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Transition metal oxides with insulator-metal transitions (IMTs) are uniquely suited for volatile memristor devices that mimic the spiking of biological neurons. Unlike most non-volatile memristors, which often operate via ion migration into filaments, volatile devices utilize a reversible phase change that returns to a ground state in the absence of applied stimulus. In these devices, Joule heating triggers the IMT and changes the bulk resistivity rather than influencing conduction through defects, as in previous studies. This volatile resistive switching behavior has previous been leveraged in niobium and vanadium oxides, but not in rare-earth nickelates, despite their tunable transition temperatures. This study demonstrates an electrically driven IMT in the prototypical rare-earth nickelate, NdNiO3, in large area devices. While previous work examining the electrically-driven IMT in NdNiO3 suggests defect-dominated conduction, this study shows clear s-type negative differential resistance (NDR) consistent with temperature-dependent resistivity measurements. The NDR peak-to-valley voltage scales linearly with temperature as expected for conductivity pathways dominated by bulk IMT behavior. Unlike other transition metal oxides, which are modeled using the insulator-metal phase fraction as the internal state variable, a thermoelectric model with temperature as the internal state variable is found to more accurately describe the current–voltage characteristic of NdNiO3 volatile memristors. Overall, we report the synthesis, fabrication, and characterization of NdNiO3 volatile memristors with resistivity dominated by bulk-like IMT behavior which is scalable and not dependent upon oxygen vacancy migration or defect mediated conduction pathways. [ABSTRACT FROM AUTHOR]

We report the growth of La2O2Bi epitaxial thin films for the first time by utilizing multilayer solid-phase epitaxy. The films were grown only on a MgO(001) substrate among several oxide and fluoride substrates under a quite narrow growth window. A nearly stoichiometric La2O2Bi epitaxial thin film possessed a metallic ground state according to optical and electrical measurements. The hole mobility of 20.8 cm2 V–1 s–1 at 10 K was three times as high as that of the La2O2Bi bulk polycrystal due to reduced grain boundary scattering. The small Hall coefficient and temperature-induced carrier inversion suggest a semimetallic nature of La2O2Bi. [ABSTRACT FROM AUTHOR]

Layered oxyfluoride single-crystalline thin films of Sr2RuO3F2, Ca2RuO2.5F2, and Sr2IrO2.5F3 were fabricated via topochemical fluorination. All the fluorinated films exhibited an insulating behavior and a largely expanded c-axis than the precursors. Sr2RuO3F2 film was a Mott insulator with Ru4+ states and had two inequivalent F- sites in the SrO layers. In contrast, Ca2RuO2.5F2 film had the Ru3+ state and only one F- site in the CaO rock-salt blocks. This discrepancy is probably due to the larger lattice distortion in the Ca2RuO4 precursor. The conduction mechanism of Ca2RuO2.5F2 film was described by two-dimensional variable range hopping. The effective total angular momentum Jeff＝3/2 of Sr2IrO2.5F3 film was stabilized upon fluorination owing to the large electronegativity of fluorine. The conduction mechanism of Sr2IrO2.5F3 film was described by Efros-Shklovskii variable-range hopping. These results will be useful for modifying electronic states by anion doping to explore unprecedented electronic properties in layered oxides. [ABSTRACT FROM AUTHOR]

New properties and exotic quantum phenomena can form due to periodic nanotextures, including Moire patterns, ferroic domains, and topologically protected magnetization and polarization textures. Despite the availability of powerful tools to characterize the atomic crystal structure, the visualization of nanoscale strain-modulated structural motifs remains challenging. Here, we develop nondestructive real-space imaging of periodic lattice distortions in thin epitaxial films and report an emergent periodic nanotexture in a Mott insulator. Specifically, we combine iterative phase retrieval with unsupervised machine learning to invert the diffuse scattering pattern from conventional X-ray reciprocal-space maps into real-space images of crystalline displacements. Our imaging in PbTiO3/SrTiO3 superlattices exhibiting checkerboard strain modulation substantiates published phase-field model calculations. Furthermore, the imaging of biaxially strained Mott insulator Ca2RuO4 reveals a strain-induced nanotexture comprised of nanometer-thin metallic-structure wires separated by nanometer-thin Mott-insulating-structure walls, as confirmed by cryogenic scanning transmission electron microscopy (cryo-STEM). The nanotexture in Ca2RuO4 film is induced by the metal-to-insulator transition and has not been reported in bulk crystals. We expect the phasing of diffuse X-ray scattering from thin crystalline films in combination with cryo-STEM to open a powerful avenue for discovering, visualizing, and quantifying the periodic strain-modulated structures in quantum materials. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of a ferroelectric perovskite‐type oxide grown on single‐crystalline SrTiO3 (100) were transferred onto a flexible printed circuit (FPC). In the case that the thin films were directly adhered onto FPC using a copper foil double‐coated conductive adhesive tape (Cu double‐sided tape), serious cracking and exfoliation occurred during the transfer process. To avoid these damages, we have tried to insert a metal buffer layer with excellent ductility between the ferroelectric oxide thin film and the Cu double‐sided tape. The platinum buffer layer was found to be appropriate to establish a crack‐ and exfoliation‐free transfer process. [ABSTRACT FROM AUTHOR]

