Artículos (Física Aplicada I)

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Oscillatory instability and stability of stationary solutions in the parametrically driven, damped nonlinear Schrödinger equation
(ArXiv, 2024-11-15) Carreño Navas, Fernando; Álvarez Nodarse, Renato; Quintero, Niurka R.; Universidad de Sevilla. Departamento de Análisis Matemático; Universidad de Sevilla. FQM415: Modelado Físico-Matemático de Sistemas no Lineales
We found two stationary solutions of the parametrically driven, damped nonlinear Schrö\-dinger equation with nonlinear term proportional to $|\psi(x,t)|^{2 \kappa} \psi(x,t)$ for positive values of $\kappa$. By linearizing the equation around these exact solutions, we derive the corresponding Sturm-Liouville problem. Our analysis reveals that one of the stationary solutions is unstable, while the stability of the other solution depends on the amplitude of the parametric force, damping coefficient, and nonlinearity parameter $\kappa$. An exceptional change of variables facilitates the computation of the stability diagram through numerical solutions of the eigenvalue problem as a specific parameter $\varepsilon$ varies within a bounded interval. For $\kappa <2$ , an oscillatory instability is predicted analytically and confirmed numerically. Our principal result establishes that for $\kappa \ge 2$, there exists a critical value of $\varepsilon$ beyond which the unstable soliton becomes stable, exhibiting oscillatory stability.
129I in sediment cores from the Celtic Sea by AMS through a microwave digestion process
(Elsevier, 2022) Lérida Toro, Victoria; Abascal Ruíz, Unai; Villa Alfageme, María; Klar, Jessica K.; Hicks, Natalie; López Gutiérrez, José María; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH2-NH2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH2OH⋅HCl) and so dium bisulfite (Na2S2O5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in so lution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores.
Distribution of 1 236U in the U.S. GEOTRACES Eastern Pacific Zonal Transect and its use as a 2 water mass tracer
(Elsevier, 2019) Villa Alfageme, María; Chamizo Calvo, Elena; Kenna, Timothy C.; López Lora, Mercedes; Casacuberta, Nuria; Chang, Clara H.; Masqué, Pere; Christi, Marcus; Universidad de Sevilla. Departamento de Física Aplicada II; Universidad de Sevilla. Departamento de Física Aplicada I
We report dissolved concentrations of the long-lived radioisotope 236U measured in the water column along the 2013 US GEOTRACES Eastern Pacific Zonal Transect (GP16). This transect followed a 10–15°S line from Manta, Ecuador, to Papeete, Haiti, French Polynesia, crossing the southern East Pacific Rise, intercepting one of the largest hydrothermal plumes as well as a productivity gradient, which includes the upwelling zone and associated low oxygen waters offshore from Peru and the oligotrophic sub-tropical gyre. Accelerator Mass Spectrometry was used to measure dissolved seawater 236U concentrations as low as 1 × 103 atom kg−1, which are among the lowest levels reported to date. Differences in upper water column 236U distributions from east to west are a result of variable contributions from different surface and intermediate waters encountered along the transect. The distribution of 236U, both in depth and geographically, provides complementary information to that obtained from Δ14C and helium isotopes, demonstrating that 236U concentrations are diagnostic in the identification of and contributions from the different deep and bottom water masses encountered along the EPZT (Jenkins et al., 2017). For example, we observe minimum 236U concentrations along the EPZT between 2000 and 3000 m that are consistent with contributions attributed to Pacific Deep Water. We also observe increases in 236U below 3000 m at the eastern and western termini of the EPZT. This is consistent with contributions associated with Antarctic Bottom Water and Lower Circumpolar Deep Water. Our results indicate that 236U may be used in conjunction with Δ14C and 3He isotopes as an additional tool with which to identify and resolve contributions from different water masses in the Pacific Ocean.
