Dielectric Constant in Nanoscale Bubbles on MoS.

Nanoscale bubbles form inevitably during the transfer of two-dimensional (2D) materials on a target substrate due to their van der Waals interaction. Despite a large number of studies based on nanobubble structures with localized strain, the dielectric constant (κ) in nanobubbles of MoS is poorly understood. Here, we report κ measurements for nanobubbles on MoS by probing the polarization forces based on electrostatic force microscopy.

Detection of incomplete atypical femoral fracture on anteroposterior radiographs via explainable artificial intelligence.

One of the key aspects of the diagnosis and treatment of atypical femoral fractures is the early detection of incomplete fractures and the prevention of their progression to complete fractures. However, an incomplete atypical femoral fracture can be misdiagnosed as a normal lesion by both primary care physicians and orthopedic surgeons; expert consultation is needed for accurate diagnosis. To overcome this limitation, we developed a transfer learning-based ensemble model to detect and localize fractures.

Deep-learning-based gestational sac detection in ultrasound images using modified YOLOv7-E6E model.

As the population and income levels rise, meat consumption steadily increases annually. However, the number of farms and farmers producing meat decrease during the same period, reducing meat sufficiency. Information and Communications Technology (ICT) has begun to be applied to reduce labor and production costs of livestock farms and improve productivity.

Alleviation of neurotoxicity induced by polystyrene nanoplastics by increased exocytosis from neurons.

Nanoplastics (NPs) are potentially toxic and pose a health risk as they can induce an inflammatory response and oxidative stress at cellular and organismal levels. Humans can be exposed to NPs through various routes, including ingestion, inhalation, and skin contact. Notably, uptake into the body via inhalation could result in brain accumulation, which may occur directly across the blood-brain barrier or via other routes.

An intelligent method for pregnancy diagnosis in breeding sows according to ultrasonography algorithms.

Pig breeding management directly contributes to the profitability of pig farms, and pregnancy diagnosis is an important factor in breeding management. Therefore, the need to diagnose pregnancy in sows is emphasized, and various studies have been conducted in this area. We propose a computer-aided diagnosis system to assist livestock farmers to diagnose sow pregnancy through ultrasound.

Transfer learning-based ensemble convolutional neural network for accelerated diagnosis of foot fractures.

The complex shape of the foot, consisting of 26 bones, variable ligaments, tendons, and muscles leads to misdiagnosis of foot fractures. Despite the introduction of artificial intelligence (AI) to diagnose fractures, the accuracy of foot fracture diagnosis is lower than that of conventional methods. We developed an AI assistant system that assists with consistent diagnosis and helps interns or non-experts improve their diagnosis of foot fractures, and compared the effectiveness of the AI assistance on various groups with different proficiency.

Nondestructive and local mapping photoresponse of WSe by electrostatic force microscopy.

We report a local mapping photoresponse of WSe using a second-harmonic (2w) channel based on nondestructive electrostatic force microscopy (EFM). The 2w signals resulting from interaction between WSe and EFM tip are intrinsically related to the electrical conductivity of WSe. The photoresponse images and rise/decay time constants of WSe are obtained by local mapping 2w signals under illumination.

Synthesis of Vapochromic Dyes Having Sensing Properties for Vapor Phase of Organic Solvents Used in Semiconductor Manufacturing Processes and Their Application to Textile-Based Sensors.

Two vapochromic dyes (DMx and DM) were synthesized to be used for textile-based sensors detecting the vapor phase of organic solvents. They were designed to show sensitive color change properties at a low concentration of vapors at room temperature. They were applied to cotton fabrics as a substrate of the textile-based sensors to examine their sensing properties for nine organic solvents frequently used in semiconductor manufacturing processes, such as trichloroethylene, dimethylacetamide, iso-propanol, methanol, n-hexane, ethylacetate, benzene, acetone, and hexamethyldisilazane.

Observing the Layer-Number-Dependent Local Dielectric Response of WSe by Electrostatic Force Microscopy.

