Ramón Escobar Galindo

Ramón Escobar Galindo
Universidad de Sevilla | US · Departamento de Física Aplicada I

PhD Physics

About

125
Publications
13,816
Reads
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2,071
Citations
Additional affiliations
May 2014 - July 2017
Abengoa
Position
  • Senior Researcher
May 2014 - June 2017
Abengoa
Position
  • R&D Program Manager (Materials Science)
February 2010 - April 2014
Instituto de Ciencia de Materiales de Madrid
Position
  • R&D researcher

Publications

Publications (125)
Article
Full-text available
The thermal stability of two AlyTi1-y(OxN1-x) layers prepared by cathodic vacuum arc deposition with different oxygen content was studied after high temperature annealing of the samples in air. These layers were designed to be part of solar-selective coating (SSC) stacks. Compositional and microstructural characterization of the thin films was perf...
Article
Full-text available
Titanium oxide films were deposited at room temperature and with no applied bias using a filtered cathodic vacuum arc (FCVA) system in a reactive oxygen environment. The dependence of film growth on two process parameters, the working pressure (Pw) and the O2 partial pressure (pO2), is described in detail. The composition, morphological features, c...
Chapter
Concentrated Solar Power (CSP) technology harnesses the solar power to generate electricity using solar thermal absorbers. Due to the lack of solar thermal materials and components stable under the harsh conditions of central receivers, their operational temperature is limited to <600°C (well below the optimal value). While CSP has a great potentia...
Article
Two multilayer solar selective absorber coatings [Al/CrN0.95/Cr0.96Al0.04N1.08/Cr0.53Al0.47N1.12/Al2O3 (stack #1) and Cr0.96Al0.04N0.89/Cr0.62Al0.38N1.00/Cr0.53Al0.47N1.12/Al2O3 (stack #2)] were deposited on 316L steel by combining direct current (DC) and high power impulse magnetron sputtering (HiPIMS) technologies with the aim of increasing the w...
Article
The transparent conductive oxide (TCO) SnO 2 :Ta is developed as a selectively solar-transmitting coating for concentrated solar power (CSP) absorbers. Upon covering with an antireflective layer, a calculated absorptivity of 95% and an emissivity of 30% are achieved for the model configuration of SnO 2 :Ta on top of a perfect black body (BB). High-...
Article
Full-text available
ZnO films with Ti atoms incorporated (TZO) in a wide range (0–18 at.%) have been grown by reactive co-sputtering on silicon and glass substrates. The influence of the titanium incorporation in the ZnO matrix on the structural and optical characteristics of the samples has been determined by Rutherford backscattering spectroscopy (RBS), X-ray photoe...
Preprint
ZnO films with Ti atoms incorporated (TZO) in a wide range (0-18 at. %) have been grown by reactive co-sputtering on silicon and glass substrates. The influence of the titanium incorporation in the ZnO matrix on the structural and optical characteristics of the samples has been determined by Rutherford backscattering spectroscopy (RBS), X-ray photo...
Article
Full-text available
The optimisation of the specular reflectance of solar collectors is a key parameter to increase the global yield of concentrated solar power (CSP) plants. In this work, the influence of filtered cathodic vacuum arc deposition parameters, particularly working pressure and deposition time, on the specular and diffuse reflectance of aluminium thin fil...
Article
Aluminium titanium oxynitrides were studied as candidate materials for high temperature absorbers in solar selective coatings due to their excellent stability and their tuneable optical behaviour. A set of individual AlyTi1−y(OxN1−x) layers with different oxygen content was prepared by cathodic vacuum arc (CVA) deposition. The composition, morpholo...
Article
The durability of two solar-selective aluminium titanium oxynitride multilayer coatings was studied under conditions simulating realistic operation of central receiver power plants. The coatings were deposited by cathodic vacuum arc applying an optimized design concept for complete solar-selective coating (SSC) stacks. Compositional, structural and...
