The Evaluation of Interface Quality in HfO2 Films Probed by Time-Dependent Second-Harmonic Generation.

Time-dependent second-harmonic generation (TD-SHG) is an emerging sensitive and fast method to qualitatively evaluate the interface quality of the oxide/Si heterostructures, which is closely related to the interfacial electric field. Here, the TD-SHG is used to explore the interface quality of atomic layer deposited HfO2 films on Si substrates. The critical SHG parameters, such as the initial SHG signal and characteristic time constant, are compared with the fixed charge density (Qox) and the interface state density (Dit) extracted from the conventional electrical characterization method. It reveals that the initial SHG signal linearly decreases with the increase in Qox, while Dit is linearly correlated to the characteristic time constant. It verifies that the TD-SHG is a sensitive and fast method, as well as simple and noncontact, for evaluating the interface quality of oxide/Si heterostructures, which may facilitate the in-line semiconductor test.

Realization of sextuple polarization states and interstate switching in antiferroelectric CuInP2S6.

Realization of higher-order multistates with mutual interstate switching in ferroelectric materials is a perpetual drive for high-density storage devices and beyond-Moore technologies. Here we demonstrate experimentally that antiferroelectric van der Waals CuInP2S6 films can be controllably stabilized into double, quadruple, and sextuple polarization states, and a system harboring polarization order of six is also reversibly tunable into order of four or two. Furthermore, for a given polarization order, mutual interstate switching can be achieved via moderate electric field modulation. First-principles studies of CuInP2S6 multilayers help to reveal that the double, quadruple, and sextuple states are attributable to the existence of respective single, double, and triple ferroelectric domains with antiferroelectric interdomain coupling and Cu ion migration. These findings offer appealing platforms for developing multistate ferroelectric devices, while the underlining mechanism is transformative to other non-volatile material systems.

Electric Field Switching of Magnon Spin Current in a Compensated Ferrimagnet.

Manipulation of directional magnon propagation, known as magnon spin current, is essential for developing magnonic devices featuring nonvolatile functionalities and ultralow power consumption. Magnon spin current can usually be modulated by magnetic field or current-induced spin torques. However, these approaches may lead to energy dissipation due to Joule heating. Electric-field switching of magnon spin current without charge current is highly preferred but challenging to realize. By integrating magnonic and piezoelectric materials, the manipulation of the magnon spin current generated by the spin Seebeck effect in the ferrimagnetic insulator Gd3Fe5O12 (GdIG) film on a piezoelectric substrate is demonstrated. Reversible electric-field switching of magnon polarization without applied charge current is observed. Through strain-mediated magnetoelectric coupling, the electric field induces the magnetic compensation transition between two magnetic states of the GdIG, resulting in its magnetization reversal and the simultaneous switching of magnon spin current. This work establishes a prototype material platform that paves the way for developing magnon logic devices characterized by all electric field reading and writing and reveals the underlying physics principles of their functions.

Optical Modulation of MoTe2/Ferroelectric Heterostructure via Interface Doping.

Optical modulation through interface doping offers a convenient and efficient way to control ferroelectric polarization, thereby advancing the utilization of ferroelectric heterostructures in nanoelectronic and optoelectronic devices. In this work, we fabricated heterostructures of MoTe2/BaTiO3/La0.7Sr0.3MnO3 (MoTe2/BTO/LSMO) and demonstrated opposite ultraviolet (UV) light-induced polarization switching behaviors depending on the varied thicknesses of MoTe2. The thickness-dependent band structure of MoTe2 film results in interface doping with opposite polarity in the respective heterostructures. The polarization field of BTO interacts with the interface charges, and an enhanced effective built-in field (Ebi) can trigger the transfer of massive UV light-induced carriers in both MoTe2 and BTO films. As a result, the interplay among the contact field of MoTe2/BTO, the polarization field, and the optically excited carriers determines the UV light-induced polarization switching behavior of the heterostructures. In addition, the electric transport characteristics of MoTe2/BTO/LSMO heterostructures reveal the interface barrier height and Ebi under opposite polarization states, as well as the presence of inherent in-gap trap states in MoTe2 and BTO films. These findings represent a further step toward achieving multifield modulation of the ferroelectric polarization and promote the potential applications in optoelectronic, logic, memory, and synaptic ferroelectric devices.

Clinical manifestations and risk factors of shock in children with multisystem inflammatory syndrome.

