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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 T C. Interestingly, the direction of the induced moment in the superconductors was unexpectedly parallel to that in the ferromagnet, which contrasts with earlier findings in S/F heterostructures based on metals or oxides. First-principles calculations verified that the unusual interfacial spin texture observed in our study was caused by the Heisenberg direct exchange coupling with constant J∼4.28 meV through d -orbital overlapping and severe charge transfer across the interfaces. Our work establishes an incisive experimental probe for understanding the magnetic proximity behavior at S/F interfaces and provides a prototype epitaxial 'building block' for superconducting spintronics. [ABSTRACT FROM AUTHOR]

High‐density magnetic memories are essential components for spintronics, quantum computing, and energy‐efficient electronics. Miniaturization of magnetic storage units requires reduced dimensionality and magnetic domain stability at the nanoscale. However, inducing magnetic order and selectively tuning spin‐orbital coupling at specific locations is challenging. Here, an unprecedented approach is demonstrated to construct switchable magnetic nanoislands in a nonmagnetic matrix based on cobaltite homostructures. The magnetic and electronic states are laterally modified by epitaxial strain, which is regionally controlled by freestanding membranes. Tensile‐strained cobaltite layers exhibit ferromagnetic properties, while compressively strained cobaltite layers exhibit a small magnetic response to applied fields. The minimum size of magnetic nanoislands reaches ≈35 nm in diameter, suggesting the highest possible areal density can reach upto ≈400 Gbit/in2. This methodology provides an ideal platform for precisely controlled read/write schemes and enables scalable and patterned memories on silicon and flexible supports for various applications. [ABSTRACT FROM AUTHOR]

(Mg,Zn)O films with various growth orientations were prepared on the MgO substrates with different surface structures using oxygen plasma‐assisted molecular beam epitaxy. X‐ray diffraction (XRD) revealed that the crystallographic orientation of (Mg,Zn)O thin films transforms from the polar c‐plane (0001) to a two‐fold‐symmetry inclined plane and then to the nonpolar m‐plane (10–10) as the substrate template changes from MgO(111) to MgO(011) and then to MgO(001). In addition, the surface topography and film roughness were monitored by atomic force microscopy. Interestingly, the electronic structures of the three films exhibited orientation‐dependent features, as revealed by synchrotron‐based X‐ray absorption spectroscopy. In addition, all of the (Mg,Zn)O thin films showed high optical transmittance (over 85%, 400–800 nm) and large energy gaps (around 3.33 eV). Our systematic study of the substrate‐influenced film characteristics demonstrates a method of tailoring thin films using the same substrate with different crystallographic orientations. [ABSTRACT FROM AUTHOR]

Electronic phase transition in strongly correlated materials is extremely sensitive to the dimensionality and crystallographic orientations. Transition metal nitrides (TMNs) are seldom investigated due to the difficulty in fabricating high-quality and stoichiometric single crystals. In this Letter, we report the epitaxial growth and electronic properties of CrN films grown on different-oriented NdGaO3 (NGO) substrates. Astonishingly, CrN films grown on (110)-oriented NGO substrates maintain a metallic phase, whereas the CrN films grown on (010)-oriented NGO substrates are semiconducting. We attribute the unconventional electronic phase transitions in CrN films to the strain effects. The effective modulation of bandgap by the anisotropic strain triggers the metal-to-insulator transition consequently. This work provides a convenient approach to modify the electronic ground states of functional materials using anisotropic strain and further stimulates the investigations of TMNs. [ABSTRACT FROM AUTHOR]

