Staff directory Jessica Padilla Pantoja

Jessica Padilla Pantoja

Research Technician of the X-ray Diffraction Facilities
X-Ray Diffraction Facility



  • Enhanced Thermoelectric Properties of Misfit Bi2Sr2-xCaxCo2Oy: Isovalent Substitutions and Selective Phonon Scattering

    Chatterjee, A; Banik, A; El Sachat, A; Roque, JMC; Padilla-Pantoja, J; Torres, CS; Biswas, K; Santiso, J; Chavez-Angel, E Materials (Basel); 16 (4): 1413. 2023. 10.3390/ma16041413.


  • Ferromagnetic metallic Sr-rich Ln1/2A1/2CoO3 cobaltites with spontaneous spin rotation

    Padilla-Pantoja J., Romaguera A., Zhang X., Herrero-Martín J., Fauth F., Blasco J., García-Muñoz J.L. Physical Review B; 104 (5, 054411) 2021. 10.1103/PhysRevB.104.054411. IF: 4.036

    The Pr0.50Sr0.50CoO3 perovskite exhibits unique magnetostructural properties among the rest of ferromagnetic (FM)/metallic Ln0.50Sr0.50CoO3 compounds. The sudden orthorhombic-tetragonal (Imma→I4/mcm) structural transition produces an unusual magnetic behavior vs temperature and external magnetic fields. The symmetry change is responsible for a spontaneous spin rotation in this metallic oxide. We have studied half-doped Ln0.50(Sr1-xAx)0.50CoO3 cobaltites varying the ionic radius rA of A-site cations (divalent cations and lanthanides) to complete the T-rA phase diagram. The influence of the structural distortion and the A-cation size for the occurrence of a spontaneous spin reorientation in the metallic state has been investigated. As the magnetization reorientation is driven by the temperature-induced collapse of the orthorhombic distortion, a careful investigation of the structural symmetry is presented, varying the structural distortion of the Sr-rich half-doped cobaltites by means of both compositional and temperature changes. The region in the phase diagram of these FM/metallic cobaltites where Fm′m′m magnetic symmetry replaces Im′m′a was determined. In that region, the magnetization direction has rotated 45 ° within the a-b plane from the former to the latter. © 2021 American Physical Society.

  • Pulsed laser deposition of epitaxial non-doped PbTiO3 thin films from Pbo-TiO2 mosaic targets

    Sakai J., Roque J.M.C., Vales-Castro P., Padilla-Pantoja J., Sauthier G., Santiso J. Coatings; 11 (6, 662) 2021. 10.3390/coatings11060662. IF: 2.881

    PbTiO3 (PTO) suffers from difficulty in preparing high-density robust bulk ceramics, which in turn has been a bottleneck in thin films growth with physical vapor deposition (PVD) methods. In the present work, we prepared non-doped PTO thin films by a pulsed laser deposition (PLD) method with either a single PTO target or a mosaic target consisting of PbO and TiO2 pie-shaped pieces. On the PTO single target, laser irradiation caused selective ablation of Pb, resulting in Tirich cone-shaped pillar structure on the surface, whereas the irradiated surface of PbO and TiO2 pieces was smoother. Epitaxial PTO films deposited on SrTiO3 (001) substrates from the pie-chart targets with PbO:TiO2 areal ratio from 3:5 to 5:3 resulted in composition, crystallinity, flatness, and ferroelectric properties almost independent of the areal ratio. The averaged composition of each film was close to stoichiometric, suggesting a compositional self-control mechanism. For growing epitaxial and high-quality non-doped PTO films, a PbO-TiO2 pie-chart target is advantageous in easiness of handling and stable surface structure. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

  • Strong strain gradients and phase coexistence at the metal-insulator transition in VO2 epitaxial films

    Rodríguez L., Sandiumenge F., Frontera C., Caicedo J.M., Padilla J., Catalán G., Santiso J. Acta Materialia; 220 (117336) 2021. 10.1016/j.actamat.2021.117336. IF: 8.203