BACKGROUND: Multisystem inflammatory syndrome in children (MIS-C) is a novel disease associated with COVID-19. The COVID-19 epidemic peaked in May 2022 in Taiwan, and we encountered our first case of MIS-C in late May 2022. We aimed to present patients' clinical manifestations and identify risk factors for shock. METHODS: We included patients diagnosed with MIS-C at two medical centers from May 2022 to August 2022. We separated those patients into two groups according to whether they experienced shock. We collected demographic, clinical manifestation, and laboratory data of the patients and performed statistical analysis between the two groups. RESULTS: We enrolled 28 patients, including 13 (46 %) with shock and 15 (54 %) without shock. The median age was 6.4 years (IQR: 1.9-7.5). In single variable analysis, patients with shock tended to be older, had more neurological symptoms, more conjunctivitis and strawberry tongue, lower lymphocyte count, lower platelet counts, and higher C-reactive protein, higher procalcitonin, higher ferritin, and higher D-dimer levels than those without shock. The area under the ROC curve that used procalcitonin to be the risk factor of shock with MIS-C was 0.815 (95 % CI 0.644 to 0.987). The cutoff value obtained by ROC analysis of procalcitonin was 1.68 ng/mL. With this cutoff, the test characteristics of procalcitonin were as follows: sensitivity 77 %, specificity 93 %, positive predictive value 91 %, negative predictive value 82 %. Multivariable analysis revealed that procalcitonin was the only independent risk factor of shock with MIS-C on admission (OR, 26.00, 95 % CI, 1.01-668.89). CONCLUSIONS: MIS-C patients with high initial procalcitonin levels have higher risks of experiencing shock and may need ICU admission.

E-Spin: A Stochastic Ising Spin Based on Electrically-Controlled MTJ for Constructing Large-Scale Ising Annealing Systems.

With its unique computer paradigm, the Ising annealing machine has become an emerging research direction. The Ising annealing system is highly effective at addressing combinatorial optimization (CO) problems that are difficult for conventional computers to tackle. However, Ising spins, which comprise the Ising system, are difficult to implement in high-performance physical circuits. We propose a novel type of Ising spin based on an electrically-controlled magnetic tunnel junction (MTJ). Electrical operation imparts true randomness, great stability, precise control, compact size, and easy integration to the MTJ-based spin. In addition, simulations demonstrate that the frequency of electrically-controlled stochastic Ising spin (E-spin) is 50 times that of the thermal disturbance MTJ-based spin (p-bit). To develop a large-scale Ising annealing system, up to 64 E-spins are implemented. Our Ising annealing system demonstrates factorization of integers up to 264 with a temporal complexity of around O(n). The proposed E-spin shows superiority in constructing large-scale Ising annealing systems and solving CO problems.

Giant tunable spin Hall angle in sputtered Bi2Se3 controlled by an electric field.

Finding an effective way to greatly tune spin Hall angle in a low power manner is of fundamental importance for tunable and energy-efficient spintronic devices. Recently, topological insulator of Bi2Se3, having a large intrinsic spin Hall angle, show great capability to generate strong current-induced spin-orbit torques. Here we demonstrate that the spin Hall angle in Bi2Se3 can be effectively tuned asymmetrically and even enhanced about 600% reversibly by applying a bipolar electric field across the piezoelectric substrate. We reveal that the enhancement of spin Hall angle originates from both the charge doping and piezoelectric strain effet on the spin Berry curvature near Fermi level in Bi2Se3. Our findings provide a platform for achieving low power consumption and tunable spintronic devices.

Tip-Induced In-Plane Ferroelectric Superstructure in Zigzag-Wrinkled BaTiO3 Thin Films.

The complex micro-/nanoscale wrinkle morphology primarily fabricated by elastic polymers is usually designed to realize unique functionalities in physiological, biochemical, bioelectric, and optoelectronic systems. In this work, we fabricated inorganic freestanding BaTiO3 ferroelectric thin films with zigzag wrinkle morphology and successfully modulated the ferroelectric domains to form an in-plane (IP) superstructure with periodic surface charge distribution. Our piezoresponse force microscopy (PFM) measurements and phase-field simulation demonstrate that the self-organized strain/stress field in the zigzag-wrinkled BaTiO3 film generates a corresponding pristine domain structure. These domains can be switched by tip-induced strain gradient (flexoelectricity) and naturally form a robust and unique "braided" in-plane domain pattern, which enables us to offer an effective and convenient way to create a microscopic ferroelectric superstructure. The corresponding periodic surface potential distribution provides an extra degree of freedom in addition to the morphology that could regulate cells or polar molecules in physiological and bioelectric applications.