Magnetron sputtered ß-Ti coatings for biomedical application: A HiPIMS approach to improve corrosion resistance and mechanical behavior
(Elsevier, 2025-01-30) Sánchez López, Juan Carlos; Fortio Godinho, Vanda Cristina; López Santos, Carmen; Navarro González, Paula; Rodríguez-Albelo, Luisa Marleny; Sánchez Pérez, Miriam; Jiménez Piqué, Emilio; Torres Hernández, Yadir; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Química Orgánica y Farmacéutica; Universidad de Sevilla. Departamento de Ingeniería y Ciencia de los Materiales y del Transporte; Universidad de Sevilla; Universidad de Sevilla. TEP123: Metalurgia e Ingeniería de los Materiales
This work presents the surface modification of commercially pure Ti specimens (c.p.-Ti) prepared by conventional powder metallurgy by depositing a thin film of a ß-Ti alloy (Ti-35Nb-7Zr-5Ta, wt. %, TNZT). Two types of pulsed technologies: conventional (p-DC) and high-power impulse magnetron sputtering (HiPIMS), with and without bias assistance (−60 V) under similar power conditions (250 W) were applied on titanium specimens and silicon substrates leading to different film morphologies and functional properties. Microstructural, X-ray diffraction, nanoindentation, surface wetting, XPS and electrochemical impedance measurements were done to characterize their functionality. All the coatings presented a reduced Young’s Modulus (E ≤ 80GPa) compared to the bulk Ti, representing a reduction of more than 30 %. This decrease can significantly contribute to the reduction of the stress-shielding effect, mitigating the risk of implant loosening and failure. The hardness values of TNZT coatings, slightly lower than c.p.-Ti substrate, range from 4.1 to 4.7 GPa. XPS analysis shows a passivation layer of TiO2, Nb2O5, and ZrO2, which offers high impedance and excellent corrosion resistance. The best compromise between mechanical and corrosion properties is achieved with the HiPIMS technology, thanks to its compact film microstructure with high electrical resistance, despite its limited thickness of about 1 μm.
Stability of Breathers for a Periodic Klein–Gordon Equation
(MDPI, 2024-09-04) Chirilus-Bruckner, Martina; Cuevas-Maraver, Jesús; Kevrekidis, Panayotis G.; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. FQM280: Física no Lineal
The existence of breather-type solutions, i.e., solutions that are periodic in time and exponentially localized in space, is a very unusual feature for continuum, nonlinear wave-type equations. Following an earlier work establishing a theorem for the existence of such structures, we bring to bear a combination of analysis-inspired numerical tools that permit the construction of such waveforms to a desired numerical accuracy. In addition, this enables us to explore their numerical stability. Our computations show that for the spatially heterogeneous form of the ϕ4 model considered herein, the breather solutions are generically unstable. Their instability seems to generically favor the motion of the relevant structures. We expect that these results may inspire further studies towards the identification of stable continuous breathers in spatially heterogeneous, continuum nonlinear wave equation models.
Numerical modelling of radionuclide uptake by bluefin tuna along its migration routes in the Mediterranean Sea after a nuclear accident
(Elsevier, 2024-09-20) Cortés Parejo, María del Carmen; Periáñez Rodríguez, Raúl; Block, Bárbara A.; Castleton, Michael R.; Cermeño, Pablo; Dedman, Simon; Universidad de Sevilla. Departamento de; Universidad de Sevilla. Departamento de Física Aplicada I
A numerical model which simulates the adsorption of radionuclides by migrating bluefin tuna in the Mediterranean Sea is described, in order to determine the level of contamination of these fish after a hypothetical nuclear accident and thus be able to assess the possible impact on human consumption. A 4–species foodweb model is incorporated into a Lagrangian model describing physical transport (advection, mixing, radioactive decay and interactions of radionuclides with sediments). Tuna is the last trophic level in the foodweb model and the equation providing the temporal evolution of radionuclide concentration in its flesh is solved along the fish trajectories, which were obtained through electronic tagging of fishes. The model was applied to the western Mediterranean, where several worst–case hypothetical accidents were simulated, both from a coastal nuclear power plant and from a vessel. Resulting 137Cs concentrations in migrating tuna were similar, or slightly higher, than reported background concentrations in these fishes and well below established safety levels. Maximum calculated concentrations in tuna flesh is in the order of 1 Bq/kg (wet weight). This is due to the rapid movement of the fishes, which spend only limited time over the most contaminated spots.
