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Understanding quantum tunneling principles over two-dimensional (2D) van der Waals (vdW) ferromagnets at the atomic level is essential and complementary to the fundamental study of low-dimensional strong correlated systems and is critical for the development of magnetic tunneling devices. Here, we demonstrate a local electric-field controlled negative differential conductance (NDC) in 2D vdW ferromagnet Fe3GeTe2 (FGT) by using scanning tunneling microscopy (STM). The STM reveals that NDC shows an atomic position dependence and can be precisely modulated by altering the tunneling junction. The band shift together with electric-field-driven 3d-orbital occupancy modulates the sensitive magnetic anisotropic energy (MAE) in 2D FGT and consequently leads to electric-field-tunable NDC, which is also verified by theoretical simulation. This work realizes the electric-field-driven NDC in 2D ferromagnet FGT, which paves a way to design and develop applications based on 2D vdW magnets.

Heavy Fermion (HF) states emerge in correlated quantum materials due to the intriguing interplay between localized magnetic moments and itinerant electrons but rarely appear in 3d-electron systems due to high itinerancy of d-electrons. Here, an anomalous enhancement of Kondo screening is observed at the Kondo hole of local Fe vacancies in Fe3GeTe2 which is a recently discovered 3d-HF system featuring Kondo lattice and two-dimensional itinerant ferromagnetism. An itinerant Kondo-Ising model is established to reproduce the experimental results and provides insight into the competition between Ising ferromagnetism and Kondo screening. Our work explains the microscopic origin of the d-electron HF states in Fe3GeTe2 and inspires future studies of the enriched quantum many-body effects with Kondo holes.

Surface vacancies, serving as the activation centers for surface-adsorbed species, have been widely applied in catalysts to improve their activity and selectivity. In the case of ternary compound semiconductors, there is some controversy about exposed atoms and surface defects. Two-dimensional layered BiOCl is an important photocatalyst, which has had numerous studies focused on its oxygen vacancy (OV) and bismuth vacancy (BiV). It has been realized that its (001) surface can consist of exposed halogen atoms rather than oxygen atoms, which thus needs a new explanation for its surface defect engineering mechanism. Using first-principles calculations, the activation behavior of NOX (NO2, NO, N2O) at a chlorine vacancy (ClV) on the BiOCl (001) surface is systematically studied. It is found that after introducing ClV on BiOCl (001) surfaces, NOX molecules all show excellent activities with longer chemical bonds by capturing electrons from the catalyst. Our work furnishes fundamental insight into the activation of small molecules on defect-rich surfaces of ternary compound catalysts.

Abstract Scanning tunneling microscopy (STM) has gained increasing attention in the field of electrocatalysis due to its ability to reveal electrocatalyst surface structures down to the atomic level in either ultra-high-vacuum (UHV) or harsh electrochemical conditions. The detailed knowledge of surface structures, surface electronic structures, surface active sites as well as the interaction between surface adsorbates and electrocatalysts is highly beneficial in the study of electrocatalytic mechanisms and for the rational design of electrocatalysts. Based on this, this review will discuss the application of STM in the characterization of electrocatalyst surfaces and the investigation of electrochemical interfaces between electrocatalyst surfaces and reactants. Based on different operating conditions, UHV-STM and STM in electrochemical environments (EC-STM) are discussed separately. This review will also present emerging techniques including high-speed EC-STM, scanning noise microscopy and tip-enhanced Raman spectroscopy. Graphic Abstract

Compared with traditional solder joint bonding, an anisotropic conductive adhesive (ACA) provides an efficient and simple method for the interconnection of small-scale electronics. The wider applic...

