Wilson Lopera

Wilson Lopera
University of Valle | UNIVALLE · Department of Physics

PhD

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95
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239
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Publications

Publications (95)
Article
Cobalt-doped ZnO nanoparticles at different compositions have been obtained by the polymeric precursor method. The nanoparticles were obtained at the working pH from 8.3 to 8.5 and synthesized at 550 °C. The properties were studied using X-ray diffraction (XRD), vibrational spectroscopy (FTIR/Raman), diffuse reflectance absorbance spectroscopy (DR...
Article
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In this work, we investigated the effect of doping zinc ions onto nickel ferrite upon the structure, morphology, and magnetic properties of Ni1 − xZnxFe2O4 ferrite nanoparticles (x = 0, 0.25, and 0.75) prepared via co-precipitation method. X-ray diffraction analysis showed the presence of the most intense peak corresponding to the (311) crystallogr...
Article
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Thermal conductivity and thermopower measurements as functions of temperature were carried out on SrTiO3 single crystals below room temperature and compared to those obtained for LaCoO3 polycrystalline samples. The maximum value of thermal conductivity for SrTiO3 (110) and Nb-doped SrTiO3 single crystals was 1.09 and 0.91 W/mK, respectively, at 300...
Poster
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Invasive Koronarangiographie (IKA) wird seit über 30 Jahren bei der Diagnose und Behandlung von Erkrankungen der Koronararterien eingesetzt, und die Zahl dieser jährlich durchgeführten Verfahren wächst stetig. Zu den Nachteilen von IKA gehören unter Anderem die Strahlendosis, welcher die Patienten während diesem Verfahren ausgesetzt sind. Es gibt H...
Article
Pr1-xCaxMnO3 with x = 0.2 is a ferromagnetic material at low temperature TC = 130 K, and paramagnetic at higher temperatures, while La1-xCaxMnO3 with x=0.7 is antiferromagnetic material at low temperature TN = 130 K. Bilayers with an antiferro/ferromagnetic (AF/FM) configuration based on manganites exhibit an interesting phenomenon known as exchang...
Article
HfO2 thin films were grown on Pt/TiO2/SiO2/Si substrates via RF magnetron sputtering technique at pure oxygen atmosphere with a substrate temperature of 550 °C. We studied the structural and electrical properties on HfO2 thin films, varying the thickness (ݐHfO2) from 23 to 155 nm. Grazing-incident x-ray diffraction shows a polycrystalline compositi...
Article
We have deposited Pt(50 nm)/BTO(54 nm)/LCMO(44 nm) and LCMO(55 nm)/BTO(48 nm)/LCMO(54 nm) multilayers on (001)STO substrates to study the top electrode influence in the electrical conduction mechanisms. In this case, LCMO layer was used as bottom electrode in contact with BTO, while Pt and LCMO layers were the top electrodes. From XRD we found that...
Article
Hybrid multiferroics composed of ferromagnetic (FM) / ferroelectric (FE) heterostructures offer a possible route to design artificial multiferroic material exhibiting, for example, magnetoelectric coupling. We have grown BaTiO3 (100 nm)/ La2/3Sr1/3MnO3 (25 nm) bilayers on (001)-, (110)-, and (111)-oriented SrTiO3 substrate to study the induced stra...
Poster
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Purpose. To present results of a retrospective data analysis carried out at a large academic medical centre in South America and to establish a dose reference level (DRL) for digital mammography studies in the region. Methods. All patients presenting for screening mammography between July 1 and December 30, 2017 at our imaging centre were reviewed...
Article
Purpose: To present results of a retrospective data analysis carried out at a large academic medical centre in South America and to establish a dose reference level (DRL) for digital mammography studies in the region. Methods: All patients presenting for screening mammography during a period of six months at our imaging centre were reviewed in this...
Conference Paper
The computed tomography dose index (CTDI), has long been recognised as a metric to quantify the radiation output from a CT examination that is easily measured and that captures the majority of the scatter tails for even wide X-ray beam widths. International standards now require manufacturers to display the pitch-normalised metric (CTDIvol) prior t...
Poster
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In this study we review some of the CT dose descriptors (e.g. CTDIvol and DLP) and effective doses in 20 of the most common CT protocols at a large academic medical centre in South America.
