Enhancing the Humidity Sensitivity of Ga2O3/SnO2 Core/Shell Microribbon by Applying Mechanical Strain and Its Application as a Flexible Strain Sensor

The humidity sensitivity of a single β‐Ga₂O₃/amorphous SnO₂ core/shell microribbon on a flexible substrate is enhanced by the application of tensile strain and increases linearly with the strain. The strain‐induced enhancement originates from the increase in the effective surface area where water molecules are adsorbed. This strain dependence of humidity sensitivity can be used to monitor the external strain. The strain sensing of the microribbon device under various amounts of mechanical loading shows excellent reliability and reproducibility with a gauge factor of ?41. The flexible device has high potential to detect both humidity and strain at room temperature. These findings and the mechanism involved are expected to pave the way for new flexible strain and multifunctional sensors.     

The thermodynamic database malt

The objectives of the development of the thermodynamic database MALT are described together with its main characteristic features. The database, which contains about 5000 species, also composes software for calculation of chemical equilibria and construction of generalized chemical potential diagrams. Discussion is made on the quality of the thermodynamic data to be used in the advanced software for calculating complex chemical equilibria in multicomponent systems and the importance of the chemical potential diagrams for checking the interconsistency of data in a visual manner is stressed.     

Excitons in organic-inorganic hybrid compounds (CnH2n + 1NH3)2PbBr4 (n = 4, 5, 7 and 12)

Thin films of microcrystalline (C_nH_2n + 1NH₃)₂PbBr₄ (n = 4, 5, 7 and 12) have been prepared by a modified spin-coating method, and the effect of the number of carbon atoms of the alkyl chain length (n) on optical properties has been investigated. Absorption spectra reveal that (C_nH_2n + 1NH₃)₂PbBr₄ films show stable excitons with a binding energy of a few hundred meV. The excitonic structure of (C_nH_2n + 1NH₃)₂PbBr₄ varies with the number of carbon atoms. The lowest-energy exciton splits into a few fine-structure levels at low temperature. (C_nH_2n + 1NH₃)₂PbBr₄ films (n = 5, 7 and 12) show not only singlet excitons but also triplet excitons at low temperature, while (C₄H₉NH₃)₂PbBr₄ films show only singlet excitons. The intersystem crossing from excited singlet state to triplet state plays an important role in the relaxation process of excitons.     

Multi-wavelength intermittent photoluminescence of single CdSe quantum dots

A single chromophore detection using video-microscopy is one of the latest methodologies to reveal unique characteristics, which could not be obtained from ensemble measurements. Among many kinds of subjects, dynamic optical properties observed in colloidal semiconductor nanoparticles are attractive and important not only for the basis of photo-physics but also for application studies, e.g. biological labeling, electronic devices. In this study, fluorescence video-microscopy was performed on cadmium selenide (CdSe) quantum dots (QDs) spin-coated on a glass substrate. From single CdSe QDs detection, emissions at wavelengths separated over 60 nm were observed for the first time. This spectral feature was attributed to the existence of double-emissive relaxation processes in CdSe QDs. Photoluminescence intermittency was also observed both from relaxation processes. Fluorescence video-microscopy, which was advanced in biology, can be applicable for the real-time monitoring of dynamic properties in semiconductor photo-physics.     

Synthesis and Photocrosslinking Reaction of N-Allylcarbamoylmethyl Cellulose Leading to Hydrogel

Summary The reaction of the carboxymethyl cellulose sodium salt (Na-CMC) (degrees of substitution (DS) = 1.2) with N-hydroxysuccinimide (Su-OH) in the presence of 1-hydroxybenzotriazole and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was carried out in water to obtain the Su-OH ester of carboxymethyl cellulose, Su-CMC, with the DS values of 0.19 – 1.04. N-Allylcarbamoylmethyl cellulose (Allyl-CMC), which was prepared from the reaction of Su-CMC with an excess amount of allylamine, was crosslinked by UV-irradiation. In addition, the photocrosslinked Allyl-CMC film was swollen with water to form a hydrogel having a relatively high water-swelling property, e.g., the degree of swelling (ds) was ca. 360% for Allyl-CMC with the DS of 0.93.     

Modeling of NBTI saturation effect and its impact on electric field dependence of the lifetime

Negative Bias Temperature Instability of pMOSFETs is investigated under various stress gate voltages and temperatures. It is shown that degradation tends to saturate and the dependence of lifetime on electric field (E_ox) is expressed as a power-law of E_ox. We propose new empirical and kinetic models. The E_ox dependence of the lifetime described by the power-law is derived from our empirical model describing the saturation of degradation. Moreover, our kinetic model explains the saturation behavior.     

Highly Reproducible and Regulated Conductance Quantization in a Polymer‐Based Atomic Switch

A detailed understanding of the conductance quantization and resistive switching phenomena in redox‐based memories is crucial for realizing atomic‐scale memory devices and for finding the adequate design principles on which they can be based. Here, the emergence of quantized conductance states and their correlation with resistive switching characteristics in polymer‐based atomic switches are investigated using combinations of current–voltage measurements and first‐principles density functional theory (DFT) simulations. Various conductance states, including integer and half‐integer multiples of a single atomic point contact and fractional conductance variations, are observed in an Ag/polyethylene oxide/Pt device under sweeping of bias voltage. Moreover, highly controllable and reproducible quantized conductance behaviors by tuning the voltage sweep rate and the sweep voltage range, suggesting well‐controlled formation of the atomic point contact, are demonstrated. The device also exhibits longer retention times for higher conductance states. The DFT simulations reveal the transmission eigenstate of geometrically optimized atomic point contact structures and the impact of the atomic configurations and structural stability on the conductance state, which also explains their resistive switching behaviors. The well‐defined, multiple quantized conductance states observed in these polymer‐based atomic switches show promise for the development of new multilevel memory devices.