Objective. To analyze the phenotypic features and pathogenic variants of three unrelated families presenting with nonsyndromic auditory neuropathy spectrum disorder (ANSD). Methods. Three recruited families that were affected by congenital deafness were clinically evaluated, including a detailed family history and audiological and radiological examination. The peripheral blood of all patients and their parents was collected for DNA extraction, and then, the exonic and flanking regions were enriched and sequenced using targeted capture and high-throughput sequencing technology. Bioinformatics analyses and the Sanger sequencing were carried out to screen and validate candidate pathogenic variants. The pathogenicity of candidate variants was evaluated by an approach that was based on the standards and guidelines for interpreting genetic variants as proposed by the American College of Medical Genetics and Genomics (ACMG). Results. Four patients in three families were diagnosed as nonsyndromic ANSD, and all exhibited OTOF gene mutations. Among them, two individuals in family 1 (i.e., fam 1-II-2 and fam 1-II-3) carried homozygous variants c.[2688del];[2688del] (NM_194248.3). Two individuals from family 2 (fam 2-II-1) and family 3 (fam 3-II-4) carried compound heterozygous variants c.[4960G>A];[1469C>G] and c.[2675A>G];[2977_2978del], respectively. Conclusions. Three unrelated pedigrees with ANSD were caused by pathogenic variants in the OTOF gene. Five mutations were found and included c.2688del, c.2675A>G, c.2977_2978del, c.4960G>A, and c.1469C>G, of which the first two are novel and expanded mutational spectrum of the OTOF gene, thus having important implications for genetic counseling of the family.

Understanding quantum tunneling principles over two-dimensional (2D) van der Waals (vdW) ferromagnets at the atomic level is essential and complementary to the fundamental study of low-dimensional strong correlated systems and is critical for the development of magnetic tunneling devices. Here, we demonstrate a local electric-field controlled negative differential conductance (NDC) in 2D vdW ferromagnet Fe

Heterostructures of two-dimensional (2D) layered materials with selective compositions play an important role in creating novel functionalities. Effective interface coupling between 2D ferromagnet and electronic materials would enable the generation of exotic physical phenomena caused by intrinsic symmetry breaking and proximity effect at interfaces. Here, epitaxial growth of bilayer Bi(110) on 2D ferromagnetic Fe

Heavy Fermion (HF) states emerge in correlated quantum materials due to the intriguing interplay between localized magnetic moments and itinerant electrons but rarely appear in 3d-electron systems due to high itinerancy of d-electrons. Here, an anomalous enhancement of Kondo screening is observed at the Kondo hole of local Fe vacancies in Fe

A non-enzymatic photoelectrochemical (PEC) glucose sensor based on nanoporous bismuth vanadate (BiVO4) electrode is fabricated on fluorine doped tin oxide by electrochemical deposition. The photogenerated holes of BiVO4 show a strong oxidizing ability, with adsorption of glucose on the surface of BiVO4, agreeing well with the classical Langmuir adsorption model. Under visible light irradiation, the glucose molecules adsorbed on the BiVO4 electrode surface can be oxidized by the photogenerated holes, which results in increased photocurrent. The fabricated BiVO4 non-enzymatic photoelectrochemical sensor shows outstanding catalytic activity, favourable selectivity, good reproducibility, and long-term stability for glucose detection under optimized conditions. The linear range was 0–5 mM (correlation coefficient, R = 0.997) with a detection limit of 0.13 μmol L−1 (signal-to-noise = 3). In addition, the proposed PEC sensor was successfully applied to detect glucose in human serum samples. Our work provides a new strategy for the non-enzymatic detection of glucose.

We have investigated the room temperature perpendicular exchange bias (PEB) at the ferromagnetic CoNi/antiferromagnetic (Co,Ni)O interfaces. CoNi/(Co,Ni)O multilayers with sharp interfaces have been sputter-deposited on glass substrates. It is found such multilayers show strong PMA and room temperature PEB. The PMA is considered originate from the interfacial anisotropy due to the facts that the CoNi layers are of poor crystallinity and it is difficult to obtain strain-induced anisotropy. The room temperature PEB indicates the well-balanced Neel temperature and anisotropy energy of the antiferromagnetic (Co,Ni)O mixed oxide layer.

