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In this study, the double remnant polarization (2Pr) is enhanced from ≈2 to 25 µC cm−2 at a low applied voltage of ±2 V (or from 10 to 35 µC cm−2 at a voltage of ±4 V) by decreasing the WNx interfacial capping layer (ICL) thickness from 6 to 2 nm in a novel Ru/WNx ICL/Hf0.5Zr0.5O2(HZO)/TiN structure after annealing at 400 °C in a furnace. This occurs because of the higher orthorhombic (o) plus rhombohedral (r) phases (>70%), which is analyzed by geometrical phase analysis (GPA) of high‐resolution transmission electron microscope (HRTEM) images. An optimized 2 nm WNx ICL memory capacitor shows a low coercive field (Ec) of 1.27 MV cm−1 and long endurance of > 109 cycles (remaining 2Pr value of 13.5 µC cm−2) under a low field stress of ±2 MV cm−1 and 0.1 µs hold pulse width (or ≈1.67 MHz). Even this long endurance of > 109 cycles is obtained by applying a higher stress of ±2 MV cm−1, 1 MHz, or 100 kHz. Under ±3 MV cm−1 stress, the mechanism is caused by m‐phase growth from both the HZO/TiN bottom electrode (BE) and WNx ICL/HZO interfaces, which is evidenced by HRTEM images after 2 × 107 cycles for the first time. [ABSTRACT FROM AUTHOR]

Abstract In this study, the double remnant polarization (2Pr) is enhanced from ≈2 to 25 µC cm−2 at a low applied voltage of ±2 V (or from 10 to 35 µC cm−2 at a voltage of ±4 V) by decreasing the WNx interfacial capping layer (ICL) thickness from 6 to 2 nm in a novel Ru/WNx ICL/Hf0.5Zr0.5O2(HZO)/TiN structure after annealing at 400 °C in a furnace. This occurs because of the higher orthorhombic (o) plus rhombohedral (r) phases (>70%), which is analyzed by geometrical phase analysis (GPA) of high‐resolution transmission electron microscope (HRTEM) images. An optimized 2 nm WNx ICL memory capacitor shows a low coercive field (Ec) of 1.27 MV cm−1 and long endurance of > 109 cycles (remaining 2Pr value of 13.5 µC cm−2) under a low field stress of ±2 MV cm−1 and 0.1 µs hold pulse width (or ≈1.67 MHz). Even this long endurance of > 109 cycles is obtained by applying a higher stress of ±2 MV cm−1, 1 MHz, or 100 kHz. Under ±3 MV cm−1 stress, the mechanism is caused by m‐phase growth from both the HZO/TiN bottom electrode (BE) and WNx ICL/HZO interfaces, which is evidenced by HRTEM images after 2 × 107 cycles for the first time.

This study reported the fabrication of TiO2-decorated Fe2O3QDs/g-C3N4 ternary Z-scheme photocatalyst via low-temperature calcination followed by a nonaqueous route with tunable particle size and strong interfacial contact. The subsequent Fe2O3QDs/g-C3N4 and TiO2/Fe2O3QDs/g-C3N4 were investigated in terms of structure, morphology, optical properties, and surface chemical composition analysis via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDX), UV–visible spectroscopy, ESR and photoluminescence spectroscopy (PL). The crystalline parameters of the samples were investigated by X-ray diffraction (XRD) The Williamson-Hall method and geometrical phase analysis of HRTEM micrographs were employed to investigate lattice defects. Under visible light, the photocatalytic capabilities of as-fabricated TiO2/Fe2O3QDs/g-C3N4 were examined by degrading Rhodamine B (RhB), and an enhancement in photocatalytic efficacy was found. TiO2 works as a primary photosensitizer, providing extra photoinduced electrons influenced by oxygen vacancies, while Fe2O3 acts as a "bridge" for electron transport from the TiO2 moiety to the g-C3N4 thereby establishing an indirect charge transport pathway based on the Z-scheme. Radical scavenging tests were conducted to further explore the cause of increased activity and degradation mechanisms. Designing materials with oxygen vacancies and optimized structures can lead to improved solar energy conversion capabilities, particularly regarding contaminant removal. The proposed technique might be a viable option for the removal of rhodamine b compounds and for remedying freshwater reservoirs. TiO2 /Fe2O3QDs/g-C3N4Ternary Z-Scheme Photocatalysts! A facile strategy is exploited to modulate the crystallinity and surface properties of TiO2. TiO2 is incorporated into Fe2O3QDs/g-C3N4 through solvothermal treatment, which results in the formation of surface flaws and lattice-oxygen activated regions as well as the transformation of the Fe2O3QDs/g-C3N4 heterojunction into an indirect z-scheme system by rational modulation of the band alignment of two systems. The electron–hole pair is efficiently separated, conserving the electron reduction capability and the electron oxidation capability of the hole. The adapted structure and mesocrystalline nature resulted in a 7.3-fold improvement in the photocatalytic performance of TFCN over pure g-C3N4. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets. [ABSTRACT FROM AUTHOR]