We investigate the layer-number-dependent dielectric response of WSe by measuring the phase shift (Φ) through an electrostatic force microscopy (EFM). The measured Φ results stem mainly from the capacitive coupling between the tip and WSe based on the plane capacitor model, leading to changes in the second derivative of the capacitance ('') values, which increase in a few layers and saturate to the bulk value under an applied EFM tip bias. The '' value is related to the dielectric polarization, reflecting the charge carrier concentration and mobility of WSe flakes with different numbers of layers.

Highly transparent phototransistor based on quantum-dots and ZnO bilayers for optical logic gate operation in visible-light.

Highly transparent optical logic circuits operated with visible light signals are fabricated using phototransistors with a heterostructure comprised of an oxide semiconductor (ZnO) with a wide bandgap and quantum dots (CdSe/ZnS QDs) with a small bandgap. ZnO serves as a highly transparent active channel, while the QDs absorb visible light and generate photoexcited charge carriers. The induced charge carriers can then be injected into the ZnO conduction band from the QD conduction band, which enables current to flow to activate the phototransistor.

High Efficiency Doping of Conjugated Polymer for Investigation of Intercorrelation of Thermoelectric Effects with Electrical and Morphological Properties.

Intercorrelation of thermoelectric properties of a doped conjugated semiconducting polymer (PIDF-BT) with charge carrier density, conductive morphology, and crystallinity are systematically investigated. Upon being doped with F4-TCNQ by the sequential doping method, PIDF-BT exhibited a high electrical conductivity over 210 S cm. The significant enhancement of electrical conductivity resulted from a high charge carrier density, which is attributed to the effective charge-transfer-based integer doping between PIDF-BT and dopant molecules.

Direct Mapping of the Gate Response of a Multilayer WSe/MoS Heterostructure with Locally Different Degrees of Charge Depletion.

Understanding the interlayer charge coupling mechanism in a two-dimensional van der Waals (vdW) heterojunction is crucial for optimizing the performance of heterostructure-based (opto)electronic devices. Here, we report mapping the gate response of a multilayer WSe/MoS heterostructure with locally different degrees of charge depletion through mobile carrier measurements based on electrostatic force microscopy. We observed ambipolar or unipolar behavior depending on the degree of charge depletion in the heterojunction under tip gating.

Molecularly Controlled Stark Effect Induces Significant Rectification in Polycyclic-Aromatic-Hydrocarbon-Terminated n-Alkanethiolates.

The variation of the electronic structure of individual molecules as a function of the applied bias matters for the performance of molecular and organic electronic devices. Understanding the structure-electric-field relationship, however, remains a challenge because of the lack of in-operando spectroscopic technique and complexity arising from the ill-defined on-surface structure of molecules and organic-electrode interfaces within devices. We report that a reliable and reproducible molecular diode can be achieved by control of the conjugation length in polycyclic-aromatic-hydrocarbon (PAH)-terminated n-alkanethiolate (denoted as SCPAH), incorporated into liquid-metal-based large-area tunnel junctions in the form of a self-assembled monolayer.

Intrinsic Correlation between Electronic Structure and Degradation: From Few-Layer to Bulk Black Phosphorus.

Black phosphorus (BP) has received much attention owing to its fascinating properties, such as a high carrier mobility and tunable band gap. However, these advantages have been overshadowed by the fast degradation of BP under ambient conditions. To overcome this obstacle, the exact degradation mechanisms need to be unveiled.

Vertical and In-Plane Current Devices Using NbS/n-MoS van der Waals Schottky Junction and Graphene Contact.

A van der Waals (vdW) Schottky junction between two-dimensional (2D) transition metal dichalcogenides (TMDs) is introduced here for both vertical and in-plane current devices: Schottky diodes and metal semiconductor field-effect transistors (MESFETs). The Schottky barrier between conducting NbS and semiconducting n-MoS appeared to be as large as ∼0.5 eV due to their work-function difference.

Contact Effect of ReS/Metal Interface.

Rhenium disulfide (ReS) has attracted immense interest as a promising two-dimensional material for optoelectronic devices owing to its outstanding photonic response based on its energy band gap's insensitivity to the layer thickness. Here, we theoretically calculated the electrical band structure of mono-, bi-, and trilayer ReS and experimentally found the work function to be 4.8 eV, which was shown to be independent of the layer thickness.

