Author: Ignasi Fina
Large enhancement of ferroelectric polarization in Hf0.5Zr0.5O2 films by low plasma energy pulsed laser deposition
Tingfeng Song, Raul Solanas, Mengdi Qian, Ignasi Fina and Florencio Sánchez
J. Mater. Chem. C, 2022,10, 1084-1089 ; DOI: https://doi.org/10.1039/D1TC05387F
Abstract
The ferroelectric phase of HfO2 is generally stabilized in polycrystalline films, which typically exhibit the highest polarization when deposited using low oxidizing conditions. In contrast, epitaxial films grown by pulsed laser deposition show low or suppressed polarization if a low oxygen pressure is used. Epitaxial films are essential to better understand physical properties, and obtaining films that have intrinsic polarization is of great importance. In order to advance towards this objective, we have carried out a systematic study of the epitaxial growth of Hf0.5Zr0.5O2 combining inert Ar gas with oxidizing O2 gas.
This allows us to control the oxidizing conditions (through O2 partial pressure) and the energy of the pulsed laser deposition plasma (through the total pressure of O2 and Ar). A pressure of Ar high enough to significantly reduce plasma energy and that of O2 low enough to reduce oxidation conditions are found to allow a large increase in ferroelectric polarization up to about 30 μC cm−2, representing an increase of around 50% compared to films grown by conventional pulsed laser deposition. This simple growth process, with high impact in the development of ferroelectric HfO2, can be also beneficial in the growth of thin films of other materials by pulsed laser deposition.
Ondrej Novak
Mr. Ondrej Novak graduated in Physics at the Charles University in Prague, Czech Republic. He has a Master degree in Optics and Optoelectronics. He joined the lab in September 2022 to start his PhD Thesis on “Topological phase transitions in photonic crystals” under supervision of Dr. Gervasi Herranz as a part of a co-tutelled Thesis with Prof. Martin Veis (Charles University in Prague)
Talk at the International Workshop on Oxide Electronics (WOE28)
Gervasi Herranz delivers a talk at the International Workshop on Oxide Electronics (https://iwoe28.events.yale.edu/), Portland, Maine, USA: The talk is entitled “Light-matter interactions modulated by electron-lattice coupling in transition metal oxides” and is held on Wednesday 5 October 2022 (1oh15am).
Pep Fontcuberta delivers an Invited Lecture at SPIN 2022
Pep Fontcuberta delivers an Invited Lecture on ” Electron-phonon and spin-orbit couplings in early-transition metal in conducting oxides” at SPIN 2022 (Bariloche, Argentina))
Pep Fontcuberta delivers a Lecture at Magnetism and Magnetic Materials Conferences MMM 2022
Pep Fontcuberta delivers a Lecture on “Direct exchange-interactions boost magnetic frustration and a large zero-point entropy in the novel MnTa2N4 diamond-lattice spinel” at Magnetism and Magnetic Materials Conferences MMM 2022 (MInnesota , USA)
2022
INVITED TALKS
Chiral interlayer coupling in magnetic multilayers
Can Onur Avci
12th International Conference on Magnetic and Superconducting Materials (MSM22)
Aug. 28 – Sep. 02, 2022, Duisburg, Germany
Electrical control of magnetization in magnetic insulators
Can Onur Avci
20th International Symposium on the Physics of Semiconductors and Applications (ISPSA 2022)
Jul. 17-21, 2022, Jeju, Korea
Current-induced magnetization control and chiral interlayer coupling in magnetic heterostructures
Can Onur Avci
24th International Colloquium on Magnetic Films and Surfaces (ICMFS 2022)
Jul 10-15, 2022, Okinawa, Japan
Chiral interlayer coupling in magnetic multilayers
Can Onur Avci
16th International Conference on Nanostructured Materials (Nano2022)
Jun. 6-10, 2022, Sevilla, Spain
Nonlocal detection of out-of-plane magnetization in a magnetic insulator by thermal spin drag
Can Onur Avci
APS March Meeting 2022
Mar. 14-18, 2022, Chicago, USA
Electron-phonon and spin-orbit couplings in early-transition metal in conducting oxides
J. Fontcuberta
SPIN 2022
Bariloche, Argentina, 6th November – 11th November
REGULAR TALKS
Chiral coupling between magnetic layers with orthogonal magnetization
Can Onur Avci
JEMS2022 Joint European Magnetic Symposia
Jul. 24-29, 2022, Warsaw, Poland.
Direct exchange-interactions boost magnetic frustration and a large zero-point entropy in the novel MnTa2N4 diamond-lattice spinel
J. Fontcuberta
Magnetism and Magnetic Materials Conferences MMM 2022 (MInnesota , USA)
Minnesota , USA, 31 october – 4th November
Light-matter interactions modulated by electron-lattice coupling in transition metal oxides
G. Herranz
International Workshop on Oxide Electronics (MInnesota , USA)
Portland, Maine, USA, 5 October 2022
Pep Fontcuberta at Nit de la Recerca 2022
Pep Fontcuberta participa a la Nit de la Recerca 2022 ( Dijous 29 de Setembre 2022) amb una xerrada sobre:
“La Màgia de la LLum i la Conversió Fotovoltaica”
Kyle Shen
My research focuses on investigating many-body interactions in quantum materials, with the aim of controlling potentially exotic properties such as superconductivity, magnetism, metal-insulator transitions, and topological properties. We employ a combination of techniques including angle-resolved photoemission spectroscopy (ARPES), molecular beam epitaxy (MBE), and synchrotron-based x-ray probes including x-ray absorption spectroscopy and resonant x-ray scattering. A major research thrust is the synthesis and investigation of artificially engineered heterostructures of quantum materials synthesized by molecular beam epitaxy (MBE) with strong electron correlations which allow new emergent states to be created at the interface.
Dr. Kyle Shen at MULFOX
Dr. Kyle Shen, director of Laboratory of Atomic & Solid State Physics, Cornell University, arrives to MULFOX-ICMAB for a Sabatical stay of 12 months.
Gervasi Herranz delivers a talk at the International Workshop on Oxide Electronics
Gervasi Herranz delivers a talk at the International Workshop on Oxide Electronics (https://iwoe28.events.yale.edu/), Portland, Maine, USA: The talk is entitled “Light-matter interactions modulated by electron-lattice coupling in transition metal oxides” and is held on Wednesday 5 October 2022 (1oh15am).
Congratulations Dr. Tingfeng Song, new graduate!
The PhD Committee that evaluated the Thesis was formed by José Francisco Rivadulla Fernández, Universidad Santiago de Compostela (President), Eric Langenberg Pérez, Universitat de Barcelona (Secretary) and Uwe Schroeder, Namlab, Germany (Vocal).
Doctor Tingfeng Song’s PhD thesis was part of the PhD Programme in Materials Science from the Universitat Autònoma de Barcelona (UAB).
Alejandro Sánchez Miñarro delivers a talk at “QUOROM 7 conference”
Alejandro Sánchez Miñarro delivers the talk “Light-matter interactions and spin-orbit coupling in solids” at the QUOROM 7 conference. The seminar is online and is held on September 15th (11h15am).