Oxygen vacancies in transition-metal oxides can facilitate photocatalysis activity critical for environmental remediation and solar energy conversion. Investigation of photocatalytic activity of TiO2 with different amounts of the oxygen vacancies can provide fundamental insights into the oxygen-vacancy-dependent reaction mechanisms. Here, the oxygen vacancies in TiO2 nanoparticles were investigated by the combination of transmission electron microscopy with electron energy loss spectra, x-ray near-edge structures, and x-ray absorption techniques. The results demonstrate that the oxygen vacancies mainly exist at the surface of TiO2 and the crystalline structure of TiO2 almost keeps no change during annealing under the different oxygen pressures at 500 °C. The exact quantity and distribution of the oxygen vacancies in TiO2 nanoparticles were obtained. The surface oxygen vacancies on TiO2 significantly enhance photocatalytic activity for Rhodamine B degradation and hydrogen generation. The formation of oxygen vacancies at the TiO2 surfaces is responsible for engineering the band gap of TiO2 and tailoring their electronic structures, and promoting light absorption and enhancement photocatalysis. This work could provide new insights into the understanding of the photocatalytic activity enhancement by the surface oxygen vacancies. [ABSTRACT FROM AUTHOR]

We report the epitaxial growth of monolayer copper arsenide (CuAs) with a honeycomb lattice on Cu(111) by molecular beam epitaxy (MBE). Scanning tunneling microscopy (STM), low energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) verify the superlattice of monolayer CuAs on Cu(111) substrate. Angle-resolved photoemission spectroscopy (ARPES) measurements together with DFT calculations demonstrate the electronic band structures of monolayer CuAs and reveal its metallic nature. Further calculations show that charge transfer from Cu(111) substrate to monolayer CuAs lifts the Fermi level and tunes the band structure of the monolayer CuAs. This high-quality epitaxial monolayer CuAs with potential tunable band gap holds promise on the applications in nano-electronic devices. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials are playing more and more important roles in both basic sciences and industrial applications. For 2D materials, strain could tune the properties and enlarge applications. Since the growth of 2D materials on substrates is often accompanied by strain, the interaction between 2D materials and substrates is worthy of careful attention. Here we demonstrate the fabrication of strained monolayer silver arsenide (AgAs) on Ag(111) by molecular beam epitaxy, which shows one-dimensional stripe structures arising from uniaxial strain. The atomic geometric structure and electronic band structure are investigated by low energy electron diffraction, scanning tunneling microscopy, x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy and first-principle calculations. Monolayer AgAs synthesized on Ag(111) provides a platform to study the physical properties of strained 2D materials. [ABSTRACT FROM AUTHOR]

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 ()‐terminated polar ZnO compound compared with the ()‐terminated nonpolar ZnO compound. An energy shift of the valence band maximum towards the Fermi level has been resolved for both polar and nonpolar ZnO lattices, whereas a charge redistribution of the O 2p hybridized states is only resolved for o‐plane ZnO with a polar surface. Angular‐dependent X‐ray absorption analyses at the O K‐edge reveal enhanced surface‐state contributions and asymmetric O 2p orbital occupations in the ()‐terminated o‐plane ZnO compound. The results shed light on the efficient nitrogen doping in ZnO lattices with polar surfaces. The comprehensive electronic structure investigations of correlations between impurity doping and surface polarity in ZnO lattices may also offer guidance for the material design in other transition metal oxide and semiconductor systems. [ABSTRACT FROM AUTHOR]

Charge transfer dynamics across the lying-down 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) organic semiconductor molecules on Au(111) interface has been investigated using the core-hole clock implementation of resonant photoemission spectroscopy. It is found that the charge transfer time scale at the PTCDA/Au(111) interface is much larger than the C 1s core-hole lifetime of 6 fs, indicating weak electronic coupling between PTCDA and the gold substrate due to the absence of chemical reaction and/or bonding. [ABSTRACT FROM AUTHOR]

Antimonene is a recently discovered two-dimensional semiconductor with high carrier mobility, suitable bandgap, and strong spin–orbit coupling, which is of great interest for future electronic, optoelectronic, and spintronics device applications. However, as the basic properties of materials, the electronic structure of antimonene is not fully understood. In this work, the whole and anisotropic electronic structures of antimonene modulated by a horizontal crystal field have been studied in detail by angle-resolved photoemission spectroscopy. The valence band of antimonene for semiconductor properties is characterized by a three-dimensional anisotropic "M"-shape with hexagonal deformation in (E, kx, ky) space. Moreover, the surface state of antimonene for metallic properties is characterized by an upward conelike structure with a stronger warping effect. The anisotropic electronic structure of antimonene is systematically depicted along the high symmetric direction and constant energy contours. [ABSTRACT FROM AUTHOR]

