYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2004 American Institute of Physics. This work has been supported by MCYT (Project No. MAT2003-00455)., The effect of mechanical milling on the structure and luminescent properties of CdSe powder has been investigated by means of cathodoluminescence (CL) in the scanning electron microscope, transmission electron microscopy (TEM) and x-ray diffraction. The starting powders were ball milled for times between 5 and 20h. TEM of the milled samples reveals the presence of nanocrystals with a wide range of sizes including nanocrystals of 10 nm and smaller. The CL spectra of the untreated samples show the characteristic band edge emission centered at 1.8 eV. In the milled samples a band centered at about 2.5 eV is observed which appears to be associated to the presence of nanocrystals. The evolution of defect structure with milling time has been monitored by recording infrared cathodoluminescence spectra. A partial phase transformation from wurtzite to zinc blende structure also has been observed., MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2003 American Institute of Physics. The authors acknowledge Centro de Asistencia a la Investigacıón (CAI) de Implantación Iónica [Universidad Complutense de Madrid (UCM)] for use of the deposition system and RTA furnace. CAI de Espectroscopia (UCM). Is acknowledged for providing the FTIR spectrometer. This work was partially financed by the CICYT (Spain) under Contract No. TIC 01-1253., The effect of rapid thermal annealing (RTA) processes on the structural properties of SiOxNyHz films was investigated. The samples were deposited by the electron cyclotron resonance plasma method, using SiH4, O-2 and N-2 as precursor gases. For SiOxNyHz films with composition close to that of SiO2, which have a very low H content, RTA induces thermal relaxation of the lattice and improvement of the structural order. For films of intermediate composition and of compositions close to SiNyHz, the main effect of RTA is the release of H at high temperatures (T>700degreesC). This H release is more significant in films containing both Si-H and N-H bonds, due to cooperative reactions between both kinds of bonds. In these films the degradation of structural order associated to H release prevails over thermal relaxation, while in those films with only N-H bonds, thermal relaxation predominates. For annealing temperatures in the 500-700degreesC range, the passivation of dangling bonds by the nonbonded H in the films and the transition from the paramagnetic state to the diamagnetic state of the K center result in a decrease of the density of paramagnetic defects. The H release observed at high annealing temperatures is accompanied by an increase of density of paramagnetic defects., CICYT (Spain), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2002 IOP Publishing Ltd. This work was supported byMCYT (project MAT 2000-2119)., There. has been interest in the past years in the visible luminescence properties of germanium nanocrystals. Most of the previous works refer to Ge nanocrystals embedded in an oxide matrix. In this work nanocrystalline germanium has been prepared by high-energy ball milling of Ge single crystals and Ge powder. The structure of the milled samples has been assessed by x-ray diffraction (XRD) and transmission electron microscopy (TEM) while the luminescence has been investigated by cathodoluminescence (CL) in the scanning electron microscope (SEM). The samples consist of a powder of particles with sizes of hundreds of nanometres, normally aggregated to form larger particles. TEM reveals that the particles consist of nanocrystals with a wide range of sizes including crystallites of some nanometres. Milled Ge shows two CL bands at about 2.4-2.5 eV and 3.1 eV, respectively. Both emissions appear to be related to the presence of Ge nanocrystals. The CL of untreated and milled GeO_2 powder has been also investigated for comparison., MCYT, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Physical Society. We thank Andrea Fischer for valuable discussions and a critical reading of the manuscript. CGS is grateful to the Centre for Scientific Computing for hospitality and to Ministerio de Educación, Comunidad de Madrid, and the European Social Fund for funding the research stays at Warwick during which much of this work was done. Work at Madrid was supported by MICINN (projects Mosaico and MAT2010-17180)., We study theoretically the optical properties of an exciton in a two-dimensional ring threaded by a magnetic flux. We model the quantum ring by a confining potential that can be continuously tuned from strictly one-dimensional to truly two-dimensional with finite radius-to-width ratio. We present an analytic solution of the problem when the electron-hole interaction is