Simple way to fabricate orderly arranged nanostructure arrays on diamond utilizing metal dewetting effect.

We introduce a simple method with thermal annealing round gold disk for agglomeration to fabricate orderly arranged nanostructure arrays on diamond for single photon source applications. In the annealing process, the dependence of gold sphere size on disk thickness and diameter was investigated, showing that gold sphere diameter was decreased with decreasing gold disk thickness or diameter. The condition parameters of ICP etch were adjusted to obtain different nanostructure morphologies on diamond. The collection efficiency of nitrogen-vacancy (NV) center embedded in nanostructure as-fabricated could reach to 53.56% compared with that of 19.10% in planar case with the same simulation method.

Photovoltaic modulation of ferromagnetism within a FM metal/P-N junction Si heterostructure.

Obtaining small, fast, and energy-efficient spintronic devices requires a new way of manipulating spin states in an effective manner. Here, a prototype photovoltaic spintronic device with a p-n junction Si wafer is proposed which generates photo-induced electrons and changes the ferromagnetism by interfacial charge doping. A ferromagnetic resonance field change of 48.965 mT and 11.306 mT is achieved in Co and CoFeB thin films under sunlight illumination, respectively. The transient reflection (TR) analysis and the first principles calculation reveal the photovoltaic electrons that are doped into the magnetic layer and alter its Fermi level, correspondingly. This finding provides a new method of magnetism modulation and demonstrates a solar-driven spintronic device with abundant energy supply, which may further expand the landscape of spintronics research.

Periodic Wrinkle-Patterned Single-Crystalline Ferroelectric Oxide Membranes with Enhanced Piezoelectricity.

Self-assembled membranes with periodic wrinkled patterns are the critical building blocks of various flexible electronics, where the wrinkles are usually designed and fabricated to provide distinct functionalities. These membranes are typically metallic and organic materials with good ductility that are tolerant of complex deformation. However, the preparation of oxide membranes, especially those with intricate wrinkle patterns, is challenging due to their inherently strong covalent or ionic bonding, which usually leads to material crazing and brittle fracture. Here, wrinkle-patterned BaTiO3 (BTO)/poly(dimethylsiloxane) membranes with finely controlled parallel, zigzag, and mosaic patterns are prepared. The BTO layers show excellent flexibility and can form well-ordered and periodic wrinkles under compressive in-plane stress. Enhanced piezoelectricity is observed at the sites of peaks and valleys of the wrinkles where the largest strain gradient is generated. Atomistic simulations further reveal that the excellent elasticity and the correlated coupling between polarization and strain/strain gradient are strongly associated with ferroelectric domain switching and continuous dipole rotation. The out-of-plane polarization is primarily generated at compressive regions, while the in-plane polarization dominates at the tensile regions. The wrinkled ferroelectric oxides with differently strained regions and correlated polarization distributions would pave a way toward novel flexible electronics.

Phase transition enhanced superior elasticity in freestanding single-crystalline multiferroic BiFeO3 membranes.

The integration of ferroic oxide thin films into advanced flexible electronics will bring multifunctionality beyond organic and metallic materials. However, it is challenging to achieve high flexibility in single-crystalline ferroic oxides that is considerable to organic or metallic materials. Here, we demonstrate the superior flexibility of freestanding single-crystalline BiFeO3 membranes, which are typical multiferroic materials with multifunctionality. They can endure cyclic 180° folding and have good recoverability, with the maximum bending strain up to 5.42% during in situ bending under scanning electron microscopy, far beyond their bulk counterparts. Such superior elasticity mainly originates from reversible rhombohedral-tetragonal phase transition, as revealed by phase-field simulations. This study suggests a general fundamental mechanism for a variety of ferroic oxides to achieve high flexibility and to work as smart materials in flexible electronics.

Probe and Control of the Tiny Amounts of Dopants in BHJ Film Enable Higher Performance of Polymer Solar Cells.