SnSe single crystals have drawn extensive attention for their ultralow thermal conductivity and outstanding thermoelectric performance. Here, we report super large Sn1- xSe single crystals with excellent thermoelectric properties, fabricated via an advanced horizontal Bridgman technique with great yield and high reproducibility. The obtained single crystals have a super large size of ∼70 × 50 × 15 mm with a considerable weight of 148 g, which leads to a record-high mass density of >6.1 g cm-3. Extensive chemical characterization demonstrates that ∼0.3% Sn vacancies are present, which results in a large concentration of holes, ∼1.2 × 1019 cm-3, and an enhanced power factor of ∼6.1 μW cm-1 K-2 at 793 K. Simultaneously, the Sn-vacancy-induced lattice distortions result in a low thermal conductivity of ∼0.39 W m-1 K-1 at 793 K, leading to a competitive ZT of ∼1.24. This work demonstrates that large-size off-stoichiometric SnSe single crystals hold promise to achieve high thermoelectric performance.

L11-CoPt(1 1 1) films were successfully fabricated on glass substrates at 300–400 °C, using Pt(1 1 1) underlayer. Magnetocrystalline anisotropy energy shows a maximum of 1.8 × 106 J/m3 at 350 °C. The mechanism of L11-CoPt ordering after introducing Pt underlayer is considered to be strain- or stress-induced ordering. The effect of CoPt layer thickness on phase structure and magnetic properties were investigated to confirm the ordering mechanism. Perpendicular magnetic anisotropy has been obtained in all CoPt films, while the squareness ratio and coercivity decrease with increasing film thickness, indicating decreased ordering due to the relaxation of strain or stress in thick films.

The oxygen anion or, equivalently, the oxygen vacancy transport process is a key issue in valence change memory. Herein, based on the Aurivillius phase oxygen ion conductor Bi2MoO6, resistive random access memory devices with a Pt/Bi2MoO6/fluorine-doped SnO2 structure show bipolar resistive switching behavior with high stability, excellent data retention, and potential for multilevel data storage. In addition, dielectric spectroscopy is employed to probe the characteristics of both high resistance and low resistance states to confirm oxygen ion migration and understand the dynamics of oxygen vacancies. A very large change of nearly three orders of magnitude in loss tangent is found. It has been confirmed that one relaxation peak in the LRS originates from the oriented polarization of oxygen vacancies. The activation energy for oxygen vacancy migration of 0.21 eV and the relaxation time of 6.9 × 10−8 s are further deduced. In combination with first-principles calculations, a mechanism involving the formation and rupture of conductive filaments formed by oxygen vacancies is proposed to explain the resistive switching behavior. This work provides meaningful insights for identifying the exact mobile species in resistive switching and understanding its dynamic relaxation mechanism.

Ultra-thin Ga islands of β-Ga(110), high-pressure phase Ga(iii) and a new phase of stripe superstructure are obtained on Si(111). STM combined with theoretical calculations suggests that the stripe superstructure originates from Ga(iii) (001) with stacking rearrangement. This work provides a new strategy for synthesizing low-dimensional nanomaterials and accessing high pressure phases.

Objectives Controversies regarding factors associated with distant metastasis in pediatric thyroid cancer remain among the scientific community. The aim of this study was to investigate factors influencing distant metastasis in pediatric thyroid cancer. Methods We reviewed 1376 patients (aged 2 to 18 years) with thyroid cancer treated between 2003 and 2014. Data collected and analyzed included sex, race, age at diagnosis, year of diagnosis, pathological type, number of tumor foci, tumor extension, T-stage, N-stage, surgical procedure and radiation. Univariate and multivariate analyses were conducted to evaluate factors influencing distant metastasis of pediatric thyroid cancer. Results In the univariate analysis, factors influencing distant metastasis of thyroid cancer were age at diagnosis (P P P = 0.003), tumor extension (P P = 0.803), T3 (P P P = 0.001), N-stage (P P = 0.036) and T4 (P P > 0.05). Furthermore, according to chi-squared test, younger pediatric thyroid cancer patients with higher T- and N-stages are more likely to have distant metastasis. Conclusion Age at diagnosis, T-stage and N-stage influence distant metastasis of thyroid cancer patients aged 2 to 18 years; accordingly, more radical treatments may need to be used for patients with those risk elements.