High-performance ordered arrays of nanostructure has attracted significant attention due to the needs for miniaturization in electronic and spintronic devices. However, the traditional templete-assisted method often entails expensive equipment and complicated processing. Herein, a series of high quality LiFe 5 O 8 (LFO) arrays are obtained by chemically etching the MgO phase in the self-assembly (LFO) 1 :(MgO) x nanocomposite films. The LFO arrays show excellent epitaxial quality and nano-island or nano-pillar morphology, which can be easily fabricated by controlling the thickness and chemical component of the grown nanocomposite films. In comparison with the LFO planar film, the LFO nanopillar arrays exhibit higher saturation magnetization, lower non-zero coercivity and remanence. Moreover, the morphology of the nanostructures can effectively modulate the ferromagnetic resonance spectra of the LFO nanopillar arrays, which can be explained by the calculated demagnetization field. This work shows that nanostructure engineering is very useful to modulate the magnetic properties and to design compact microwave magnetism devices. [ABSTRACT FROM AUTHOR]

• Epitaxial anatase-type Nb:TiO 2 (TNO) thin films were transferred to flexible sheet. • Cracks were generated in epitaxial TNO thin films made using an earlier process. • The formation of cracks is attributed to the relaxation of epitaxial strain. • Use of the ductile polymer SU-8 3050 greatly inhibited cracking. • Electrical conductivity of epitaxial TNO thin films with fewer cracks was improved. This work developed a technique for fabricating flexible epitaxial thin films of anatase-type Nb:TiO 2 (epitaxial TNO) via a transfer process. In our prior work, epitaxial TNO deposited on LaAlO 3 (001) single crystal substrates was lifted off and affixed to flexible polymeric sheets. However, many cracks occurred on the surfaces of the transferred thin films, such that the conductivity of the epitaxial TNO was drastically decreased. This loss of conductivity was attributed to the interruption of current paths by the cracks. These numerous cracks were linear and in most cases were oriented either parallel to the [ 100 ] anatase ∥ [ 100 ] LAO direction or parallel to the [ 010 ] anatase ∥ [ 010 ] LAO direction (where the subscripts anatase and LAO represent the materials for each Miller index). Therefore, cracking likely occurred as a consequence of the relaxation of epitaxial strain and a return to the original axial lengths of the TNO during the transfer process. In the present work, the surface of epitaxial TNO was coated with the ductile polymer SU-8 3050 as a relaxation absorber prior to the transfer. This modified transfer process greatly reduced crack formation in the TNO such that the conductivity of the thin film was improved by two orders of magnitude. Thus, pre-coating with a ductile relaxation absorber was shown to effectively suppress the cracking of flexible epitaxial TNO. [ABSTRACT FROM AUTHOR]

• Epi-Si growth on epi-Gd2O3/Si(111) virtual substrate using RF sputtering. • Pole figure and Transmission electron microscopy confirm Si epitaxy. • Lower Si thickness and higher capping deposition time facilitate epitaxial growth. • Wafer-scale epi-Si growth on epi-Gd2O3/Si(111) substrate for SOI Application. Silicon on Insulator (SOI) technology has been the promising solution for the On-chip low-power mixed-signal systems. However, the traditional smart-cut method for SOI wafer fabrication is costly. Hence, in this work, we present an optimized methodology to fabricate a wafer scale single-crystalline Si on epitaxial Gd 2 O 3 /Si(111) substrate (SOXI) using a low-cost, high volume manufacturable (HVM)-friendly Radio Frequency magnetron sputtering technique for SOI application. The grown Si and Gd 2 O 3 layers are physically characterized using high-resolution X-ray Diffraction and high-resolution Transmission Electron Microscopy (HRTEM). The Grazing Incidence X-ray Diffraction, Pole Figure, and HRTEM imaging confirm the formation of an epitaxial Top-Si layer on the epitaxial-Gd 2 O 3 /Si(111) substrate. Hence, we demonstrate a low-cost, HVM-friendly technique for the fabrication of SOXI wafers. [ABSTRACT FROM AUTHOR]