Ceramic barrier layers for flexible thin film solar cells on metallic substrates: A laboratory scale study for process optimization and barrier layer properties
(American Chemical Society, 2014) Delgado Sánchez, José María; Guilera, Nuria; Francesch, Laia; Alba, María D.; López, Laura; Sánchez, Emilio; Universidad de Sevilla. Departamento de Física Aplicada I
Flexible thin film solar cells are an alternative to both utility-scale and building integrated photovoltaic installations. The fabrication of these devices over electrically conducting low-cost foils requires the deposition of dielectric barrier layers to flatten the substrate surface, provide electrical isolation between the substrate and the device, and avoid the diffusion of metal impurities during the relatively high temperatures required to deposit the rest of the solar cell device layers. The typical roughness of low-cost stainless-steel foils is in the hundred-nanometer range, which is comparable or larger than the thin film layers comprising the device and this may result in electrical shunts that decrease solar cell performance. This manuscript assesses the properties of different single-layer and bilayer structures containing ceramics inks formulations based on Al2O3, AlN, or Si3N4 nanoparticles and deposited over stainless-steel foils using a rotogravure printing process. The best control of the substrate roughness was achieved for bilayers of Al2O3 or AlN with mixed particle size, which reduced the roughness and prevented the diffusion of metals impurities but AlN bilayers exhibited as well the best electrical insulation properties.
Observation of stochastic resonance in directed propagation of cold atoms
(American Physical Society, 2022-12) Staron, Alexander; Jiang, Kefeng; Scoggins, Casey; Wingert, Daniel; Cubero Gómez, David; Bali, Samir; Universidad de Sevilla. Departamento de Física Aplicada I; Ministerio de Ciencia e Innovación (MICIN). España
Randomly diffusing atoms confined in a dissipative optical lattice are illuminated by a weak probe of light. The probe transmission spectrum reveals directed atomic propagation that occurs perpendicular to the direction of probe beam propagation. Resonant enhancement of this directed propagation is observed as we vary the random photon scattering rate. We experimentally characterize this stochastic resonance as a function of probe intensity and lattice well depth. A simple model reveals how the probe-excited atomic density waves and optical pumping rates conspire to create directed atomic propagation within a randomly diffusing sample.
Some considerations on the dependence to numerical schemes of Lagrangian radionuclide transport models for the aquatic environment
(Elsevier, 2023-05) Periáñez Rodríguez, Raúl; Brovchenko, I.; Jung, K. T.; Kim, K. O.; Liptak, L.; Little, A.; Kobayashi, T.; Maderich, V.; Min, B. I.; Suh, K. S.; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
Lagrangian models present several advantages over Eulerian models to simulate the transport of radionuclides in the aquatic environment in emergency situations. A radionuclide release is simulated as a number of particles whose trajectories are calculated along time and thus these models do not require a spatial discretization (although it is always required in time). In this paper we investigate the dependence of a Lagrangian model output with the grid spacing which is used to calculate concentrations from the final distribution of particles, with the number of particles in the simulation and with the interpolation schemes which are required because of the discrete nature of the water circulation data used to feed the model. Also, a Lagrangian model may describe the exchanges of radionuclides between phases (liquid and solid), which is done in terms of transition probabilities. The dependence of these probabilities with time step is analyzed as well. It was found that the optimum grid size used to calculate concentrations should be carefully checked, and that temporal interpolation is more significant than spatial interpolation to obtain a more accurate solution. A method to estimate the number of particles required to have a certain accuracy level is proposed. Finally, it was found that for low sediment concentrations and small radionuclide , exact equations for the transition probabilities should be used; and that phase transitions introduce a stability condition as in Eulerian models.
The Transport of Radionuclides Released From Nuclear Facilities and Nuclear Wastes in the Marine Environment at Oceanic Scales
(The Korean Radioactive Waste Society, 2022-09) Periáñez Rodríguez, Raúl; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. RNM138: Física Nuclear Aplicada
The transport of radionuclides at oceanic scales can be assessed using a Lagrangian model. In this review an application of such a model to the Atlantic, Indian and Pacific oceans is described. The transport model, which is fed with water currents provided by global ocean circulation models, includes advection by three–dimensional currents, turbulent mixing, radioactive decay and adsorption/release of radionuclides between water and bed sediments. Adsorption/release processes are described by means of a dynamic model based upon kinetic transfer coefficients. A stochastic method is used to solve turbulent mixing, decay and water/sediment interactions. The main results of these oceanic radionuclide transport studies are summarized in this paper. Particularly, the potential leakage of 137Cs from dumped nuclear wastes in the north Atlantic region was studied. Furthermore, hypothetical accidents, similar in magnitude to the Fukushima accident, were simulated for nuclear power plants located around the Indian Ocean coastlines. Finally, the transport of radionuclides resulting from the release of stored water, which was used to cool reactors after the Fukushima accident, was analyzed in the Pacific Ocean.
