Synthesis and Characterization of UV-Curable Resin with High Refractive Index for a Luminance-Enhancing Prism Film.

A novel monomer, 9-bis[4-(2-hydroxyethoxy)phenyl]fluorene di(mercaptopropionate), with a highly refractive index, purity, and excellent UV-curable properties, is synthesized through an optimized Fischer esterification process, reacting 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene with 3-mercaptopropionic acid. The structural characterization of this monomer is performed using Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and liquid chromatography-mass spectrometry. The synthesis conditions are optimized using a design-of-experiments approach.

NaCl Ionization-Based Moisture Sensor Prepared by Aerosol Deposition for Monitoring Respiratory Patterns.

A highly polarizable moisture sensor with multimodal sensing capabilities has great advantages for healthcare applications such as human respiration monitoring. We introduce an ionically polarizable moisture sensor based on NaCl/BaTiO composite films fabricated using a facile aerosol deposition (AD) process. The proposed sensing model operates based on an enormous NaCl ionization effect in addition to natural moisture polarization, whereas all previous sensors are based only on the latter.

Fabrication of Large-Area Mullite-Cordierite Composite Substrates for Semiconductor Probe Cards and Enhancement of Their Reliability.

This work aims to fabricate a large-area ceramic substrate for the application of probe cards. Mullite (M) and cordierite (C), which both have a low thermal expansion coefficient, excellent resistance to thermal shock, and high durability, were selected as starting powders. The mullite-cordierite composites were produced through different composition ratios of starting powders (M:C = 100:0, M:C = 90:10, M:C = 70:30, M:C = 50:50, M:C = 30:70, and M:C = 0:100).

Thermoelectric Properties of CuTe Nanoparticle Incorporated N-Type BiTeSe.

To develop highly efficient thermoelectric materials, the generation of homogeneous heterostructures in a matrix is considered to mitigate the interdependency of the thermoelectric compartments. In this study, CuTe nanoparticles were introduced onto BiTeSe n-type materials and their thermoelectric properties were investigated in terms of the amount of CuTe nanoparticles. A homogeneous dispersion of CuTe nanoparticles was obtained up to 0.

Enhanced Production of Bacterial Cellulose from as Sustainable Feedstock through Statistical Optimization of Culture Conditions.

Biorefineries are attracting attention as an alternative to the petroleum industry to reduce carbon emissions and achieve sustainable development. In particular, because forests play an important role in potentially reducing greenhouse gas emissions to net zero, alternatives to cellulose produced by plants are required. Bacterial cellulose (BC) can prevent deforestation and has a high potential for use as a biomaterial in various industries such as food, cosmetics, and pharmaceuticals.

Development of Colorimetric Whole-Cell Biosensor for Detection of Heavy Metals in Environment for Public Health.

Heavy metals cause various fetal diseases in humans. Heavy metals from factory wastewater can contaminate drinking water, fish, and crops. Inductively coupled plasma-mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) are commonly used to analyze heavy metal contents; however, these methods require pre-treatment processes and are expensive and complex.

Classification of Standing and Walking States Using Ground Reaction Forces.

The operation of wearable robots, such as gait rehabilitation robots, requires real-time classification of the standing or walking state of the wearer. This report explains a technique that measures the ground reaction force (GRF) using an insole device equipped with force sensing resistors, and detects whether the insole wearer is standing or walking based on the measured results. The technique developed in the present study uses the waveform length that represents the sum of the changes in the center of pressure within an arbitrary time window as the determining factor, and applies this factor to a conventional threshold method and an artificial neural network (ANN) model for classification of the standing and walking states.

Improved Electrical Characteristics of Gallium Oxide/P-Epi Silicon Carbide Static Induction Transistors with UV/Ozone Treatment Fabricated by RF Sputter.

In this study, static induction transistors (SITs) with beta gallium oxide (β-GaO) channels are grown on a p-epi silicon carbide (SiC) layer via radio frequency sputtering. The GaO films are subjected to UV/ozone treatment, which results in reduced oxygen vacancies in the X-ray photoelectron spectroscopy data, lower surface roughness (3.51 nm) and resistivity (319 Ω·cm), and higher mobility (4.