Different methods for evaluation of displacement and strain fields based on phase field crystal (PFC) simulations are shown. Methods originally devised for molecular dynamics (MD) simulations or analysis of high-resolution microscopy images are adapted to a PFC setting, providing access to displacement and strain fields for systems of discrete atoms, such as in MD, as well as to continuous deformation fields. The latter being achieved by geometrical phase analysis. As part of the study, the application of prescribed non-affine deformations in a 3D structural PFC (XPFC) setting is demonstrated as well as an efficient numerical scheme for evaluation of PFC phase diagrams, such as, for example, those required to stabilize solid/liquid coexistence. The present study provides an expanded toolbox for using PFC simulations as a versatile numerical method in the analysis of material behavior at the atomic scale. [ABSTRACT FROM AUTHOR]

The stress and strain play an important role in strengthening of the precipitation‐hardened Aluminum (Al) alloys. Despite the determination of relationship between the mechanical properties and the precipitation existing in the microstructure of these alloys, a quantitative analysis of the local stress and the strain fields at the hardening‐precipitates level has been seldom reported. In this paper, the microstructure of a T8 temper AA2195 Al alloy is investigated using aberration corrected scanning transmission electron microscopy (AC‐STEM). The strain fields in Al matrix in the vicinity of observed precipitates, namely T1 and β′, are determined using geometric phase analysis (GPA). Young's modulus (Ym) mapping of the corresponding areas is determined from the valence electron energy loss spectroscopy (VEELS) measured bulk Plasmon energy (Ep) of the alloys. The GPA‐determined strains were then combined with VEELS‐determined Ym under the linear theory of elasticity to give rise the local stresses in the alloy. The obtained results show that the local stresses in Al matrix having no precipitates were in the range of 138 ± 2 MPa. Whereas, in the vicinity of thin and thick T1 platelet shape precipitates, the stresses were found to be about 202 ± 3 MPa and 195 ±3 MPa, respectively. The stresses measured in the vicinity of β′ spherical shape precipitates found out to be 140 ± 3 MPa which was near to the local stress value in Al matrix. Our findings suggest that the precipitate hardening in T8 temper AA2195 Al alloy predominantly stems from thin T1 precipitates. [ABSTRACT FROM AUTHOR]

A strain characterization technique based on Moiré interferometry in a scanning transmission electron microscope (STEM) and geometrical phase analysis (GPA) method is demonstrated. The deformation field is first captured in a single STEM Moiré hologram composed of multiple sets of periodic fringes (Moiré patterns) generated from the interference between the periodic scanning grating, fixing the positions of the electron probe on the sample, and the crystal structure. Applying basic principles from sampling theory, the Moiré patterns arrangement is then simulated using a STEM electron micrograph reference to convert the experimental STEM Moiré hologram into information related to the crystal lattice periodicities. The GPA method is finally applied to extract the 2D relative strain and rotation fields. The STEM Moiré interferometry enables the local information to be de-magnified to a large length scale, comparable to what can be achieved in dark-field electron holography. The STEM Moiré GPA method thus extends the conventional high-resolution STEM GPA capabilities by providing comparable quantitative 2D strain mapping with a larger field of view (up to a few microns). [ABSTRACT FROM AUTHOR]