short ranged. The oscillatory dependence of the oscillator strength as a function of the magnetic flux is attributed to the Aharonov-Bohm effect. The amplitude of the oscillations changes upon increasing the width of the quantum ring. We find that the Aharonov-Bohm oscillations of the ground state of the exciton decrease with increasing the width, but, remarkably, the amplitude remains finite down to radius-to-width ratios less than unity. We attribute this resilience of the excitonic oscillations to the nonsimple connectedness of our chosen confinement potential with its centrifugal core at the origin., MICINN (Spain), Comunidad de Madrid, European Social Fund, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2012. The American Astronomical Society. All rights reserved. Artículo firmado por 21 autores. S.E.M. thanks Arjen van der Wel for discussion and Angela Adamo and Anibal Garcia for their helpful comments on the manuscript. E.A. and A.B. thank the Centre National d'Etudes Spatiales for financial support., We examine the effect of circumstellar dust extinction on the near-IR (NIR) contribution of asymptotic giant branch (AGB) stars in intermediate-age clusters throughout the disk of M100. For our sample of 17AGB-dominated clusters we extract optical-to-mid-IR spectral energy distributions (SEDs) and find that NIR brightness is coupled to the mid-IR dust emission in such a way that a significant reduction of AGB light, of up to 1 mag in the K band, follows from extinction by the dust shell formed during this stage. Since the dust optical depth varies with AGB chemistry (C-rich or O-rich), our results suggest that the contribution of AGB stars to the flux from their host clusters will be closely linked to the metallicity and the progenitor mass of the AGB star, to which dust chemistry and mass-loss rate are sensitive. Our sample of clusters-each the analogue of a similar to 1 Gyr old post-starburst galaxy-has implications within the context of mass and age estimation via SED modeling at high-z: we find that the average similar to 0.5 mag extinction estimated here may be sufficient to reduce the AGB contribution in the (rest-frame) K band from similar to 70%, as predicted in the latest generation of synthesis models, to similar to 35%. Our technique for selecting AGB-dominated clusters in nearby galaxies promises to be effective for discriminating the uncertainties associated with AGB stars in intermediate-age populations that plague age and mass estimation in high-z galaxies., Centre National d'Etudes Spatiales (CNES), Francia, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 American Chemical Society. This work was supported by MEC (MAT2006-01259 and MAT2009-07782) and BSCH-UCM (Group 910146)., Mn-doped In(2)O(3) nanopyramids have been grown by a catalyst-free thermal process at 700 degrees C using InN and Mn(2)O(3) powders as precursors. Energy dispersive spectroscopy, as well as X-ray photoelectron spectroscopy, demonstrate the presence of Mn in the pyramids in a content below 1 at. %. In addition to pyramids, nanowires with diameters of about 100 nm grow during treatments at 800 degrees C. Luminescence has been studied by cathodoluminescence in the scanning electron microscope, showing emissions at 1.9, 2.65, and 3.3 eV. Dopant incorporation into the nanostructures and their oxidation states, as well as the effect on the electronic structure, have been measured and discussed., MEC, BSCH-UCM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

This paper explores the impact of dysprosium (Dy) doping on structural, optical, and photocatalytic properties of tin oxide (SnO2) thin films fabricated via spray pyrolysis. Dysprosium doping levels ranged from 0 to 7 at%, and films were grown on glass substrates at 350 °C. X-ray diffraction (XRD) analysis revealed an increase in crystallite size with Dy doping, signifying improved crystalline quality. Simultaneously, dislocation density and strain decreased, indicating enhanced film quality. Texture coefficient (Tchkl) results showed a predominant crystal orientation along the (110) plane due to Dy doping. Optical band gap energy (Eg) decreased with Dy doping up to 5%. Urbach energy increased with Dy doping, suggesting atomic structural flaws and defects. Scanning electron microscopy (SEM) analysis revealed the presence of numerous micro-aggregates on the film's surface. Notably, the density of these micro-aggregates increased proportionally with higher Dy doping levels, particularly emphasizing the pronounced effect observed in SnO2:Dy 5% thin films. These findings underscore the potential of Dy-doped SnO2 thin films for advanced photocatalytic applications, with SnO2:Dy 5% exhibiting favorable properties and demonstrating a 90.99% degradation efficiency in three hours under solar irradiation.