Article
Full-text available
ZnO is probably one of the most studied oxides since ZnO nanostructures are a very reach family of nanomaterials with a broad variety of technological applications. Although several chemical techniques offer the possibility to obtain such ZnO nanostructures, here we show that the controlled modification of the zinc surface by low-energy O2⁺ bombard...
Article
The optimum reflection of the solar spectrum at well-defined incident directions as well as its durability in time are, both, fundamental requirements of the optics of thermosolar and photovoltaic energy conversion systems. The stringent high performance needed for these applications implies that, almost exclusively, second face mirrors based on si...
Cover Page
Full-text available
Front Cover: The Authors present a technique to grow thin films with composition raging from pure metallic to full stoichiometric by magnetron sputtering, using the oblique angle configuration. The film stoichiometry is tuned by tilting the substrate with respect to the target, and using low amounts of reactive gases. This method has been tested by...
Article
Target poisoning in reactive magnetron sputtering deposition of thin films is an undesired phenomenon, well known for causing a drastic fall of the process efficiency. We demonstrate that when this technique is operated at oblique angles, films with composition raging from pure metallic to stoichiometric compound can be grown in non-poisoned condit...
Article
The deposition of SiOx () compound thin films by the reactive magnetron sputtering technique at oblique angles is studied from both theoretical and experimental points of view. A simple mathematical formula that links the film stoichiometry and the deposition conditions is deduced. Numerous experiments have been carried out to test this formula at...
Article
ZnO p-type thin films were deposited by dual acceptor co-doping using nitrogen and silver via DC reactive magnetron co-sputtering. As precursor material were used a Zn and an Ag metallic targets with a purity of 99.99%. X-ray energy dispersive spectroscopy (EDX) confirmed the presence of Ag and N in ZnO:Ag,N films. The electrical properties were ex...
Article
Target poisoning in reactive magnetron sputtering deposition of thin films is an undesired phenomenon, well known for causing a drastic fall of the process efficiency. We demonstrate that when this technique is operated at oblique angles, films with composition raging from pure metallic to stoichiometric compound can be grown in non-poisoned condit...
Article
CrAlYN coatings with different aluminum (4–12 at.%) and yttrium (2–5 at.%) contents are deposited by d.c. reactive magnetron sputtering on silicon and M2 steel substrates using metallic targets and Ar/N2 mixtures. The influence of the nanostructure and chemical elemental distribution on the oxidation resistance after heating in air at 1000 °C is st...
Article
The preparation of (Bi0.50Na0.50)1-xBaxTiO3 films requires a compositional/structural control, as they determine the functionality of these materials. We report a systematic compositional and structural analysis on (Bi0.50Na0.50)1-xBaxTiO3 films fabricated by chemical solution deposition. The effects of incorporating Na(I) and Bi(III) excesses are...
Conference Paper
Full-text available
A systematic study of TiO2 films deposited by dc filtered cathodic vacuum arc (FCVA) was carried out by varying the deposition parameters in a reactive oxygen atmosphere. The influence of the oxygen partial pressure on film properties is analyzed. Composition was obtained by Rutherford backscattering spectroscopy (RBS) measurements, which also allo...
Conference Paper
Full-text available
The design of an efficient and stable solar selective coating for Concentrating Solar Power central receivers requires a complex study of the materials candidates that compose the coating. Carbon-transition metal nanocomposites were studied in this work as absorber materials because they show appropriate optical properties with high absorption in t...
Article
Nowadays, with the increase of elderly population and related health problems, knee and hip joint prosthesis are being widely used worldwide. However, failure of these invasive devices occurs in a high percentage thus demanding the revision of the chirurgical procedure. Within the reasons of failure, microbial infections, either hospital or subsequ...
Article
We determine the optical properties of nanocomposites comprising gold nanoparticles embedded in a titania matrix using spectroscopic ellipsometry. We then apply the spectral representation formalism due to Bergman [1], to extract the dielectric function of the individual gold NPs. We show that analytical forms of the spectral representation functio...