Epitaxially orthorhombic DyMnO3 films were deposited on Nb:SrTiO3 (100) substrates by pulsed laser deposition. DyMnO3 film with weakly ferromagnetic at low temperatures, probably resulting from the strained Mn-spin configuration in the ab plane, is observed. The dielectric change under the magnetic field from 0 to 9 T at around 16 K indicates the magnet-dielectric effect, which should be related with Mn3+ spin reorientation and magneto-elastically inducing lattice modulation under DM (Dzyaloshinsky-Moriya) interaction in perovskite rare-earth manganites RMnO3. [ABSTRACT FROM AUTHOR]

In the context of solid oxide fuel cells (SOFCs), vertically aligned nanocomposite (VAN) thin films have emerged as a leading material type to overcome performance limitations in cathodes. Such VAN films combine conventional cathodes like La x Sr 1- x Co y Fe 1- y O 3 (LSCF) and La 1-x Sr x MnO 3 (LSM) together with highly O 2- ionic conducting materials including yttria-stabilized zirconia (YSZ) or doped CeO 2 . Next-generation SOFCs will benefit from the exceptionally high ionic conductivity (1 S cm -1 at 730 °C) of Bi 2 O 3 -based materials. Therefore, an opportunity exists to develop Bi 2 O 3 -based VAN cathodes. Herein, we present the first growth and characterization of a Bi 2 O 3 -based VAN cathode, containing epitaxial La-doped Bi 2 O 3 (LDBO) columns embedded in a LSM matrix. Our novel VANs exhibit low area specific resistance (ASR) (8.3 Ω cm 2 at 625 °C), representing ∼3 orders of magnitude reduction compared to planar LSM. Therefore, by demonstrating a high-performance Bi 2 O 3 -based cathode, this work provides an important foundation for future Bi 2 O 3 -based VAN SOFCs.

MnxAl100-x and MnyGe100−y alloy epitaxial films of 20 nm thickness are prepared on Cr(001) single-crystal underlayers at 300 °C by varying the Mn content, $x$ or $y$ , from 0 to 100 at. %. The formation of crystallographic phase is systematically investigated as a function of composition by reflection high-energy electron and X-ray diffractions. The phases in MnxAl100−x and MnyGe100−y films are determined to vary in the orders of $A 1=> L 1_{0} + A 12=> L 1_{0} => A 2=> A12$ and $A 4=> tP => cP => D 0_{22} => A12$ with increasing the Mn content, respectively. Metastable fct-based ordered $L1$ 0 phase is formed in the MnxAl100−x films with $x $ = 50– $65. L1$ 0 single phase is obtained at an Mn-rich composition of $x $ = 58, whereas bcc-based disordered $A12$ and $A2$ phases are, respectively, involved at the $L1$ 0 stoichiometric composition of $x $ = 50 and at a more Mn-rich composition of $x $ = 65. Employment of a slight Mn-rich composition stabilizes $L1$ 0 phase. On the other hand, metastable fct-based ordered $D0$ 22 phase is formed in the MnyGe100−y films with $y$ = 60– $75. D0$ 22 single phase is obtained in the range from the stoichiometric composition of $y$ = 75 to a slightly Mn-poor composition of $y $ = 68. The $c$ -axis orientation is normal to the film surface for both $L1$ 0 and $D0$ 22 crystals. The present study has clarified the crystal structure and growth of MnxAl100−x and MnyGe100−y films for the respective full compositional ranges and has shown that control of the composition is important to obtain $L1$ 0 and $D0$ 22 ordered Mn-based alloy films with perpendicular magnetic anisotropies. [ABSTRACT FROM AUTHOR]

It has been proposed by Müller and Shengelaya that underdoped ultrathin layers of copper-oxide high-temperature superconductors (HTSs) sandwiched between high-dielectric-constant insulator layers could manifest increased superconducting critical temperature T c . To check this hypothesis, we investigated structural and transport properties of YBa 2 Cu 3 O 7 - δ (YBCO) thin films sandwiched between SrTiO 3 (STO) layers. Scanning transmission electron microscopy (STEM) showed that a high-quality interface is formed between YBCO and the top STO layers. An increase of T c up to Δ T ≈ 20 K was observed at these interfaces in case of underdoped YBCO films. [ABSTRACT FROM AUTHOR]

