Three central themes in the study of the phenomenon of resistive switching are the nature of the conducting phase, why it forms, and how it forms. In this study, the answers to all three questions ...are provided by performing switching experiments in situ in a transmission electron microscope on thin films of the model system polycrystalline SrTiO3. On the basis of high‐resolution transmission electron microscopy, electron‐energy‐loss spectroscopy and in situ current–voltage measurements, the conducting phase is identified to be SrTi11O20. This phase is only observed at specific grain boundaries, and a Ruddlesden–Popper phase, Sr3Ti2O7, is typically observed adjacent to the conducting phase. These results allow not only the proposal that filament formation in this system has a thermodynamic origin—it is driven by electrochemical polarization and the local oxygen activity in the film decreasing below a critical value—but also the deduction of a phase diagram for strongly reduced SrTiO3. Furthermore, why many conducting filaments are nucleated at one electrode but only one filament wins the race to the opposite electrode is also explained. The work thus provides detailed insights into the origin and mechanisms of filament generation and rupture.
Formation and rupture of nanofilaments are directly observed by in situ current–voltage/transmission electron microscopy to investigate the resistive‐switching mechanism in a model oxide system of polycrystalline SrTiO3 thin film. High‐resolution transmission electron microscopy, electron‐energy‐loss spectroscopy, and in situ current–voltage measurements reveal the filament‐phase SrTi11O20 and its neighboring structure, which fundamentally establishes the thermodynamic origin and mechanism.
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The atomic structure of a 0.94-nm-thick T1 precipitate in an Al–Cu–Li–Mg–Ag alloy is investigated by combining aberration-corrected scanning transmission electron microscopy (STEM) ...and energy-dispersive X-ray spectroscopy (EDX). Ag segregates at the first layer of the T1 precipitate interface, revealing a significant compositional variation of Ag throughout the interface. Moreover, the T1 precipitate thickened from 0.94nm with successive stacking of identical 0.94nm thick layers.
This study aimed to gain a broader understanding of the clinical practice experience of Doctor of Philosophy nurses working in nursing positions.
Participants were 15 full-time nurses who are current ...Doctor of Philosophy candidates or have acquired a Doctor of Philosophy in nursing. Data were collected through face-to-face interviews and the participants' diaries, which were analysed using a descriptive qualitative method.
The patient care experiences of Doctor of Philosophy nurses in clinical practice were grouped into four themes: "providing evidence-based and patient-specific education," "proactively taking responsible for communicating with patients," "enhancing the quality of nursing through reflective attitudes," and "advocating for patients using a multifaceted approach." The factors facilitating or inhibiting clinical practice were identified with three themes.
This study revealed that the Doctor of Philosophy nurses used the knowledge and experience they gained in their Doctor of Philosophy nursing programme to serve as role models for the advancement of nursing education and evidence-based practice.
Metabolic syndrome (MS) is diagnosed using absolute criteria that do not consider age and sex, but most studies have shown that the prevalence of MS increases with age in both sexes. Thus, the ...evaluation of MS should consider sex and age. We aimed to develop a new index that considers the age and sex for evaluating an individual's relative overall MS status. Data of 16,518,532 subjects (8,671,838 males and 7,846,694 females) who completed a validated health survey of the National Health Insurance Service of the Republic of Korea (2014‒2015) were analyzed to develop an MS-biological age model. Principal component score analysis using waist circumference, pulse pressure, fasting blood sugar, triglyceride levels, and high-density lipoprotein level, but not age, as independent variables were performed to derive an index of health status and biological age. In both sexes, the age according to the MS-biological age model increased with rising smoking and alcohol consumption habits and decreased with rising physical activity. Particularly, smoking and drinking affected females, whereas physical activity affected males. The MS-biological age model can be a supplementary tool for evaluating and managing MS, quantitatively measuring the effect of lifestyle changes on MS, and motivating patients to maintain a healthy lifestyle.
