Domain Matching Epitaxy Research Articles

Structural analysis and transport properties of [010]-tilt grain boundaries in Fe(Se,Te)

ABSTRACT Understanding the nature of grain boundaries is a prerequisite for fabricating high-performance superconducting bulks and wires. For iron-based superconductors [e.g. Ba(Fe,Co) 2 As 2 , Fe(Se,Te), and NdFeAs(O,F)], the dependence of the critical current density J c on misorientation angle ( θ GB ) has been explored on [001]-tilt grain boundaries, but no data for other types of orientations have been reported. Here, we report on the structural and transport properties of Fe(Se,Te) grown on CeO 2 -buffered symmetric [010]-tilt roof-type SrTiO 3 bicrystal substrates by pulsed laser deposition. X-ray diffraction and transmission electron microscopy revealed that θ GB of Fe(Se,Te) was smaller whereas θ GB of CeO 2 was larger than that of the substrate. The difference in θ GB between the CeO 2 buffer layer and the substrate is getting larger with increasing θ GB . For θ GB ≥ 24 ∘ of the substrates, θ GB of Fe(Se,Te) was zero, whereas θ GB of CeO 2 was continuously increasing. The inclined growth of CeO 2 can be explained by the geometrical coherency model. The c -axis growth of Fe(Se,Te) for θ GB ≥ 24 ∘ of the substrates is due to the domain matching epitaxy on (221) planes of CeO 2 . Electrical transport measurements confirmed no reduction of inter-grain J c for θ GB ≤ 9 ∘ , indicative of strong coupling between the grains.

Texture in atomic layer deposited Hf0.5Zr0.5O2 ferroelectric thin films

HfO2-based ferroelectric materials have excellent CMOS compatibility and polarization even in ultrathin films, which is regarded as promising candidate material for memory devices and related electronic devices. However, as the ferroelectric layer thickness scaling down, the consistency of device performance is inevitably affected by the complex polyphase and polycrystalline nature of HfO2-based ferroelectric thin films. Therefore, obtaining and controlling the texture of HfO2-based ferroelectric thin films is extremely important for regulating polarization orientation and improving ferroelectric polarization. In this work, 10 nm Hf0.5Zr0.5O2 (HZO) films were prepared by atomic layer deposition (ALD) on Nb-doped SrTiO3 (NSTO) single crystal substrates. The texture and orientation of HZO films were analyzed through the state-of-the-art spherical aberration corrected transmission electron microscope (Cs-TEM) technique. The domain matching epitaxy between HZO films and NSTO substrate helps eliminate lattice mismatch and residual misfit strain, and ultimately leads to the formation of <112> texture in HZO ferroelectric films. The obtained results represent lattice and interface play an extremely important role in regulating the ferroelectricity of HfO2-based films, which provides a way to design ultra-thin HfO2-based materials with excellent ferroelectric polarization by controlling the crystal structure and orientation.

Direct growth of ferroelectric orthorhombic ZrO2 on Ru by atomic layer deposition at 300 °C.

Fluorite-structured binary oxide ferroelectrics exhibit robust ferroelectricity at a thickness below 10 nm, making them highly scalable and applicable for high-end semiconductor devices. Despite this promising prospect, achieving highly reliable ferroelectrics still demands a significant thermal budget to form a ferroelectric phase, being a hurdle for their use in high-end complementary metal oxide semiconductor (CMOS) processing. Here, we report a robust ferroelectric behavior of an 8 nm-thick ZrO2 film deposited via plasma-enhanced atomic layer deposition at 300 °C on a (002)-oriented Ru without any post-annealing process, demonstrating high compatibility with CMOS processing. We propose that a plausible mechanism for this is the local domain matching epitaxy based on the high-resolution transmission electron microscopy and piezoelectric force microscopy results, where the templating effect between [101]-oriented grains of orthorhombic ZrO2 and [010]-oriented grains of Ru enables the direct growth of ferroelectric ZrO2. The 2Pr value is 20 μC cm-2, and it can be further improved by post-annealing at 400 °C to 23 μC cm-2 without showing the wake-up behavior. Ferroelectric switching shows stable endurance for up to 109 cycles, showcasing its high potential in CMOS-compatible applications and nanoelectronics with a low thermal budget.