Alejandro Sánchez Miñarro delivers a talk at “XXXVIII Reunión Bienal de la Real Sociedad Española de Física”
Alejandro Sánchez Miñarro delivers the talk “Spin-orbit mixed states in an electromagnetic field” at the Symposium “S15 Nuevas fronteras y retos en magnetismo (CEMAG-IEEE Magnetics)” of the XXXVIII Reunión Bienal de la Real Sociedad Española de Física Murcia, 11 -15 July 2022
MnTa2N4: A Ternary Nitride Spinel with a Strong Magnetic Frustration
Rafael Trócoli, Carlos Frontera, Judith Oró-Solé, Clemens Ritter, Pere Alemany, Enric Canadell, M. Rosa Palacín, Josep Fontcuberta, and Amparo Fuertes
Chem. Mater. 2022, 34, 13, 6098–6107 (2022); DOI:doi.org/10.1021/acs.chemmater.2c01240
Abstract
Magnetic frustration results from competing magnetic interactions and leads to unusual ground states, ranging from non-collinear magnetic orders to spin liquids (SLs), opening the path to new physics and emerging properties. We report the engineered magnetic interaction design and synthesis of the new ternary nitride MnTa2N4 with a normal spinel structure, where the magnetic cations Mn2+ occupy exclusively the tetrahedral sites forming a diamond lattice.
Although the magnetic interactions are strongly antiferromagnetic (θCW ≈ −140 K), a long-range magnetic order is not established, but a smooth magnetic anomaly is observed at T* ≈ 5.1 K, fingerprinting a large magnetic frustration. A short-range helicoidal magnetic order emerges at low temperatures. The ordered moment is ≈70% of the expected magnetic moment of Mn2+ ions and a large part (≈28%) of the spin entropy remains at 400 mK, signaling the coexistence of a helicoidal order with spin-glass-like or SL textures. First-principles calculations unveil an unexpected large direct Mn–Mn exchange interaction that balances the superexchange and accounts for the magnetic frustration. These findings open new avenues toward the design of quantum materials.
Dynamic control of octahedral rotation in perovskites by defect engineering
Jiahui Jia, Xu He, Arsalan Akhtar, Gervasi Herranz, and Miguel Pruneda
Phys. Rev. B 105, 224112 (2022); DOI:doi.org/10.1103/PhysRevB.105.224112
Abstract
Engineering oxygen octahedra rotation patterns in ABO3 perovskites is a powerful route to design functional materials. Here we propose a strategy that exploits point defects that create local electric dipoles and couple to the oxygen sublattice, enabling direct actuation on the rotational degrees of freedom. This approach, which relies on substituting an A site with a smaller ion, paves a way to couple dynamically octahedra rotations to external electric fields.
A common antisite defect, AlLa, in rhombohedral LaAlO3 is taken as a prototype to validate the idea, with atomistic density functional theory calculations supported with an effective lattice model to simulate the dynamics of switching of the local rotational degrees of freedom to long distances. Our simulations provide an insight of the main parameters that govern the operation of the proposed mechanism, and allow to define guidelines for screening other systems where this approach could be used for tuning the properties of the host material.
Bulk photovoltaic effect modulated by ferroelectric polarization back-switching
Yunwei Sheng, Ignasi Fina, Marin Gospodinov, and Josep Fontcuberta
Appl. Phys. Lett. 120, 242901 (2022); DOI:doi.org/10.1063/5.0094837
Abstract
Short-circuit photocurrent due to bulk photovoltaic effect displays an oscillatory dependence on the polarization state of light. Here, we explore how the ferroelectric polarization direction in h-LuMnO3 crystals affects the oscillating short-circuit photocurrent. It is shown that after prepoling the crystal at saturation, at remanence, the direction and amplitude of photocurrent oscillations are no longer dictated by prepoling voltage but are largely modulated by polarization back-switching, here ruled by the imprint field.
Thus, the light polarization dependence of photocurrent is also ruled by the imprint field. The impact of these effects on the determination of the Glass coefficients of the material is discussed.
Spintronic Materials and Devices
RESEARCH AREAS
Spintronic Materials and Devices
Spintronics is a broad and interdisciplinary research field at the intersection of physics, materials science, and nanotechnology. It aims to utilize charge carriers’ intrinsic property “spin” as an active variable in electronic circuits and to offer innovative solutions to future Information Technologies.
In MULFOX, we investigate a wide variety of spintronic-related physical phenomena and materials. On the materials side, our recent efforts focus on thin-film metallic (CoTb, FeTb) and insulating (YIG, TmIG, TbIG, etc.) ferrimagnetic heterostructures with perpendicular magnetic anisotropy. On the physics side, we are interested in spin-orbit torques, spin-charge interconversion, chiral spin textures (domain walls, skyrmions) with the main goal of developing spintronic memory and logic devices with enhanced functionality and high efficiency. Our materials are developed in-house by pulsed laser deposition and magnetron sputtering tools. We then fabricate devices and characterize them using our state-of-the-art electrical and optical probe stations performing harmonic Hall effect, magnetoresistance, Magneto-optic Kerr effect microscopy measurements, etc.
Researchers
Click here to go to this research line website
Atomic scale mappig of materials
RESEARCH AREAS
Atomic scale mappig of materials
The role of reduced dimensionality and the structure of interfaces, point and planar defects, dislocations, etc, remains obscure in many cases but are central to macroscopic materials properties. Imaging interfaces and defects at sub-Angstrom resolution, and chemical mapping at atomic level are some of the hot points to be addressed in materials science.
We concentrate on establishing relations between the structure, chemistry and physical properties of transition-metal oxide nanostructures by means of scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). The recent successful correction of aberrations in electron optics allows us accessing the structure and chemistry of low dimensional materials due to its unparalleled spatial resolution, and combined with monochromated EELS it has the potential to probe optical excitations—plasmons, photons, excitons— with sub-nanometer resolution. This gives unprecedented power to understand the ultimate origin of the properties of materials at the nanoscale.
Researchers
Voltage-driven strain-mediated modulation of exchange bias in Ir20Mn80/Fe80Ga20/Ta/⟨011⟩-oriented PMN-32PT heterostructures
E. Demirci, J. de Rojas, A. Quintana, I. Fina, E. Menéndez, and J. Sort
Appl. Phys. Lett. 121, 081904 (2022); DOI:doi.org/10.1063/5.0091231
Abstract
Manipulation of exchange bias with electric field is appealing to boost energy efficiency in spintronic devices. Here, this effect is shown at room temperature in Ir20Mn80/Fe80Ga20/Ta layers grown onto ⟨011⟩-oriented PMN-32PT single crystals. After magnetic field-cooling (FC) along the [01-1] and [100] in-plane directions of PMN-32PT and upon allowing the system to relax through consecutive hysteresis loops (training effect), the exchange bias field (HEB) is measured under the action of voltage (out-of-plane poling). Depending on the applied voltage (magnitude and sign), HEB can either increase or decrease with respect to its value at 0 V. The relative variations of HEB are 24% and 5.5% after FC along the [01-1] and [100] directions, respectively.
These results stem from strain-mediated magnetoelectric coupling. The applied electric field causes changes in the coercivity and the squareness ratio of the films, suggesting a reorientation of the effective magnetic easy axis in Fe80Ga20. However, larger HEB values are observed when the squareness ratio is lower. It is claimed that the effect of voltage is equivalent to an in-plane component of an applied magnetic field oriented perpendicular to the cooling field direction. Perpendicular in-plane magnetic fields have been shown to induce an increase in exchange bias in some ferromagnetic/antiferromagnetic systems due to partial recovery of the untrained antiferromagnetic state. Remarkably, here, this effect is directly induced with voltage, therefore enhancing energy efficiency.
Orders and dynamics in oxides
RESEARCH AREAS
Orders and dynamics in oxides
Solids may display a variety of order parameters, such as magnetic, polar, charge, orbital, etc. that determine complex phase diagrams where different properties are at display. Exciting prospects emerge towards new understanding that goes deep into the nature of condensed matter and its responsiveness and open perspectives of novel applications.