The electronic structure of PC61BM film on clean Ag(100) and Ag(111) surfaces has been measured with photoemission spectroscopy. The interfaces are chemisorption. It is necessary to combine the two sub-interfaces model and the integer charge transfer model for thoroughly understanding the interfacial electronic structure. The electron injection barrier can then be determined without inverse photoemission measurements, and the PC61BM/Ag(111) system is found to be ohmic contact for electron transport. The analysis method should be applicable to many other organic/metal interfaces. [ABSTRACT FROM AUTHOR]

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. A 5 m APPLE II‐type undulator with a relatively long magnetic period (55 mm) is used as the only radiation source. To optimize the optical efficiency for the full energy range, the beamline is split into a soft X‐ray branch that is based on a variable‐line‐spacing plane‐grating monochromator and a tender X‐ray branch that uses a four‐bounce monochromator with three Si channel‐cut pairs. To allow both PES and XPEEM to be performed over the entire energy range, two toroidal mirrors and a bendable KB mirror pair are employed to deliver the soft and tender beams, respectively, to either of two experimental stations. A two‐color beamline (0.5–11 keV) using only one source (5 m APPLE II), allowing two stations (PES and PEEM) over the entire energy range and proposed for the High Energy Photon Source (HEPS) to be built in Beijing, China, is described. [ABSTRACT FROM AUTHOR]

2D materials with anisotropic symmetry are likely, in general, to possess strain that is artificially adjustable in a single direction, inspiring strategies of artificial regulation of local structures and related properties. Herein, strain‐induced wrinkles in an anisotropic 2D transition‐metal‐trichalcogenide HfTe3 film are fabricated and illustrated for the first time. The corresponding localized electronic structures in the 1D corrugated wrinkles are revealed by a combination of experiment and simulation. The wrinkled HfTe3 film probably features electrical transport properties never before seen and useful for developing wrinkle‐based heterojunctions for novel nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Mixed-valence manganites gain increasing attentions thanks to their extraordinary properties including half-metallicity and colossal magnetoresistive response, rendering them ideal candidate for oxide spintronics applications. Oxygen vacancies in oxides have been approved to be important functional defects and are effective to manipulating their multifunctional properties. To gain a deep insight into the roles of oxygen vacancies on regulating the atomic structure and electronic properties of the mixed-valence manganites, two high-quality epitaxial La2/3Sr1/3MnO3 films around a critical point (without/with oxygen vacancies) were designed and fabricated. From the experiments and theoretical calculations, it was found that the oxygen vacancies induce a weakening of Mn-O-Mn hybridized bond and an increase of concentration of Mn3+ ions, impair the double exchange between Mn3+ and Mn4+, and therefore lead to the transition from metal to insulator and the degraded magnetic properties. Our finding demonstrates a practical approach to tune the magnetic and transport properties of oxide thin films by precisely controlling the oxygen vacancies for high performance spintronics applications. [ABSTRACT FROM AUTHOR]

The article discusses a study that demonstrates that the electronic phase of manganite films was successfully manipulated by the interfacial electrochemistry route using ionic liquids (IL) gating. The transition temperature of the usual metal to insulator transition in LSMO films becomes lower with longer gating time, and a novel insulator to metal transition in LSMO films could be achieved at low temperature after applying a small gate voltage.

Fe-doped ZnO film has been grown by laser molecular beam epitaxy (L-MBE) and structurally characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), all of which reveal the high quality of the film. No secondary phase was detected. Resonant photoemission spectroscopy (RPES) with photon energies around the Fe 2p-3d absorption edge is performed to detect the electronic structure in the valence band. A strong resonant effect at a photon energy of 710 eV is observed. Fe3+ is the only valence state of Fe ions in the film and the Fe 3d electronic states are concentrated at binding energies of about 3.8 eV and 7 eV∼8 eV. There are no electronic states related to Fe near the Fermi level. Magnetic measurements reveal a typical superparamagnetic property at room temperature. The absence of electronic states related to Fe near the Fermi level and the high quality of the film, with few defects, provide little support to ferromagnetism. [ABSTRACT FROM AUTHOR]