Setting a comprehensive strategy to face the runback icing phenomena
(Elsevier, 2023-07) Mora, Julio; García, Paloma; Carreño, Francisco; González, Miguel; Gutiérrez, Marcos; Montes, Laura; Rico-Gavira, Víctor Joaquín; López Santos, Carmen; Vicente, Adrián; Rivero, Pedro; Rodríguez, Rafael; Larumbe, Silvia; Acosta, Carolina; Ibáñez-Ibáñez, Pablo; Corozzi, Alessandro; Raimondo, Mariarosa; Kozera, Rafal; Przybyszewski, Bartlomiej; González-Elipe, Agustín R.; Borrás, Ana; Redondo, Francisco; Agüero, Alina; Universidad de Sevilla. Departamento de Física Aplicada I; European Union (UE). H2020; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Consejo Superior de Investigaciones Científicas (CSIC)
The development of anti-icing robust surfaces is a hot topic nowadays and particularly crucial in the aeronautics or wind energy sectors as ice accretion can compromise safety and power generation efficiency. However, the current performance of most anti-icing strategies has been proven insufficient for such demanding applications, particularly in large unprotected zones, which located downstream from thermally protected areas, may undergo secondary icing. Herein, a new testing methodology is proposed to evaluate accretion mechanisms and secondary icing phenomena through, respectively, direct impact and running-wet processes and systematically applied to anti-icing materials including commercial solutions and the latest trends in the state-of-the-art. Five categories of materials (hard, elastomeric, polymeric matrix, SLIPS and superhydrophobic) with up to fifteen formulations have been tested. This Round-Robin approach provides a deeper understanding of anti-icing mechanisms revealing the strengths and weaknesses of each material. The conclusion is that there is no single passive solution for anti-ice protection. Thus, to effectively protect a given real component, different tailored materials fitted for each particular zone of the system are required. For this selection, shape analysis of such a component and the impact characteristics of water droplets under real conditions are needed as schematically illustrated for aeronautic turbines.
Geodesic Half-Maxwell Fish-Eye-Lens Antenna
(Institute of Electrical and Electronics Engineers, 2023-03) Yang, Shiyi; Chen, Qiao; Mesa Ledesma, Francisco Luis; Fonseca, Nelson J. G.; Quevedo Teruel, Óscar; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. TIC112: Microondas
We propose and implement a geodesic half-Maxwell fish-eye (MFE)-lens antenna. The lens was optimized using an in-house physical optics (PO) code adapted for generalized geodesic lenses. The final antenna design was validated with commercial electromagnetic simulation software. The antenna combines a modulated geodesic half-MFE lens and a transition to a linear flare, which is needed to preserve the linear polarization in the aperture. The antenna prototype, designed to operate in the Ka -band, was manufactured with computer numerical control (CNC) milling and measured in an anechoic chamber. The design provides continuous beam scanning because of a mechanically actuated feed. Promising beam scanning properties are demonstrated in an angular range of ±45° with a scan loss below 3 dB, as well as good frequency stability from 26 to 32 GHz. Since the antenna is fully metallic, its radiation efficiency is high (approximately 90%).