Article
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La2/3Sr1/3MnO3 (LSMO)/BaTiO3 (BTO) bilayers were deposited on (001) SrTiO3 substrates via DC and RF sputtering at pure oxygen atmosphere at a substrate temperature of 830±C. We studied the structural, electrical and magnetic properties on LSMO/BTO bilayers, when LSMO thickness is fixed at 40 nm and BTO thickness is varied from 20 to 100 nm. Recipro...
Article
Full-text available
The 2014 Workshop on Oxide Materials: Novel Multifunctional Properties was held in Cali, Colombia, from September 15 to September 19 on the campus of Universidad del Valle. It was a great privilege to have had this workshop in Cali after the first workshop on oxide materials commemorating the first centennial of the discovery of the superconductivi...
Article
Full-text available
Se desarrolló un protocolo estándar de control de calidad en la Fundación Valle del Lili, para la puesta en marcha de un tomógrafo multimodal por emisión de positrones BIOGRAPH mCT X-3R de SIEMENS® que abarca las pruebas rutinarias, periodicidad, rangos de aceptación necesarias, acciones correctivas y preventivas para detectar y corregir posibles f...
Conference Paper
Full-text available
We have deposited ferroelectric BaTiO3 (BTO), and ferromagnetic La2/3Ca1/3MnO3 bilayers on SrTiO3 substrates by pulsed-laser deposition at pure oxygen atmosphere and substrate temperature of 820 °C, keeping fixed the magnetic layer thickness (tLCMO) at 50 nm and varying the thickness of the ferroelectric layer (tBTO) from 20 to 100 nm. X-ray diffra...
Article
Full-text available
BiFeO3 (BFO) is an interesting material due to the coexistence of magnetic and ferroelectric order at room temperature. Moreover, mixed manganese perovskite oxides like ferromagnetic La2/3Ca1/3MnO3 (LCMO-F) present remarkable properties, like colossal magnetoresistance and non-volatile memory. Bilayers of BFO/LCMO-F and LCMO-F/BFO were grown on (10...
Article
Full-text available
We have deposited bilayers of the FM La2/3Ca1/3MnO3 and FE BaTiO3 as a route to design systems with artificial magnetoelectric coupling. We have optimized the growth parameters for depositing LCMO/BTO/(001)Nb:STO by PLD at pure oxygen atmosphere and a substrate temperature of 820°C, keeping fixed the magnetic layer thickness (tLCMO~50 nm) and varyi...
Article
Metal oxides show fascinating physical properties such as ferromagnetism, antiferromagnetism, high temperature superconductivity, ferroelectricity, or even multiferroicity. For many possible electronic applications as well as fundamental studies, it is essential to fabricate epitaxial layered films and multilayers of these materials having complex...
Article
BaTiO<sub>3</sub> (BTO)/La<sub>2/3</sub>Ca<sub>1/3</sub>MnO<sub>3</sub> (LCMO) bilayers were deposited on (001) SrTiO<sub>3</sub> substrates via pulsed-laser deposition (PLD) at pure oxygen atmosphere at a substrate temperature of 820 <sup>°</sup>C. For LCMO layers, magnetization measurements indicate that electric and magnetic properties are affec...
Article
We have grown ferroelectric BaTiO3(BTO) and ferromagnetic La2/3Ca1/3MnO3 (LCMO) onto (001) SrTiO3 and Nb:SrTiO3 by pulsed laser deposition (PLD) at pure oxygen atmosphere, and a substrate temperature of 820^o C, seeking for a multiferroic behavior in this structure. From x-ray diffraction (XRD) we found lattice parameter aBTO=4.068 å, and aLCMO=3.8...
Article
We report synthesis of multiferroic BiFeO3 thin films as a magnetoelectric material. Films were prepared by using RF magnetron sputtering technique in pure oxygen atmosphere at 0.4 mbar grown on Pt/TiO2/SiO2/Si substrates at 600 degrees C. Films were characterized by x-ray diffraction (XRD), Atomic force microscopy (AFM) and angular-dependent magne...
Article
Bulk samples of Ti1−x Vx O2 nominal composition with x=0.08 were fabricated with the standard solid-state reaction. Appropriate proportions of Titanium dioxide (TiO2) and vanadium pentoxide (V2O5) high-purity powders were thoroughly mixed according to the desired stoichiometry. The solid-state reaction was conducted for 30 min. Pellets were formed...