The last few years have seen a great deal of progress in the development of transmission electron microscopy based techniques for strain mapping. New techniques have appeared such as dark field electron holography and nanobeam diffraction and better known ones such as geometrical phase analysis have been improved by using aberration corrected ultra-stable modern electron microscopes. In this paper we apply dark field electron holography, the geometrical phase analysis of high angle annular dark field scanning transmission electron microscopy images, nanobeam diffraction and precession diffraction, all performed at the state-of-the-art to five different types of semiconductor samples. These include a simple calibration structure comprising 10-nm-thick SiGe layers to benchmark the techniques. A SiGe recessed source and drain device has been examined in order to test their capabilities on 2D structures. Devices that have been strained using a nitride stressor have been examined to test the sensitivity of the different techniques when applied to systems containing low values of deformation. To test the techniques on modern semiconductors, an electrically tested device grown on a SOI wafer has been examined. Finally a GaN/AlN superlattice was tested in order to assess the different methods of measuring deformation on specimens that do not have a perfect crystalline structure. The different deformation mapping techniques have been compared to one another and the strengths and weaknesses of each are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Quantitative deformation analysis of micro-fabricated electromechanical systems is of importance for the design and functional control of microsystems. In this paper, two modified digital moiré processing methods, Gaussian blurring algorithm combined with digital phase shifting and geometrical phase analysis (GPA) technique based on digital moiré method, are developed to quantitatively analyse the deformation behaviour of micro-electro-mechanical system (MEMS) structures. Measuring principles and experimental procedures of the two methods are described in detail. A digital moiré fringe pattern is generated by superimposing a specimen grating etched directly on a microstructure surface with a digital reference grating (DRG). Most of the grating noise is removed from the digital moiré fringes, which enables the phase distribution of the moiré fringes to be obtained directly. Strain measurement result of a MEMS structure demonstrates the feasibility of the two methods. [ABSTRACT FROM AUTHOR]

Abstract: The Geometrical phase analysis, which is a very efficient method to measure deformation from High resolution transmission electron microscopy images, is studied from a theoretical point of view. We point out that the basic property of this method is its ability to measure local reciprocal lattice parameters with a high level of accuracy. We attempt to provide some insights into (a) different formula used in the geometrical phase analysis such as the well-known relation between phase and displacement: , (b) the two different definitions of strain, each of which corresponding to a different lattice reference and (c) the meaning of a continuous displacement in a dot-like high resolution image. The case of one-dimensional analysis is also presented. Finally, we show that the method is able to give the position of the dot that is nearest to a given pixel in the image. [Copyright &y& Elsevier]

Two-dimensional (2D) crystals provides a material platform to explore the physics and chemistry at the single-atom scale, where surface characterization techniques can be applied straightforwardly. Recently there have been emerging interests in engineering materials through structural deformation or transformation. The strain field offers crucial information of lattice distortion and phase transformation in the native state or under external perturbation. Example problems with significance in science and engineering include the role of defects and dislocations in modulating material behaviors, and the process of fracture, where remarkable strain is built up in a local region, leading to the breakdown of materials. Strain is well defined in the continuum limit to measure the deformation, which can be alternatively calculated from the arrangement of atoms in discrete lattices through methods such as geometrical phase analysis from transmission electron imaging, bond distortion or virial stress from atomic structures obtained from molecular simulations. In this paper, we assess the accuracy of these methods in quantifying the strain field in 2D crystals through a number of examples, with a focus on their localized features at material imperfections. The sources of errors are discussed, providing a reference for reliable strain mapping. [ABSTRACT FROM AUTHOR]

• Atomic scale displacement fields of dislocations within a HEA are characterized. • TeMA and GPA are assessed by comparison of experimental and simulated images. • The ascertainable maximum displacement is limited for both techniques. • The dislocation plane is directly obtained for small displacements only. • A methodology for burgers vector determination using two projections is introduced. The paper assesses the applicability of advanced atomic resolution displacement measurement techniques to characterize dislocation character in metallic materials using simulated images derived from anisotropic elasticity and actual measurements in high entropy alloys. We draw attention to two techniques: the real space method of template matching (TeMA) and the reciprocal space method of geometric phase analysis (GPA) and provide a critical assessment. These techniques have limitations for direct evaluation of full dislocations Burgers vector or when local displacements are exceeding 50% lattice spacing. This is clearly illustrated with simulated arctangent displacement profiles reminiscent of dislocation cores. An approach for circumventing this limitation is suggested in the form of a nearest neighbor correction. Additionally, a methodology for determination of the Burgers vector is introduced on the basis of a vectorial rendering of the displacement field upon consideration of two zone axis measurements and applied to TeMA and GPA. The experimental results conform to the Burgers vector of a full lattice dislocation in the FCC crystal structure of the High-Entropy Alloy (HEA). The comparison of simulated and experimental images proves the efficacy of the HR-TEM (High Resolution Transmission Electron Microscopy) displacement mapping techniques while pointing to the need for caution in case of large displacements. [ABSTRACT FROM AUTHOR]