Building on a long and wide expertise on transition metal oxides, our current research spans several branches. First, charge dynamics in transition metals oxides as a tool to explore charge-lattice coupling. Next, light-matter interaction in polar materials and heterostructures which offer new opportunities for above-band gap photoresponsive materials and sensing. Last, spin-orbit interactions in solids is emerging as new tool towards energy efficient spintronic devices. Whereas spin-orbit coupling in heavy metals is known and much used, plenty of room is still available for light transition metals, which are cheaper and more abundant, and were spin dynamics may offer new opportunities.
Researchers
Two-gap s±-wave superconductivity at an oxide interface
G. Singh, G. Venditti, G. Saiz, G. Herranz, F. Sánchez, A. Jouan, C. Feuillet-Palma, J. Lesueur, M. Grilli, S. Caprara, and N. Bergeal
Phys. Rev. B 105, 064512 (2022); DOI:doi.org/10.1103/PhysRevB.105.064512
Abstract
After half a century of debate, superconductivity in doped SrTiO3 has come to the fore again with the discovery of interfacial superconductivity in the LaAlO3/SrTiO3 heterostructures. While these interfaces share the interesting properties of bulk SrTiO3 , quantum confinement generates a complex band structure involving bands with different orbital symmetries whose occupancy is tunable by electrostating doping.
Multigap superconductivity has been predicted to emerge in LaAlO3/SrTiO3 at large doping, with a Bose-Einstein condensation character at the Lifshtiz transition. In this article, we report on the measurement of the upper critical magnetic field Hc2 of superconducting (110)-oriented LaAlO3/SrTiO3 heterostructures and evidence a two-gap superconducting regime at high doping. Our results are quantitatively explained by a theoretical model based on the formation of an unconventional s±-wave superconducting state with a repulsive coupling between the two condensates.
Enhanced electroresistance endurance of capped Hf0.5Zr0.5O2 ultrathin epitaxial tunnel barriers
Xiao Long, Huan Tan, Saúl Estandía, Jaume Gazquez, Florencio Sánchez, Ignasi Fina and Josep Fontcuberta
APL Materials 10, 031114 (2022); DOI:doi.org/10.1063/5.0076865
Abstract
Electroresistance in ultrathin Hf0.5Zr0.5O2 (HZO) films is pivotal toward the implementation of hafnia-based ferroelectrics in electronics. Here, we show that the electroresistance yield and endurance of large capacitors (∼314 µm2) of epitaxial HZO films only 2.2 nm thick grown on SrTiO3 or GdScO3 can be improved using 1 nm SrTiO3 capping layers. It is argued that the main role of the capping layer is to minimize charge transport along grain boundaries, and, thus, a similar strategy can be explored in polycrystalline films
Electroresistance in ultrathin Hf0.5Zr0.5O2 (HZO) films is pivotal toward the implementation of hafnia-based ferroelectrics in electronics. Here, we show that the electroresistance yield and endurance of large capacitors (∼314 µm2) of epitaxial HZO films only 2.2 nm thick grown on SrTiO3 or GdScO3 can be improved using 1 nm SrTiO3 capping layers. It is argued that the main role of the capping layer is to minimize charge transport along grain boundaries, and, thus, a similar strategy can be explored in polycrystalline films
Impact of non-ferroelectric phases on switching dynamics in epitaxial ferroelectric Hf0.5Zr0.5O2 films
Tingfeng Song, Florencio Sánchez, and Ignasi Fina
APL Materials 10, 031108 (2022); DOI:doi.org/10.1063/5.0083661
Abstract
Determining the switching speed and mechanisms in ferroelectric HfO2 is essential for applications. Switching dynamics in orthorhombic epitaxial ferroelectric Hf0.5Zr0.5O2 films with either significant or negligible presence of monoclinic paraelectric phase is characterized.
Switching spectroscopy reveals that the polarization dynamics in pure orthorhombic ferroelectric phase films can be modeled by the Kolmogorov–Avrami–Ishibashi mechanism with large characteristic time (≈1 µs), which is shortened in fatigued junctions. The long switching time indicates that non-archetypical switching mechanisms occur and that ionic motion or other extrinsic contributions might be at play. Films containing a higher amount of paraelectric monoclinic phase show a shorter switching time of 69 ns, even in pristine state, for applied electric field parallel to the imprint field, enabling synaptic-like activity using fast electric stimuli. Thus, the presence of defects or paraelectric phase is found to improve the switching speed, contrary to what one can expect a priori.
Josep Fontcuberta Key note Lecture at “Materials for Oxide Electronics”
Josep Fontcuberta delivers an opening “Key note Lecture” at the kick-off workshop “Materials for Oxide Electronics” at IKZ-Berlin (Leibniz-Institut für Kristallzüchtung on 10th February 2022 (https://www.ikz-berlin.de/en/about-us/events/)
Improved polarization and endurance in ferroelectric Hf0.5Zr0.5O2 films on SrTiO3(110)
Tingfeng Song, Huan Tan, Saúl Estandía, Jaume Gàzquez, Martí Gich, Nico Dix, Ignasi Fina and Florencio Sánchez
Nanoscale, 2022,14, 2337-2343 (2022); DOI:10.1039/D1NR06983G
Abstract
The metastable orthorhombic phase of Hf0.5Zr0.5O2 (HZO) can be stabilized in thin films on La0.67Sr0.33MnO3 (LSMO) buffered (001)-oriented SrTiO3 (STO) by intriguing epitaxy that results in (111)-HZO oriented growth and robust ferroelectric properties. Here, we show that the orthorhombic phase can also be epitaxially stabilized on LSMO/STO(110), presenting the same out-of-plane (111) orientation but a different distribution of the in-plane crystalline domains.
The remanent polarization of HZO films with a thickness of less than 7 nm on LSMO/STO(110) is 33 μC cm−3, which corresponds to a 50% improvement over equivalent films on LSMO/STO(001). Furthermore, HZO on LSMO/STO(110) presents higher endurance, switchable polarization is still observed up to 4 × 1010 cycles, and retention of more than 10 years. These results demonstrate that tuning the epitaxial growth of ferroelectric HfO2, here using STO(110) substrates, allows the improvement of functional properties of relevance for memory applications.
Impact of La Concentration on Ferroelectricity of La-Doped HfO2 Epitaxial Thin Films
T. Song, H. Tan, R. Bachelet, G. Saint-Girons, I. Fina,* F. Sánchez*
ACS Appl. Electron. Mater. 2021, 3, 11, 4809–4816; DOI: doi.org/10.1021/acsaelm.1c00672
Abstract
Epitaxial thin films of HfO2 doped with La have been grown on SrTiO3(001) and Si(001), and the impact of the La concentration on the stabilization of the ferroelectric phase has been determined. Films with 2–5 at. % La doping present the least amount of paraelectric monoclinic and cubic phases and exhibit the highest polarization, having a remanent polarization above 20 μC/cm2. The dopant concentration results in an important effect on the coercive field, which is reduced with increasing La content. Combined high polarization, high retention, and high endurance of at least 1010 cycles is obtained in 5 at. % La-doped films.