2D crystals are attractive due to their unique atomic, electronic structures, and physiochemical properties, which strongly rely on the synthesis conditions. The atomic structure and presence of ...defects in the crystal lattice, such as vacancies, dopants, grain boundaries, and edge terminations, significantly influence the properties of 2D materials. Due to its high spatial resolution, aberration‐corrected scanning transmission electron microscopy (AC‐STEM) has become a powerful tool to provide atomic‐scale insights into the crystal structure, defects, heterointerfaces, ferroelectricity, and in situ observations of 2D materials. This review will cover the status of atomic‐scale studies on various 2D materials, including graphene, boron nitride, transition metal dichaogenides, MXenes, and phosphorene using AC‐STEM. The future perspective of AC‐STEM for new findings in 2D materials using machine learning is further discussed.
The status of atomic‐scale studies on various 2D materials such as graphene, boron nitride, transition metal dichaogenides, MXenes, and phosphorene using aberration‐corrected scanning transmission electron microscopy (AC‐STEM) is reviewed. Future perspectives for AC‐STEM in new findings of 2D materials using in situ observations and machine learning are further discussed.
Ferroelectric materials owning a polymorphic nanodomain structure usually exhibit colossal susceptibilities to external mechanical, electrical, and thermal stimuli, thus holding huge potential for ...relevant applications. Despite the success of traditional strategies by means of complex composition design, alternative simple methods such as strain engineering have been intensively sought to achieve a polymorphic nanodomain state in lead‐free, simple‐composition ferroelectric oxides in recent years. Here, a nanodomain configuration with morphed structural phases is realized in an epitaxial BaTiO3 film grown on a (111)‐oriented SrTiO3 substrate. Using a combination of experimental and theoretical approaches, it is revealed that a threefold rotational symmetry element enforced by the epitaxial constraint along the 111 direction of BaTiO3 introduces considerable instability among intrinsic tetragonal, orthorhombic, and rhombohedral phases. Such phase degeneracy induces ultrafine ferroelectric nanodomains (1–10 nm) with low‐angle domain walls, which exhibit significantly enhanced dielectric and piezoelectric responses compared to the (001)‐oriented BaTiO3 film with uniaxial ferroelectricity. Therefore, the finding highlights the important role of epitaxial symmetry in domain engineering of oxide ferroelectrics and facilitates the development of dielectric capacitors and piezoelectric devices.
A polymorphic nanodomain structure with coexistent metastable tetragonal, orthorhombic, and rhombohedral phases is constructed in BaTiO3 films by growing on SrTiO3 (111) substrates. The domain state results from a threefold rotational symmetry around the surface normal of the substrate imposed on inherently tetragonal BaTiO3. Consequently, (111)‐oriented BaTiO3 films yield significantly enhanced dielectric and piezoelectric responses compared to the (001)‐counterpart.
The nature of magnetic ordering in LaCoO3 epitaxial thin films has been the subject of considerable debate. We present direct observations of the spin-state modulation of Co ions in LaCoO3 epitaxial ...thin films on an atomic scale using aberration-corrected scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and ab initio calculations based on density functional theory (DFT) calculations. The results of an atomic-resolution STEM/EELS study indicate that the superstructure is not associated with oxygen vacancies; rather, it is associated with a higher spin state of Co3+ ions and their ordering. DFT calculations successfully reproduced the modulation of lattice spacing with the introduction of spin ordering. This result identifies the origins of intrinsic phenomena in strained LaCoO3 and provides fundamental clues for understanding ferromagnetism in Co-based oxides.
The prevalence of non-suicidal self-injury among South Korean adolescents has increased significantly, requiring academic attention. This methodological study aims to develop a non-suicidal ...self-injury motivation scale for adolescents and evaluate its validity and reliability.