Effect of Gas Annealing on the Electrical Properties of Ni/AlN/SiC.

It is shown in this work that annealing of Schottky barrier diodes (SBDs) in the form of Ni/AlN/SiC heterojunction devices in an atmosphere of nitrogen and oxygen leads to a significant improvement in the electrical properties of the structures. Compared to the non-annealed device, the on/off ratio of the annealed SBD devices increased by approximately 100 times. The ideality factor, derived from the current-voltage (IV) characterization, decreased by a factor of ~5.

Influence of Gas Annealing on Sensitivity of AlN/4H-Sic-Based Temperature Sensors.

In this study, the physical and electrical characteristics of an AlN/4H-SiC Schottky barrier diode-based temperature sensor annealed in various gas atmospheres were investigated. An aluminum nitride (AlN) thin film was deposited on a 4H-SiC substrate via radio-frequency sputtering followed by annealing in N or O gas. The chemical composition of the film was determined by X-ray photoelectron spectroscopy (XPS) before and after annealing, and its electrical properties were evaluated by plotting a current-voltage (I-V) curve.

Comparison of Temperature Sensing Performance of 4H-SiC Schottky Barrier Diodes, Junction Barrier Schottky Diodes, and PiN Diodes.

We present a comparison between the thermal sensing behaviors of 4H-SiC Schottky barrier diodes, junction barrier Schottky diodes, and PiN diodes in a temperature range from 293 K to 573 K. The thermal sensitivity of the devices was calculated from the slope of the forward voltage versus temperature plot. At a forward current of 10 μA, the PiN diode presented the highest sensitivity peak (4.

Effect of Sacrificial AlN (Aluminum Nitride) Layer on the Deep Surface States of 4H-SiC.

We investigated the effect of a sacrificial AlN layer on the deep energy level states of 4H-SiC surface. The samples with and without AlN layer have been annealed at 1300 °C for 30 minutes duration using a tube furnace. After annealing the samples, the changes of the carbon vacancy () related defect characteristics were analyzed by deep level transient spectroscopy.

Effect of ZnO and SnO Nanolayers at Grain Boundaries on Thermoelectric Properties of Polycrystalline Skutterudites.

Nanostructuring is considered one of the key approaches to achieve highly efficient thermoelectric alloys by reducing thermal conductivity. In this study, we investigated the effect of oxide (ZnO and SnO) nanolayers at the grain boundaries of polycrystalline InYbCoSb skutterudites on their electrical and thermal transport properties. Skutterudite powders with oxide nanolayers were prepared by atomic layer deposition method, and the number of deposition cycles was varied to control the coating thickness.

Fabrication and Characterization of Oxygenated AlN/4H-SiC Heterojunction Diodes.

The effects of rapid thermal annealing (RTA) on Schottky barrier diodes (SBDs) made from oxygenated aluminum nitride (AlN) thin films deposited on a silicon carbide (SiC) substrate using radio frequency sputtering were investigated. The annealed SBD devices exhibited a 10x increase in the on/off current ratio vs. non-annealed devices for measurement temperatures ranging from 300 K to 450 K.

Enzymatic Synthesis of Formate Ester through Immobilized Lipase and Its Reuse.

Octyl formate is an important substance used in the perfume industry in products such as cosmetics, perfumes, and flavoring. Octyl formate is mostly produced by chemical catalysts. However, using enzymes as catalysts has gathered increasing interest due to their environment-friendly proprieties.

High-Performance Temperature Sensors Based on Dual 4H-SiC JBS and SBD Devices.

Schottky diode-based temperature sensors are the most common commercially available temperature sensors, and they are attracting increasing interest owing to their higher Schottky barrier height compared to their silicon counterparts. Therefore, this paper presents a comparison of the thermal sensitivity variation trend in temperature sensors, based on dual 4H-SiC junction barrier Schottky (JBS) diodes and Schottky barrier diodes (SBDs). The forward bias current-voltage characteristics were acquired by sweeping the DC bias voltage from 0 to 3 V.

