Superfine Nanodomain Engineering Unleashing Ferroelectricity in Incipient Ferroelectrics.

Incipient ferroelectrics have emerged as an attractive class of functional materials owing to their potential to be engineered for exotic ferroelectric behavior, holding great promise for expanding the ferroelectric family. However, thus far, their artificially engineered ferroelectricity has fallen far short of rivaling classic ferroelectrics. In this study, we address this challenge by developing a superfine nanodomain engineering strategy.

Syntropic spin alignment at the interface between ferromagnetic and superconducting nitrides.

The magnetic correlations at the superconductor/ferromagnet (S/F) interfaces play a crucial role in realizing dissipation-less spin-based logic and memory technologies, such as triplet-supercurrent spin-valves and 'π' Josephson junctions. Here we report the observation of an induced large magnetic moment at high-quality nitride S/F interfaces. Using polarized neutron reflectometry and DC SQUID measurements, we quantitatively determined the magnetization profile of the S/F bilayer and confirmed that the induced magnetic moment in the adjacent superconductor only exists below .

ANiBi (A = K, Rb, and Cs): Quasi-One-Dimensional Metals Featuring [NiBi] Double-Walled Column with Strong Diamagnetism.

A new series of compounds, ANiBi (where A = K, Rb, and Cs) are discovered with a quasi-one-dimensional (Q1D) [NiBi] double-walled column and a coaxial inner one-dimensional Bi atomic chain. The columns are linked to each other by intercolumn Bi-Bi bonds and separated by an A cation. Typical metallic behaviors with strong correlation of itinerant electrons and the Sommerfeld coefficient enhanced with the increasing cationic radius were experimentally observed and supported by first-principles calculations.

Single-Atom Fe Catalysts for Fenton-Like Reactions: Roles of Different N Species.

Recognizing and controlling the structure-activity relationships of single-atom catalysts (SACs) is vital for manipulating their catalytic properties for various practical applications. Herein, Fe SACs supported on nitrogen-doped carbon (SA-Fe/CN) are reported, which show high catalytic reactivity (97% degradation of bisphenol A in only 5 min), high stability (80% of reactivity maintained after five runs), and wide pH suitability (working pH range 3-11) toward Fenton-like reactions. The roles of different N species in these reactions are further explored, both experimentally and theoretically.

Room-Temperature Ferromagnetism at an Oxide-Nitride Interface.

Heterointerfaces have led to the discovery of novel electronic and magnetic states because of their strongly entangled electronic degrees of freedom. Single-phase chromium compounds always exhibit antiferromagnetism following the prediction of the Goodenough-Kanamori rules. So far, exchange coupling between chromium ions via heteroanions has not been explored and the associated quantum states are unknown.

Electronic-structure evolution of SrFeOduring topotactic phase transformation.

Oxygen-vacancy-induced topotactic phase transformation between the ABObrownmillerite structure and the ABOperovskite structure attracts ever-increasing attention due to the perspective applications in catalysis, clean energy field, and memristors. However, a detailed investigation of the electronic-structure evolution during the topotactic phase transformation for understanding the underlying mechanism is highly desired. In this work, multiple analytical methods were used to explore evolution of the electronic structure of SrFeOthin films during the topotactic phase transformation.

Strong Ferromagnetism Achieved via Breathing Lattices in Atomically Thin Cobaltites.

Low-dimensional quantum materials that remain strongly ferromagnetic down to monolayer thickness are highly desired for spintronic applications. Although oxide materials are important candidates for the next generation of spintronics, ferromagnetism decays severely when the thickness is scaled to the nanometer regime, leading to deterioration of device performance. Here, a methodology is reported for maintaining strong ferromagnetism in insulating LaCoO (LCO) layers down to the thickness of a single unit cell.

Strain-Mediated High Conductivity in Ultrathin Antiferromagnetic Metallic Nitrides.