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• B2-phase formation in Fe(Cu)/Rh multilayers as a function of annealing temperature (T ann = 423–1023 K) on silica and MgO(001) substrates. • XRR and XRD analysis indicates the formation of B2-phase at T ann ≥ 673 K on both substrates. • The FeRh(Cu) films are polycrystalline on silica substrate, and a change in bulk-like to (001)-preferred orientation at T ann = 1023 K is observed. • Cu-doped FeRh films have good epitaxial quality with (001)-orientation on MgO(001) substrate. • The transition temperature during heating on silica and MgO(001) substrate is 209 K and 200 K, and is expected to reduce due to Cu-doping in FeRh. The structural and magnetic properties of [Fe(Cu){36 Å}/Rh{41 Å}] 20 multilayers on silica and MgO(001) substrates are examined as a function of annealing temperature (T ann). The multilayers are annealed in the temperature range of 423 K to 1023 K for 1 h in vacuum. X-ray reflectivity (XRR) and X-ray diffraction (XRD) measurements are used to study the inter-diffusion, phase evolution and B2-ordered alloy formation. XRR results indicate that the intermixing begins at 423 K and the multilayer periodicity is lost by 673 K, indicating the formation of FeRh(Cu) alloy. XRD measurements confirm the formation of B2-ordered FeRh(Cu) alloy phase at T ann ≥ 673 K on both silica and MgO(001) substrate supporting the XRR results. The FeRh(Cu) alloy film is polycrystalline on silica substrate, while films exhibit (001) preferred orientation on MgO(001) substrate. Rocking curves indicate the good epitaxial quality of the films. The film/substrate orientation relationship is FeRh(001)[1 1 ¯ 0] // MgO(001)[100] as determined using phi (ϕ) scans. M−T curves show a partial antiferromagnetic (AF) – ferromagnetic (FM) phase transition for both FeRh(Cu)/silica and FeRh(Cu)/MgO films annealed at 1023 K. The AF-FM transition temperature (T t) during heating for FeRh(Cu) thin films on silica and MgO(001) substrate is 209 and 200 K, respectively, indicating that doping of Cu in FeRh dramatically reduced T t. [ABSTRACT FROM AUTHOR]

The intimate coexistence of multiple phases in ferroelectrics has been shown to result in exotic electromechanical properties, such as giant piezoelectricity. Here, via a thickness‐driven phase transition, the phase coexistence and enhanced piezoelectricity in a few tens of nanometers thick, Pb‐free CaTiO3 films are demonstrated. Due to the competition between interfacial and bulk energies, as film thickness increases, epitaxial CaTiO3 films exhibit a ferroelectric‐to‐paraelectric phase transition that is concomitant with the rhombohedral‐to‐orthorhombic structural transition. This so‐called thickness‐driven morphotropic phase transition (MPT) in nanoscale CaTiO3 films stems from the metastable nature of ferroelectricity. The resulting morphotropic phase boundary at the atomic scale in nanoscale CaTiO3 films is visualized. It is also shown that this thickness‐driven MPT can lead to reasonably good piezoelectricity at the nanoscale. This study highlights the rich phase evolution of complex ferroelectrics as a novel platform to control the functionality of nanoscale electromechanical devices. [ABSTRACT FROM AUTHOR]

In the present work, full Heusler alloy (FHA) Co2FeSi (CFS) epitaxial thin films with thickness (tCFS) ranging from 5–25 nm were grown by Pulse laser deposition (PLD) on MgO (001)substrates at an optimized deposition temperature of 600°C. Dynamic magnetization response of PLD-grown CFS thin films was systematically investigated as a function of tCFS. Thickness-dependent structural and magnetic correlation exhibit a non-monotonic variation in Gilbert damping parameter, α. The ferromagnetic resonance (FMR) investigation revealed that the presence of lattice strain and a lower degree of atomic ordering in the thinner FHA CFS films, results in additional enhancement of α. The lowest α value of 4×10−3is obtained from the theoretical fit of experimental data in a 20 nm thick film. This low value of α is suitable in magnonic devices, such as spin-transfer torque magnetic random-access memories (STT-MRAMs) where an efficient spin injecting source from a FHA ferromagnet to a non-magnetic interface is required. Further, in-plane angle-dependent (φ-variation) FMR measurements of the sample yield an intrinsic four-fold magnetocrystalline anisotropy (MCA) along with the presence of uniaxial anisotropy that has non-monotonicity with tCFS. A significant value of cubic anisotropy constant of 5.16×105erg/cm3has been obtained in the film with a thickness of around 15nm. Further investigation suggests that uniaxial anisotropy in the CFS/MgO film is a combination of strain-induced magneto-elastic and interface-related contribution that is intrinsic in nature. The experimental observations have been verified by using micromagnetic simulations run on the epitaxial crystal structure. FMR mode position and linewidth of varied thickness CFS films are generated by micromagnetic simulations utilizing the Landau–Lifshitz–Gilbert formalism.