Large enhancement of ferroelectric polarization in Hf0.5Zr0.5O2 films by low plasma energy pulsed laser deposition
T. Song, R. Solanas, M. Qian, I. Fina,* F. Sánchez*
Journal of Materials Chemistry C, 2021; DOI: doi.org/10.1039/D1TC05387F
Abstract
The ferroelectric phase of HfO2 is generally stabilized in polycrystalline films, which typically exhibit the highest polarization when deposited using low oxidizing conditions. In contrast, epitaxial film grown by pulsed laser deposition show low or suppressed polarization if low oxygen pressure is used. Epitaxial films are essential to better understand physical properties, and obtaining films that have intrinsic polarization is of great importance. In order to advance towards this objective, we have carried out a systematic study of the epitaxial growth of Hf0.5Zr0.5O2 combining inert Ar gas with oxidizing O2 gas. This allows us controlling the oxidizing conditions (through O2 partial pressure) and the energy of the pulsed laser deposition plasma (through the total pressure of O2 and Ar). A pressure of Ar high enough to significantly reduce plasma energy and low enough O2 to reduce oxidation conditions is found to allow a large increase in ferroelectric polarization up to 32 μC/cm2, representing an increase of around 50% respect films grown by conventional pulsed laser deposition. This simple growth process, with high impact in the development of ferroelectric HfO2, can be also beneficial in the growth of thin films of other materials by pulsed laser deposition.
Efficient spin pumping into metallic SrVO3 epitaxial films
Ferran Macià, Mathieu Mirjolet and Josep Fontcuberta
J. Magnetism and Magnetic Materials 546, 168871, 15 March 2022; DOI: doi.org/10.1016/j.jmmm.2021.1688716
Abstract
Spin-charge conversion requires materials with a large spin-orbit coupling, which is typically obtained in heavy metal (Pt, etc.) ions.
Here we demonstrate spin pumping across interfaces between metallic SrVO3, where V is a 3d1 ion, epitaxial thin films and ferromagnetic Ni80Fe20. Data shows an efficient spin pumping with a spin mixing conductance value (11.8 × 1018 m−2). These results demonstrate that heavy ions are not longer required and illustrated an yet undisclosed relevance of density of states at the Fermi level and suggest new toggles to tune spin-mixing conductance across interfaces.
Bulk photovoltaic effect in hexagonal LuMnO3 single crystals
Yunwei Sheng, Ignasi Fina,* Marin Gospodinov, Aaron M. Schankler Andrew M. Rappe, and Josep Fontcuberta,*
Physical ReviewB 104, 184116 (2021); DOI: doi.org/10.1103/PhysRevB.104.184116
Abstract
When illuminating a non-centrosymmetric material with light of energy higher than the bandgap, a net current appears because the electrons do not see the same electronic environment in one direction and the opposite direction, thus they hold a net momentum. This is the bulk photovoltaic effect (BPE), which depends on the light polarization. Here we report for the first time, in hexagonal manganites h-LuMnO3 which is ferroelectric with a narrow bandgap of ≈ 1.5 eV, that the short circuit photocurrent density (Jsc) is dependent on the direction of the polarization plane of the linearly polarized incoming light, indicating its contribution of BPE. It is found the BPE tensor elements and Glass coefficients are significantly larger than in BiFeO3, suggesting possible advantages for photoconversion.
Positive Effect of Parasitic Monoclinic Phase of Hf0.5Zr0.5O2 on Ferroelectric Endurance
Tingfeng Song, Saúl Estandía, Huan Tan, Nico Dix, Jaume Gàzquez, Ignasi Fina,* Florencio Sánchez*
Inorb. Adv. Electron. Mater. 2021, 2100420; DOI: doi.org/10.1002/aelm.202100420
Abstract
Endurance of ferroelectric HfO2 needs to be enhanced for its use in commercial memories. This work investigates fatigue in epitaxial Hf0.5Zr0.5O2 (HZO) instead of polycrystalline samples. Using different substrates, the relative amount of orthorhombic (ferroelectric) and monoclinic (paraelectric) phases is controlled. Epitaxial HZO films almost free of parasitic monoclinic phase suffer severe fatigue. In contrast, fatigue is mitigated in films with a greater amount of paraelectric phase.
This suggests that fatigue can be intrinsically pronounced in ferroelectric HZO. It is argued that the enhancement of endurance in films showing coexisting phases results from the suppression of pinned domain propagation at ferroelectric–paraelectric grain boundaries, in contrast with a rapid increase of the size of the pinned domains in single ferroelectric regions.
Florencio Sánchez invited HfO2-talk at EPIDOX
Florencio Sánchez gives a invited talk about Epitaxial ferroelectric doped HfO2 thin films on Si(001) in EPIDOX organized by GDR Oxyfun!
Lecture at III CANN 2021
Pep Fontcuberta delivers an invited lecture (17/11/2021) on “The magic of oxide
The magic of oxides for advanced technologies” at “III CANN 2021: Nanoscience for Information and Computing Technologies” (https://www.scn2.cat/congres/)
La-doped HfO2 epitaxial thin films ACS Editors’ Choice
Our paper”Impact of La concentration on ferroelectricity of La-doped HfO2 epitaxial thin films” published in ACS Appl. Electron. Mater. has been selected as an ACS Editors’ Choice (https://pubs.acs.org/editorschoice/, October 19, 2021). The ACS Editors’ Choice initiative highlights one article each day that is chosen from the entire ACS portfolio.
Dr. Jike Lyu Special Award for Doctoral Studies in Materials Science!
The Universitat Autonoma de Barcelona has granted Dr. Jike Lyu (PhD defended in September 2019, Supervisor Florencio Sánchez, Excellent cum laude) with the Special Award for Doctoral Studies in Materials Science. Congratulations, Jike!
Josep Fontcuberta at INTERSECT workshop
Josep Fontcuberta delivers an Invited Lecture on “Electroresistance in epitaxial HZO films” at the International Workshop on “Advanced Materials-to-Device Solutions for Synaptic Electronics” (H2020 INTERSECT project; Barcelona, 10/11/2021) (https://intersect-workshop.icn2.cat/)
High-Temperature Synthesis and Dielectric Properties of LaTaON2
Augustin Castets, Ignasi Fina, Jhonatan R. Guarín, Judith Oró-Solé, Carlos Frontera, Clemens Ritter, Josep Fontcuberta*, and Amparo Fuertes*
Inorg. Chem. 2021, 60, 16484−16491; DOI: doi.org/10.1021/acs.inorgchem.1c02325
Abstract
The development of new synthetic methodologies of perovskite oxynitrides is challenging but necessary for the search of new compounds and the investigation of their properties. Here, we report on the synthesis of LaTaO1+xN2-x under N2 at 1500 °C, that allows to obtain highly sintered compounds with x ≤ 0.35, suitable for dielectric characterization. It is found that of LaTaO1+xN2-x crystallizes in the monoclinic space group I2/m. In contrast to earlier reports, two anion sites show strongly preferred occupancy by nitride indicating a dependence of the anion distribution on the synthetic approach. The dielectric permittivity for LaTaON2 (εr ≈ 200), reported for the first time, is similar to that observed in perovskites with one nitrogen per formula
OPEN CALL FOR PhD FELLOWSHIP
DEADLINE FOR APPLICATION: 11th November 2021
Project Title: “Symmetry and Low-Dimensionality Mine-and-Craft for Efficient Spin Manipulation and Photoconversion (SymDim) (SIMETRIA Y BAJA DIMENSIONALIDAD COMO PLATAFORMA PARA MATERIALES ESPINTRONICOS Y FOTOCONVERSION)”
Project number PID2020-118479RB-I00
Profile of the candidate: We seek for a candidate desiring to get a multidisciplinary training on transport properties and optical (ellipsometry, plasmonics, etc.) measurements, and understanding of electron-correlated metallic systems and thin film growth. This combination should provide a solid scientific broad background. The candidate’s scientific education will be framed within the PhD program of “Materials Science “ of UAB (Universitat Autònoma de Barcelona) and complemented with participation to appropriate Schools to boost the education and networking skills. Other courses will include training on a) IPR protection, b) Communication skills and c) Building leadership and team management. Regular presentations at weekly group’s meeting and International conferences shall provide adequate training.
