Electron Devices Research Articles

Fabrication and Electrical Characterization of GaAs/GaN Junctions

GaAs/GaN heterojunctions are likely to be an ideal platform for high-frequency/high-output-power electron devices because of excellent electrical properties of GaAs and GaN as well as the similarity in their coefficients of thermal expansion. We have to note, however, that heteroepitaxial growth of GaAs/GaN junctions is quite difficult because of difference in crystal structures (in case of GaAs/wurtzite GaN junctions) and large mismatch in lattice constants (GaAs/zincblende GaN junctions). In this work we fabricate p+-GaAs/n-GaN heterojunctions by bonding GaAs and GaN epi wafers to each other using surface-activated-bonding technologies [1,2], selectively etching off the GaAs substrate used in the epitaxial growth, making ohmic contacts on the exposed surface of GaAs layer, and forming GaAs mesas. Ohmic contacts on the backside of GaN epi wafer are formed before bonding. The junctions are annealed at 400 ℃ in contact formation on GaAs surfaces. The temperature is much lower in comparison with the temperature in a wafer-fusion process of GaAs and GaN (750 ℃), which were reportedly applied for fabricating group-III arsenide/nitride heterojunction bipolar transistors [3]. Observation using cross sectional transmission electron microscope (TEM) of as-bonded and 400-℃ annealed GaAs/GaN interfaces shows that no voids are formed at the GaN/GaAs interfaces by the 400-℃ annealing. We also fabricate n+-GaAs/n-GaN heterojunctions for comparison.We measure the capacitance-voltage characteristics and current-voltage characteristics for reverse-bias voltages of the p+-GaAs/n-GaN and n+-GaAs/n-GaN junctions and find that the characteristics of the two junctions are close to each other, which suggests that the band profiles of GaN layers in the p+-GaAs/n-GaN and n+-GaAs/n-GaN junctions are almost the same, i.e., the Fermi-level pinning occurs at the GaAs/GaN interfaces. More importantly, the reverse-bias characteristics are measured up to -60 V. The reverse-bias voltage corresponds to an electric field of as high as ~2 MV/cm, which is comparable to the breakdown field of GaN (3-4 MV/cm) [4]. We also excite minority electrons in the p+-GaAs layer using a 488-nm Ar laser and successfully observe the photo current due to the transport of minority electrons across the reverse-biased GaAs/GaN interfaces.Acknowledgement: TEM samples were fabricated under the Inter-University Cooperative Research in IMR of Tohoku University. Epi wafers used in the work were provided from Sciocs (present Sumitomo Chemical) Co., Ltd.[1] H. Takagi, et al. Appl. Phys. Lett. 68, 2222 (1996). [2] S. Yamajo, et al., Jpn. J. Appl. Phys. 57, 02BE02 (2018). [3] C. Lian, et al. Appl. Phys. Lett. 91, 063502 (2007). [4] T. Maeda, et al., IEEE Electron Device Lett., 43, 96 (2022).