With the aim of developing new electronic functionalities for flexible devices, a transfer process for the preparation of flexible conductive thin films was examined using epitaxially grown anatase Nb: TiO2. Using pulsed laser deposition (PLD), water-soluble Sr3Al2O6 (SAO) was deposited on a single-crystalline LaAlO3 (100) substrate (LAO) as a sacrificial layer, followed by the epitaxial growth of anatase Nb: TiO2 on the sacrificial layer. The Nb: TiO2/SAO/LAO multilayer sample bonded onto a flexible polymer sheet via an adhesive tape was soaked into distilled water to transfer the epitaxially grown Nb: TiO2 thin film from SAO/LAO to the polymer sheet. The transferred anatase Nb: TiO2 thin film retained the clear X-ray diffraction peaks. Moreover, the areal transfer ratio was almost 100%, without the generation of significant impurity phases during the transfer process. On the basis of these results, the examined process was found promising for the preparation of flexible anatase Nb: TiO2 thin films. The voltage drop-current characteristics were measured successfully at room temperature for the transferred anatase Nb: TiO2 thin film using the standard four-probe method with gold electrodes. [ABSTRACT FROM AUTHOR]

Several photophysical properties of chromophores depend crucially on intermolecular interactions. Thermally‐activated delayed fluorescence (TADF) is often influenced by close packing of the chromophore assembly. In this context, the metal‐organic framework (MOF) approach has several advantages: it can be used to steer aggregation such that the orientation within aggregated structures can be predicted using rational approaches. We demonstrate this design concept for a DPA‐TPE (diphenylamine‐tetraphenylethylene) chromophore, which is non‐emissive in its solvated state due to vibrational quenching. Turning this DPA‐TPE into a ditopic linker makes it possible to grow oriented MOF thin films exhibiting pronounced green electroluminescence with low onset voltages. Measurements at different temperatures clearly demonstrate the presence of TADF. Finally, this work reports that the layer‐by‐layer process used for MOF thin film deposition allows the integration of the TADF‐DPA‐TPE in a functioning LED device. [ABSTRACT FROM AUTHOR]

Spinel lithium ferrite LiFe 5 O 8 (LFO) has attracted robust research interests due to their potential applications in isolators, circulators, and phase shifters. In this work, a series of LFO thin film with various thickness were fabricated on SrTiO 3 (STO) single-crystalline substrates by pulsed laser deposition technology. We systematically investigated the influences of the thickness of LFO thin film on the crystal structure and magnetic properties. The in-plane lattice parameter a and in-plane lattice parameter c were modulated by controlling the thickness of LFO thin film, which was confirmed using reciprocal space mappings (RSMs) technology. Furthermore, the microwave magnetism of LFO thin film with various thickness were studied systematically by ferromagnetic resonance (FMR) measurement. Moreover, with increasing the thickness of LFO thin film from 50 to 180 nm, the difference of the ferromagnetic resonance field between easy- and hard-magnetization axis can be enhanced and reach to 330 Oe. These results illustrate that dynamic magnetic properties can be controlled by tuning the thickness of LFO thin film. Our work provides an effective method to tailor the lattice parameter and modify the magnetic properties of the LFO thin film and contributes to further design high-frequency functional device. Image 1 • A series of LFO thin film with various thickness were fabricated by PLD technique. • The microwave magnetism of LFO thin film was studied by using FMR measurement. • The thickness can affect lattice parameter and magnetic property of LFO thin film. [ABSTRACT FROM AUTHOR]

Semiconductor photocatalysis has two important applications: environmental remediation and H2 production. Bismuth vanadate has attracted great interests as an ideal candidate for use as high-performance photocatalysts for visible light-driven water splitting and photoanode in photoelectrochemical cells. Single crystal film is invaluable to deepen the fundamental understanding of materials. The object of this article was to provide a brief review on the advances in the preparation of epitaxial BiVO4 thin film, the physical and photoelectrochemical properties. The epitaxial BiVO4 thin film could be fabricated on (001) yttria-stabilized cubic zirconia or SrTiO3(001) by molecular beam epitaxy, chemical vapor deposition, and, pulsed laser deposition. Three crystal structures, namely, monoclinic scheelite, monoclinic clinobisvanite, and orthorhombic, were mentioned in the literatures. The optical band gap was reported to be 2.5~2.7 eV for a direct transition. The highest photocurrent of 4.83 mA cm−2at 1.23 V vs. the RHE was obtained at the sample with Lu2O3 as a hole blocking layer. [ABSTRACT FROM AUTHOR]

