Nanoscale InGaSb heterostructure membranes on Si substrates for high hole mobility transistors

As of yet, III-V p-type field-effect transistors (p-FETs) on Si have not been reported, due partly to materials and processing challenges, presenting an important bottleneck in the development of complementary III-V electronics. Here, we report the first high-mobility III-V p-FET on Si, enabled by the epitaxial layer transfer of InGaSb heterostructures with nanoscale thicknesses. Importantly, the use of ultrathin (thickness, ~2.5 nm) InAs cladding layers results in drastic performance enhancements arising from (i) surface passivation of the InGaSb channel, (ii) mobility enhancement due to the confinement of holes in InGaSb, and (iii) low-resistance, dopant-free contacts due to the type III band alignment of the heterojunction. The fabricated p-FETs display a peak effective mobility of ~820 cm(2)/(V s) for holes with a subthreshold swing of ~130 mV/decade. The results present an important advance in the field of III-V electronics.     

Preparation of acetamiprid-loaded polymeric microcapsules: Influence of preparation parameter in emulsion system on microcapsule characteristics

Microencapsulation of pesticides is a promising technique for avoiding high initial doses and multiple applications of the chemicals to agricultural land which cause environmental pollution. It is because the formulation is possible to improve the stability of the chemicals against environmental degradation and control the release rate. In the present study, polymeric microcapsules prepared by the solvent evaporation method via water-in-oil-in-water (W/O/W) emulsion were used as immobilization supports of acetamiprid, a water-soluble pesticide. The pesticide was loaded in the microcapsules by impregnating the polymeric supports with acetamiprid dissolved in an organic solvent. Increased volume ratio (ϕ) of inner aqueous phase to oil phase in the emulsion system contributed to more pores in the microcapsules and increase in the content of acetamiprid in the polymeric supports. Release rate of acetamiprid from the microcapsules could be controlled by changing ϕ.     

Characterisation of a TES-Based X-ray Microcalorimeter in the Energy Range from 150 to 1800 eV Using an Adiabatic Demagnetisation Refrigerator

We characterised a TES-based X-ray microcalorimeter in an adiabatic demagnetisation refrigerator (ADR) using synchrotron radiation. The detector response and energy resolution was measured at the beam-line in the PTB radiometry laboratory at the electron storage ring BESSY II in the range from 200 to 1800 eV. We present and discuss the results of the energy resolution measurements as a function of energy, beam intensity and detector working point. The measured energy resolution ranges between 1.5 to 2.1 eV in the investigated energy range and is weakly dependent on the detector set point. A first analysis shows a count-rate capability, without considerable loss of performance, of about 500 counts per second.      

Development of High Count-Rate Digital Processing System with SpaceWire for TES-Calorimeter Array

A digital processing system for a TES microcalorimeter array is being developed based on “SpaceWire” interface. In this system, we introduced a trigger logic which can handle double-pulse events due to high count rate in future X-ray missions and several application on the ground experiments. The detailed design and performance of this system is described.      

Performance Measurement of the 8-Input SQUIDs for TES Frequency Domain Multiplexing

We report on performance of 8-input superconducting quantum interference devices (SQUIDs) for multiplexing transition-edge sensor signals by using frequency-domain multiplexing. We found the typical critical current and the flux noise to be 17–19 μA and 0.7–1.1 μ , respectively. We also measured the crosstalk current between the input coils of the SQUIDs, and found that the mutual inductance was consistent with the design value, 800 pH. We confirmed that the cross talk current due to the mutual inductance was reduced by the flux-locked-loop (FLL) feedback, and its reduction rate was consistent with 1/(1+ℒ), where ℒ is the FLL feedback gain. We also show the result of 2-channel DC-driven TES signals readout using the 8-input SQUIDs.      

Preparation of new zirconium phosphates by solvothermal reaction

Two types of new zirconium phosphates, [enH₂]Zr(OH)(PO₄)(HPO₄) (en; ethylene diamine) and (NH₄)₅[Zr₃(OH)₉(PO₄)₂(HPO₄)] were prepared under solvothermal condition using diethylene glycol as a solvent and their crystal structures were determined by using single crystal X-ray diffraction data. The former compound has the layer structure similar to that of γ-Zr(PO₄)(H₂PO₄) · 2H₂O, and protonated ethylene diamines were located in the interlayer space. At elevated temperatures, this compound decomposed by releasing protonated ethylene diamines and finally changed to ZrP₂O₇. The interlayer space was soft-chemically inactive unlike α-Zr(HPO₄)₂ · H₂O and γ-Zr(PO₄)(H₂PO₄) · 2H₂O. The later compound has the tunnel structure built up by corner-sharing ZrO₆ octahedra and PO₄ tetrahedra, and NH₄ ⁺ ion was located in the tunnel.     