    The proximity of a thermodynamic triple point and the formation of transient metastable phases may result in complex phase and microstructural trajectories across the metal-insulator transition in strained VO2 films. A detailed analysis using in-situ synchrotron X-ray diffraction unveils subtle fingerprints of this complexity in the structure of epitaxial films. During phase transition the low-temperature monoclinic M1 phase is constrained along the {111}R planes by the coexisting high-temperature R phase domains, which remain epitaxially clamped to the substrate. This geometrical constraint induces counteracting local stresses that result in a combined tilt and uniaxial in-plane compression of M1 domains, and a concomitant anomalous cR-axis elongation. This mechanism progressively transforms the M1 phase into the transitional triclinic phase (T), and ultimately into the monoclinic M2 phase, generating strong strain and tilt gradients that remain frozen after the complete transformation of the R phase upon cooling to RT. The transformation path of VO2 films, the complex competition between stable and metastable VO2 polymorphs and its impact on the structure of the low temperature monoclinic state, provide essential insights for understanding the electronic and mechanical properties of the films at the nanoscale, as well as to control their use in functional devices. © 2021


  • Control of lateral composition distribution in graded films of soluble solid systems A1-xBx by partitioned dual-beam pulsed laser deposition

    Sakai J., Roque J.M.C., Vales-Castro P., Padilla-Pantoja J., Sauthier G., Catalan G., Santiso J. Coatings; 10 (6, 540) 2020. 10.3390/COATINGS10060540. IF: 2.436

    Lateral compositionally-graded thin films are powerful media for the observation of phase boundaries aswell as for high-throughputmaterials exploration.We herein propose amethod to prepare epitaxial lateral compositionally-graded films using a dual-beampulsed laser deposition (PLD)method with two targets separated by a partition. Tuning the ambient pressure and the partition-substrate gap makes it possible to control of the gradient length of the deposits at the small sizes (≤ 10 mm) suitable for commercial oxide single crystal substrates. A simple Monte Carlo simulation qualitatively reproduced the characteristic features of the lateral thickness distribution. To demonstrate this method, we prepared (1-x)PbTiO3-xPbZrO3 and (1-x)LaMnO3-xLa0.6Sr0.4MnO3 films with lateral composition gradient widths of 10 and 1 mm, respectively, with the partitioned dual PLD. © 2020 by the authors.

  • Large thermoelectric power variations in epitaxial thin films of layered perovskite GdBaCo2O5.5±δwith a different preferred orientation and strain

    Chatterjee A., Chavez-Angel E., Ballesteros B., Caicedo J.M., Padilla-Pantoja J., Leborán V., Sotomayor Torres C.M., Rivadulla F., Santiso J. Journal of Materials Chemistry A; 8 (38): 19975 - 19983. 2020. 10.1039/d0ta04781c. IF: 11.301

    This work describes the growth of thin epitaxial films of the layered perovskite material GdBaCo2O5.5±δ(GBCO) on different single crystal substrates SrTiO3(STO), (LaAlO3)0.3(Sr2TaAlO6)0.7(LSAT) and LaAlO3(LAO) as an approach to study changes in the thermoelectric properties by means of the induced epitaxial strain. In addition to strain changes, the films grow with considerably different preferred orientations and domain microstructures: GBCO films on STO are purelyc-axis oriented (c⊥) with an average 0.18% in-plane tensile strain; GBCO on LSAT is composed of domains with a mixed orientation (c‖andc⊥) with an average 0.71% in-plane compressive strain; while on LAO it isb-axis oriented (c‖) with an average 0.89% in-plane compressive strain. These differences result in important cell volume changes, as well as in the orthorhombicity of thea-bplane of the GBCO structure, which in turn induce a change in the sign and temperature dependence of the thermopower, while the electrical conductivity remains almost unchanged. In general, compressively strained films show negativeSthermopower (n-type) while tensile strained films show a positiveS(p-type) at low temperatures, probing the adaptive nature of the GdBaCo2O5.5±δcompound. These results point to the spontaneous generation of oxygen vacancies to partially accommodate the epitaxial stress as the main cause for this effect. © The Royal Society of Chemistry 2020.


  • Electrochemical biosensors: Enzyme kinetics and role of nanomaterials

    Alarcon-Angeles G., Álvarez-Romero G.A., Merkoçi A. Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry; : 140 - 155. 2018. 10.1016/B978-0-12-409547-2.13477-8.

    Enzymatic biosensors based in electrochemical responses are one of the most developed and studied devices for quantitative analysis. The combination of both electroanalytical methods and enzyme characteristics makes biosensors a very powerful technology for fast, selective, and low-cost analysis with applications in environmental, food, and clinical studies. In the present article, a brief description of these devices including their classification and the different construction strategies is given. Enzymatic activity and the various variables that might affect it are discussed along with strategies such as the use of nanomaterials to solve some drawbacks that such kind of biosensors uses to present. © 2018 Elsevier Inc. All rights reserved.