Please, address any questions to:
Ignasi Fina crazy about physics
Ignasi Fina delivers a hands on work lecture to high school students crazy about physics. Crazy about physics (Bojos per la física) is a program for high school students.
Ignasi Fina visits University of Cambridge in the framework of i-link project
Ignasi Fina has given a talk entitled “Epitaxial ferroelectric hafnium oxide at ICMAB” in the framework of the i-link project funded by CSIC.
Switchable photovoltaic response in hexagonal LuMnO3 single crystals
Yunwei Sheng, Ignasi Fina, Marin Gospodinov, and Josep Fontcuberta
Appl. Phys. Lett. 118, 232902 (2021); DOI: doi.org/10.1063/5.0053379
Abstract
Hexagonal manganites, such as h-LuMnO3, are ferroelectric with its polar axis along the hexagonal axis and have a narrow electronic bandgap (≈1.5 eV). Using Pt electrodes, h-LuMnO3 single crystals display a strong rectification, characteristic of a Schottky diode, and a large photoresponse. It is found that the short circuit photocurrent density Jsc along the polar axis is modulated (up to 25%) by the direction of the ferroelectric polarization P, leading to a short circuit photocurrent loop that mimics the ferroelectric polarization. However, a non-switchable Jsc persists. Diffusion photocurrent is shown to dominate current-in-plane measurements and contributes to the non-switchable Jsc. This observation illustrates the dramatic role of the large optical absorption in hexagonal manganites. The accompanying optical dichroism might challenge disentangling a genuine bulk photovoltaic response in h-LuMnO3 single crystals, contributing to the non-switchable Jsc. Epitaxial thin films may offer a suitable alternative.
Orbital occupancy and hybridization in strained SrVO3 epitaxial films
Mathieu Mirjolet , Hari Babu Vasili, Adrian Valadkhani, José Santiso , Vladislav Borisov, Pierluigi Gargiani, Manuel Valvidares, Roser Valentí , and Josep Fontcuberta
Phys Rev. Materials 5, 095002 (2021), DOI:10.1103/PhysRevMaterials.5.09500212K
Abstract
Strain is a knob that allows tuning the electronic bandwidth or the electronic distribution within the atomic orbitals is solids, to promote dramatic changes of their properties or even to induce emerging ones, such as metal-insulator transitions, ferroelectricity, ferromagnetism or superconductivity, to mention a few.
SrVO3 is an excellent metal of the highest interest in technology. Epitaxial strain affects the electronic conductivity supposedly by changing the electronic distribution within the 3d(t2g) orbitals and their corresponding bandwidth.
Here, we show that the role of strain is more involved. It turns out that the V-O hybridization is substantially modified by unbalancing the 3d(t2g)-2p molecular orbital mixtures. It follows that not only the orbital hierarchy of the (xy, xz and yz) orbitals of the t2g manifold is modified but also the amount of electrons at 3d(t2g) orbitals of the metal ion also change with strain. In other words, a rigid band picture does not hold even in this seemingly simple metallic oxide
Alejandro Sánchez Miñarro
Hello all! My name is Alex and after finish my Bachelor degree on Physics at Universitat de Barcelona and my Master degree on Photonics at Universitat Politècnica de Catalunya I’ve just joined to MULFOX group to start my PhD about photonic metasurfaces with topological properties under the supervision of Dr. Gervasi Herranz. I’m glad to be here and eager to start this new stage!
Thickness effect on ferroelectric properties of La-doped HfO2 epitaxial films down to 4.5 nm
Tingfeng Song, Romain Bachelet, Guillaume Saint-Girons, Nico Dix, Ignasi Fina and Florencio Sanchez
J. Mater. Chem. C, 2021, DOI: doi.org/10.1039/D1TC02512K
Abstract
Stabilization of the orthorhombic phase of HfO2 with La allows very high polarization and endurance. However, these properties have not been confirmed yet in films having thickness of less than 10 nm. We have grown (111)-oriented La (2 at%) doped epitaxial HfO2 films on SrTiO3(001) and Si(001) substrates, and we report on the thickness dependence of their ferroelectric properties.
Films of less than 7 nm have a high remanent polarization of about 30 µC cm-2, show slight wake-up, endurance of at least 1010 cycles and retention of more than 10 years, both latest properties measured at the same poling voltage. La-doped HfO2 films even as thin as 4.5 nm also show robust ferroelectric properties.
Congratulations Dr. Mathieu Mirjolet!
Doctor Mathieu Mirjolet from the Laboratory of Multifunctional Thin Films and Complex Structures (MULFOX) group at ICMAB, defended his PhD thesis titled “Transparent Conducting Oxides Based on Early Transition Metals: From Electrical and Optical Properties of Epitaxial Thin Films, to Integration in All-Oxide Photoabsorbing Heterostructures.” on Friday, 23 July 2021 in an online session. Congrats!
Electron–Phonon Coupling and Electron–Phonon Scattering in SrVO3
M. Mirjolet, F. Rivadulla, P. Marsik, V. Borisov, R. Valentí, J. Fontcuberta,
J. Adv. Sci. 2021, 2004207. https://doi.org/; DOI:doi.org/10.1002/advs.202004207
Abstract
- The nature of electron-electron and electron-lattice interactions in metallic oxides is revised. The common wisdom is that the strong correlations among electrons determine their properties.
- Here we argue that the unavoidable coupling between free electrons and the lattice in ionic materials leads to the formation of polarons. These are carriers dressed by a lattice distortion that travel with them and largely determine the transport and some optical properties.
- Moreover, we argue that in early transition metal oxides, the Fermi surface has a cylindrical shape that limits the phonons available for scattering.
- Taking SrVO3as illustrative example of a Fermi liquids, we demonstrate that both mechanisms can contribute to the ubiquitously observed quasi-T2temperature dependence of the electrical resistivity in many metallic oxides.
- A new twist on the physics of Fermi liquids in ionic lattices.
Optical Plasmon Excitations in Transparent Conducting SrNbO3 and SrVO3 Thin Films
Mathieu Mirjolet, Mikko Kataja, Tommi K. Hakala, Philipp Komissinskiy, Lambert Alff, Gervasi Herranz, Josep Fontcuberta,
Adv. Opt. Materials First published: 14 June 2021; DOI:doi.org/10.1002/adom.202100520
Abstract
From catalysis and flat panel displays to photovoltaics, transparent and conducting transition metal oxides are gaining momentum toward more sustainable and cost-efficient applications.
Here it is shown that, without using phase-matching arrangements, bulk plasmons can be excited in continuous epitaxial films of metallic SrVO3 and SrNbO3, with plasma absorption edges at visible range, and tuned mainly by electron correlations and phonon dressing.
Films can be made reflective or transparent at whish.
Stabilization of the Ferroelectric Phase in Epitaxial Hf1–xZrxO2 Enabling Coexistence of Ferroelectric and Enhanced Piezoelectric Properties
Tingfeng Song, Huan Tan, Nico Dix, Rahma Moalla, Jike Lyu, Guillaume Saint-Girons, Romain Bachelet, Florencio Sánchez, and Ignasi Fina
ACS Appl. Electron. Mater. 2021, 3, 5, 2106–2113 (2021); DOI:doi.org/10.1021/acsaelm.1c00122
Abstract
Systematic studies on polycrystalline Hf1–xZrxO2 films with varying Zr contents show that HfO2 films are paraelectric (monoclinic). If the Zr content is increased, films become ferroelectric (orthorhombic) and then antiferroelectric (tetragonal). HfO2 shows very good insulating properties and it is used in metal-oxide-semiconductor field-effect devices, while ZrO2 shows good piezoelectric properties, but it is antiferroelectric. In between, Hf0.5Zr0.5O2 shows good ferroelectric properties at the expense of poorer insulating and piezoelectric properties than HfO2 and ZrO2, respectively.