Porphyrin-based metal-organic frameworks for solar fuel synthesis photocatalysis: Band gap tuning: Via iron substitutions
(Royal Society of Chemistry, 2017) Aziz, Alex; Ruiz-Salvador, A. Rabdel; Cruz Hernández, Norge; Calero, Sofía; Hamad, Said; Grau-Crespo, Ricardo; Universidad de Sevilla. Departamento de Física Aplicada I; Ministerio de Economia, Industria y Competitividad (MINECO). España
Photocatalysts based on metal-organic frameworks (MOFs) are very promising due to a combination of high tuneability and convenient porous structure. Introducing porphyrin units within MOFs is a potential route to engineer these natural photosynthesis molecular catalysts into artificial photosynthesis heterogeneous catalysts. Using computer simulations based on density functional theory, we explore how to modify the electronic structure of porphyrin-based MOFs to make them suitable for the photocatalysis of solar fuel synthesis via water splitting or carbon dioxide reduction. In particular, we have investigated the effect that Fe substitutions have on the electronic properties of porphyrin-based metal organic frameworks. By aligning the electron levels with a vacuum reference, we show that Fe at the porphyrin metal centre has the effect of slightly raising the position of the valence band edge, whereas Fe at the octahedral metal node has the ability to significantly lower the position of the conduction band edge on the absolute scale. Iron is therefore a very useful dopant to engineer the band structure and alignment of these MOFs. We find that the porphyrin-based structure with Al in the octahedral sites and Zn in the porphyrin centres has a band gap that is slightly too wide to take advantage of visible-light solar radiation, while the structure with Fe in the octahedral sites has bandgaps that are too narrow for water splitting photocatalysis. We then show that the optimal composition is achieved by partial substitution of Al by Fe at the octahedral sites, while keeping Zn at the porphyrin centres. Our study demonstrates that porphyrin-based MOFs can be engineered to display intrinsic photocatalytic activity in solar fuel synthesis reactions.
Anthracological study of a Chalcolithic funerary deposit from Perdigões (Alentejo, Portugal). A new analytical methodology to establish the wood burning temperature
(Public Library of Science, 2023-07) Coradeschi, Ginevra; Jiménez Morillo, Nicasio T.; Barrocas Dias, Cristina; Beltrame, Massimo; Belo, Anabela D.F.; Pascual Granged, Arturo José; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. RNM-364: MED_Soil Research Group
Anthracological analyses of charcoal samples retrieved from Pit 16 of Perdigões (Reguengos de Monsaraz, Portugal), a secondary deposition of cremated human remains dated back to the middle of the 3rd millennium BC, enabled the identification of 7 different taxa: Olea europaea, Quercus spp. (evergreen), Pinus pinaster, Fraxinus cf. angustifolia, Arbutus unedo, Cistus sp. and Fabaceae. All taxa are characteristic of both deciduous and evergreen Mediterranean vegetation, and this data might indicate that the gathering of woods employed for the human cremation/s occurred either on site, or in its vicinity. However, considering both the large distribution of the identified taxa and data about human mobility, it is not possible to conclusively determine the origin of the wood used in the cremation(s). Chemometric analysis were carried out to estimate the absolute burning temperature of woods employed for the human cremation/s. An in-lab charcoal reference collection was created by burning sound wood samples of the three main taxa identified from Pit 16, Olea europaea var. sylvestris, Quercus suber (evergreen type) and Pinus pinaster, at temperatures between 350 and 600 ˚C. The archaeological charcoal samples and the charcoal reference collection were chemically characterized by using mid-infrared (MIR) spectroscopy in the 1800–400 cm-1 range, and Partial Least Squares (PLS) regression method was used to build calibration models to predict the absolute combustion temperature of the archaeological woods. Results showed successful PLS forecasting of burn temperature for each taxon (significant (P <0.05) cross validation coefficients). The anthracological and chemometric analysis evidenced differences between the taxa coming from the two stratigraphic units
Structural control in porous/compact multilayer systems grown by magnetron sputtering
(Institute of Physics Publishing (IOPSCIENCE), 2017-10-23) García Valenzuela, Aurelio; López Santos, Carmen; Álvarez Molina, Rafael; Rico, Víctor; Cotrino Bautista, José; González Elipe, Agustín Rodríguez; Palmero Acebedo, Alberto; Universidad de Sevilla. Departamento de Física Aplicada I; Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear; Universidad de Sevilla; Junta de Andalucía; Ministerio de Economía y Competitividad (MINECO). España
In this work we analyze a phenomenon that takes place when growing magnetron sputtered porous/compact multilayer systems by alternating the oblique angle and the classical configuration geometries. We show that the compact layers develop numerous fissures rooted in the porous structures of the film below, in a phenomenon that amplifies when increasing the number of stacked layers. We demonstrate that these fissures emerge during growth due to the high roughness of the porous layers and the coarsening of a discontinuous interfacial region. To minimize this phenomenon, we have grown thin interlayers between porous and compact films under the impingement of energetic plasma ions, responsible for smoothing out the interfaces and inhibiting the formation of structural fissures. This method has been tested in practical situations for compact TiO2/porous SiO2 multilayer systems, although it can be extrapolated to other materials and conditions.