Influence of Annealing Atmosphere on the Characteristics of GaO/4H-SiC n-n Heterojunction Diodes.

GaO/4H-SiC n-n isotype heterojunction diodes were fabricated by depositing GaO thin films by RF magnetron sputtering. The influence of annealing atmosphere on the film quality and electrical properties of GaO layers was investigated. X-ray diffraction (XRD) analysis showed a significant increase in the peak intensities of different faces of β-GaO {(-201), (-401) and (002)}.

Possibility of Thermal Energy Recycling Based Light Emitting Diodes Grid System.

Light Emitting Diodes (LED) are highly energy efficient and offer long-life times for display applications. Long life and minimal energy consumption are often the most attractive advantages for electronic devices. Because LEDs are based on compound semiconductors, which explore the direct transition between the conduction and valance band edges, thermal energy loss can be minimized during operation.

Enhanced Electrical Mobilities of Laser Annealed Ga Doped ZnO Thin Films.

In this study, Ga-doped ZnO thin films were prepared, and their potential for transparent conducting oxide applications was assessed. To increase the electrical mobility and reduce the resistance of Ga-doped ZnO thin films, CO₂ laser annealing was employed. Recently, the use of transparent conducting oxides (TCOs) have increased, particularly ZnO-based TCOs have been intensively investigated for display applications.

Applicability of Aerosol Deposition Process for flexible electronic device and determining the Film Formation Mechanism with Cushioning Effects.

In this paper, we demonstrated the feasibility of the Aerosol Deposition (AD) method which can be adapted as a future fabrication process for flexible electronic devices. On the basis of this method's noticeable advantages such as room-temperature processing, suitability for mass production, wide material selectivity, and direct fabrication on a flexible substrate, we fabricated and evaluated a flexible conductive bridge random access memory (CBRAM) to confirm the feasibility of this method. The CBRAM was fabricated by the AD-method, and a novel film formation mechanism was observed and analyzed.

Titanium-oxide based nanoscale and embeddable subzero temperature sensor using MIT deformation characteristics.

In this research, we propose a nanoscale and embeddable subzero temperature sensor that is made with a temperature-dependent titanium-oxide based metal-insulator-transition (MIT) device. For a nanoscale two-terminal structured MIT device, the MIT device's characteristics are noticeably changed from abrupt to gradual MIT under zero temperature, which is called MIT deformation. On the basis of the MIT deformation characteristics, subzero temperatures can be detected by reading current levels as temperature changes.

Recycled Thermal Energy from High Power Light Emitting Diode Light Source.

In this research, the recycled electrical energy from wasted thermal energy in high power Light Emitting Diode (LED) system will be investigated. The luminous efficiency of lights has been improved in recent years by employing the high power LED system, therefore energy efficiency was improved compared with that of typical lighting sources. To increase energy efficiency of high power LED system further, wasted thermal energy should be re-considered.

Improved Photo-Induced Stability in Amorphous Metal-Oxide Based TFTs for Transparent Displays.

In this paper, we investigate the origin of photo-induced instability in amorphous metal-oxide based thin-film transistors (oxide-TFTs) by exploring threshold voltage (Vth) shift in transfer characteristics. The combination of photo irradiation and prolonged gate bias stress enhanced the shift in Vth in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs. Such results stem from the extended trapped charges at the localized defect states related to oxygen vacancy which play a role in a screening effect on the electric field induced by gate voltage.

Elevated Temperature Operation of 4H-SiC Nanoribbon Field Effect Transistors.

We fabricated 4H-SiC nanoribbon field effect transistors (FETs) of various channel thickness (tch) of 100~500 nm by a "top-down" approach, using a lithography and plasma etching process. We studied the dependence of the device transfer characteristics on the channel geometry. This demonstrated that fabricated SiC nanoribbon FETs with a tch of 100 nm show normally-on characteristics, and have a threshold voltage of -12 V, and a maximum transconductance value of 8.