Charge transport and rectification in molecular junctions formed with carbon-based electrodes.

Molecular junctions formed using the scanning-tunneling-microscope-based break-junction technique (STM-BJ) have provided unique insight into charge transport at the nanoscale. In most prior work, the same metal, typically Au, Pt, or Ag, is used for both tip and substrate. For such noble metal electrodes, the density of electronic states is approximately constant within a narrow energy window relevant to charge transport.

Determination of energy level alignment and coupling strength in 4,4'-bipyridine single-molecule junctions.

We measure conductance and thermopower of single Au-4,4'-bipyridine-Au junctions in distinct low and high conductance binding geometries accessed by modulating the electrode separation. We use these data to determine the electronic energy level alignment and coupling strength for these junctions, which are known to conduct through the lowest unoccupied molecular orbital (LUMO). Contrary to intuition, we find that, in the high-conductance junction, the LUMO resonance energy is further away from the Au Fermi energy than in the low-conductance junction.

Graphene nanonet for biological sensing applications.

We report a simple but efficient method to fabricate versatile graphene nanonet (GNN)-devices. In this method, networks of V2O5 nanowires (NWs) were prepared in specific regions of single-layer graphene, and the graphene layer was selectively etched via a reactive ion etching method using the V2O5 NWs as a shadow mask. The process allowed us to prepare large scale patterns of GNN structures which were comprised of continuous networks of graphene nanoribbons (GNRs) with chemical functional groups on their edges.

Multilayered nano-prism vertex tips for tip-enhanced Raman spectroscopy and imaging.

We presented a scalable fabrication method for the preparation of multilayered nano-prism vertex (NV)-tips whose dimensions can be controlled for tip-enhanced Raman spectroscopy (TERS). The NV-tip had sharp vertices (diameter ~20 nm) originated from the chemical lift-off process after the angle-grinding process, enabling high resolution imaging. TERS measurements were performed on brilliant cresyl blue (BCB) molecules using a Ag/Au NV-tip, revealing the enhanced field localization at the vertices of the NV-tip.

Conductance of molecular junctions formed with silver electrodes.

We compare the conductance of a series of amine-terminated oligophenyl and alkane molecular junctions formed with Ag and Au electrodes using the scanning tunneling microscope based break-junction technique. For these molecules that conduct through the highest occupied molecular orbital, junctions formed with Au electrodes are more conductive than those formed with Ag electrodes, consistent with the lower work function for Ag. The measured conductance decays exponentially with molecular backbone length with a decay constant that is essentially the same for Ag and Au electrodes.

Nanotube-bridged wires with sub-10 nm gaps.

We report a simple but efficient method to synthesize carbon nanotube-bridged wires (NBWs) with gaps as small as 5 nm. In this method, we have combined a strategy for assembling carbon nanotubes (CNTs) inside anodized aluminum oxide pores and the on-wire lithography technique to fabricate CNT-bridged wires with gap sizes deliberately tailored over the 5-600 nm range. As a proof-of-concept demonstration of the utility of this architecture, we have prepared NBW-based chemical and biosensors which exhibit higher analyte sensitivity (lower limits of detection) than those based on planar CNT networks.

Floating electrode transistor based on purified semiconducting carbon nanotubes for high source-drain voltage operation.

We report floating-electrode-based thin-film transistors (F-TFTs) based on a purified semiconducting single-walled carbon nanotube (swCNT) network for a high source-drain voltage operation. At a high source-drain voltage, a conventional swCNT-TFT exhibited poor transistor performance with a small on-off ratio, which was attributed to the reduced Schottky barrier modulation at a large bias. In the F-TFT device, an swCNT network channel was separated into a number of channels connected by floating electrodes.

Scanning noise microscopy on graphene devices.

We developed a scanning noise microscopy (SNM) method and demonstrated the nanoscale noise analysis of a graphene strip-based device. Here, a Pt tip made a direct contact on the surface of a nanodevice to measure the current noise spectrum through it. Then, the measured noise spectrum was analyzed by an empirical model to extract the noise characteristics only from the device channel.