Here, we explore the ferroelectric, insulating, and piezoelectric properties of a series of epitaxial films of Hf1–xZrxO2 with different compositions. We show that epitaxial growth permits the stabilization of the ferroelectric phase in a whole range of Zr content (from x = 0 to x = 1). In epitaxial ZrO2 films, ferroelectricity coexists with better piezoelectric and insulating properties than Hf0.5Zr0.5O2, and in HfO2 epitaxial films, ferroelectricity coexists with better insulating properties than Hf0.5Zr0.5O2. For the case of ZrO2 films, large electroresistance is also observed. In both cases, the ferroelectric endurance is poorer than that for Hf0.5Zr0.5O2.
Cum laude for Saul Estandia and Milena Cervo Suzlbach!
Congratulations to both!
2021
INVITED CONFERENCES
“Epitaxial ferroelectric doped HfO2 thin films on Si(001)”
F. Sánchez
EPIDOX : Virtual workshop on oxide epitaxy
Virtual, 18 November2021
“Light-Matter Interactions in New Materials and Meta-Architectures”
J. Fontcuberta
META 2021-The 11th International Conference on Metamaterials, Photonic Crystals and Plasmonics
Warsaw (P0land), 20 – 23 July 2021
“Spin currents. A probe of interfacial magnetism”
J. Fontcuberta
In-operando adjustable orbital polarization in nickelate perovskites
Moena (Italy), 13 – 16 June 2021
Pep Fontcuberta delivers an invited lecture at Advances in Magnetics AMI-2020(21)
Pep Fontcuberta delivers an invited lecture on ” In-operando adjustable orbital polarization in nickelate perovskites” at Advances in Magnetics AMI-2020(21), June 2021, Moena Italy. (http://aim2020.poliba.it/wordpress/)
Saúl Estandía defens his PhD Thesis
Nanoscale Study of Epitaxial Ferroelectric Hf0.5Zr0.5O2 Thin Films and BaTiO3/SrTiO3 Superlattices
Date: Friday, 28 May 2021
Time: 11 am
Abstract: This thesis focuses on the characterization of ferroelectric Hf0.5Zr0.5O2 thin films and BaTiO3/SrTiO3 superlattices by combining scanning transmission electron microscopy, which allows to image the structure and chemistry locally with atomic resolution, with ferroelectric and structure measurements as x-ray diffraction. The first block revealed the ferroelectric dipole configurations in ferroelectric/paraelectric BaTiO3/SrTiO3 superlattices of different periods. A distinct configuration was found in the longest period BaTiO3/SrTiO3 superlattice (10 unit cell-BaTiO3/10 unit cell-SrTiO3), where unforeseen rotations of the polarization were directly imaged. The second block studied the stabilization of ferroelectric Hf0.5Zr0.5O2 on perovskite substrates. Since the discovery of ferroelectricity in HfO2-based materials in 2011 these materials have attracted much attention, given their CMOS compatibility and robust nanoscale ferroelectricity, which bears profound advantages for applications. The strong effects of the bottom electrode and the epitaxial stress on the ferroelectricity of Hf0.5Zr0.5O2 thin films were studied in detail.
Supervisors:
- Florencio Sánchez, MULFOX group, ICMAB-CSIC
- Jaume Gázquez, MULFOX group, ICMAB-CSIC
Critical Effect of Bottom Electrode on Ferroelectricity of Epitaxial Hf0.5Zr0.5O2 Thin Films
Saúl Estandía, Jaume Gazquez, Maria Varela, N. Dix, Mengdi Qian, Raul Solanas, Ignasi Fina and Florencio Sanchez
J. Mater. Chem. C, 9, 3486 – 3492 (2021); DOI:doi.org/10.1039/D0TC05853J
Abstract
Epitaxial orthorhombic Hf0.5Zr0.5O2 (HZO) films on La0.67Sr0.33MnO3 (LSMO) electrodes show robust ferroelectricity, with high polarization, endurance and retention. However, no similar results have been achieved using other perovskite electrodes so far. Here, LSMO and other perovskite electrodes are compared.
A Small amount of orthorhombic phase and low polarization is found in HZO films grown on La-doped BaSnO3 and Nb-doped SrTiO3, while null amounts of orthorhombic phase and polarization are detected in films on LaNiO3 and SrRuO3.The critical effect of the electrode on the stabilized phases is not consequence of differences in the electrode lattice parameter. The interface is critical, and engineering the HZO bottom interface on just a few monolayers of LSMO permits the stabilization of the orthorhombic phase. Furthermore, while the specific divalent ion (Sr or Ca) in the manganite is not relevant, reducing the La content causes a severe reduction of the amount of orthorhombic phase and the ferroelectric polarization in the HZO film.
Epitaxial Ferroelectric HfO2 Films: Growth, Properties, and Devices
Ignasi Fina* and Florencio Sánchez*
ACS Appl. Electron. Mater. 2021, 3, 4, 1530-1549; DOI:doi.org/10.1021/acsaelm.1c00110
Abstract
About ten years after ferroelectricity was first reported in doped HfO2 polycrystalline films, there is tremendous interest in this material and ferroelectric oxides are once again in the spotlight of the memories industry. Great efforts are being made to understand and control ferroelectric properties. Epitaxial films, which have fewer defects and a more controlled microstructure than polycrystalline films, can be very useful for this purpose. Epitaxial films of ferroelectric HfO2 have been much less investigated, but after the first report in 2015 significant progress has been achieved.
This review summarizes and discusses the main advances on epitaxial HfO2, considering growth, study of structural and ferroelectric properties, identification of the ferroelectric phase, and fabrication of devices. We hope this review will help researchers investigating epitaxial HfO2. It can also help extend the interest of the ferroelectric HfO2 community, now basically focused on polycrystalline samples, to epitaxial films.
Milena Cervo Sulzbach defens his PhD Thesis
Resistive Switching in Hf0.5Zr0.5O2 ferroelectric tunnel junctionecs
Date: Wednesday, 26 May 2021
Time: 3 pm
Abstract: HfO2-based oxides have been explored as ReRAM elements due to their resistance change caused by redox reactions. However, the discovery of ferroelectricity in doped-HfO2 opens doors to use polarization reversal as a phenomenon to control the resistance. Here, Hf0.5Zr0.5O2 epitaxial ferroelectric tunnel junctions with thickness smaller than 5 nanometers are studied. Electrical and structural analyses have allowed identifying the coexistence of genuine ferroelectric switching and ionic-like motion as mechanisms to induce resistance change in the same junction. By engineering the film’s microstructure, the ferroelectric switching was optimized and the ionic motion was suppressed. In addition, its memristive behavior were. The results presented indicate HZO tunnel junctions are feasible alternatives for application in non-volatile memories.
Supervisors:
- Josep Fontcuberta, MULFOX, ICMAB, CSIC
Josep Fontcuberta, Florencio Sánchez and Ignasi Fina deliver regular talks in the main ferroelectric conference.
The annual International Symposium on Applications of Ferroelectrics (ISAF) is sponsored by the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society (UFFC-S). The first ISAF meeting was held in 1968; since that time, meetings have been hosted all around the world. The first ISAF meeting held in Japan was in the year 2002 (Nara) and again in 2007.