Article
Surface topography on epitaxial HoBa2Cu3O7-δ (HBCO) and Bi2Sr2CaCu2O8+δ (BSCCO) thin films analysis by using the atomic force microscopy (AFM) technique was carried out. The films were deposited in situ on SrTiO3 substrates with thicknesses ranging from 100 to 300 nm by a high-pressure sputtering process. Chemical etching with a nonaqueous solution...
Article
Multiferroic materials exhibiting simultaneous ferroelectricity and ferromagnetism have potential applications in information storage and in the emerging field of spintronics. Ferromagnetic / ferroelectric multilayers could be a way to obtain a multiferroic heterostructure. We addressed to deposit the ferromagnetic phase of the La1-xCaxMnO3 and the...
Article
Full-text available
We report the epitaxial growth of Sr 2 YSbO 6 films over a MgO single crystal using magnetron sputtering technique. Sr 2 YSbO 6 films were used as a buffer layer for growth of YBa 2 Cu 3 O 7-δ films by DC sputtering. It was experimentally determined that the films evidence superconducting properties, such as a critical temperature of 90 K and a sel...
Article
Full-text available
We report the epitaxial growth of Sr2YSbO6 films over a MgO single crystal using magnetron sputtering technique. Sr2YSbO6 films were used as a buffer layer for growth of YBa2Cu3O7−δ films by DC sputtering. It was experimentally determined that the films evidence superconducting properties, such as a critical temperature of 90 K and a self-field cri...
Article
Full-text available
Resumen El óxido tipo perovskita del compuesto LaCoO 3 ha suscitado un gran interés debido a su comportamiento magnético y eléctrico. Este material, que es conocido dentro de los aislantes tipo Mott, corresponde a un ter-moeléctrico con buenas expectativas para aplicaciones en dispositivos electrónicos. Sus propiedades de trans-porte están fuerteme...
Article
Full-text available
The perovskite oxide-type of the compound LaCoO3 has attracted considerable interest because of its magnetic and electrical behavior. This material, which is known within the insulating Mott-type, corresponds to a thermoelectric with good expectations for applications in electronic devices. Its properties of transport are strongly related to the sp...
Article
Full-text available
The LaCoO3 belongs to the class of compounds called Mott insulators. These oxide perovskite-type cobaltites with p-type are considered alternative materials to improve the efficiency of the process of conversion of energy in thermoelectric devices. The interest in LaCoO3 is mostly related to its non-magnetic ground at low temperature. We have fabri...
Conference Paper
Full-text available
Electrical and thermal transport properties of LaCoO3 in bulk are reported in the temperature range from 10 to 390 K. The crystalline structure of the samples was determined by x-ray diffractometry (XRD). XRD measurements indicated that the formation of LaCoO3 was completed, and it was verified that a pure phase with rhombohedral crystalline struct...
Article
Electrical and thermal transport properties of LaCoO3 in bulk are reported in the temperature range from 10 to 390 K. The crystalline structure of the samples was determined by x-ray diffractometry (XRD). XRD measurements indicated that the formation of LaCoO3 was completed, and it was verified that a pure phase with rhombohedral crystalline struct...
Article
Full-text available
In this work, thin films of VO2 were grown on (0001) sapphire, (100) silicon, and glass substrates, in an argon and oxygen atmosphere at 480°C of deposition temperature. We used a target of pure metallic vanadium in an rf magnetron sputtering technique at 13.56 MHz. After deposition we have carried out an annealing �in situ� of the films at the sam...
Article
We grew rhombohedrally distorted BiFeO <sub>3</sub> and hexagonal YMnO <sub>3</sub> thin films on Pt/TiO <sub>2</sub>/SiO <sub>2</sub>/Si substrates via RF magnetron sputtering technique in a pure oxygen atmosphere. BiFeO <sub>3</sub> and YMnO <sub>3</sub> targets were self-made by the usual solid-state reaction method. We investigated the effects...
Article
Se estudiaron las propiedades magnéticas de películas delgadas de La 2/3 Ca 1/3 MnO 3 crecidas por medio de deposición por láser pulsado (PLD) depositadas sobre sustratos de SrTiO 3 (001). Todas las películas exhibieron baja rugosidad y una bue-na cristalinidad como se indica de los perfiles de rayos X y de perfilometría. Mediante la técnica de esp...