To achieve efficient doping in polymer solar cells (PSCs), the dopant needs to be selectively located in the binary components of a bulk heterojunction (BHJ) film according to its polarity. The rarely studied n-type dopant is thoroughly examined in a simplified planar heterojunction (PHJ) device to address its favored location in the active layer. Results show that the n-dopant distribution in the acceptor layer or at the donor/acceptor interface produces enhanced device performance, whereas it harms the device when located in the donor layer. Based on the results, the benefit of n-type doping is then transferred to the highly efficient BHJ devices via a sequential coating procedure. The performance improvement is closely linked to the variations in the dopant's location in the BHJ film, which is carefully examined by the synchrotron techniques with delicate chemical sensitivity. More interestingly, the sequential coating procedure can be easily extended to the p-doped device only by changing the dopant's polarity in the middle layer. These findings pave the way for ambipolar doping in PSCs and enable performance improvement by molecular doping within the expectations.

Sunlight Control of Interfacial Magnetism for Solar Driven Spintronic Applications.

The inexorable trend of next generation spintronics is to develop smaller, lighter, faster, and more energy efficient devices. Ultimately, spintronics driven by free energy, for example, solar power, is imperative. Here, a prototype photovoltaic spintronic device with an optical-magneto-electric tricoupled photovoltaic/magnetic thin film heterojunction, where magnetism can be manipulated directly by sunlight via interfacial effect, is proposed. The magnetic anisotropy is reduced evidenced by the out-of-plane ferromagnetic resonance (FMR) field change of 640.26 Oe under 150 mW cm-2 illumination via in situ electron spin resonance (ESR) method. The transient absorption analysis and the first-principles calculation reveal that the photovoltaic electrons doping in the cobalt film alter the band filling of this ferromagnetic film. The findings provide a new path of electron doping control magnetism and demonstrate an optical-magnetic dual controllable logical switch with limited energy supply, which may further transform the landscape of spintronics research.

Percolated Strain Networks and Universal Scaling Properties of Strain Glasses.

Strain glass is being established as a conceptually new state of matter in highly doped alloys, yet the understanding of its microscopic formation mechanism remains elusive. Here, we use a combined numerical and experimental approach to establish, for the first time, that the formation of strain glasses actually proceeds via the gradual percolation of strain clusters, namely, localized strain clusters that expand to reach the percolating state. Furthermore, our simulation studies of a wide variety of specific materials systems unambiguously reveal the existence of distinct scaling properties and universal behavior in the physical observables characterizing the glass transition, as obeyed by many existing experimental findings. The present work effectively enriches our understanding of the underlying physical principles governing glassy disordered materials.

[Effects of CSN4 knockdown on proliferation and apoptosis of breast cancer MDA-MB-231 cells].

Breast cancer is one of the most common malignant tumors endangering women. It has been found that the subunits of the COP9 complex are closely related to the occurrence and development of malignant tumors, and the CSN4 subunit plays an important role in regulating the whole complex. In the breast cancer cell line MDA-MB-231, we successfully established a lentivirus-mediated CSN4-knockdown cell line. CCK8 cell proliferation assays and colony formation experiments confirmed that CSN4 knockdown significantly decreased the cellular proliferation rate. Cell cycle analysis showed that CSN4 knockdown increased sub-G1 population and induced apoptosis. In addition, Western blotting assays confirmed that CSN4 regulates the expression of CDK6 and Caspase3, suggesting that CSN4 modulates the proliferation and apoptosis of breast cancer cells by regulating the expression of CDK6 and Caspase3 genes and thereby tumorigenesis. This study has deepened our understanding of the molecular mechanism of apoptosis and cell growth in breast cancers, and further revealed the role and mechanism of CSN4 in cancer biology.

Tunable magnetic ground states of iron monolayer on nonmagnetic metallic substrates by small in-plane strains.

The magnetic states of one single atomic layer of iron epitaxially grown on 4d and 5d nonmagnetic metals are studied under strain systematically using first principle calculations. Our results show that, without strain, the iron on top of different 4d and 5d nonmagnetic metals shows distinct antiferromagnetic or ferromagnetic ground states: a parallel antiferromagnetic ground state (p-AFM) on Rh and a central antiferromagnetic ground state (c-AFM) on Ir and ferromagnetic (FM) ground state on Pd, Ag, Pt and Au. However, when introducing in-plane biaxial and uniaxial strain (Δε xx ) on the substrates, the ground state of iron can be manipulated easily. In detail, for biaxial strain, the ground state of iron on an Rh substrate becomes FM when Δε xx < -2.0% and c-AFM when Δε xx > 0.8%, and on an Ir substrate, the ground state of iron becomes FM when Δε xx < -2.8% and c-AFM when Δε xx > -0.8%. However, for the uniaxial strain along the x direction, while using the corresponding Poisson's ratios to determine the strain along the y direction, the ground state of iron on an Rh substrate remains the p-AFM state, but on an Ir substrate, the ground state of iron changes from c-AFM to p-AFM at Δε xx = 0.2% or Δε xx = -0.3% along the x direction respectively.