Direct Current Reactive Sputtering Deposition and Plasma Annealing of an Epitaxial TiHfN Film on Si (001)

Deposition of a heteroepitaxial TiHfN film with a growth rate of about 1 μm/h was successfully achieved on a Si (001) substrate at a temperature above 700 °C by direct current magnetron reactive sputtering of a Ti0.6Hf0.4 (in atomic fraction) target with an Ar/N2 gas mixture. Annealing of the as-deposited TiHfN/Si sample at a temperature above 1000 °C using microwave plasma with H2/N2 gas was performed to further improve the TiHfN film’s quality. X-ray diffraction results show that the heteroepitaxial TiHfN film on Si exhibits a cube-on-cube relationship as {001}TiHfN//{001}Si and &lt;110&gt;TiHfN//&lt;110&gt;Si. X-ray rocking curve measurements show that the full width at half maximum of (200)TiHfN is 1.36° for the as-deposited TiHfN film, while it is significantly reduced to 0.53° after microwave plasma annealing. The surface morphologies of the as-deposited and annealed TiHfN films are smooth, with a surface roughness of around ~2 nm. Cross-sectional scanning/transmission electron microscopy (S/TEM) shows a reduction in defects in the annealed film, and X-ray photoelectron spectroscopy shows that the film composition remains unchanged. Additionally, S/TEM examinations with atomic resolution illustrate domain matching epitaxy (DME) between TiHfN and Si at the interface. The TiHfN films have good electrical conducting properties with resistivities of 40–45 μΩ·cm.

Formation of Q-carbon with wafer scale integration

We describe the formation of highly uniform Quenched-carbon (Q-carbon) layers by plasma-enhanced chemical vapor deposition (PECVD) followed by low-energy Ar+ ion bombardment to achieve wafer-scale integration of Q-carbon films. After PECVD, 9 nm and 20 nm thick silicon-doped diamond-like carbon (Si-DLC) films showed complete conversion into Q-carbon using 250eV Ar+ ions via negative biasing. However, this conversion was only partial for 30 nm thick films. Detailed EELS, XPS, Raman, and EDS studies were carried out to confirm the formation of Q-carbon by this method. We discuss the mechanism of Q-carbon formation as a result of low-energy ion bombardment during PECVD of thin films. These ions during negative biasing are energetic enough to create Frenkel defects, which support the conversion of the three-fold coordinated sp2 carbon units in as-deposited carbon into sp3 bonded five-atom tetrahedron units in Q-carbon. This process enhances the atomic number density and fraction of sp3 bonded carbon. These diamond tetrahedra are randomly packed and provide easy nucleation sites for diamond. If the underlying substrate can provide an epitaxial template for diamond growth via domain matching epitaxy, then wafer-scale growth of diamond epitaxial films can be achieved for wafer-scale integration and next-generation novel device manufacturing from diamond-related materials.

Epitaxial (110)-oriented La0.7Sr0.3MnO3 film directly on flexible mica substrate

Manufacture and characterizations of perovskite-mica van der Waals epitaxy heterostructures are a critical step to realize the application of flexible devices. However, the fabrication and investigation of the van der Waals epitaxy architectures grown on mica substrates are mainly limited to (111)-oriented perovskite functional oxide thin films up to now and buffer layers are highly needed. In this work, we directly grew La0.7Sr0.3MnO3 (LSMO) thin films on mica substrates without using any buffer layer. By the characterizations of x-ray diffractometer and scanning transmission electron microscopy, we demonstrate the epitaxial growth of the (110)-oriented LSMO thin film on the mica substrate. The LSMO thin film grown on the mica substrate via van der Waals epitaxy adopts domain matching epitaxy instead of conventional lattice matching epitaxy. Two kinds of domain matching relationships between the LSMO thin film and mica substrate are sketched by Visualization for Electronic and STructural Analysis software and discussed. A decent ferromagnetism retains in the (110)-oriented LSMO thin film. Our work demonstrates a new pathway to fabricate (110)-oriented functional oxide thin films on flexible mica substrates directly.