(Invited) Benchmarking of Beyond the State-of-the-Art Vertical GaN Devices

In this paper theoretical benchmarking of semi-vertical and vertical gallium nitride (GaN) MOSFETs with rated voltage of 1.2 kV to 3.3 kV is performed against corresponding silicon carbide (SiC) devices. Specific design features and technology requirements for realization of high voltage vertical GaN MOSFETs are discussed and implemented in simulated structures. The main findings are that a) specific on-resistance of vertical GaN devices is expected to be 75% and 40% of that for 1.2 kV and 3.3 kV SiC MOSFETs, respectively, b) semi-vertical GaN do not offer any advantage over SiC MOSFETs for medium and high voltage devices (>1.0 kV), and c) vertical GaN has largest potential advantage for high and ultra-high voltage devices (>2.0 kV).Gallium nitride (GaN) devices experience an explosive and rapid development with new device providers entering the market at an impressive speed. However, the devices are HEMT (High Electron Mobility Transistor) type lateral devices utilizing the two-dimensional electron gas (2DEG) properties of the GaN/AlGaN interface. The required GaN layers in the devices are grown epitaxially on hetero substrates like Si, SiC, sapphire and poly-AlN using buffer layers to control the strain caused by lattice mismatch which prevents the vertical current flow. For power applications the lateral current flow close to the surface leads to thermal limitations and complicates thermal management in packaging. Furthermore, it leads to large footprint of the devices for large currents. The devices also lack the robust avalanche breakdown characteristics. At present the HEMT power devices are limited to operational voltages of less than 650V with some first devices from VisIC and iGaNPower demonstrating 1200V capability. For these reasons there is an interest in the development of vertical GaN devices opening the possibilities of small footprint and thus lower cost due to smaller chip sizes, high power densities and robust avalanche breakdown characteristics with large avalanche energy capability [1]. The development of vertical devices has been hindered by the lack of large area freestanding GaN substrates facilitating homoepitaxial growth of drift layers. An alternative are semi-vertical structures grown on Si which are the subject of this study along with true vertical structures on GaN. In addition to the material issues there are technological issues that require further attention like dopant compensation and activation and Mg implantation technology for junction termination. This paper focuses on prospective benchmarking of semi-vertical and vertical GaN MOSFETs against SiC devices. A beyond the state-of-the-art benchmarking, in wide voltage range, is missing in the literature. Most of the benchmarking publications report results of experimental structures based on state-of-the-art technology and simple junction termination [2], [3], [4].The main objective of the work has been to design competitive semi-vertical and vertical GaN structures and perform benchmarking against SiC devices in the voltage range 1.2 kV to 3.3 kV. The structures have been characterized by calculating the output, transfer and voltage blocking characteristics using default Sentaurus models. In the next step, the structures have been modified based on the experience and know-how from SiC devices. The electric field crowding occurring at the trench gate corners must be mitigated both with respect to the breakdown voltage in the bulk material and the reliability of the gate dielectric [5]. Efficient junction termination (JT) is also necessary for both types of structures. This is especially important in the semi-vertical structures where junction termination is an integral part of each device segment and has a significant impact on the resulting on-state resistance. The structure design was optimized by reducing the cell pitch and introducing a multi-cell-per-device-segment design in semi-vertical structures to improve the on-resistance. Removal of the performance limitations in the structures based on the state-of-the-art GaN technology and device cell optimization was done to make benchmarking with more mature SiC devices based on the prediction of what may become feasible beyond the state-of-the-art.1. Matteo Meneghini et al., Journal of Applied Physics, vol. 130, p. 181101, 2021.2. Oka, T. Ina, Y. Ueno and J. Nishii, 2019 31st International Symposium on Power Semiconductor Devices and ICs (ISPSD), pp. 303-306, 2021.3. A. Khadar, C. Liu, R. Soleimanzadeh and E. Matioli, IEEE Electron Device Letters, vol. 40, no. 3, pp. 443-446, 2019.4. Wei He et al., Nanoscale Research Letters, 17:14, 2022.5. Nakamura et al., 2011 International Electron Devices Meeting, pp. 26.5.1-26.5.3, 2011.

(Invited) Characterization of Metal/GaN Schottky Contacts - Review from the Early Days

