Record cryogenic cooling in ferroelectric hafnia proximity induced via Mott transition

On-chip refrigeration at cryogenic temperatures is becoming an important requirement in the context of quantum technologies and nanoelectronics. Ferroic materials with enhanced electrocaloric effects at phase transitions are good material candidates for the same. By exploiting the Mott metal-insulator transition (MIT) of TiOx(Ny), the bottom electrode, we engineer a depolarization field controlled reversible polar to non-polar phase transition in thick La-doped hafnia (40 nm). This transition occurs between ~125 and 140 K and produces giant negative pyroelectric and electrocaloric effects. Refrigeration metrics were estimated between 120 to 200 K, with a peak refrigerant capacity of 25 kJ Kg-1 (2 kJ Kg-1), peak isothermal entropy {\Delta}S~ 8 kJ Kg-1 K-1 (0.5 kJ Kg-1 K-1) and adiabatic {\Delta}Tcooling ~ 106 K (11 K) at ~140 K and 5 MV cm-1 (0.5 MV cm-1, and these are the largest reported in any electrocaloric system. Our work fundamentally proposes design guidelines to induce significant solid-state refrigeration through proximity effects, even at cryogenic temperatures relevant to quantum technologies

Room temperature Mott transistor based on resistive switching in disordered V2O3 films grown on Si

Electric field-induced giant resistive switching triggered by insulator-to-metal transition (IMT) is one of the promising approaches for developing a new class of electronics often referred to as Mottronics. Achieving this resistive switching by minimal external field at room temperature is of paramount research and technological interest. Mott-IMT is often associated with structural modification, which is very important for optoelectronic and actuator applications. Here, we report a giant resistive switching of about 900 % at room temperature in disordered polycrystalline V2O3-Si thin film stabilized at the IMT phase boundary and associated structural transformation under a small electric field. The increase of electron population in the a1g band under the field is responsible for the Mott gap collapse that drives the structural transition. Furthermore, we also fabricated a room temperature Mott-FET with a channel ON/OFF resistive ratio of about 15. This study provides a fundamental mechanism of the Mott-IMT in V2O3 as well as its device applications.16 pages, 5 figure

Wavelength-dependent anisotropic light-matter interaction in 2D ferroelectric In2Se3

The anisotropic light-matter interactions in 2D materials have garnered significant attention for their potential to develop futuristic polarization-based optoelectronic devices, such as photodetectors and photo-actuators. In this study, we investigate the polarization-dependent interactions in ferroelectric 3R alpha-In2Se3 using Angle-Resolved Polarized Raman Spectroscopy (ARPRS) with different excitation lasers. Our experimental findings supported by complementary Density Functional Theory calculations demonstrate that the light-matter interactions depend not only on the crystallographic orientation but also on the excitation energy. Scanning transmission electron microscopy (STEM) confirms the highly anisotropic 3R crystal structure of alpha-In2Se3. This anisotropy in crystal structure facilitates significant optical anisotropy, driven by a complex interplay of electron-photon and electron-phonon interactions, which is reflected in the complex nature of the Raman tensor elements. These anisotropy interactions extend to the materials electrical response under light illumination. Remarkably, the anisotropic photo-response can be tuned by both polarization and wavelength of the incident light, making In2Se3 a promising material for advanced polarization-sensitive photodetection applications.19 pages, 6 figures, supporting informatio

Heterogeneous integration of high endurance ferroelectric and piezoelectric epitaxial BaTiO3_3 devices on Si

Integrating epitaxial BaTiO$_3$ (BTO) with Si is essential for leveraging its ferroelectric, piezoelectric, and nonlinear optical properties in microelectronics. Recently, heterogeneous integration approaches that involve growth of BTO on ideal substrates followed by transfer to a desired substrate show promise of achieving excellent device-quality films. However, beyond simple demonstrations of the existence of ferroelectricity, robust devices with high endurance were not yet demonstrated on Si using the latter approach. Here, using a novel two-step approach to synthesize epitaxial BTO using pulsed laser deposition (PLD) on water soluble Sr3Al2O7 (SAO) (on SrTiO$_3$ (STO) substrates), we demonstrate successful integration of high-quality BTO capacitors on Si, with Pr of 7 uC/cm2, Ec 150 kV/cm, ferroelectric and electromechanical endurance of greater than $10^6$ cycles. We further address the challenge of cracking and disintegration of thicker films by first transferring a large area (5 mm x 5 mm) of the templated layer of BTO (~30 nm thick) on the desired substrate, followed by the growth of high-quality BTO on this substrate, as revealed by HRXRD and HRSTEM measurements. These templated Si substrates offer a versatile platform for integrating any epitaxial complex oxides with diverse functionalities onto any inorganic substrate.Comment: 29 pages, 12 figure

Giant electrostriction-like response from defective non-ferroelectric epitaxial BaTiO3 integrated on Si (100)