Domain matching epitaxy stabilized metastable, tetragonal BiFeO3 on symmetry-mismatched c-plane ZnO

We report the stabilization of metastable tetragonal BiFeO3 epilayer on ZnO(0001) surface. X-ray reciprocal space map characterizations show that the BiFeO3 film is of true tetragonal symmetry, but not the commonly observed monoclinic structure. The critical thickness of the tetragonal BiFeO3 is higher than 140 nm, much larger than that reported previously. Despite the considerable lattice mismatch and symmetry mismatch, tetragonal BiFeO3 can be formed on ZnO(0001) though domain matching epitaxy which is featured by anisotropic growth. We show that by taking into account the elastic energy during the initial semi-coherent growth, the tetragonal phase is lower than the thermally stable rhombohedral phase in total energy by 70 meV per formula unit. Moreover, local piezoelectric characterizations reveal a coercive field of 360 kV cm−1 and a piezoelectric constant of 48 pm V−1. The integration of tetragonal BiFeO3 with robust ferroelectricity on the platform of ZnO has potentials for all-oxide electronics applications.

Atomic-Scale Insights on Large-Misfit Heterointerfaces in LSMO/MgO/c-Al2O3

Understanding the interfaces in heterostructures at an atomic scale is crucial in enabling the possibility to manipulate underlying functional properties in correlated materials. This work presents a detailed study on the atomic structures of heterogeneous interfaces in La0.7Sr0.3MnO3 (LSMO) film grown epitaxially on c-Al2O3 (0001) with a buffer layer of MgO. Using aberration-corrected scanning transmission electron microscopy, we detected nucleation of periodic misfit dislocations at the interfaces of the large misfit systems of LSMO/MgO and MgO/c-Al2O3 following the domain matching epitaxy paradigm. It was experimentally observed that the dislocations terminate with 4/5 lattice planes at the LSMO/MgO interface and with 12/13 lattice planes at the MgO/c-Al2O3 interface. This is consistent with theoretical predictions. Using the atomic-resolution image data analysis approach to generate atomic bond length maps, we investigated the atomic displacement in the LSMO/MgO and MgO/c-Al2O3 systems. Minimal presence of residual strain was shown at the respective interface due to strain relaxation following misfit dislocation formation. Further, based on electron energy-loss spectroscopy analysis, we confirmed an interfacial interdiffusion within two monolayers at both LSMO/MgO and MgO/c-Al2O3 interfaces. In essence, misfit dislocation configurations of the LSMO/MgO/c-Al2O3 system have been thoroughly investigated to understand atomic-scale insights on atomic structure and interfacial chemistry in these large misfit systems.

Stabilization of thick, rhombohedral Hf0.5Zr0.5O2 epilayer on c-plane ZnO

Metastable rhombohedral hafnia-based ferroelectric films are emerging as a promising candidate in ferroelectric nonvolatile memory technologies, but the limited critical thickness impedes their applications. Herein, a 35-nm-thick rhombohedral Hf0.5Zr0.5O2 epilayer was stabilized on ZnO(0001) under an oxygen-deficient condition. Domain matching epitaxy, which facilitates the accommodation of misfit strain, allows the epitaxial growth of the (111)-oriented rhombohedral Hf0.5Zr0.5O2 film. We propose that a strong symmetry constraint is imposed on the epilayer at the initial epitaxial growth stage, i.e., the plane adjacent to ZnO(0001) should have a threefold symmetry. Although the bulk monoclinic phase is much more stable than the rhombohedral phase, our first principles calculations reveal that these two phases are energetically comparable with each other when this symmetry constraint is considered. Moreover, our results show that the incorporation of doubly charged oxygen vacancies is also powerful in shifting the energy balance between competing phases, making the metastable rhombohedral phase more stable.

