Scaling the silicon bipolar transistor for sub-100-ps ECL circuit operation at liquid nitrogen temperature

Ce14Fe78Co2B6 nanopowders with hard-magnetic properties have been successfully prepared by ball milling at low temperatures in liquid nitrogen. The morphology, structure, and magnetic properties of Ce14Fe78Co2B6 powders have been investigated using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. It was found that powder ball milling at low temperature in liquid nitrogen, has the advantage that the oxidation of powders is inhibited and the particles rapidly reach nanometric dimensions. In comparison to the Ce14Fe78Co2B6 powders prepared by ball milling at room temperature, the powders milled at low temperature present a more uniform particle size and no rare-earth oxides, which leads thus to remarkable magnetic properties. The nanocrystalline Ce14Fe78Co2B6 powders with optimum characteristics, prepared at low temperature, have the size of 153 nm or less, present a coercivity of 5.1 kOe, and a saturation magnetization of 113 emu/g after milling for 6 h at low temperature. Low temperature milling may become a promising technique for the fabrication of high performance powders used for permanent magnets preparation.

Titanium alloy has the advantages of low thermal conductivity, a small expansion coefficient and being non-magnetic, making it an ideal low-temperature structural material. In this paper, the typical TC4 titanium alloy in industrial titanium alloy is selected as the research object. The microstructure deformation law and mechanical behavior of TC4 titanium alloy at liquid nitrogen temperature are mainly investigated, and compared with the microstructure and properties at room temperature. The macroscopic and microscopic deformation mechanism of the simultaneous increase in elongation and hardening index of titanium alloy at low temperature is revealed, which provides a basic basis for the low-temperature deformation mechanism and strengthening and toughening design of titanium alloy. Based on the uniaxial tensile tests at room temperature (298 K) and low temperature (77 K), the effects of low temperature on the yield strength, elongation, tensile strength and work hardening curve of titanium alloy were compared and analyzed. The strength/plasticity synergistic improvement of TC4 titanium alloy under low-temperature deformation was found. At low temperature, the yield strength, tensile strength and elongation of TC4 titanium alloy are improved compared with room temperature. The tensile strength increases from 847.93 MPa at 298 K to 1318.70 MPa at 77 K, and the elongation increases from 21.8% at 298 K to 24.9% at 77 K. The grain morphology, grain orientation, dislocation density and fracture morphology of titanium alloy under room temperature and low-temperature tensile conditions were studied by SEM and EBSD. The results of fracture morphology characterization at room temperature and low temperature show that TC4 titanium alloy exhibits ductile fracture characteristics and a large number of dimples are formed on the fracture surface. The dimple depth at low temperature is shallower than that at room temperature and the overall surface is more flat. Compared with room temperature deformation, the deformation process of TC4 titanium alloy in a low-temperature environment produces stronger dislocation pile-up and forms a large number of twins, but the grain rotation is more significant, which effectively alleviates the stress concentration and delays the initiation and propagation of cracks at grain boundaries.

Kink phenomena in InAlAs/InGaAs HEMTs are investigated using a two-dimensional (2-D) device simulation that takes into account impact ionization, including nonlocal field effects, and the surface states in a side-etched region at the gate periphery. The simulation model enables us to represent the kink, and it is found that the accumulation of holes generated by the impact ionization has the channel electron density in the side-etched region increase at the bias point where kink appears. When the electron density in the side-etched region is small, the hole accumulation causes a significant increase in that electron density, resulting in a large kink. The simulation results suggest a model in which the kink is described in terms of the modification of the parasitic source resistance induced by the hole accumulation. This model implies a way to eliminate the kink, that is, keeping the electron density in the side-etched region high.

The gate length and gate contour of a GaAs metal–semiconductor field effect transistor (MESFET) device play important roles in determining the small signal circuit parameters and large signal breakdown voltage behavior. GaAs MESFETs with different gate lengths and gate contours were studied by the two-dimensional (2-D) semiconductor device simulations to investigate the dependence of small signal circuit parameters and breakdown voltage on gate length and gate contour. The results show that gate length affects small-signal circuit parameter Cgs while gate contour affects Cgd. The breakdown voltage has strong dependence on gate contour and little dependence on gate length.

Optical properties of the irradiation-induced-defects in neutron-irradiated CsI single crystals have been investigated. The nominally pure CsI crystals are irradiated by reactor fast neutrons (E > 0.1 MeV) with a fluence of 1.4 × 1015 n/cm2 at 20 K and by γ-rays from 60Co source to a dose of 1.5 × 104 Gy at liquid nitrogen temperature (LNT). After the irradiations, isochronal annealings are performed to investigate the thermal behavior of the defects. The glow peaks of the thermoluminescence (TL) in each sample irradiated with neutrons at 20 K and with γ-rays at LNT are observed at about 100, 160 and 220 K. In the neutron-irradiated samples at 20 K, the emission band at 338 nm is observed at LNT. It is supposed that this emission band occurs by an excitation of γ-rays from 134Cs, which is radioactivated by thermal neutrons among the reactor radiations. It is confirmed that the temperature dependence of the 338 nm band is similar with that of the emission band due to the self-trapped exciton which is introduced into the non-irradiated samples illuminated by higher energy photons.