Optically- and thermally-responsive programmable materials based on carbon nanotube-hydrogel polymer composites

A simple approach is described to fabricate reversible, thermally- and optically responsive actuators utilizing composites of poly(N-isopropylacrylamide) (pNIPAM) loaded with single-walled carbon nanotubes. With nanotube loading at concentrations of 0.75 mg/mL, we demonstrate up to 5 times enhancement to the thermal response time of the nanotube-pNIPAM hydrogel actuators caused by the enhanced mass transport of water molecules. Additionally, we demonstrate the ability to obtain ultrafast near-infrared optical response in nanotube-pNIPAM hydrogels under laser excitation enabled by the strong absorption properties of nanotubes. The work opens the framework to design complex and programmable self-folding materials, such as cubes and flowers, with advanced built-in features, including tunable response time as determined by the nanotube loading.     

Dramatic reduction of surface recombination by in situ surface passivation of silicon nanowires

Nanowires have unique optical properties and are considered as important building blocks for energy harvesting applications such as solar cells. However, due to their large surface-to-volume ratios, the recombination of charge carriers through surface states reduces the carrier diffusion lengths in nanowires a few orders of magnitude, often resulting in the low efficiency (a few percent or less) of nanowire-based solar cells. Reducing the recombination by surface passivation is crucial for the realization of high-performance nanosized optoelectronic devices but remains largely unexplored. Here we show that a thin layer of amorphous silicon (a-Si) coated on a single-crystalline silicon nanowire, forming a core-shell structure in situ in the vapor-liquid-solid process, reduces the surface recombination nearly 2 orders of magnitude. Under illumination of modulated light, we measure a greater than 90-fold improvement in the photosensitivity of individual core-shell nanowires, compared to regular nanowires without shell. Simulations of the optical absorption of the nanowires indicate that the strong absorption of the a-Si shell contributes to this effect, but we conclude that the effect is mainly due to the enhanced carrier lifetime by surface passivation.     

Rate of droplet deposition in steam-water annular flow and effect of a flow obstacle

Deposition rate of droplets in steam-water annular two-phase flow was measured using a 5 mm diameter vertical round tube as a test section. In the experimental conditions tested in this work, the droplet mass transfer coefficient decreased with an increase in the droplet concentration in the gas core flow and with an increase in the length of a deposition section. The dependence on these two parameters agreed fairly well with predictions by available correlations. Placing a small cylindrical tube concentrically in the test section round tube, the effect of a flow obstacle on the deposition rate of droplets was also experimentally investigated. It was found that the obstacle effect was significant and the deposition rate of droplets increased approximately three times in average. The obstacle effect measured in this work was compared with an empirical correlation and a simple mechanistic model that were developed using experimental results of air-water annular flows. Fairly good agreement was achieved in both cases, which would indicate that the mechanism of deposition enhancement induced by the flow obstacle is similar between air-water and steam-water flows.     

Focal calcium monitoring with targeted nanosensors at the cytosolic side of endoplasmic reticulum

Ca²⁺ distribution is spatially and temporally non-uniform inside cells due to cellular compartmentalization. However, Ca²⁺ sensing with small organic dyes, such as fura-2 and fluo-4, has been practically applied at a single cell level where the averaged signal from freely diffusing dye molecules is acquired. In this study, we aimed to target azide-functionalized fura-2 (N₃-fura-2) to a specific site of subcellular compartments to realize focal Ca²⁺ sensing. Using scAVD (single-chain avidin)–biotin interaction and a copper-free click reaction system, we linked N₃-fura-2 to specifically-targeted scAVD protein fused with a red fluorescent protein mCherry, so that Ca²⁺ sensors conjugated with four N₃-fura-2 dyes with dibenzocyclooctyne (DBCO)-PEG4-biotin as a linker were generated at subcellular compartments in living cells. In cytoplasm, N₃-fura-2 showed a prolonged retention period after binding to scAVD. Furthermore, the reacted N₃-fura-2 was retained inside cells even after free dyes were washed out by methanol fixation. When scAVD was overexpressed on endoplasmic reticulum (ER) membranes, N₃-fura-2 was accumulated on ER membranes. Upon histamine stimulation, which increases cytosolic Ca²⁺ concentration, ER-localized N₃-fura-2 successfully sensed the Ca²⁺ level changes at the cytosolic side of ER membrane. Our study demonstrated specific targeting of N₃-fura-2 to subcellular compartments and the ability of sensing focal Ca²⁺ level changes with the specifically targeted Ca²⁺ sensors.