SiOx by magnetron sputtered revisited: tailoring the photonic properties of multilayers
(Elsevier B.V., 2019-09-15) García Valenzuela, Aurelio; Álvarez Molina, Rafael; Espinós, Juan P.; Rico, Víctor; Gil Rostra, Jorge; Palmero Acebedo, Alberto; González Elipe, Agustín Rodríguez; Universidad de Sevilla. Departamento de Física Aplicada I; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Economia, Industria y Competitividad (MINECO). España; Universidad de Sevilla
Traditionally porous silicon based photonic structures have been prepared by electrochemically etching of silicon. In this work, porous multilayers of nanocolumnar SiOx and SiO2 thin films acting as near infrared (NIR) 1D-photonic nanostructures are prepared by magnetron sputtering deposition at oblique angles (MS-OA). Simultaneous control of porosity and stoichiometry of the stacked films is achieved by adjusting the deposition angle and oxygen partial pressure according to a parametric formula. This new methodologoy is proved for the synthesis of SiOx thin films with x close to 0.4, 0.8, 1.2, 1.6 and nanostructures varying from compact (at 0° deposition angle) to highly porous and nanocolumnar (at 70° and 85° deposition angles). The strict control of composition, structure and nanostructure provided by this technique permits a fine tuning of the absorption edge and refraction index at 1500 nm of the porous films and their manufacturing in the form of SiOx-SiO2 porous multilayers acting as near infrared (NIR) 1D-photonic structures with well-defined optofluidic responses. Liquid tunable NIR Bragg mirrors and Bragg microcavities for liquid sensing applications are presented as proof of concept of the possibilities of this MS-OA manufacturing method as an alternative to the conventional electrochemical fabrication of silicon based photonic structures.
2D compositional self-patterning in magnetron sputtered thin films
(Elsevier B.V., 2019-06-30) García Valenzuela, Aurelio; Álvarez Molina, Rafael; Rico, Víctor; Espinos, Juan P.; López Santos, Carmen; Solís, Javier; Siegel, Jan; del Campo, Adolfo; Palmero Acebedo, Alberto; González Elipe, Agustín Rodríguez; Universidad de Sevilla. Departamento de Física Aplicada I; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Ministerio de Economia, Industria y Competitividad (MINEICO). España; Universidad de Sevilla
Unlike topography patterning, widely used for numerous applications and produced by means of different technologies, there are no simple procedures to achieve surface compositional patterning at nanometric scales. In this work we have developed a simple method for 2D patterning the composition of thin films. The method relies on the magnetron sputtering deposition at oblique angles onto patterned substrates made by laser induced periodic surface structures (LIPSS). The method feasibility has been demonstrated by depositing SiOx thin films onto LIPSS structures generated in Cr layers. A heterogeneous and aligned distribution of O/Si ratios (and different Si n+ chemical states) along the LIPSS structure in length scales of some hundreds nm's has been proven by angle resolved X-ray photoelectron spectroscopy and a patterned arrangement of composition monitored by atomic force microscopy-Raman analysis. The obtained results are explained by the predictions of a Monte Carlo simulation of this deposition process and open the way for the tailored one-step fabrication of surface devices with patterned compositions.