• Highly oriented crystalline si on epi‑Gd2O3/Si(111) substrate by RF sputtering. • At 850oC annealing, epi‑regrowth at Gd2O3/Si interface improves Gd2O3 crystallinity. • 850oC annealing fuses smaller Si grains into larger ones, enhancing crystallinity. • Low-cost technique for the fabrication of Silicon-on-Insulator technology. Silicon-on-Insulator (SOI) technology has been the center of attraction with the advancement in Radio Frequency (RF) technology and the advent of Internet-of-Things due to its low-power operation with reduced parasitic and short-channel effects. However, the state-of-the-art smart-cut method used for the SOI wafer is costly. Alternatively, the notion of using the Si channel layer on epitaxial rare-earth oxide has been proposed. In literature, the existing techniques used to achieve the same, such as Molecular beam Epitaxy or reduced-pressure chemical vapor deposition technique, are either costly or non-high-volume manufacturable. In this context, we propose a method to fabricate the highly oriented crystalline Si(111) channel layer (Top-Si) on an epitaxial Gd 2 O 3 /Si(111) virtual substrate (SOXI) utilizing the solid phase epitaxy using the high-volume manufacturing friendly (HVM), low-cost RF magnetron sputtering technique. First, we have shown the multicrystalline Si and epitaxial Gd 2 O 3 layer grown on Si(111) substrate, as confirmed using high-resolution X-ray diffraction (HRXRD) and Transmission Electron Microscopy (TEM). Second, we investigated the impact of rapid thermal annealing at 850 °C on the heterostructure using HRXRD and TEM. It is observed that the high-temperature annealing transforms the Top-Si layer into the highly oriented crystalline Si(111) layer by fusing smaller grains towards larger grains. Hence, we demonstrate a low-cost, HVM-friendly technique for the fabrication of SOXI wafers. [ABSTRACT FROM AUTHOR]

Despite the fundamental and technological importance of the elastic constants, a suitable method for their full characterization in epitaxial films is missing. Here we show that transient grating spectroscopy (TGS) with highly k -vector-selective generation and detection of acoustic waves is capable of determination of all independent elastic coefficients of an epitaxial thin film grown on a single-crystalline substrate. This experimental setup enables detection of various types of guided acoustic waves and evaluation of the directional dependence of their speeds of propagation. For the studied model system, which is a 3 μ m thin epitaxial film of the NiTi shape memory alloy on an MgO substrate, the TGS angular maps include Rayleigh-type surface acoustic waves as well as Sezawa-type and Love-type modes, delivering rich information on the elastic response of the film under different straining modes. The resulting inverse problem, which means the calculation of the elastic constants from the TGS maps, is subsequently solved using the Ritz–Rayleigh numerical method. Using this approach, tetragonal elastic constants of the NiTi film and their changes with the austenite → martensite phase transition are analyzed. • Guided acoustic waves in a film were measured by transient grating spectroscopy. • Austenitic and martensitic states of a 3 μ m NiTi epitaxial film were analyzed. • Angular dispersion of Rayleigh, Sezawa, and Love wave modes was identified. • Elasticity was determined by an inverse method based on the Ritz–Rayleigh approach. • Tetragonal elastic constants of the film were obtained. [ABSTRACT FROM AUTHOR]