Article
Nowadays, antibacterial properties are becoming a viable feature to be introduced in biomaterials due to the possibility of modifying the materials surface used in medical devices in a micro/nano metric scale. As a result, it is mandatory to understand the mechanisms of the antimicrobial agents currently used and their possible failures. In this wo...
Conference Paper
Full-text available
Environmental characterization of optical and structural properties of thin films continues to be a challenging task. To understand the failure mechanism in thin films for high temperature applications it is critical to understand how material properties change with temperature. An accurate understanding of the variation of the dielectric function...
Article
AgDLC coatings were deposited by magnetron sputtering in order to evaluate: i) the Ag nanoparticles size distribution along the coatings thickness and ii) the silver stability in DLC coatings. Four different coatings were deposited, two AgDLC nanocomposite coatings containing 20 at.% of Ag, with thicknesses of 250 nm and 1000 nm, a 250 nm AgDLC nan...
Article
Full-text available
The main requirements for transparent conducting oxide (TCO) films acting as electrodes are a high transmission rate in the visible spectral region and low resistivity. However, in many cases, tolerance to temperature and humidity exposure is also an important requirement to be fulfilled by the TCOs to assure proper operation and durability. Beside...
Article
Full-text available
The growth of nanostructured ZnO thin films on nanoporous anodic alumina substrates (NAAF) by dc reactive magnetron sputtering using a pure Zn metal target is reported. ZnO nanostructures reproduce the pore arrays of the NAAF substrates used as templates mimicking their hexagonal long range order. Stoichiometric nanostructured ZnO samples were grow...
Article
Full-text available
The aim of this study was to verify the possible physical and chemical changes that may occur on the surface of Ag–TiCN coatings after exposure to the culture media used in microbiological and cytotoxic assays, respectively tryptic soy broth (TSB) and Dulbecco's modified eagle's medium (DMEM). After sample immersion for 24 h in the media, analyses...
Article
The roughness induced during glow-discharge optical-emission spectroscopy (GDOES) measurements has been reported to cause a loss of resolution during GDOES depth-profiling analysis. In this paper, we undertake for the first time a study of the dynamics of the surface morphology of chromium and titanium thin films (designed in mono and multilayer st...
Article
(Bi0.5Na0.5)1-xBaxTiO 3 (BNBT), which exhibits compositions for the morphotropic phase boundary (MPB) where exist an intimate coexistence of the rhombohedral and tetragonal structures, is being considered as promising lead-free alternative to the well known Pb(Zrx, Ti1-x)O3 (PZT). In this work, BNBT thin films were fabricated by chemical solution d...
Article
Full-text available
Considering it is somewhat difficult to crystallize thermochromic nickelates through a soft process, a major challenge in NdNiO3 crystallization is the stabilization of the Ni3+ oxidation state against Ni2+. The aim of the present work was to understand why a soft annealing is sufficient while an oxygen high pressure (200 bar) is usually considered...
Article
A novel selective coating material based on Mo–Si3N4 has been investigated for the first time. Accurate combination of the individual component layers based on optical simulations and precise control of layers thickness and composition leads to high solar absorptivity (αSol=0.926) and low thermal emissivity (ε25 °C=0.017) on a silver film, resultin...
Article
The oxidation resistance of CrAl(Y)N coatings deposited by reactive magnetron sputtering on P92 steel substrates was tested at 650 degrees C in 100% steam atmosphere up to 2000 h of oxidation. Mass gain measurements and characterisation of coatings and scales after oxidation show the enhanced oxidation resistance provided by the coatings with respe...
Article
Full-text available
For many high-temperature applications, coatings are applied in order to protect structural materials against a wide range of different environments: oxidation, metal dusting, sulphidation, molten salts, steam, etc. The resistance achieved by the use of different kind of coatings, such as functionally graded material coatings, has been optimized wi...