Conference Paper
Full-text available
We report a detailed study of the magnetic properties of Cu1-xCox with Co concentrations between 7 and 10 at% produced by mechanical alloying, through a reactive milling process by using a Retsch PM 400 planetary ball mill under argon atmosphere. We have magnetically characterized our samples by using a Vibrating Sample magnetometer, VSM, from Quan...
Article
We report a detailed study of the magnetic properties of Cu1-xCox with Co concentrations between 7 and 10 at% produced by mechanical alloying, through a reactive milling process by using a Retsch PM 400 planetary ball mill under argon atmosphere. We have magnetically characterized our samples by using a Vibrating Sample magnetometer, VSM, from Quan...
Article
Full-text available
Current measurements, as functions of voltage (I –V curves), at different temperatures were carried out in SrTiO3+Nb/Pb(Zr0.52Ti0.48)O3/Ag capacitor structures grown on (100) SrTiO3 Nb-doped substrates by using a technique of high-oxygen pressure on axis sputtering. Crystalline quality and structure were measured by X-ray diffractometry (XRD). Surf...
Article
NiZn ferrites films deposited by RF sputtering technique on (100)-Si substrates have been studied by the magneto-optical Kerr effect. The coercivity behavior as a function of the thickness indicates a spin reversal mainly governed by the single domain regime. The Jiles–Atherton Model was used to fit the experimental hysteresis loop. The k pinning p...
Article
Full-text available
NiZn ferrites films deposited by RF sputtering technique on (1 0 0)-Si substrates have been studied by the magneto-optical Kerr effect. The coercivity behavior as a function of the thickness indicates a spin reversal mainly governed by the single domain regime. The Jiles–Atherton Model was used to fit the experimental hysteresis loop. The k pinning...
Article
Full-text available
A dynamic scaling and kinetic roughening study was done on digitized atomic force microscope (AFM) images of Pb(Zr0.52,Ti0.48)O3 (PZT) thin films. The films were grown on Si(001) and Nb – SrTiO3(001) (STNO) substrates via rf-sputtering technique at high oxygen pressures at substrate temperatures of 600 ºC by varying the deposition time and keeping...
Article
NiZn ferrites films deposited by RF sputtering technique on (1 0 0)-Si substrates have been studied by the magneto-optical Kerr effect. The coercivity behavior as a function of the thickness indicates a spin reversal mainly governed by the single domain regime. The Jiles–Atherton Model was used to fit the experimental hysteresis loop. The k pinning...
Article
Full-text available
P - E hysteresis loops were measured in SrRuO 3 /Pb(Zr 0.52 Ti 0.48 )O 3 /Pt capacitor structures grown on (100) SrTiO 3 single-crystal substrates using high-oxygen pressure on axis dc-sputtering technique. PZT films were grown by rf magnetron sputtering in a pure oxygen atmosphere. Capacitor structures with electrode areas of 5.0 × 10 −4 and 6.5 ×...
Article
Full-text available
RESUMEN Se ha implementado un sistema de caracterización Magneto-Óptica basado en el Efecto Kerr MO-KE, en geometría polar, esto es, en donde la magnetización es paralela al plano de incidencia y normal a la interfase, y en geometría longitudinal, en la cual la magnetización es paralela al plano de incidencia y paralela a la interfase. Se presentan...
Article
A system based on the Magneto-optical Kerr (MOKE) effect has been implemented. Two different geometrical configurations are available: longitudinal and polar MOKE. In the first one, the magnetization lies in the plane of incidence of the radiation and surface of the sample, in the second one the magnetization lies in the plane of incidence and it i...
Conference Paper
Full-text available
Self-affine scaling behavior of ferroelectric Pb(Zr1−xTix)O3 (PZT) thin films grown on Si(001) substrates has been investigated by AFM \underline {A}tomic \underline {F}orce \underline {M}icroscope. PZT thin films were grown via Rf-sputtering technique at high oxygen pressures and at substrate temperatures 600 oC varying the deposition time and kee...
Article
P-E hysteresis loops were measured in SrRuO 3 /Pb(Zr 0.52 Ti 0.48)O 3 /Pt capacitor struc-tures grown on (100) SrTiO 3 single-crystal substrates using high-oxygen pressure on axis dc-sputtering technique. PZT films were grown by rf magnetron sputtering in a pure oxygen atmosphere. Capacitor structures with electrode areas of 5.0 × 10 −4 and 6.5 × 1...