It has been reported that some male breast cancer patients may refuse the recommended surgery, but the incidence rate in the United States is not clear. The purpose of this study was to identify the incidence, trends, risk factors, and eventual survival outcomes associated with the rejection of such cancer-directed surgery. We collected data on 5860 patients with male breast cancer (MBC) from the Surveillance, Epidemiology, and End Results database, including 50 patients refusing surgery as recommended. Kaplan–Meier survival analysis and Cox proportional hazard regression were used to identify the effects of refusing surgery on cancer-specific survival (CSS) and overall survival (OS). The association between acceptance or rejection of surgery and mortality were estimated by nested Cox proportional hazards regression models with adjustment for age, race, clinical characteristics, and radiation. Of the 5860 patients identified, 50 (0.9%) refused surgery. Old age (≥65: hazard ratio [HR]: 3.056, 95% confidence interval [CI]: 1.738–5.374, P

In this paper, we develop a new classification method for manifold-valued data in the framework of probabilistic learning vector quantization. In many classification scenarios, the data can be naturally represented by symmetric positive definite matrices, which are inherently points that live on a curved Riemannian manifold. Due to the non-Euclidean geometry of Riemannian manifolds, traditional Euclidean machine learning algorithms yield poor results on such data. In this paper, we generalize the probabilistic learning vector quantization algorithm for data points living on the manifold of symmetric positive definite matrices equipped with Riemannian natural metric (affine-invariant metric). By exploiting the induced Riemannian distance, we derive the probabilistic learning Riemannian space quantization algorithm, obtaining the learning rule through Riemannian gradient descent. Empirical investigations on synthetic data, image data , and motor imagery EEG data demonstrate the superior performance of the proposed method., 15 pages, 7 figures

Purpose: The purpose of the study was to analyze the ultrasound findings and imaging features of patients with special types of ectopic pregnancy. Methods: The ultrasound findings of 40 patients with special types of ectopic pregnancy in our hospital were retrospectively analyzed. Results: Among 40 patients, there were 17 cases of corneal pregnancy, 12 cases of cervical pregnancy, 8 cases of uterine scar pregnancy, and 3 cases of incomplete abortion confirmed by operation and pathology. The accuracy rate of ultrasound findings in the diagnosis of 40 special types of ectopic pregnancy was 77.50%, with a consistency rate of 70.59% for cornual pregnancy, 83.33% for cervical pregnancy, 100.00% for cesarean scar pregnancy and 33.33% for incomplete abortion. There were 9 misdiagnoses in ultrasound diagnosis, including 5 misdiagnoses of angular pregnancy (misdiagnosed as 4 cases of tubal interstitial pregnancy and 1 case of trophoblastic tumor), 2 misdiagnoses of cervical pregnancy (misdiagnosed as incomplete abortion), and 2 misdiagnoses of incomplete abortion (misdiagnosed as isthmus pregnancy). There was no misdiagnosed case of cesarean scar pregnancy. Conclusion: Ultrasound findings have some value in the diagnosis of specific types of ectopic pregnancy and can help identify different types of ectopic pregnancy. Transabdominal ultrasound and transvaginal ultrasound should be clinically combined to obtain more information for diagnosis.

Two-dimensional (2D) materials with a Lieb lattice can host exotic electronic band structures. Such a system does not exist in nature, and it is also difficult to obtain in the laboratory due to its structural instability. Here, we experimentally realized a 2D system composed of a tin overlayer on an aluminum substrate by molecular beam epitaxy. The specific arrangement of Sn atoms on the Al(100) surface, which benefits from favorable interface interactions, forms a stabilized buckled Lieb lattice. Our theoretical calculations indicate a partially broken nodal line loop protected by its mirror reflection symmetry and a topologically nontrivial insulating state with a spin-orbital coupling (SOC) effect in the band structure of this Lieb lattice. The electronic structure of this system has also been experimentally characterized by scanning tunnelling spectroscopy and angle-resolved photoemmision spectroscopy. Our work provides an appealing method for constructing 2D quantum materials based on the Lieb lattice., 14 pages, 4 figures