CRUE-CSIC (Acuerdos Transformativos 2021) The authors acknowledge the "CAI de Tecnicas Fisicas", the "CAI de Difraccion de Rayos X '' of Universidad Complutense de Madrid, and "Laboratorio de Caracterizacion de Superficies" of CENIM for sample fabrication, GIXRD and XPS measurements, respectively. Also we acknowledge J. Gandia for his support in the analysis of the optical measurements. This work is part of the project MADRID-PV2 (P2018/EMT-4308) funded by the Comunidad Autonoma de Madrid with the support from FEDER Funds, project TEC2017-84378-R, funded by MICINN and European Social Fund, and projects SCCell (PID2020-116508RB-I00) , HyperPHIR (PID2020-117498RB-I00) and SCALED (PID2019-109215RB-C42) , funded by the Spanish Ministry of Science and Innovation. D.Pastor acknowledges financial support from the MEC to the program Ramon y Cajal (No. RYC-2014-16936) . D. Caudevilla would also acknowledge grant PRE2018-083798, financed by MICINN and European Social Fund., This article studies the physical and electrical behavior of indium tin oxide layers (ITO) grown by an unconventional technique: High Pressure Sputtering (HPS), from a ceramic ITO target in a pure Ar atmosphere. This technique has the potential to reduce plasma induced damage to the samples. The aim is to obtain, at low temperature via HPS, good quality transparent conductive oxide layers for experimental photovoltaic cells with emerging selective contacts such as transition metal oxides, alkaline metal fluorides, etc. We found that the resistivity of the films was strongly dependent on Ar pressure. To obtain device-quality resistivity without intentional heating during deposition a pressure higher than 1.0 mbar was needed. These films deposited on glass were amorphous, presented a high electron mobility (up to 45 cm2V- 1s- 1) and a high carrier density (2.9 x 1020 cm-3 for the sample with the highest mobility). The optimum Ar pressure range was found at 1.5-2.3 mbar. However, the resistivity degraded with a moderate annealing temperature in air. Finally, the feasibility of the integration with photovoltaic cells was assessed by depositing on Si substrates passivated by a-Si:H. The film deposited at 1.5 mbar was uniform and amorphous, and the carrier lifetime obtained was 1.22 ms with an implied open circuit voltage of 719 mV after a 215 degrees C air anneal. The antireflective properties of HPS ITO were also demonstrated. These results show that ITO deposited by HPS is adequate for the research of solar cells with emerging selective contacts., Ministerio de Ciencia e Innovación (MICINN)/ESF, Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid/FEDER, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Very recently, the 2D form of BeO monolayer has been successfully fabricated [Hui Zhang et al., ACS Nano, 2021, 15, 2497]. Motivated by these exciting experimental results on 2D layered BeO structures, the effect of atom adsorption, substitutional doping and vacancy defects on the electronic and magnetic properties of a hexagonal BeO monolayer have been systematically investigated employing density functional theory-based first-principles calculations. We found out that BeO monolayer is a semiconductor with an indirect band gap of 5.9 eV. Next, a plethora of atoms (27 in total) were adsorbed on the surface of BeO monolayer to tailor its electronic properties. The bond length, work function, difference in charge and magnetic moment were also calculated for all modifications covering the vacancy defects and substitutional doping. The band gap is also supplied for these changes, showing how these adjustments can provide amazing opportunities in granting a variety of options in band gap engineering and in transforming the BeO monolayer from a semiconductor to a dilute magnetic semiconductor or half-metal in view of different applications. The formation energy of the defects was also computed as an important indicator for the stability of the defected structures, when created in a real experiment. We have theoretically demonstrated several possible approaches to modify the properties of BeO monolayer in a powerful and controllable manner. Thus, we expect to inspire many experimental studies focused on two dimensional BeO growth and property tuning, and exploration for applications in advanced nanoelectronics., National Research Foundation of Korea (NRF) - Korea government (MSIT) [NRF-2015M2B2A4033123], This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (NRF-2015M2B2A4033123).