Article
Full-text available
Se realizó un estudio del escalamiento dinámico y la cinética de rugosidad usando imágenes de Microscopia de Fuerza Atómica (AFM) de películas delgadas de Pb(Zr0.48Ti0.52)O3 (PZT) sobre substratos de Si(100). Las películas fueron crecidas por la técnica de Magnetrón RF-sputtering en altas presiones de oxigeno y a una temperatura de substrato aproxi...
Article
Full-text available
Las propiedades ferroeléctricas y los estados de enlace químico de películas delgadas de PbZr0.52Ti0.48O3 (PZT) depositadas sobre SrRuO3/SrTiO3 por pulverización catódica fueron inves-tigados mediante la técnica de Espectroscopía de Fotoelectrones de rayos-X (XPS). Se logró de-terminar las energías de enlace en la superficie, así como también la co...
Article
Tunneling measurements at different temperatures were carried out in SrRuO3/Pb(Zr0.52Ti0.48)O3/Pt capacitor structures grown on (100) SrTiO3 single-crystal substrates using a high-oxygen pressure on axis sputtering technique. Crystalline quality and structure were measured by X-ray diffractometry (XRD). The surface roughness and morphology were stu...
Article
Tunneling measurements at different temperatures were carried out in SrRuO3/Pb(Zr0.52Ti0.48)O3/Pt capacitor structures grown on (100) SrTiO3 single-crystal substrates using a high-oxygen pressure on axis sputtering technique. Crystalline quality and structure were measured by X-ray diffractometry (XRD). The surface roughness and morphology were stu...
Conference Paper
Full-text available
Tunneling and fatigue measurements at different temperatures were carried out in capacitor structures based on Pb(Zr0.52Ti0.48)O3 (PZT) ferroelectric thin films with bottom electrodes of SrRuO3 (SRO) and top electrodes of Platinum (Pt). SRO electrodes were deposited on (100) SrTiO3 single crystal substrates using a high oxygen pressure on-axis dc-s...
Article
In this work, we show experimental results for growth conditions of thermoelectric Ce0.9CoFe3Sb12 thin films. An rf-magnetron sputtering system has been used to grow the films on single crystal substrates of sapphire (Al2O3), silicon (Si), and magnesium oxide (MgO) at different substrate temperatures between 250 and 450°C. The films were thermoelec...
Article
Full-text available
Utilizando un sistema de pulverización RF (Magnetrón Sputtering ) a 13.56 MHz en una atmósfera de argón puro a presiones de 9 x 10-3 mbar hemos depositado ¿in situ¿ películas delgadas de VO2 sobre sustratos de Si, las cuales muestran una transición semiconductor ¿ metal con cambios en la resistencia eléctrica desde 2 x 103 W hasta 19 W a una temper...
Article
Full-text available
Para una película delgada epitaxial superconductora de Bi2Sr2CaC2O8+d crecida sobre un substra-to de LaAlO3, por el método de pulverización catódica a altas presiones de oxígeno, se comparan las mediciones de la resistividad dc en el plano ab con los valores encontrados al calcular la con-ductividad infraroja, cuando la frecuencia tiende a cero, a...
Article
Full-text available
The in-plane infrared and visible (3meV-3eV) reflectivity of Bi2Sr2CaCu2O8+delta (Bi-2212) thin films is measured between 300K and 10K for different doping levels with unprecedented accuracy. The optical conductivity is derived through an accurate fitting procedure. We study the transfer of spectral weight from finite energy into the superfluid as...
Article
A quantitative statistical study was done on digitized Atomic Force Microscope (AFM) images of La_2/3Ca_1/3MnO3 thin films grown on (100) oriented SrTiO3 substrates. The films were grown by a sputtering technique at high oxygen pressures and at substrate temperatures of 850^oC. From the AFM-images the roughness parameters: interface width, correlat...
Article
Full-text available
Resumen. La nucleación y el crecimiento de películas delgadas de Pb(Zr,Ti)O 3 (PZT) sobre substratos de Pt/TiO 2 /SiO 2 /Si fueron analizadas utilizando microscopía de fuerza atómica (AFM) en el modo de no contacto. Las películas fueron crecidas por la técnica de deposición por láser pulsado (PLD) a una temperatura de 430 °C Las película s presenta...