E-field Control of the RKKY Interaction in FeCoB/Ru/FeCoB/PMN-PT (011) Multiferroic Heterostructures.

E-field control of antiferromagnetic (AFM) orders is promising for the realization of fast, compact, and energy-efficient AFM applications. However, as the AFM spins are strongly pinned, the E-field control process is mainly based on the exchange bias regulation that usually confines at a low temperature. Here, a new magnetoelectric (ME) coupling mechanism for the modulation of AFM orders at room temperature is explored. Based on the FeCoB/Ru/FeCoB/(011) Pb(Mg1/3 Nb2/3 )O3 -PbTiO3 (PMN-PT) synthetic antiferromagnetic (SAF) heterostructures, the external E-field generates relative magnetization switching in the two ferromagnetic (FM) layers, leading the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction tuning. This voltage-induced switching behavior can be repeated in a stable and reversible manner for various SAFs, which is a key challenge in the E-field control of AFM coupling and is not resolved yet. The voltage-induced RKKY interaction changes by analyzing the dynamic optical and acoustic modes is quantified, and with first-principles calculations, it is found that the distortion of the Fermi surface by the lattice reconstruction is the key of the relative magnetization switching and RKKY interaction modulation. This voltage control of the RKKY interaction in ME heterostructures provides an easy way to achieve the next generation of AFM/FM spintronic applications.

Ionic Modulation of the Interfacial Magnetism in a Bilayer System Comprising a Heavy Metal and a Magnetic Insulator for Voltage-Tunable Spintronic Devices.

The voltage modulation of yttrium iron garnet (YIG) is of practical and theoretical significance; due to its advantages of compactness, high-speed response, and energy efficiency, it can be used for various spintronic applications, including spin-Hall, spin-pumping, and spin-Seebeck effects. In this study, a significant ferromagnetic resonance change is achieved within the YIG/Pt bilayer heterostructures uisng ionic modulation, which is accomplished by modifying the interfacial magnetism in the deposited "capping" platinum layer. With a small voltage bias of 4.5 V, a large ferromagnetic field shift of 690 Oe is achieved in heterostructures of YIG (13 nm)/Pt (3 nm)/(ionic liquid, IL)/(Au capacitor). The remarkable magnetoelectric (ME) tunability comes from the additional and voltage-induced ferromagnetic ordering, caused by uncompensated d-orbital electrons in the Pt metal layer. Confirmed by first-principle calculations, this finding paves the way for novel voltage-tunable YIG-based spintronics.

Ionic Liquid Gating Control of Spin Reorientation Transition and Switching of Perpendicular Magnetic Anisotropy.

Electric field (E-field) modulation of perpendicular magnetic anisotropy (PMA) switching, in an energy-efficient manner, is of great potential to realize magnetoelectric (ME) memories and other ME devices. Voltage control of the spin-reorientation transition (SRT) that allows the magnetic moment rotating between the out-of-plane and the in-plane direction is thereby crucial. In this work, a remarkable magnetic anisotropy field change up to 1572 Oe is achieved under a small operation voltage of 4 V through ionic liquid (IL) gating control of SRT in Au/[DEME]+ [TFSI]- /Pt/(Co/Pt)2 /Ta capacitor heterostructures at room temperature, corresponding to a large ME coefficient of 378 Oe V-1 . As revealed by both ferromagnetic resonance measurements and magnetic domain evolution observation, the magnetization can be switched stably and reversibly between the out-of-plane and in-plane directions via IL gating. The key mechanism, revealed by the first-principles calculation, is that the IL gating process influences the interfacial spin-orbital coupling as well as net Rashba magnetic field between the Co and Pt layers, resulting in the modulation of the SRT and in-plane/out-of-plane magnetization switching. This work demonstrates a unique IL-gated PMA with large ME tunability and paves a way toward IL gating spintronic/electronic devices such as voltage tunable PMA memories.