2021
REGULAR ORAL PRESENTATIONS
“Electroresistance in epitaxial HZO films”
J. Fontcuberta
International Workshop on “Advanced Materials-to-Device Solutions for Synaptic Electronics”.
Barcelona, 10/11/2021
“Electroresistance and Ferroelectric Polarization in HZO Films Down to 2 nm “
J. Fontcuberta
International Symposium on Applications of Ferroelectrics (ISAF).
Virtual, 16-21 May 2021
“Optical Switch of Resistance in Ferroelectric Junctions “
I. Fina
International Symposium on Applications of Ferroelectrics (ISAF).
Virtual, 16-21 May 2021
“Enhanced Ferroelectric Properties of Epitaxial La-Doped Hf0.5Zr0.5O2 Thin Films “
F. Sánchez
International Symposium on Applications of Ferroelectrics (ISAF).
Virtual, 16-21 May 2021
“Enhanced Stability of Orthorhombic Ferroelectric Phase in HfxZr1-xO2 Films Enabled by
Epitaxial Stabilization “
I .Fina
International Symposium on Applications of Ferroelectrics (ISAF).
Virtual, 16-21 May 2021
Pep Fontcuberta delivers a Lecture at BeMAGIC
Pep Fontcuberta delivers a Lecture on “Oxide materials for electronics: oxitronics ” at the BeMAGIC Summer School: Setting gateway to academia University of Cambridge 7-9 April 2021 (Workshop)
2021
Current-induced magnetization control in insulating ferrimagnetic garnets
C. O. Avci
J. Phys. Soc. Japan 90, 081007 (2021)
Impact of La Concentration on Ferroelectricity of La-Doped HfO2 Epitaxial Thin Films
T. Song, H. Tan, R. Bachelet, G. Saint-Girons, I. Fina,* F. Sánchez*
ACS Appl. Electron. Mater. 2021, 3, 11, 4809–4816; DOI: doi.org/10.1021/acsaelm.1c00672
Large enhancement of ferroelectric polarization in Hf0.5Zr0.5O2 films by low plasma energy pulsed laser deposition
T. Song, R. Solanas, M. Qian, I. Fina,* F. Sánchez*
Journal of Materials Chemistry C, 2021; DOI: doi.org/10.1039/D1TC05387F
Efficient spin pumping into metallic SrVO3 epitaxial films
Ferran Macià, Mathieu Mirjolet and Josep Fontcuberta
J. Magnetism and Magnetic Materials 546, 168871, 15 March 2022; DOI: doi.org/10.1016/j.jmmm.2021.1688716
Bulk photovoltaic effect in hexagonal LuMnO3 single crystals
Yunwei Sheng, Ignasi Fina,* Marin Gospodinov, Aaron M. Schankler Andrew M. Rappe, and Josep Fontcuberta,*
Physical ReviewB 104, 184116 (2021); DOI: doi.org10.1103/PhysRevB.104.184116
Positive Effect of Parasitic Monoclinic Phase of Hf0.5Zr0.5O2 on Ferroelectric Endurance
Tingfeng Song, Saúl Estandía, Huan Tan, Nico Dix, Jaume Gàzquez, Ignasi Fina,* Florencio Sánchez*
Adv. Electron. Mater. 2021, 2100420; DOI: doi.org/10.1002/aelm.202100420
High-Temperature Synthesis and Dielectric Properties of LaTaON2
Augustin Castets, Ignasi Fina, Jhonatan R. Guarín, Judith Oró-Solé, Carlos Frontera, Clemens Ritter, Josep Fontcuberta*, and Amparo Fuertes*
Inorg. Chem. 2021, 60, 16484−16491; DOI: doi.org/10.1021/acs.inorgchem.1c02325
Switchable photovoltaic response in hexagonal LuMnO3 single crystals
Yunwei Sheng, Ignasi Fina, Marin Gospodinov, and Josep Fontcuberta
Appl. Phys. Lett. 118, 232902 (2021); DOI: doi.org/10.1063/5.0053379
Orbital occupancy and hybridization in strained SrVO3 epitaxial films
Mathieu Mirjolet , Hari Babu Vasili, Adrian Valadkhani, José Santiso , Vladislav Borisov, Pierluigi Gargiani, Manuel Valvidares, Roser Valentí , and Josep Fontcuberta
Phys Rev. Materials 5, 095002 (2021); DOI:doi.org/10.1103/PhysRevMaterials.5.095002
Thickness effect on ferroelectric properties of La-doped HfO2 epitaxial films down to 4.5 nm
Tingfeng Song, Romain Bachelet, Guillaume Saint-Girons, Nico Dix, Ignasi Fina and Florencio Sanchez,
J. Mater. Chem. C, 2021.; DOI:doi.org/10.1039/D1TC02512K
Electron–Phonon Coupling and Electron–Phonon Scattering in SrVO3
M. Mirjolet, F. Rivadulla, P. Marsik, V. Borisov, R. Valentí, J. Fontcuberta,
J. Adv. Sci. 2021, 2004207. ; DOI:doi.org/10.1002/advs.202004207
Optical Plasmon Excitations in Transparent Conducting SrNbO3 and SrVO3 Thin Films
Mathieu Mirjolet, Mikko Kataja, Tommi K. Hakala, Philipp Komissinskiy, Lambert Alff, Gervasi Herranz, Josep Fontcuberta
Adv. Opt. Materials First published: 14 June 2021; DOI:doi.org/10.1002/adom.202100520
Stabilization of the Ferroelectric Phase in Epitaxial Hf1–xZrxO2 Enabling Coexistence of Ferroelectric and Enhanced Piezoelectric Properties
Tingfeng Song, Huan Tan, Nico Dix, Rahma Moalla, Jike Lyu, Guillaume Saint-Girons, Romain Bachelet, Florencio Sánchez, and Ignasi Fina
ACS Appl. Electron. Mater. 2021, 3, 5, 2106–2113 (2021); DOI:doi.org/10.1021/acsaelm.1c00122
Critical Effect of Bottom Electrode on Ferroelectricity of Epitaxial Hf0.5Zr0.5O2 Thin Films
Saúl Estandía, Jaume Gazquez, Maria Varela, N. Dix, Mengdi Qian, Raul Solanas, Ignasi Fina and Florencio Sanchez
J. Mater. Chem. C, 9, 3486 – 3492 (2021); DOI:doi.org/10.1039/D0TC05853J
Epitaxial Ferroelectric HfO2 Films: Growth, Properties, and Devices
Ignasi Fina* and Florencio Sánchez*
ACS Appl. Electron. Mater. 2021, 3, 4, 1530-1549; DOI:doi.org/10.1021/acsaelm.1c00110
Non-volatile optical switch of resistance in photoferroelectric tunnel junctions
X.Long, H. Tan, F. Sánchez, I. Fina, J. Fontcuberta
Nature Communications volume 12, Article number: 382 (2021); DOI:10.1038/s41467-020-20660-9
Non-volatile optical switch of resistance in photoferroelectric tunnel junctions
Xiao Long, Huan Tan, Florencio Sánchez, Ignasi Fina, Josep Fontcuberta
Nature Communications volume 12, Article number: 382 (2021); DOI:10.1038/s41467-020-20660-9
Abstract
In the quest for energy efficient and fast memory elements, optically controlled ferroelectric memories are promising candidates. Here, we show that, by taking advantage of the imprint electric field existing in the nanometric BaTiO3 films and their photovoltaic response at visible light, the polarization of suitably written domains can be reversed under illumination. We exploit this effect to trigger and measure the associate change of resistance in tunnel devices. We show that engineering the device structure by inserting an auxiliary dielectric layer, the electroresistance increases by a factor near 2 × 103%, and a robust electric and optic cycling of the device can be obtained mimicking the operation of a memory device under dual control of light and electric fields.