Article
In the present study, nanocomposite coatings of Au clusters embedded in two different oxides, TiO2 and Al2O3, were synthesized using pulsed DC magnetron sputtering. The depositions were carried out in three steps, by depositing the oxide, the Au clusters, and again the oxide. The deposition time of the Au clusters was varied in order to achieve dif...
Article
In this work, ferroelectric (Bi0.5Na0.5)1−xBaxTiO3 thin films were fabricated by chemical solution deposition (CSD) with compositions x = 0.050–0.150. Stoichiometric thin films (hereinafter BNBT) and others containing 10 mol% excesses of Bi3+ and Na+ (BNBTxs) were spin coated onto Pt/TiO2/SiO2/(100)Si substrates and crystallized by rapid thermal pr...
Article
New multifunctional materials based on well-established materials to which functional properties are added, such as antibacterial performance, have become a relevant research topic, in order to meet the requirements of today's technological advances. This paper reports the results of a detailed structural and chemical characterization study of ZrCN...
Article
Surface modification by means of wear protective and antibacterial coatings represents, nowadays, a crucial challenge in the biomaterials field in order to enhance the lifetime of bio-devices. It is possible to tailor the properties of the material by using an appropriate combination of high wear resistance (e.g., nitride or carbide coatings) and b...
Article
Zirconium carbonitride coatings with silver nanoparticles were produced by DC unbalanced dual magnetron sputtering system, using two targets, Zr and Zr/Ag in an Ar, C2H2 and N2 atmosphere. Stainless steel 316L and silicon (100) substrates were used for electrochemical and structural characterization, respectively. Silver was found to be well distri...
Article
Hard x-ray photoelectron spectroscopy (HAXPES), angle-resolved x-ray photoelectron spectroscopy (ARXPS) and x-ray photoelectron spectroscopy (XPS) with simultaneous Ar+ bombardment are used to obtain chemical information and concentration depth profiles of thin film oxides on Cr, Al, Si substrata and to explore the capabilities of analyzing buried...
Article
Full-text available
In this work, we report the successful growth of ZnO nanostructured films by oblique angle magnetron sputtering deposition (OAD) from a Zn target in a mixture gas of Ar/O2. The film microstructure and the surface morphology of the samples were explored by HRSEM. The crystalline structure and the composition were determined by XRD and RBS, respectiv...
Article
Full-text available
XANES and RBS were used to explore the structural phase and composition transitions of ultrathin films with Ti(1-x)Zn2xO2 stoichiometries, from very low (similar to 0.5 at.%) to high (similar to 25 at.%) titanium content. In this way, the coordination chemistry of Ti4+ and Zn2+ cations was examined for a wide range of oxide compositions.
Article
Full-text available
The great interest of mixed metal–silicon oxides lies in their suitability, among other applications, as optical coatings with an adjustable refractive index. In this paper we investigate a new method to obtain chromium and silicon mixed oxides. Using as starting point a metallic chromium film deposited on a silicon substrate by magnetron sputterin...
Article
Full-text available
A systematic study for the optimization of the deposition process of ZnO thin films grown by dc magnetron sputtering at room temperature was carried out using different oxygen partial pressures and deposition times. We have established a correlation between the oxygen partial pressure, the chemical composition and the crystalline structure of the f...
Article
Low-emissivity (low-e) coatings on glass are nowadays extensively used for energy saving applications in architectural windows and on solar thermal collectors. In this work the feasibility of TiN-based layers as low-e coatings has been studied. TiN samples were deposited by reactive magnetron sputtering and, in order to improve their optical proper...
Article
Cr–O–Al thin film mixed oxides grown on Si (100) substrates by reactive magnetron sputtering using different target compositions from 90% Cr (10% Al) to 10% Cr (90% Al) and oxygen fluxes in the range from 0 to 15sccm have been investigated using ex situ XPS, XPS depth profiles and ARXPS. The chemical information obtained with XPS as well as the obs...