Growth and properties of multi-layer nano CrAlN/TiAlN composite coating on the cermets with CrFeCoNiMo, CrFeCoNiMn, CrFeCoNiAl high entropy alloy phase

In the work, multi-layer nano CrAlN/TiAlN composite coating was deposited on the cermets with CrFeCoNiMo, CrFeCoNiMn, CrFeCoNiAl high entropy alloy phase. Growth and properties of the coating were systematically investigated. The results showed that CrAlN, TiAlN and Ti(C,N) possessed same crystal plane spacing as well as diffraction angles. Thus, higher possibility forcrystallization of CrAlN (200), TiAlN (200) plane on Ti(C,N) phase were obtained rather than on the binder phase. For cermets with CrFeCoNiAl, little white binder phase and smallest grains attributed to the densest and thinnest coatings on the cermets with CrFeCoNiAl. TEM revealed that columnar CrAlN monolayer exhibited a thickness of 23.4 nm and TiAlN showed thickness of 1.2 nm. Crystal planes of (0–2 0) for CrAlN was exactly parallel to (0–2 0) of core-rim phase, showing an epitaxial growth characteristic. The domain-matching epitaxy took place when the CrAlN layer was deposited on the Ti(C,N) phase, where lattice planes matched across the interface to release the mismatch strain. Besides, the multi-layer nano CrAlN/TiAlN coating deposited on the cermets with CrFeCoNiAl achieved the highest average nano-hardness of 33.4 Gpa, Young’s modulus of 445.3 Gpa and best adhesion strength of 68.11 N due to the dense and smooth coating microstructure.

Space-charge-controlled field emission analysis of current conduction in amorphous and crystallized atomic-layer-deposited Al2O3 on GaN

As previously reported, postdeposition annealing at 800 °C and higher simultaneously crystallizes atomic-layer-deposited (ALD) Al2O3 films and reduces the current in Al/ALD-Al2O3/(0001) GaN capacitors by two orders of magnitude. This current reduction is caused by the enhancement of conduction band offset from 1.4 to 1.8 eV, as revealed by the space-charge-controlled field emission analysis. Selected area electron diffraction (SAED) patterns demonstrate that the crystallized films consist of twinned (111)-oriented cubic γ-Al2O3 with an epitaxial relation of Al2O3 ⟨01¯1⟩∥ GaN ⟨21¯1¯0⟩. The SAED patterns additionally include spots that are specific to triaxially tripled γ-Al2O3. The aforementioned epitaxy is due to the similarity of hexagonal close-packed sublattices between oxygen on a (111) γ-Al2O3 plane and nitrogen on a (0001) GaN plane. However, the hexagonal close-packed lattice constant of γ-Al2O3 is 12% smaller than that of GaN, necessitating domain matching epitaxy. The thickness of the interfacial transition layer caused by the large misfit is estimated to be thinner than four monolayers of oxygen sublattice, by using the methodology developed here. Based on these results, the effect of Al2O3 crystallinity on the characteristics of Al2O3/GaN capacitors, such as conduction current, dielectric breakdown, interface states, and bias instability, was comprehensively captured. According to x-ray diffraction analyses, Al2O3 films crystallize at 700 °C, which is ∼100 °C lower than the threshold temperature estimated by transmission electron microscope observations. This difference was possibly caused by locally crystallized Al2O3 films, as confirmed by the slightly reduced current. These findings form a basis for improving ALD-Al2O3 films as gate insulator.