Graphical abstract Pb(NO 3) 2 photooxidation or photoreduction reactions can be controlled in aqueous solution with and without adding NaIO 3 as a electron scavenger, leading to the selective deposition of PbO 2 or Pb on {110} or (010) surfaces of BiVO 4 , respectively. Highlights • Phase-pure, monoclinic BiVO 4 nanoislands grown on (001) yttria-stabilized zirconia. • BiVO 4 nanoislands with a truncated pyramid shape containing (010) and {110} facets. • A strong size-dependent photocatalytic activity for rhodamine B degradation. • Selective deposition of PbO 2 or Pb on {110} or (010) surfaces of BiVO 4. Abstract Photocatalytic studies performed on well-defined epitaxial thin films and heterostructures allow the direct investigation of crystallographic-dependent reactivity, and can provide fundamental insights into the reaction mechanisms. In this work, we show that phase-pure, monoclinic BiVO 4 nanoislands with a truncated pyramid shape with the (010) top surface and {110} sidewalls can be grown on (001)-oriented yttria-stabilized zirconia (YSZ) substrates with an epitaxial relationship of BiVO 4 (010)[001] // YSZ(001)[100]. The resulting nanostructures show a strong size-dependent mass-normalized photocatalytic activity, with highly dispersed nanoislands at low coverage being the most active. Pb(NO 3) 2 photooxidation or photoreduction reactions can be controlled in aqueous solution with and without adding NaIO 3 as a electron scavenger, leading to the selective deposition of PbO 2 or Pb on {110} or (010) surfaces of BiVO 4 , respectively. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition is widely used to grow BaTiO3 thin films. We investigated the influence of oxygen pressure during growth on the topography, microstructure, and roughness of ferroelectric epitaxial BaTiO3 thin films. It also presented an analysis of the epitaxial growth mode and defects throughout the film thickness using aberration-corrected transmission electron microscopy. Although ferroelastic (twin boundary) domain walls are absent, several misfit dislocations were observed and might be the primary cause of the observed island growth mode. [ABSTRACT FROM AUTHOR]

Abstract Co doped SrSnO 3 films (SrSn 1-x Co x O 3 (0 ≤ x ≤ 1. 0), i.e., SSCO) was grown on MgO single crystal substrates by pulsed laser deposition method. Effects of the Co doping content on the crystallinity, microstructure, optical and magnetic properties were examined. For all the films the epitaxial growth along (002) plane was realized, and the lattice constant dropped from 4.065 Å to 3.854 Å with the 'x' value changing from 0 to 1.0. The Co doping promoted the growth of grains and the RMS roughness of the film increased from 3.17 nm to 9.44 nm. With the increase of the Co doping level, the optical transmittance decreased from 95% to 28% at 500 nm, and the band gap varied from 4.51 eV to 3.16 eV. All the films exhibited the room temperature ferromagnetism, and the highest saturated magnetization of 61 emu/cm3 and the coercive force of 0.018 T were realized in the SSCO (x = 1.0) film. Highlights • Co doped SrSnO 3 films were epitaxially grown on MgO single crystal substrates via pulse laser deposition method. • The Co doping level had significant effects on the crystallinity and morphology of the epitaxial films. • The optical band gap of the film was tuned from 4.46 eV to 2.96 eV with different Co doping level. • The room temperature ferromagnetism with the highest M s of 61 emu/cm3 and H c of 0.018 T were realized. [ABSTRACT FROM AUTHOR]

Abstract The decrease in the resistance at solid electrolyte and electrode interfaces has become a critical issue in the development of solid-state lithium batteries. To understand the ionic transport properties across solid electrolyte and electrode interfaces, thin-film batteries consisting of flat epitaxial films are of considerable importance. Herein, we report the operation of bottom-current-collector-free thin-film batteries using LiNi 0.8 Co 0.2 O 2 epitaxial thin films. As the bottom current collector is not inserted between the substrates and LiNi 0.8 Co 0.2 O 2 , the surface of LiNi 0.8 Co 0.2 O 2 is very flat, with a surface roughness average of approximately 0.44 nm. This study proposes a very flat electrode surface suitable for the investigation of interfacial phenomena at solid electrolyte and electrode interfaces. Graphical abstract A top-view picture (Left) and schematic cross section (Center) of a fabricated thin-film lithium batteries using LiNi 0.8 Co 0.2 O 2 epitaxial thin films. Right: Schematic side view of lithium-ion conduction across the interface between LiNi 0.8 Co 0.2 O 2 and Li 3 PO 4. Image 1 Highlights • Bottom-current-collector-free 4-V-class thin film lithium batteries are fabricated. • LiNi 0.8 Co 0.2 O 2 is selected because of high electrical conductivity. • A very flat LiNi 0.8 Co 0.2 O 2 surface with a roughness of 0.44 nm was obtained. • LiNi 0.8 Co 0.2 O 2 thin-film batteries exhibit stable operation. [ABSTRACT FROM AUTHOR]