Article
Keywords: Al 2 O 3 –Au Au clusters Alumina RBS This paper is focused on the sputtering process and on the structure, chemical composition and mechanical prop-erties of coatings consisting of Al\O dielectric matrix incorporated with increasing Au contents. The maximum Au content incorporated in the coatings was 9 at.%. Al was in deficient values in...
Article
Full-text available
Ag-TiCN coatings were deposited by dc reactive magnetron sputtering and their structural and morphological properties were evaluated. Compositional analysis showed the existence of Ag-TiCN coatings with different Ag/Ti atomic ratios (ranging from 0 to 1.49). The structural and morphological properties are well correlated with the evolution of Ag/Ti...
Article
Full-text available
Transparent Al-doped ZnO thin films were deposited by reactive magnetron sputtering with different oxygen flow rates. The electronic resistivity, measured by the 4 point-probe method, is very sensitive to the sample position relative to the magnetron axis: the closer the magnetron from the axis the higher the resistivity. This is more pronounced fo...
Article
A simple diffusion model is proposed to estimate the growth kinetics of Fe2B layers created at the surface of pure iron. This model employs the mass balance equation at the Fe2B/substrate interface to evaluate the boron diffusion coefficient (DFe2B) in the boride layer. The Fe2B layers were formed using the paste boriding process, at four temperatu...
Article
Ti-Si-C-ON films were deposited by DC reactive magnetron sputtering and their chemical properties, biofilm formation and toxicity were characterized. Based on the films composition three different growth regimes were identified on the films; (I) N/Ti = 2.11 (high atomic ratio) and low oxygen content; (II) 0.77 < N/Ti < 1.86 (intermediate atomic rat...
Article
Positron Beam Analysis was for the first time performed in combination with a four-point bending stage. Applications of this novel technique on PVD TiN (5 m thick), WC:H (2.5 m) and CrN (1.5 m m) layers on tool steel, low carbon steel and stainless steel substrates are discussed. It appeared from PBA results that for these systems the coatings did...
Article
The effects of helium implantation parameters and heating schemes on the formation of surface porosity have been studied. Confinement of the implanted helium by a coating on the metal leads to a prolonged development of the bubble structure. Finally, delamination and blistering occurs and rather open surface structures remain.
Article
Silver-containing diamond-like-carbon (DLC) is a promising material for biomedical implants due to its excellent combination of antibacterial and mechanical properties. In this work, a dual-cathode pulsed filtered cathodic arc source containing silver and graphite rods was employed in order to obtain DLC samples with various silver contents. Chemic...
Article
ZrCN coatings were deposited by dc reactive magnetron sputtering with N2 flows ranging from 2 to 10sccm in order to investigate the influence of the nitrogen incorporation on structure and properties. Information about the chemical composition was obtained by glow discharge optical emission spectroscopy and Rutherford backscattering spectroscopy. T...
Article
In this work, we have studied the improvement on the oxidation resistance of AlCrN-based coatings by adding a subsurface titanium nitride barrier layer. Since oxidation is interrelated with the inward diffusion of oxygen into the surface of AlxCr1−xN (x = 0.70) coatings and the outward diffusion of Cr to the surface, the oxidation behaviour of the...
Article
Detailed structural, microstructural, biofilm formation and cytotoxicity studies were performed on Ti–Si–C–ON hard coatings prepared by DC reactive magnetron sputtering, in order to evaluate the relation among these properties. Compositional analysis showed the existence of two distinct regimens; regime I: high C/Si atomic ratio (C/Si≥1.42) and int...
Article
We have investigated the relation between the structure and morphology of TiN coatings with their optical properties. Samples were deposited by magnetron sputtering and, by changing the deposition parameters, different textures and chemical compositions can be obtained as measured by X-ray diffraction and glow discharge optical emission spectroscop...