Strain engineering provides the ability to control the ground states and associated phase transition in epitaxial films. However, the systematic study of the intrinsic character and strain dependency in transition-metal nitrides remains challenging due to the difficulty in fabricating stoichiometric and high-quality films. Here the observation of an electronic state transition in highly crystalline antiferromagnetic CrN films with strain and reduced dimensionality is reported.

Electronic structure variations of polar and nonpolar ZnO lattices with nitrogen-ion bombardment using synchrotron-based in situ photoemission and X-ray absorption spectroscopy.

Surface polarity with different crystal orientations has been demonstrated as a crucial parameter in determining the physical properties and device applications in many transition metal oxide and semiconductor compound systems. The influences of surface polarity on electronic structures in nitrogen-incorporated ZnO lattices have been investigated in the present work. The successful doping of nitrogen atoms in ZnO lattices is suggested by the existence of N-related chemical bonds obtained from X-ray photoelectron spectroscopy analysis where a pronounced N-Zn peak intensity has been observed in the (000\bar 1)-terminated polar ZnO compound compared with the (10\bar 10)-terminated nonpolar ZnO compound.

Interaction between the Non-Fullerene Acceptor ITIC and Potassium.

Using density functional theory calculations and photoemission measurements, we have studied the interaction between the non-fullerene small-molecule acceptor ITIC and K atoms (a representative of reactive metals). It is found that the acceptor-donor-acceptor-type geometric structure and the electronic structure of ITIC largely decide the interaction process. One ITIC molecule can combine with more than 20 K atoms.

Evidence of Topological Edge States in Buckled Antimonene Monolayers.

Two-dimensional topological materials have attracted intense research efforts owing to their promise in applications for low-energy, high-efficiency quantum computations. Group-VA elemental thin films with strong spin-orbit coupling have been predicted to host topologically nontrivial states as excellent two-dimensional topological materials. Herein, we experimentally demonstrated for the first time that the epitaxially grown high-quality antimonene monolayer islands with buckled configurations exhibit significantly robust one-dimensional topological edge states above the Fermi level.

Synchrotron X-ray Absorption Spectroscopy Study of Local Structure in Al-Doped BiFeO Powders.

The Al-doped BiFeO, i.e., BFAO powder samples with x = 0, 0.

Synthesis of NiO Nanotubes via a Dynamic Thermal Oxidation Process.

Nickel oxide (NiO) nanotubes were synthesized via a thermal oxidation process from Ni nanowires. The effects of oxidation temperature on the morphology, microstructures, and composition of nanowires were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results show that the Ni nanowires convert initially to Ni/NiO core-shell nanowires with increasing annealing temperatures, and then to the nanotubes at the critical transition temperature of about 425 °C.

Proposal for a photoelectron spectroscopy and microscopy beamline (0.5-11 keV) at the High Energy Photon Source.

An optical design study of a beamline proposed for the new 6 GeV synchrotron, the High Energy Photon Source (HEPS), to be built in Beijing, China, is described. The beamline is designed to cover an energy range from 0.5 to 11 keV with two experimental stations, one for X-ray photoelectron spectroscopy (PES) experiments and the other for photoelectron emission microscopy (XPEEM) experiments.

Strain-Enhanced Charge Transfer and Magnetism at a Manganite/Nickelate Interface.

The strain effect on charge transfer in correlated oxide LaSrMnO/NdNiO (LSMO/NNO) heterostructures is investigated. This is achieved by carefully tailoring the strain on the two layers using various substrates. In contrast to bare LSMO films, the strain dependence of the enhanced magnetic moment of the LSMO/NNO bilayers strongly suggests that the charge transfer can be controlled via strain engineering in complex oxide heterostructures.

The formation of (NiFe)S pyrite mesocrystals as efficient pre-catalysts for water oxidation.

Designing intricate structures and searching for functional materials has attracted wide interest in nanoscience. Herein we have fabricated (NiFe)S pyrite mesocrystals in the form of nearly-single crystalline porous cubes, and studied their self-optimization to realize efficient activity toward water oxidation under electrochemical conditions. The growth mechanism of the mesocrystals was a non-classical mechanism, which was initiated by the formation of a large quantity of small nickel sulfide clusters, followed by the aggregation and transformation of these small clusters in an oriented manner.