Article
Surface topography on epitaxial HoBa2Cu3O7-delta (HBCO) and Bi2Sr2CaCu2O8+delta (BSCCO) thin films analysis by using the atomic force microscopy (AFM) technique was carried out. The films were deposited in situ on SrTiO3 substrates with thicknesses ranging from 100 to 300 nm by a high-pressure sputtering process. Chemical etching with a nonaqueous...
Article
Full-text available
Using a dc sputtering method at hi gh oxygen pressures we have deposited YBa 2 Cu 3 O 7-x (YBCO) and YBCO+5% Ag thin films, with different oxygen content, on SrTiO 3 (100). These films were illuminated with 632.8 nm laser light, at room temperature. The change of the electrical resistance caused by illumination indicates the presence of two effects...
Article
A morphological study on the surface of epitaxial thin films of HoBa2Cu3O7-delta was realized by atomic force microscopy. The films were grown using a high-pressure sputtering technique. Chemical etching process with a non-aqueous solution of Br-ethanol was used to modify the thickness of the films. The progress of morphology with thickness variati...
Article
We have performed a study on the preparation conditions and electrical transport properties of epitaxial Bi2Sr2Ca1−xYxCu2O8+δ thin films. The deposition of the films was carried out “in situ” by a high oxygen pressure dc-sputtering technique on (100) SrTiO3 substrates. The structural properties were determined by x-ray diffraction. By increasing th...
Article
An in situ deposition sputtering process at high pressure has been developed for preparing high quality superconducting Bi2Sr2CaCu2O8+δ thin films on different substrates. Both microstructural and electrical properties were well characterized by TEM, AFM, RBS, X-ray diffraction, resistivity and magnetic susceptibility. The high reproducibility of t...
Chapter
Persistent photoconductivity is an interesting and unusual property of high Tc superconductors. Underdoped YBa2Cu3O6+δ shows upon illumination a decrease of resistivity and an increase of Tc. These photoinduced changes are persistent at low temperatures and relax at room temperatures. A possible model for persistent photoconductivity in these mater...
Article
We have fabricated step-stack Josephson junctions based on high quality epitaxial BSCCO (2212 phase) thin films, deposited on Y-doped bismuth (Bi-22Y2) steps. Bi-2212 and Bi-22Y2 films were grown by a high oxygen pressure dc-sputtering technique. The structural characteristics have been analyzed by X-ray, transmission electron microscopy (TEM), and...
Article
We performed a detailed study of the structure and transport properties of Bi2212/22Y2/2212 planar-type tunnel junctions. Both high-temperature superconducting electrodes and semiconducting barriers are highly epitaxial thin films deposited onto SrTiO <sub> 3 </sub> single-crystal (001) substrates. Deposition of the films was carried out by a high...
Article
Persistent Photoconductivity (PPC) is characterized by a long term increase in the conductivity due to illumination, and has been observed in oxygen deficient YBa_2Cu_3O_7-x thin films(For a brief review see: A. Hoffmann, D. Reznik, and I.K. Schuller, Adv. Mater. 9), 271 (1997).. A possible mechanism for PPC in these materials is that the electron...
Article
Using a dc sputtering method at high oxygen pressures we have deposited epitaxial Ag-doped YBa2Cu3O7−x thin films on SrTiO3 bicrystals with missorientation angle of 36.8°. A 15 % Ag-doped YBa2Cu3O7−x sintered target was used to sputter the films. Critical current of 4–5 106 A/cm2 at 77 K were measured in doped films. When compared with 1 × 106 A/cm...
Article
Using a multitarget high oxygen pressure sputtering system, we have produced in situ high quality epitaxial YBa2Cu3O7-x/PrBa2Cu3O7-x/YBa2Cu3O7-x trilayer structures on SrTiO3 (001) substrates with PrBa2Cu3O7-x, barrier thicknesses ranging from 10 to 30 nm. The structural properties were determined by x-ray diffaction. Rutherford Back Scattering (RB...
Article
We deposited YBa2Cu3O7-x/Y2O3/YBa2Cu3O7-x heterostructures by a dc/rf sputtering process at high oxygen pressures on (001) SrTiO3 substrates. The deposition conditions of Y2O3 are completely compatible with those of YBa2Cu3O7-x. The crystal structure of Y2O3 provides a close lattice match with YBa2Cu3O7-x which results in high quality epitaxial tri...