Data is self-explanatory and labelled well. It follows the order from the paper

Positive Magneto‐Electric Couplings in Epitaxial Multiferroic SrMnO3_3 Thin Film

This study demonstrates the magneto-dielectric (MD) properties of high quality epitaxially strain multiferroic SrMnO$_3$ thin film on conducting Nb doped SrTiO$_3$ substrate. The study observes considerable high positive MD coupling near room temperature and across the anti-ferromagnetic transition temperature of SrMnO$_3$. The dielectric maxima of the grown film is above room temperature, which confirms the room temperature ferroelectric nature of the grown film. From out-of-plan polarization and PUND (Positive Up Negative Down) measurements in the presence of magnetic field, it is confirmed that the polarization value of grown SrMnO$_3$ thin film increases with an increase in magnetic field. In this study, the oxygen off-stoichiometry concentration is also varied by varying oxygen partial pressure during deposition and is able to create Mn$^{4+}$, Mn$^{3+}$, and Mn$^{2+}$ in the grown films. Despite having mixed Mn states, SrMnO$_3$ thin films remain in the insulating phase. So, the insulating nature of SrMnO$_3$ thin film is robust with respect to oxygen off-stoichiometry and vacancy/substrate induced strain mediated change in the crystal field. The study has also demonstrated the variation of MD in SrMnO$_3$ thin film by change in oxygen vacancy induced modification in crystal field

A 3.2 V Binary Layered Oxide Cathode for Potassium‐Ion Batteries

International audienceAbstract Potassium‐ion batteries (KIBs) can offer high energy density, cyclability, and operational safety while being economical due to the natural abundance of potassium. Utilizing graphite as an anode, suitable cathodes can realize full cells. Searching for potential cathodes, this work introduces P3‐type K 0.5 Ni 1/3 Mn 2/3 O 2 layered oxide as a potential candidate synthesized by a simple solid‐state method. The material works as a 3.2 V cathode combining Ni redox at high voltage and Mn redox at low voltage and exhibits highly reversible K + ion (de)insertion at ambient and elevated (40–50 °C) temperatures. First‐principles calculations suggest the ground state in‐plane Mn–Ni ordering in the MO 2 sheets is strongly correlated to the K‐content in the framework, leading to an interwoven and alternative row ordering of Ni–Mn in K 0.5 Ni 1/3 Mn 2/3 O 2 . Postmortem and electrochemical titration reveal the occurrence of a solid solution mechanism during K + (de)insertion. The findings suggest that the Ni addition can effectively tune the electronic and structural properties of the cathode, leading to improved electrochemical performance. This work provides new insights in the quest to develop potential low‐cost Co‐free KIB cathodes for practical applications in stationary energy storage

Role of Hemigraphis alternata in wound healing: metabolomic profiling and molecular insights into mechanisms

Abstract Hemigraphis alternata (H. alternata), commonly known as Red Flame Ivy, is widely recognized for its wound healing capabilities. However, the pharmacologically active plant components and their mechanisms of action in wound healing are yet to be determined. This study presents the mass spectrometry-based global metabolite profiling of aqueous and ethanolic extract of H. alternata leaves. The analysis identified 2285 metabolites from 24,203 spectra obtained in both positive and negative polarities. The identified metabolites were classified under ketones, carboxylic acids, primary aliphatic amines, steroids and steroid derivatives. We performed network pharmacology analysis to explore metabolite–protein interactions and identified 124 human proteins as targets for H. alternata metabolites. Among these, several of them were implicated in wound healing including prothrombin (F2), alpha-2A adrenergic receptor (ADRA2A) and fibroblast growth factor receptor 1 (FGFR1). Gene ontology analysis of target proteins enriched cellular functions related to glucose metabolic process, platelet activation, membrane organization and response to wounding. Additionally, pathway enrichment analysis revealed potential molecular network involved in wound healing. Moreover, in-silico docking analysis showed strong binding energy between H. alternata metabolites with identified protein targets (F2 and PTPN11). Furthermore, the key metabolites involved in wound healing were further validated by multiple reaction monitoring-based targeted analysis

Giant electrostriction-like response from defective non-ferroelectric epitaxial BaTiO3 integrated on Si (100)

Data is self-explanatory and labelled well. It follows the order from the paper

Giant electromechanical response from defective non-ferroelectric epitaxial BaTiO3 integrated on Si (100)

Abstract Lead-free, silicon compatible materials showing large electromechanical responses comparable to, or better than conventional relaxor ferroelectrics, are desirable for various nanoelectromechanical devices and applications. Defect-engineered electrostriction has recently been gaining popularity to obtain enhanced electromechanical responses at sub 100 Hz frequencies. Here, we report record values of electrostrictive strain coefficients (M31) at frequencies as large as 5 kHz (1.04×10− 14 m2/V2 at 1 kHz, and 3.87×10− 15 m2/V2 at 5 kHz) using A-site and oxygen-deficient barium titanate thin-films, epitaxially integrated onto Si. The effect is robust and retained even after cycling the devices &gt; 5000 times. Our perovskite films are non-ferroelectric, exhibit a different symmetry compared to stoichiometric BaTiO3 and are characterized by twin boundaries and nano polar-like regions. We show that the dielectric relaxation arising from the defect-induced features correlates very well with the observed giant electrostrictive response. These films show large coefficient of thermal expansion (2.36 ⋅ 10− 5/K), which along with the giant M31 implies a considerable increase in the lattice anharmonicity induced by the defects. Our work provides a crucial step forward towards formulating guidelines to engineer large electromechanical responses even at higher frequencies in lead-free thin films.</jats:p