An epitaxial Li2MnO3(001) thin film electrode with layered rock-salt structure was tested in an all-solid-state battery configuration for the first time. Using amorphous Li3PO4 solid electrolyte, good discharge capacity after the 5th cycle, excellent reversibility for 100 cycles, and high rate capability at room temperature were observed. The same electrode showed significant capacity fading when cycled in liquid electrolyte. The all-solid configuration could prevent electrolyte decomposition, Mn dissolution, and oxygen extraction from Li2MnO3 electrode. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Epitaxial D0 19 -Mn 3 Ga layers were grown on MgO(1 1 1), GaN(0 0 1) and Pt(1 1 1) substrates. • D0 19 -Mn 3 Ga is a non-collinear antiferromagnet with an hexagonal spin structure. • The ferromagnetic component along the c axis is manipulated due to induced strain. • The ferromagnetism of D0 19 -Mn 3 Ga has been tuned from 23.7 to 11.8 and 2.5 kAm−1. Abstract The hexagonal D0 19 -Mn 3 Ga phase is a non-collinear antiferromagnet with a triangular spin configuration. The Mn magnetic moments, lying in the (0 0 1) basal plane, are slightly canted towards the c axis producing a ferromagnetic component (FMC), which saturation magnetization in bulk samples is 7.7 kAm−1. Here, we report on the epitaxial growth of Mn 3 Ga epitaxial thin films on MgO(1 1 1), GaN(0 0 1) and MgO(0 0 1)/Pt(1 1 1) substrates with lattices mismatches of −4.77%, 2.1%, and 2.45%, respectively. Structural characterization with reflection high-energy electron diffraction was used to evaluate the critical thicknesses at which relaxation is reached. We provide evidence of the manipulation of the magnitude of the FMC of the Mn 3 Ga thin films grown under tensile and compressive deformations. The FMC has been tuned from 23.7 to 11.8 and 2.5 kAm−1 for the growth of Mn 3 Ga on MgO(1 1 1), GaN(0 0 1), and MgO(0 0 1)/Pt(1 1 1) substrates. The modulation of the FMC is explained in terms of the Dzyaloshinskii-Moriya interaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights: • 57Fe Mössbauer spectroscopy at truly dilute level (<10−3 at%) is applied. • An ultrathin epitaxial TiN thin film structure is studied. • Theoretical calculations are provided to assist the analysis of the experimental measurement results. • The structure and mobility of the lattice defects in the TiN film are probed at atomic scale. Abstract The properties and performance of TiN thin films are closely related to the concentration and mobility of lattice defects in the thin film structures of TiN. This makes a local atomic scale study of TiN thin films an ever-growing demand. Emission 57Fe Mössbauer spectroscopy (eMS) is a powerful tool in this regard, which we apply here to study an ultrathin TiN film epitaxially grown on MgO (1 0 0). With the help of theoretical calculations, our results show that most implanted Fe ions adopt a 2+ valence state and locate at the Ti sublattice in the bulk-like single crystalline grains, with the rest Fe residing at the grain boundaries as interstitials. A small percentage of nitrogen point defects (vacancy V N and interstitial N I) are observed in the bulk-like crystalline grains. A temperature-dependent, interstitial N I mediated site-exchange between N I and V N inside the crystal grain are deduced via a N 2 dimmer like diffusion of N I through the crystal grains in the temperature range of 540–620 K. This is interesting in the perspective of exploring the catalytic property of TiN nanostructures. The titanium vacancy (V Ti) is only detected at the grain boundaries. Annealing up to 813 K, both the V N and N I are annihilated in the crystalline grains and the V Ti is fully recovered with healing of the grain boundaries. However, no evidence of ferromagnetism due to dilute implantation of 57Mn/57Fe and or structural defects in the film is obtained. This suggests that the so far reported dilute magnetism and defect-induced ferromagnetism in TiN nanostructures requires a further systematic investigation. [ABSTRACT FROM AUTHOR]

A high configurational entropy, achieved through a proper design of compositions, can minimize the Gibbs free energy and stabilize the quasi-equilibrium phases in a solid-solution form. This leads to the development of high-entropy materials with unique structural characteristics and excellent performance, which otherwise could not be achieved through conventional pathways. This work develops a high-entropy nonlinear dielectric system, based on the expansion of lead magnesium niobate-lead titanate. A dense and uniform distribution of nano-polar regions is observed in the samples owing to the addition of Ba, Hf, and Zr ions, which lead to enhanced performance of nonlinear dielectrics. The fact that no structural phase transformation is detected up to 250 °C, and no noticeable change or a steep drop in structural and electrical characteristics is observed at high temperatures suggests a robust thermal stability of the dielectric systems developed. With these advantages, these materials hold vast potential for applications such as dielectric energy storage, dielectric tunability, and electrocaloric effect. Thus, this work offers a new high-entropy configuration with elemental modulation, with enhanced dielectric material features., (© 2023 Wiley-VCH GmbH.)