Article
We have produced Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>0<sub>8+δ</sub>/ Bi<sub>2</sub>Sr<sub>2</sub>YCu<sub>2</sub>0<sub>8+δ</sub>/Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>0<sub>8+δ</sub> herostructures using a high pressure dc sputtering technique. The films have been deposited in situ at high oxygen pressure on (001) SrTi0<sub>3</sub> su...
Article
We have prepared Bi2Sr2CaCu2O8−δ/Bi2Sr2YCu2O8−δ/Bi2Sr2CaCu2O8−δ (2 2 1 2 Y 2 1 2) planar heterojunctions (trilayer structures) using an in situ d.c.-sputtering process at high oxygen pressures onto (0 0 1) SrTiO3 substrates. Bi2Sr2YCu2O8−δ films (semiconducting-like) 10 and 12 nm thick were used as artificial barriers. Composition and structure of...
Article
High-quality YBa2Cu3O7−x films have been produced on SrTiO3 (001) and NdGaO3 (001) substrates. X-ray Φ scans show a good in-plane texture but do not exclude the presence of domains at 90°. Diamagnetic shielding properties obtained from mutual-inductance measurements show a double peak structure which may be ascribed to the presence of those domains...
Article
We have deposited Bi 2 Sr 2 CaCu 2 O 8 + δ /Bi 2 Sr 2 YCu 2 O 8 + δ /Bi 2 Sr 2 CaCu 2 O + δ (2212/22Y2/2212) heterostructures by an in situ dc sputtering technique at high oxygen pressures on (001) SrTiO 3 substrates. The formation of highly c‐axis oriented trilayers with sharp interfaces is demonstrated by x‐ray diffraction and transmission electr...
Article
We report on the X-ray diffraction, secondary ion mass spectrometry, and atomic force microscopy on Ho(123) and Bi(2212) films dc sputtered in pure oxygen atmosphere onto heated sapphire substrates with CeO2 buffer layers. The films were c-axis oriented. The Ho(123) films had a Tc of 88 K but had a relatively high room temperature resistivity of 40...
Article
We have prepared Bi2Sr2CaCu2O8-delta/Bi2Sr2YCu2O8-delta/Bi2Sr2CaCu2O8-delta trilayer structures, using a ``in situ'' DC-sputtering process at high oxygen pressures on (001) SrTiO3 substrates. Bi2Sr2CaCu2O8-delta films were used for superconducting electrodes and semiconductor-like Bi2Sr2YCu2O8-delta films with thickness down 5 nm were used as barri...
Article
A characterization of the high-pressure dc-Sputtering system, used for the “in situ” preparation of high-quality high-Tc superconducting thin films, was performed by plasma electrical measurements using a single Langmuir probe. A correlation between plasma characteristics and thin film properties (transition temperature, Tc, transition width, ΔTc a...
Article
Full-text available
Este artículo forma parte del "Volumen Suplemento" S1 de la Revista Latinoamericana de Metalurgia y Materiales (RLMM). Los suplementos de la RLMM son números especiales de la revista dedicados a publicar memorias de congresos. Este suplemento constituye las memorias del congreso "X Iberoamericano de Metalurgia y Materiales (X IBEROMET)" celebrado e...
Article
Highly conductive SrRuO3 (SRO) oxide thin films have been grown "in situ" on (001) SrTiO3 by using a DC sputtering technique at high oxygen pressures (3.5 mbar). SRO thin films grew highly (001)-oriented for substrate temperatures above 600 ^oC. AFM analysis showed surface roughness of about 3.6 nm for SRO-film thickness of 100 nm. The samples have...
Article
Self-affine scaling behavior of ferroelectric Pb(Zr1-xTix)O3 (PZT) thin films grown on Si(001) substrates has been investigated by AFM Atomic Force Microscope. PZT thin films were grown via Rf-sputtering technique at high oxygen pressures and at substrate temperatures 600 ^oC varying the deposition time and keeping all parameters. growth constant....
Article
Epitaxial La_0.7Ca_0.3MnO_3/La_0.3Ca_0.7MnO3 bilayers were grown in-situ on (001) SrTiO3 substrates by a high oxygen pressure sputtering process. Typical deposition conditions include a substrate temperature of 850 °C, oxygen pressure of 3.5 mbar, cooling in O2 after deposition and, a low growth rate of 0.3 Ås. Several sample series with a 20 nm fe...