As a new group of advanced 2D layered materials, bismuth oxyhalides, i.e., BiOX (X = Cl, Br, I), have recently become of great interest. In this work, we characterize the third-order optical nonlinearities of BiOBr, an important member of the BiOX family. The nonlinear absorption and Kerr nonlinearity of BiOBr nanoflakes at both 800 nm and 1550 nm are characterized via the Z-Scan technique. Experimental results show that BiOBr nanoflakes exhibit a large nonlinear absorption coefficient β ~ 10-7 m/W as well as a large Kerr coefficient n2 ~ 10-14 m2/W. We also note that the n2 of BiOBr reverses sign from negative to positive as the wavelength is changed from 800 nm to 1550 nm. We further characterize the thickness-dependent nonlinear optical properties of BiOBr nanoflakes, finding that the magnitudes of β and n2 increase with decreasing thickness of the BiOBr nanoflakes. Finally, we integrate BiOBr nanoflakes into silicon integrated waveguides and measure their insertion loss, with the extracted waveguide propagation loss showing good agreement with mode simulations based on ellipsometry measurements. These results confirm the strong potential of BiOBr as a promising nonlinear optical material for high-performance hybrid integrated photonic devices.

Differentiated thyroid cancer (DTC) is the most common thyroid cancer with a relatively high survival rate. The association between certain risk factors of distant metastasis (DM) remains uncertain. In order to assess the prognosis of patients with DTC better, the present study aimed to investigate the synergistic effects between histologic subtype, tumor size, lymph node metastasis (LNM) status and extrathyroidal extension (ETE) on the incidence of DM in DTC. Data of 96,788 patients with DTC were obtained from the Surveillance, Epidemiology and End Results database. The association between clinicopathological factors and DM was evaluated by univariate and multivariate analyses. The synergistic effects of relevant factors were determined by measuring the relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP) and synergy index (SI). The results demonstrated that tumor size, LNM status, histologic subtype and ETE were independent risk factors for DM [odds ratio (OR)=2.433; P

We report a high Kerr optical nonlinearity in BiOBr nanoflakes that varies with thickness via Z-Scan technique. We integrate BiOBr nanoflakes onto silicon nanowires and characterize the linear optical properties of the hybrid integrated devices. © 2020 The Author(s)

We experimentally characterize the third-order optical Kerr nonlinearity of BiOBr nanoflakes via Z-Scan technique. Strong nonlinear absorption as well as high Kerr nonlinearity (n2) are observed at both 800 nm and 1550 nm, with a large nonlinear absorption coefficient on the order of 10-7 m/W and a high Kerr coefficient on the order of 10-14 m2/W being measured.

Exploring stable two-dimensional materials with appropriate band gaps and high carrier mobility is highly desirable due to the potential applications in optoelectronic devices. Here, the electronic structures of phosphorene on a Au(111) substrate are investigated by scanning tunneling spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations. The substrate-induced phosphorene superstructure gives a superlattice potential, leading to a strong band folding effect of the sp band of Au(111) on the band structure. The band gap could be clearly identified in the ARPES results after examining the folded sp band. The value of the energy gap (∼1.1 eV) and the high charge carrier mobility comparable to that of black phosphorus, which is engineered by the tensile strain, are revealed by the combination of ARPES results and DFT calculations. Furthermore, the phosphorene layer on the Au(111) surface displays high surface inertness, leading to the absence of multilayer phosphorene. All these results suggest that the phosphorene on Au(111) could be a promising candidate, not only for fundamental research but also for nanoelectronic and optoelectronic applications.