The Al-doped BiFeO3, i.e., BFAxO powder samples with x = 0, 0.025, 0.05, and 0.1, were prepared via the hydrothermal route. The effects of Al substitution on the structural, electrical, and optical properties of BFAxO samples were investigated. It is found that the substitution of Al ions at B-site of BiFeO3 did not cause structural change and it still retains the rhombohedral perovskite structure with R3c symmetry, which was confirmed by the X-ray diffraction (XRD) and Raman measurements. X-ray absorption fine structure (XAFS) above the Fe K-edge and Bi L3-edge in BFAxO powders was also measured and analyzed. Fe ions exhibit mixed valence states (Fe2+/Fe3+) while Bi ions keep the + 3 valence state in all the samples. Fe K-edge XAFS also indicated that there was a competition between hybridization of Fe 3d and Al 3d with O 2p orbitals and occurrence of the more 4p orbitals with Al doping. The Bi L3-edge XAFS revealed that transition from 2p3/2 to 6d state increased, so did the energy of 6d state. Besides, Al ion doping affected both the nearest-neighbor and next-nearest coordination shells of Fe atom and nearest-neighbor shells of Bi atom. Ultraviolet-visible (UV-Vis) spectroscopy results show the BFAxO prepared by hydrothermal method could be an appropriate visible-light photocatalytic material. [ABSTRACT FROM AUTHOR]

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. Our findings provide useful information for the preparation of NiO nanotubes to meet the required applications. [ABSTRACT FROM AUTHOR]

The effect of temperature on the electronic structure of Nb-doped SrTiO3 (100) surface is investigated by high-resolution synchrotron radiation photoemission spectroscopy. According to the x-ray photoemission spectroscopy (XPS) results, at an annealing temperature of less than 700 °C, the adsorbed carbon and hydroxyl on the STO surface could be removed, to expose the fresh intrinsic surface with a constant ratio of Ti/O. It is obvious that the STO would be doped by Ca+ impurities of bulks and O vacancies in the surface after annealing at 920 °C for one hour. [ABSTRACT FROM AUTHOR]

Silicon nanopillars are fabricated by inductively coupled plasma (ICP) dry etching with the cesium chloride (CsCl) islands as masks originally from self-assembly. Wafers with nanopillar texture or planar surface are subjected to phosphorus (P) diffusion by liquid dopant source (POCl3) at 870 °C to form P—N junctions with a depth of 300 nm. The X-ray photoelectron spectroscopy (XPS) is used to measure the Si 2p core levels of P—N junction wafer with nanopillar texture and planar surface. With a visible light excitation, the P—N junction produces a new electric potential for photoelectric characteristic, which causes the Si 2p core level to have a energy shift compared with the spectrum without the visible light. The energy shift of the Si 2p core level is −0.27 eV for the planar P—N junction and −0.18 eV for the nanopillar one. The difference in Si 2p energy shift is due to more space lattice defects and chemical bond breaks for nanopillar compared with the planar one. [ABSTRACT FROM AUTHOR]

Abstract: Zn0.95Co0.05O and Zn0.91Co0.05Cu0.04O thin films were fabricated on Si (111) substrate by the reactive magnetron sputtering method at different O-Ar ratios. Detailed characterizations by X-ray diffractometry (XRD), X-ray photo-electronic spectrum (XPS), and electron paramagnetic resonance (EPR) indicate that the doped Cu ions substitute the Zn2+ ions in the ZnO lattice. The doped Cu ions are in Cu+ and Cu2+ mixture valence states. The ferromagnetism of the Zn0.91Co0.05Cu0.04O film increases gradually the increasing Cu+ ions concentration. The results indicate that the increase of ferromagnetism is not owing to the magnetic contribution of Cu+ ions themselves, but owing to the enhancement of magnetic interaction between Co ions, which suggests that p-type doping of Cu+ ions plays an important role in mediating the ferromagnetic coupling between Co ions. [Copyright &y& Elsevier]