Heteroepitaxial Hexagonal (00.1) CuFeO2 Thin Film Grown on Cubic (001) SrTiO3 Substrate Through Translational and Rotational Domain Matching

Heteroepitaxy of complex oxide thin films is a significant challenge when a large mismatch in the lattice parameters (&gt;8%) and difference in the crystallographic symmetry coexist between the film and substrate. Herein, the heteroepitaxial growth of a hexagonal delafossite CuFeO2 thin film with (00.1) orientation on a cubic perovskite (001) SrTiO3 substrate through translational and rotational domain matching epitaxy is reported. The rotational in‐plane domain orientation relationships are CuFeO2 [11.0]//SrTiO3 [110] and CuFeO2 [2.0]//SrTiO3 [110] with about 10% in‐plane lattice mismatch. The 14.8 nm‐thick (00.1) CuFeO2 thin film shows high‐crystalline quality with a full width at half maximum of rocking curve of about 0.24° and exhibits a possible indirect optical bandgap of 1.43 eV or direct optical bandgap of 1.94 eV. Herein, not only a model system demonstrating translational and rotational domain matching heteroepitaxy of complex oxides is reported, but also a way to thin‐film heterostructures integrating hexagonal delafossite with cubic perovskite materials for functional oxide devices is opened.

Template Engineering of CuBi2 O4 Single-Crystal Thin Film Photocathodes.

To develop strategies for efficient photo-electrochemical water-splitting, it is important to understand the fundamental properties of oxide photoelectrodes by synthesizing and investigating their single-crystal thin films. However, it is challenging to synthesize high-quality single-crystal thin films from copper-based oxide photoelectrodes due to the occurrence of significant defects such as copper or oxygen vacancies and grains. Here, the CuBi2 O4 (CBO) single-crystal thin film photocathode is achieved using a NiO template layer grown on single-crystal SrTiO3 (STO) (001) substrate via pulsed laser deposition. The NiO template layer plays a role as a buffer layer of large lattice mismatch between CBO and STO (001) substrate through domain-matching epitaxy, and forms a type-II band alignment with CBO, which prohibits the transfer of photogenerated electrons toward bottom electrode. The photocurrent densities of the CBO single-crystal thin film photocathode demonstrate -0.4 and -0.7mA cm-2 at even 0 VRHE with no severe dark current under illumination in a 0.1 m potassium phosphate buffer solution without and with H2 O2 as an electron scavenger, respectively. The successful synthesis of high-quality CBO single-crystal thin film would be a cornerstone for the in-depth understanding of the fundamental properties of CBO toward efficient photo-electrochemical water-splitting.

Reactive Sputtering Deposition of Epitaxial TiC Film on Si (100) Substrate

Epitaxial (100) TiC film deposition on Si (100) substrate by direct current magnetron reactive sputtering of a metallic Ti target with 3%–6% CH4 in Ar gas was investigated. X-ray diffraction and cross-sectional scanning transmission electron microscopy (STEM) reveal that epitaxial cubic TiC can be grown on the Si substrate by domain matching epitaxy in 5/4 ratio with the epitaxial relationship of TiC (100)[0 1 ¯ 1] // Si (100)[0 1 ¯ 1]. For sputtering with 3% and 4% CH4, the deposited films are found to consist of both TiC and metallic Ti phases. Increasing the CH4 flow ratio to 5% results in a deposited film completely consisting of TiC without metallic Ti phase. The crystallinity of the deposited TiC is also improved with increasing the CH4 ratio to 5%. X-ray photoelectron spectroscopy shows that the [C]/[Ti] atomic ratio in TiC is nearly close to 1 for growth with 5% CH4 flow ratio and above. The measured electrical resistivities of the deposited films also increase from 41 to 153 μΩ·cm with increasing the CH4 ratio from 3% to 6%. With film growth beyond 50 nm thickness, it is shown that some disoriented TiC grains are formed.