Pursuing efficient and low-cost electrocatalysts is crucial for the performance of water–alkali electrolyzers toward water splitting. Earth-abundant transition-metal oxides, in spite of their alluring performances in the oxygen evolution reaction, are thought to be inactive in the hydrogen evolution reaction in alkaline media. Here, we demonstrate that pure TiO2 single crystals, a typical transition-metal oxide, can be activated toward electrocatalytic hydrogen evolution reaction in alkaline media through engineering interfacial oxygen vacancies. Experimental and theoretical results indicate that subsurface oxygen vacancies and low-coordinated Ti ions (Ti3+) can enhance the electrical conductivity and promote electron transfer and hydrogen desorption, which activate reduced TiO2 single crystals in the hydrogen evolution reaction in alkaline media. This study offers a rational route for developing reduced transition-metal oxides for low-cost and highly active hydrogen evolution reaction catalysts, to reali...

• The s-p orbital hybridization has been interpreted as an efficient strategy for active photocatalysts with high carrier mobility, owing to its ability of obtaining large overlap between valence electrons which reslut in dispersive energy bands.

Heterostructures of two-dimensional (2D) layered materials with selective compositions play an important role in creating novel functionalities. Effective interface coupling between 2D ferromagnet and electronic materials would enable the generation of exotic physical phenomena caused by intrinsic symmetry breaking and proximity effect at interfaces. Here, epitaxial growth of bilayer Bi(110) on 2D ferromagnetic Fe3GeTe2 (FGT) with large magnetic anisotropy has been reported. Bilayer Bi(110) islands are found to extend along fixed lattice directions of FGT. The six preferred orientations could be divided into two groups of three-fold symmetry axes with the difference approximately to 26{\deg}. Moreover, dI/dV measurements confirm the existence of interface coupling between bilayer Bi(110) and FGT. A variation of the energy gap at the edges of bilayer Bi(110) is also observed which is modulated by the interface coupling strengths associated with its buckled atomic structure. This system provides a good platform for further study of the exotic electronic properties of epitaxial Bi(110) on 2D ferromagnetic substrate and promotes potential applications in the field of spin devices., Comment: 15 pages, 4 figures

The compelling experimental evidence of multilayer silicene synthesis on one monolayer of silver deposited on a silicon substrate, Si(111)√3 × √3-Ag, used as a template is reported. Auger electron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy/spectroscopy, in situ Raman spectroscopy, and energy-dispersive in-plane X-ray diffraction were applied to achieve the fingerprints of √3 × √3 multilayer silicene. Density functional theory calculations provided the structural models of single, bilayer, and three-layer silicene on the Si(111)√3 × √3-Ag surface. Single-layer silicene retains its free-standing form. The structural models, which are consistent with the experimental findings, feature atomic structure substantially different from that of Si(111).

Highly efficient visible-light photocatalysts are strongly in demand because they make it possible to achieve higher efficiency in utilization of solar energy, which is renewable and abundant. A narrow band gap, effective separation of photoexcited charge carriers, and proper band-edge positions, which depend on the band structure of the photocatalyst, are crucial for solar-energy conversion efficiency. In this review, we have summarized reports on the strategy of exploiting highly efficient visible-light photocatalysts by constructing their band structure with anisotropic p and s-p hybridization states. Taking advantage of their dispersive and easily tunable band properties, enhanced efficiency in solar light absorption, efficient separation of photoexcited charge carriers and catalytic reactions are expected to be simultaneously achieved.

Bismuth-based compounds have been regarded as an important class of visible-light photocatalysts due to their special electronic structures. In this paper, iodide ions are introduced to modify bismuth-based compound, Bi24O31Br10, forming a Bi24O31Br10/BiOI heterojunction structure. A significant enhancement of photocatalytic activity compared to the parent compounds is observed in de-coloration of rhodamine B (Rh.B) solution. The improved photocatalytic property of Bi24O31Br10/BiOI heterojunction is ascribed to the unique electronic structure consisting of complementary band structures of BiOI and Bi24O31Br10. Iodide ions are regarded as an effective reagent to construct bismuth-based photocatalytic heterojunctions with improved photocatalytic activity.