In the first phase of scale development, the factors constituting self-injury motivation were identified through a literature review and analysis of online counseling data from self-injuring adolescents. In the second phase, 45 initial preliminary items were derived based on the identified factors, and 38 preliminary items were selected through content validation by experts. In the scale validation phase, the survey was conducted using 38 items. Data were collected from adolescents with a history of self-injury, using exploratory factor analysis (EFA) involving 715 participants and confirmatory factor analysis (CFA) involving 537 participants. The EFA involved 27.0% male and 73.0% female participants, with a mean age of 16.83 years, and the CFA involved 20.7% male and 79.3% female participants, with a mean age of 16.15 years. The data collected were tested for validity and reliability using SPSS 28.0 and M-plus.
The EFA yielded four factors and 24 items. The factors were named interpersonal influence, emotion regulation, sensation seeking, and anti-suicide, and the scale had an explanatory power of 55.8%. In the CFA, the fit of the 23-item model after deleting one item with low standardized factor loadings was x
= 1081.52 (p < .001), CFI = 0.829, RMSEA = 0.084, and SRMR = 0.075, confirming the acceptability of the self-injury motivation scale for adolescents. The scale evaluation results for convergent validity and discriminant validity met the criteria. The reliability test results showed that the overall reliability (Cronbach's α) was 0.88, and the reliability (Cronbach's α) of each factor was 0.89 for interpersonal influence, 0.83 for emotion regulation, 0.63 for sensation seeking, and 0.80 for anti-suicide, satisfying internal consistency.
In this study, the self-injury motivation scale for adolescents in the community comprised four factors and 23 items. The scale can be used to examine self-injury motivation among adolescents in the community and to develop self-injury prevention intervention programs.
Two small molecular hole-transporting type materials, namely 4-(9,9-dimethylacridin-10(9
)-yl)-
-(4-(9,9-dimethylacridin-10(9
)-yl)phenyl)-
-phenylaniline (TPA-2ACR) and 10,10'-(9-phenyl-9
...-carbazole-3,6-diyl)bis(9,9-dimethyl-9,10-dihydroacridine) (PhCAR-2ACR), were designed and synthesized using a single-step Buchwald-Hartwig amination between the dimethyl acridine and triphenylamine or carbazole moieties. Both materials showed high thermal decomposition temperatures of 402 and 422 °C at 5% weight reduction for PhCAR-2ACR and TPA-2ACR, respectively. TPA-2ACR as hole-transporting material exhibited excellent current, power, and external quantum efficiencies of 55.74 cd/A, 29.28 lm/W and 21.59%, respectively. The achieved device efficiencies are much better than that of the referenced similar, 1,1-Bis(di-4-tolylamino)phenylcyclohexane (TAPC)-based device (32.53 cd/A, 18.58 lm/W and 10.6%). Moreover, phenyl carbazole-based PhCAR-2ACR showed good device characteristics when applied for host material in phosphorescent OLEDs.
Ruddlesden–Popper (RP) phases (A n+1 B n O3n+1, n = 1, 2,···) have attracted intensive research with diverse functionalities for device applications. However, the realization of a high-quality ...RP-phase film is hindered by the formation of out-of-phase boundaries (OPBs) that occur at terrace edges, originating from lattice mismatch in the c-axis direction with the A′B′O3 (n = ∞) substrate. Here, using strontium ruthenate RP-phase Sr2RuO4 (n = 1) as a model system, an experimental approach for suppressing OPBs was developed. By tuning the growth parameters, the Sr3Ru2O7 (n = 2) phase was formed in a controlled manner near the film–substrate interface. This higher-order RP-phase then blocked the subsequent formation of OPBs, resulting in nearly defect-free Sr2RuO4 layer at the upper region of the film. Consequently, the Sr2RuO4 thin films exhibited superconductivity up to 1.15 K, which is the highest among Sr2RuO4 films grown by pulsed laser deposition. This work paves the way for synthesizing pristine RP-phase heterostructures and exploring their unique physical properties.
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