Domain-Matching Epitaxy of Ferroelectric Hf0.5Zr0.5O2(111) on La2/3Sr1/3MnO3(001)

Epitaxial ferroelectric HfO2 films are the most suitable to investigate intrinsic properties of the material and for prototyping emerging devices. Ferroelectric Hf0.5Zr0.5O2(111) films have been epitaxially stabilized on La2/3Sr1/3MnO3(001) electrodes. This epitaxy, considering the symmetry dissimilarity and the huge lattice mismatch, is not compatible with conventional mechanisms of epitaxy. To gain insight into the epitaxy mechanism, scanning transmission electron microscopy characterization of the interface was performed, revealing arrays of dislocations with short periodicities. These observed periodicities agree with the expected for domain matching epitaxy, indicating that this unconventional mechanism could be the prevailing factor in the stabilization of ferroelectric Hf0.5Zr0.5O2 with (111) orientation in the epitaxial Hf0.5Zr0.5O2(111)/La2/3Sr1/3MnO3(001) heterostructure.

Complex Epitaxy of Tetragonal Tungsten Bronze K–Ta–Nb–O Nanorods

Tetragonal tungsten bronze (TTB) phases possess numerous important properties (ferroelectricity, multiferroicity, piezoelectricity, optical nonlinearity, electro-optics) that can be achieved by modifying their composition, in addition to their ability to grow as very anisotropic crystals. In this study, K-5.06(Ta0.57Nb0.43)(10.99)O-30 tetragonal tungsten bronze phase thin films were grown by a pulsed laser deposition technique on (001)SrTiO3 and R-plane sapphire substrates. The films grew according to two modes with respect to the substrate surface, that is, as vertical nanorods with the [001] direction perpendicular to the substrate surface and as horizontal nanorods with the [001] orientation parallel to the substrate surface and out-of-plane direction. Both vertical and horizontal nanorods present epitaxial relationships with the substrates. Careful study of epitaxial relationships showed a complex growth on both substrates that can be described in the framework of domain matching epitaxy resulting in several antiphase domain formations for both kinds of nanorods. These particular configurations are due to a high degree of coincidence between cations (anions) of the film with those of the substrate. This study shows the ability of ferroelectric TTB phases to grow as one-dimensional objects with the possibility to tailor their polarization direction either normal to or parallel to the substrate surface.

Plasma-assisted molecular beam epitaxy of NiO on GaN(00.1)

The growth of NiO on GaN(00.1) substrates by plasma-assisted molecular beam epitaxy under oxygen-rich conditions was investigated at growth temperatures between 100°C and 850°C. Epitaxial growth of NiO(111) with two rotational domains, with epitaxial relation NiO(11¯0)‖GaN(11.0) and NiO(101¯)‖GaN(11.0), was observed by X-ray diffraction and confirmed by in situ reflection high-energy electron diffraction as well as transmission electron microscopy (TEM) and electron backscatter diffraction. With respect to the high lattice mismatch of 8.1% and a measured low residual tensile layer strain, growth by lattice matching epitaxy or domain-matching epitaxy is discussed. The morphology measured by atomic force microscopy showed a grainy surface, probably arising from the growth by columnar rotational domains visible in TEM micrographs. The domain sizes measured by AFM and TEM increase with the growth temperature, indicating an increasing surface diffusion length. Growth at 850°C, however, involved local decomposition of the GaN substrate that leads to an interfacial β-Ga2O3(2¯01) layer and a high NiO surface roughness. Raman measurements of the quasiforbidden one-phonon peak indicate increasing layer quality (decreasing defect density) with increasing growth temperature.

Precursor-templated synthesis of thermodynamically unfavored platinum nanoplates for the oxygen reduction reaction.