Ignasi Fina Three receives an i-Link+ grant for International collaborations
Ignasi Fina, Florencio Sánchez, Huan Tan, and Tingfeng Song, from the Multifunctional Thin Films and Complex Structures (MULFOX) group, are joining forces with the Politecnico di Milano and the University of Cambridge to aid in the ongoing efforts in device miniaturization. They are doing so by trying to face one of the main bottlenecks in the process: heating.
As miniaturized devices become more powerful, it becomes more and more important to find solutions to dissipate the extra heat that comes with it. This team is trying to develop solid materials that can refrigerate the device using the electrocaloric effects that are very pronounced in ferroelectric materials. Ferroelectricity has been recently discovered in hafnium oxide, a CMOS compatible material, but its electrocaloric properties are yet to be investigated.
To further study the properties and applications of hafnium oxide films, Ignasi Fina’s group is pitching in their experience in ferroelectric characterization and material development. They will join the University of Cambridge’s group (UK), led by Xavier Moya, who has experience in the characterization of electrocaloric effects, and the one from Politecnico di Milano (Italy), led by Christian Rinaldi, with experience in device fabrication, in order to reduce the heating and power consumption of small devices.
Tetiana Zakusylo succesfully defended her Master’s thesis!
The group wants to congratulate Tetiana Zakusylo for her very successful defense of her master thesis supervised by Ignasi Fina. We thank Tetiana for all what we learned thanks to her, and for being a very enthusiastic member of the group. 
Thermal evolution of ferroelectric behavior in epitaxial Hf0.5Zr0.5O2
J. W. Adkins, I. Fina, F. Sanchez, S. R. Bakaul, and J. T. Abiade
Appl. Phys. Lett. 117, 142902 (2020);
Abstract
Herein, we report a cryogenic-temperature study on the evolution of the ferroelectric properties of epitaxial Hf0.5Zr0.5O2 thin films on silicon. Wake-up, endurance, and fatigue of these films are found to be intricately correlated, strongly hysteretic, and dependent on available thermal energy. Field-dependent measurements reveal a decrease in polarization with temperature, which has been determined not to be an intrinsic change of the material property, rather a demonstration of the increase in the coercive bias of the material. Our findings suggest that a deficiency in thermal energy suppresses the mobility of defects presumed to be oxygen vacancies during wake-up and trapped injected charge during fatigue, which is responsible for polarization evolution during cycling. This permits accelerated wake-up and fatigue effects at high temperatures where thermal energy is abundant but delays these effects at cryogenic temperatures.
Carlos Zarco is starting bachelor stage with us
Hello everyone! My name is Carlos Zarco and I’m from Barcelona. I am a last-year student of Phisics and Chemistry at UAB and I am performing my degree’s final project at ICMAB with Ignasi Fina. 
OPTOFEM2020 starts
School on Optically Controlled Ferroelectric #Memristors has started today morning! Welcome
Inside Cover in Materials Horizons
Our work “Local manipulation of metamagnetism by strain nanopatterning ” has been highlighted in the inside cover of Materials Horizons.
Optically Controlled Ferroelectric Memristors Summer School
We announce the “summer” school on “Optically Controlled Ferroelectric Memristors” (OPTOFEM 2020) goes Online! The School will finally take place on October, 22-23, 2020, in an online format, due to the current COVID-19. Great and experienced lectureres from around the world will participate. Register now before October 11, 2020 to attend! All-optically controlled resistive switching could offer advantages, in terms of energy dissipation and speed, for logic and data storage functions in solid-state devices. Ferroelectrics may constitute a building block of this emerging technology, when integrated in nanometric tunnel devices. The functioning of these devices, from photon absorption to the resistive switching involve a subtle interplay between electronic and optical properties, polarization effects and materials issues.
Objective of the school and target audience
The OPTOFEM 2020 school aims at introducing the scientific knowledge, in a tutorial style, required to contribute to this emerging field. Most reputed scientist active in the field will deliver lectures in a strongly interacting atmosphere.
The school is targeting an audience of PhD fellows and researchers initiating their activity on photoresponse in oxides, with interest on polar materials (ferroelectric), with applications spanning from photovoltaics to resistive switching.
Registration
The school will take place on 22-23 October in an online format.
The school will be limited to a maximum of 50 students, selected on the basis of their motivation and recommendation letter provided. Priority will be for PhD fellows and MSc students in the school-related field.
Deadline for registration is October 11, 2020. Registration is through the conference website.
Invited Lecturers
- Prof. Juan Bisquert, Director of the Institute of Advanced Material. Universitat Jaume I de Castelló, Spain.
- Prof. Marin Alexe, Department of Physics, University of Warwick, UK.
- Prof. Alexei Gruverman, Department of Physics and Astronomy, University of Nebraska–Lincoln, USA.
- Prof. Andrew Rappe, Department of Chemistry, University of Pennsylvania, USA.
- Dr. Giuliana Di Martino, Department of Materials Science & Metallurgy University of Cambridge, UK
- Prof. Junling Wang School of Materials Science and Engineering Nanyang Technological University, Singapore.
- Prof. Dr. Andreas Klein, Electronic Structure of Materials Department Technische Universität Darmstadt, Germany
Organizers
Josep Fontcuberta and Ignasi Fina
Chairs of OPTOFEM 2020
Laboratory of Multifunctional Oxides and Complex Structures (MULFOX)
For additional information and registration, please refer to the conference webpage: optofem2020.icmab.esor contact us by email at optofem2020@icmab.es.
Ignasi Fina awarded with Leonardo project from BBVA
Ignasi Fina has been recently awarded with Leonardo project from BBVA. The project should allow to advance in the understanding of the interaction between ferroelectricity and light, ultimately enabling to make devices out of that.
Mikko Kataja
Hello everyone! I’m Mikko Kataja and I come from Finland, where I did my PhD in Aalto University on magneto-optically active plasmonic nanoparticles. I am now in ICMAB in Multifunctional Oxides and Complex Structures research group to explore the possibilities that active oxide materials, such as ferromagnetic and ferroelectric oxides, offer in the field of optics, especially for active nanoscale optical devices. In my freetime, I enjoy cooking and board games.
Engineering Polar Oxyitrides: Hexagonal Perovskite BaWON2
Judith Oró‐Solé, Ignasi Fina, Carlos Frontera, Jaume Gàzquez, Clemens Ritter, Marina Cunquero, Pablo Loza‐Alvarez, Sergio Conejeros, Pere Alemany, , Enric Canadell, Josep Fontcuberta, Amparo Fuertes;
Angew. Chem. Int. Ed. 2020, 59, 18395–18399; DOI:10.1002/anie.202006519
Abstract
In the quest for materials of narrow band gap, oxynitrides are excellent candidates. Aiming at obtaining a polar materials of narrow gap, oxynitides are developed here having an hexagonal structure and anion ordering that leads to a non centrosymmetric structures. As such, here BaWON2 is synthesized and we demonstrate its polar character and large photo absorptivity.
Dr. Ingrid Cañero from CNRS will give a talk at ICMAB
Next Tuesday July 25th, at 11:30h, Ingrid Cañero will give the talk entitled “Electronic, chemical and structural effects on the optical properties of (nano)ferroelectric oxides and related compounds” at Sala d’Actes Matgas at ICMAB.
Michael Foester
Physicist from Germany, Mainz.