Study of effective carrier lifetime and ideality factor of BPW 21 and BPW 34B photodiodes from above room temperature to liquid nitrogen temperature

Cathode coating is a key technology in sulfide-based all-solid-state batteries (ASSBs). The coating serves as a protector, suppressing side reactions at the sulfide/cathode active material interface. Lithium niobate (LiNbO3) is a well-known coating material. In this study, sulfide-based ASSBs, which were uncoated and surface-coated with LiNbO3, are subjected to cell operation testing and electrochemical impedance spectroscopy (EIS) in a low-temperature environment (i.e., −60 °C), where a commercial liquid-type lithium-ion battery (LIB) is unable to operate because of partial freezing and significant viscosity increase. Unlike liquid-type LIBs, the coated and uncoated ASSBs successfully discharge at −60 °C, emphasizing their applicability in low-temperature environments. The coated ASSB exhibits better low-temperature performance than the uncoated one. In the absence of coating, the deconvoluted EIS resistance data show an increase in some resistance components at low temperature.

Homemade solid state CaSO4:Dy detectors were tested to evaluate their response to gamma radiation at liquid nitrogen temperature (77 K). The dosemeters were irradiated with doses between 12 and 1071 Gy. For this study these dosemeters were exposed to gamma rays with a dose rate of 1.19 Gy.min(-1). The analysis for these crystals was made by thermoluminiscence. The dose response at liquid nitrogen temperature was linear in the dose range studied and it is about 20% lower with respect to the response at room temperature. The response is reproducible with the same geometric set-up.

Uniaxial compression tests of cylindrical alumina samples were carried out at room and liquid nitrogen temperatures. An increase in the fracture toughness of samples deformed at low temperature was accompanied by the intensification of fragmentation. Fragment area distribution and fragment mass distribution were built for both temperatures. The first inflection points on the graphs testify to the presence of structural scaling, which governs the fragmentation of alumina samples.

Synthesis and hydrogen sorption properties of Mg–Ti–Ni composite, produced by mechanical milling at liquid nitrogen temperature

An efficient management of the newborn dairy calf around birth results in reduced rearing costs and increased future milk yield. To maintain young calves healthy and maximize performance and profit it is important to create an environment that maintain low levels of stress. Low environment temperature directly affects newborn and young calves’ performance, health and survival due hypothermia. For that reason, the adaptation of the dairy calf to the cold environment is important, with body responses of primary importance. However, some strategies may also be adopted to reduce cold stress induced by heat loss. There are several ways to aid the young calf in low environmental temperature, starting immediately after birth with colostrum feeding. Besides that, factors such as adequate housing, management and nutrition, result in significantly decrease morbidity and mortality, and similar growth rates as calves in the zone of thermoneutrality. The calf physiology adaptation to cope with cold stress and the positive effect of feeding systems, resulting in greater heat production, health, and performance will be approach in this literature review.

High temperature lifetesting of silicon metal-thin insulator-semiconductor heterojunction emitter bipolar transistors

Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) is a novel method for detecting low-energy neutrinos. We propose an innovative low-temperature detection approach based on pure CsI scintillator coupled with silicon photomultiplier (SiPM) readout. This method leverages the high light yield property of CsI scintillator at low temperatures, which can significantly enhance the detector performance. In our preliminary experiments, we tested the light yield of CsI scintillator at liquid nitrogen temperature, and the light yield reached 30.1 P.E./keV. This result verified the excellent performance of the detector in a low-temperature environment. Meanwhile, performance studies on multiple types of SiPMs at 40 K showed that all of them could operate normally. It is expected that the light yield of pure CsI scintillator will be further improved at 40 K. This detection technology is expected to become an important tool for CEνNS experiments and holds great significance for neutrino physics research.

This study investigates the effects of environmental factors on tensile properties of laminated composites containing a central hole. Tensile tests were carried out on three types of specimens that are exposed to low temperature, room temperature and hydrothermal environment respectively. Tensile experiments were performed according to the ASTM D 5766. The results of moisture absorption tests indicated that the saturated moisture content of the specimens was around 0.7% after 1200 hours. Tensile tests results showed that the tensile strength, stiffness and fail strain of open hole increased with the content of 0° fiber, the tensile strength and stiffness increased in low temperature environment and decreased in hydrothermal environment.

A practical method to mass-produce gratings with limited lateral dimension is to emboss master grating into a Sol-gel waveguide film. Sol-gel titanium dioxide (TiO2) thin film has been deposited on glass substrate using titanium precursors at low temperature environment. As-deposited films were amorphous. The morphology of the deposited film was analyzed by using high resolution SEM (HRSEM).The contact angle of water droplet on the film surface (hydrophilic properties) was measured by contact angle analysis. From the results; the formation of nano diffractive structure TiO 2 film obtained at low load and temperature environment was suggested for high quality structure.