Epitaxially grown monolayer VSe: an air-stable magnetic two-dimensional material with low work function at edges.

Recent experimental breakthroughs open up new opportunities for magnetism in few-atomic-layer two-dimensional (2D) materials, which makes fabrication of new magnetic 2D materials a fascinating issue. Here, we report the growth of monolayer VSe by molecular beam epitaxy (MBE) method. Electronic properties measurements by scanning tunneling spectroscopy (STS) method revealed that the as-grown monolayer VSe has magnetic characteristic peaks in its electronic density of states and a lower work-function at its edges.

Manipulating the Structural and Electronic Properties of Epitaxial SrCoO Thin Films by Tuning the Epitaxial Strain.

Structure determines material's functionality, and strain tunes the structure. Tuning the coherent epitaxial strain by varying the thickness of the films is a precise route to manipulate the functional properties in the low-dimensional oxide materials. Here, to explore the effects of the coherent epitaxial strain on the properties of SrCoO thin films, thickness-dependent evolutions of the structural properties and electronic structures were investigated by X-ray diffraction, Raman spectra, optical absorption spectra, scanning transmission electron microscopy (STEM), and first-principles calculations.

Epitaxial Growth of Flat Antimonene Monolayer: A New Honeycomb Analogue of Graphene.

Group-V elemental monolayers were recently predicted to exhibit exotic physical properties such as nontrivial topological properties, or a quantum anomalous Hall effect, which would make them very suitable for applications in next-generation electronic devices. The free-standing group-V monolayer materials usually have a buckled honeycomb form, in contrast with the flat graphene monolayer. Here, we report epitaxial growth of atomically thin flat honeycomb monolayer of group-V element antimony on a Ag(111) substrate.

Epitaxial Growth and Air-Stability of Monolayer Antimonene on PdTe.

Monolayer antimonene is fabricated on PdTe by an epitaxial method. Monolayer antimonene is theoretically predicted to have a large bandgap for nanoelectronic devices. Air-exposure experiments indicate amazing chemical stability, which is great for device fabrication.

Electronic structure evolution of single bilayer Bi(1 1 1) film on 3D topological insulator Bi2Se x Te3-x surfaces.

The electronic state evolution of single bilayer (1BL) Bi(1 1 1) deposited on three-dimensional (3D) Bi2Se x Te3-x topological insulators at x  =  0, 1.26, 2, 2.46, 3 is systematically investigated by angle-resolved photoemission spectroscopy (ARPES).

Spontaneous Formation of a Superconductor-Topological Insulator-Normal Metal Layered Heterostructure.

2D materials with heterolayered structures beyond graphene are explored. A theoretically predicted superconductor-topological insulator-normal metal heterolayered structure is realized experimentally. The generated hybrid structure HfTe3 /HfTe5 /Hf has potential applications in both quantum-spin Hall effect-based and Majorana-based devices.

Data analysis method to achieve sub-10 pm spatial resolution using extended X-ray absorption fine-structure spectroscopy.

Obtaining sub-10 pm spatial resolution by extended X-ray absorption fine structure (EXAFS) spectroscopy is required in many important fields of research, such as lattice distortion studies in colossal magnetic resistance materials, high-temperature superconductivity materials etc. However, based on the existing EXAFS data analysis methods, EXAFS has a spatial resolution limit of π/2Δk which is larger than 0.1 Å.

Tailoring of polar and nonpolar ZnO planes on MgO (001) substrates through molecular beam epitaxy.

Polar and nonpolar ZnO thin films were deposited on MgO (001) substrates under different deposition parameters using oxygen plasma-assisted molecular beam epitaxy (MBE). The orientations of ZnO thin films were investigated by in situ reflection high-energy electron diffraction and ex situ X-ray diffraction (XRD). The film roughness measured by atomic force microscopy evolved as a function of substrate temperature and was correlated with the grain sizes determined by XRD.