Enhancing Essential Oil Extraction from Lavandin Grosso Flowers via Plasma Treatment
(MDPI, 2024-02) Molina, Ricardo; López Santos, Carmen; Balestrasse, Karina; Gómez Ramírez, Ana María; Sauló, Jordi; Universidad de Sevilla. Departamento de Física Aplicada I; Ministerio de Ciencia e Innovación (MICIN). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); European Commission (EC); Universidad de Sevilla. FQM196: Nanotecnología en Superficies y Plasma
This study explores the impact of plasma treatment on Lavandin Grosso flowers and its influence on the extraction of essential oils (EOs) via hydrodistillation. Short plasma treatment times enhance the yield of EO extraction from 3.19% in untreated samples to 3.44%, corresponding to 1 min of plasma treatment, while longer treatment times (10 min) show diminishing returns to 3.07% of yield extraction. Chemical characterization (GC/MS and ATR-FTIR) indicates that plasma treatments do not significantly alter the chemical composition of the extracted EOs, preserving their aromatic qualities. Investigations into plasma–surface interactions reveal changes at the nanometer level, with XPS confirming alterations in the surface chemistry of Lavandin Grosso flowers by reducing surface carbon and increasing oxygen content, ultimately resulting in an increased presence of hydrophilic groups. The presence of hydrophilic groups enhances the interaction between the surface membrane of the glandular trichomes on Lavandin Grosso flowers and water vapor, consequently increasing the extraction of EOs. Furthermore, microscopic SEM examinations demonstrate that plasma treatments do not affect the morphology of glandular trichomes, emphasizing that surface modifications primarily occur at the nanoscale. This study underscores the potential of plasma technology as a tool to enhance EO yields from botanical sources while maintaining their chemical integrity.
Spectral Properties of Exact Polarobreathers in Semiclassical Systems
(MDPI, 2023-04-27) Archilla, Juan F. R.; Bajārs, Jānis; Universidad de Sevilla. Departamento de Física Aplicada I; FQM280: Física No Lineal
In this paper, we study the spectral properties of polarobreathers, that is, breathers carrying charge in a one-dimensional semiclassical model. We adapt recently developed numerical methods that preserve the charge probability at every step of time integration without using the Born–Oppenheimer approximation, which is the assumption that the electron is not at equilibrium with the atoms or ions. We develop an algorithm to obtain exact polarobreather solutions. The properties of polarobreathers, both stationary and moving ones, are deduced from the lattice and charge variable spectra in the frequency–momentum space. We consider an efficient approach to produce approximate polarobreathers with long lifespans. Their spectrum allows for the determination of the initial conditions and the necessary parameters to obtain numerically exact polarobreathers. The spectra of exact polarobreathers become extremely simple and easy to interpret. We also solve the problem that the charge frequency is not an observable, but the frequency of the charge probability certainly is an observable.
Alloy [FA,Cs]PbI₃ perovskite surfaces. The role of surface cesium composition in stability and tolerance to defect formation
(Elsevier, 2024-09) Montero-Alejo, Ana L.; Silva-Portales, María José; Lodeiro, Lucas; Menéndez-Proupin, Eduardo; Universidad de Sevilla. Departamento de Física Aplicada I; Agencia Nacional de Investigación y Desarrollo (ANID). Chile; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT). Chile; Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT). Chile; Fondo de Equipamiento Científico y Tecnológico (FONDEQUIP). Chile; Universidad de Sevilla. FQM401: Simulación y Aplicación de Materiales
Halide-perovskite alloys that include cesium have achieved records of stability and efficiency in solar cells. Controlling the surface composition, defects, and electronic properties guarantees interface stability and improves performance. By using density functional theory and molecular dynamic simulations, we analyzed which surface compositions of the formamidinium (FA) and cesium (Cs) lead iodide perovskite FA₁₋ₓCsₓPbl₃ with 25 and 50% of Cs become more stable than pure perovskites. Structural and electronic properties and tolerance to defect formation were also evaluated. Surface energy calculations show that only the alloys with 25% Cs and F Al-enriched surfaces are more stable than pure FAPbl₃ ones. The most stable alloy surface shows electronic energy levels similar to the FAPbl₃ perovskite, suggesting that this alloy may also be efficient for charge transport in the cell. However, the presence of Cs on the alloy surface, although low, favors the formation of FAI vacancies, which is detrimental to the stability of the perovskite. These results suggest evaluating FA₁₋ₓCsₓPbl₃ alloys with small Cs compositions to mitigate the formation of defects or using a passivation scherne. This study delivers valuable information for efficiency device improvement from the perspective of interface stability.

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