Controlling the shape of Pt-based nanomaterials is a major strategy to enhance the electrocatalytic performance towards the oxygen reduction reaction (ORR). Since the Pt (111) facet exhibits desirable electrochemical properties, Pt nanoplates enclosed by {111} facets are promising candidates. However, plate-shaped Pt crystals have thermodynamically unfavored structures, making syntheses challenging. Here we report a novel precursor-templated route to synthesize Pt nanoplates. Specifically, precipitated (NH4)2PtCl6 prepared in aqueous solution is used as the Pt precursor followed by the addition of NaBH4 as a reducing agent. With domain matching epitaxy, Pt nanoplates grow on the surface of the precipitated precursor, selectively exposing the {111} facets. Compared to those of commercial Pt/C at 0.90 and 0.85 V, the ORR properties of Pt nanoplates display a 1.5- and 5.2-fold enhancement in the mass activity, and a 3.3- and 11.6-fold enhancement in the specific activity, respectively. The superior ORR activities and the unique shape of Pt nanoplates are maintained for at least 5000 potential cycles.

Evidence of weak antilocalization in epitaxial TiN thin films

Defect engineering provides a tremendous opportunity to impart novel functionalities to nanomaterials. This report is focused on TiN metallic system, where the unpaired spin structure and electron-transport are controlled by injecting nitrogen vacancies (VN). The TiN films are epitaxial, with the TiN/Al2O3 epitaxial relationship given by: (1 1 1) TiN//(0 0 0 1) Al2O3 as out-of-plane, and 〈11-0〉 TiN//〈1 0 1- 0〉 Al2O3 and 〈1 1 2-〉 TiN//〈1 1 2-0〉 Al2O3 as in-plane, after 30° rotation. Epitaxy in such a large misfit system (~9.24%) is rationalized to arise via domain matching epitaxy (DME) paradigm. Following the report of room-temperature ferromagnetism [1] in TiN1−x films formed by injecting nitrogen vacancies, we provide direct experimental evidence of weak antilocalization (WAL) effects by plugging VN using nitrogen annealing of TiN films. This evidence with simultaneous loss of magnetization in nitrogen annealed TiN films is the tell-tale sign of VN acting as magnetically active defects in TiN, as their removal facilitates Berry’s phase formation and generation of time-reversal symmetry. Through detailed EELS and Raman analysis, we have explicitly shown the absence of Ti+2 polarons in TiN films on N2 annealing. The resistivity minima in TiN films are attributed to the WAL effect with persistent log T behavior under 0–7 Tesla magnetic fields. The temperature-dependent coherence length analysis also highlights the emergence of WAL under the two-dimensional localization theory. The WAL effect in TiN is similar to topological insulators, quenching on the introduction of magnetically active defects, while stable against non-magnetic defects. Our findings demonstrate the prime importance of nitrogen vacancies in tuning the magentotransport characteristics in epitaxial nitride films for optoelectronic device applications.

Characterization of MgO/TiN bilayer deposited on cube-textured copper using pulsed-laser deposition technique

Here, we demonstrate heteroepitaxial growth of MgO/TiN thin films on flexible metal foil of copper substrates using pulsed laser deposition. X-ray and electron diffraction measurements revealed that the epitaxial MgO/TiN bilayer was oriented along [002] direction. The large mismatch between TiN film and Cu substrate was effectively reduced by the 5/6 and 6/7 variations of domains. Despite the local irregularity of misfit dislocations at TiN/Cu, the domain-matching epitaxy paradigm is a remarkably accurate theory. MgO/TiN bilayer is chemically homogeneous and Mg, Ti, or Cu atoms do not segregate into the low-angle grain boundaries regardless of MgO/TiN films thickness. Thus, it appears that thickness may be reduced up to the value in which TiN fully covers the rough surface of Cu tape. Unfortunately, issues related to the presence of in-plane TiN contraction, probably generated by the difference in thermal expansion coefficient, and the origin of misfit dislocations irregularity at TiN/Cu interface remain unresolved. Our findings can make a substantial contribution to further research on Cu-based coated conductors and help in better understanding the ways that MgO/TiN bilayer are grown on Cu tape.