GaN-based materials have been intensively developed for blue light-emitting-diodes, blue laser diodes, power amplifiers in wireless base-stations, and high-power switching devices. Schottky contacts are one of the most important components in electron device fabrication. The electrical characteristics of GaN Schottky barrier contacts have been continuously studied for more than twenty years as improvement of GaN crystal quality and understanding physics of metal/semiconductor interfaces.In the early days, for the achievement of the high-power and high-temperature operation, thermally stable contacts were explored. Interfacial reactions and electrical characteristics were intensively examined by annealing studies for various kinds of metal contacts such as Ni, Pd, Pt, and Re. As a result of those, Ni has been widely used as a stable Schottky contact, because less thermal reaction with N atoms, high Schottky barrier height (qφ B), and good adhesion.As for the correlation with GaN crystal quality, in the early days, because a GaN epitaxial layer contained large-structure killer defects, rectifying characteristics were hardly observed in the Schottky contacts. Since after the n-GaN crystal quality improved with electron mobility over 100 cm2V−1 s−1, rectifying characteristics have been reproducibly obtained.[1] Even though the dislocation density was as high as 109–1010 cm−2 in epitaxial GaN layers, good current–voltage (I–V) characteristics and qφ B values below 1.1 eV were reported in Ni/n-GaN contacts. Moreover, in order to clarify the effect of dislocations on I–V characteristics, a 0.5-µm-diameter Schottky-dot array was formed on n-GaN grown by MOCVD, and I –V measurements were conducted using AFM with a conductive probe.[2] Neither mixed nor pure edge dislocations affected the I –V characteristics, but a large structural defect with a diameter of a few hundred nanometers shorted the contact.In addition, further improvement of the GaN layer grown on low dislocation (∼106 cm−2) free-standing GaN substrates provided ideal Schottky contacts with high qφ B values around 1.1 eV. It has been reported that the forward and reverse I–V characteristics of Ni contacts formed on hydride-vapor-phase-epitaxy grown n-GaN obeyed the thermionic emission and the thermionic field emission (TFE) models, respectively.[3] The same trend was also reported in nine different metal contacts on both c- and cleaved m-plane n-GaN crystals.[4] We also reported a post-metallization annealing at 400°C for 10 min was effective to reduce the reverse biased current significantly to the prediction by the TFE model.[5]Basic understanding of p-GaN Schottky contacts was slower than that of n-GaN, because p-GaN contacts were intensively studied for ohmic contacts of p-n-junction-base optical devices. In the early days, very leaky characteristics were reported and a reasonable qφ B value was not obtained. We improved leaky characteristics of Ni/p-GaN Schottky contacts by low Mg doping. The qφ B as high as 2.4 eV and the n-values of 1.8 were obtained from I –V.[6] We found a memory effect that carrier capture and emission from acceptor-like deep level defects caused depletion layer width to vary significantly.[7]Finally, as our original technique, scanning internal photoemission spectroscopy was developed to map the electrical characteristics of metal/semiconductor interfaces nondestructively.[8] We have demonstrated the mapping of characteristics for interfacial reactions of Ni/n-GaN at 400°C; degradation under applied voltage stress up to 45 V for vertical n-GaN contacts; and process induced surface damages by ion-implantation, dry etching, and photo-electrochemical etching.[9] This technique was confirmed to be useful for the development of the wide-bandgap-semiconductor high-power devices. K. Shiojima, J. Woodall, P. Grudowski, C. Eiting and R. Dupuis, J. Vac. Sci. Tech., B17(5), p. 2030 (1999).K. Shiojima, and T. Suemitsu, J. Vac. Scie. Tech., B21(2) p. 698(2003).J. Suda, K. Yamaji, Y. Hayashi, T. Kimoto, K. Shimoyama, H. Namita, and S. Nagao, Appl. Phys. Express, 3, p. 101003 (2010).H. Imadate, T. Mishima, and K. Shiojima, Jpn. J. Appl. Phys., 57, p. 04FG13 (2018).K. Shiojima, R. Tanaka, S. Takashima, K. Ueno, and M. Edo, Jpn. J. Appl. Phys., 60, 056503 (2021).K. Shiojima, T. Sugahara and S. Sakai, Appl. Phys. Lett., 74, p. 1936 (1999).K. Shiojima, T. Sugahara and S. Sakai, Appl. Phys. Lett. 77, p. 4353 (2000).T. Okumura and K. Shiojima, Jpn. J. Appl. Phys., vol. 28, p. L1108 (1989).K. Shiojima, ECS Transactions, 104, p. 69 (2021).

Analysis of Operational Characteristics of AlGaN/GaN MIS-HEMT with Different Slant-Recessed-Gate Structures

Purpose of WorkRecessed-gate metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) have emerged as a promising technology for normally-off operation because of their ability to withstand high gate voltage sweeps while maintaining low levels of leakage current [1, 2]. Despite their excellent performance, the etch to leave nanometer-thin layers of AlGaN has proven to be a significant challenge due to difficulties in precisely controlling the etching process. Achieving a positive threshold voltage (Vth) while maintaining the high electron mobility characteristic of the two-dimensional electron gas (2DEG) requires atom-level etch control. Additionally, conventional dry etching techniques can potentially cause damage, presenting a second challenge [3]. However, atomic layer etching (ALE) offers a promising solution with its potential for low damage, uniformity, and high-resolution depth control [4]. In this work, we not only focus on the ALE process to leave nanometer-thin layers of AlGaN/GaN as recessed-gate structures but also analyze the breakdown voltage characteristics of the slant-recessed gate structure.ApproachNormally-off AlGaN/GaN MIS-HEMT with a recessed gate structure was fabricated on a 6-inch commercial Si substrate by MOCVD. The process involved mesa isolation by ICP-RIE, followed by the formation of the ohmic contact (Ti/Al/Ni/Au) at 825 °C annealing for source and drain metals, and the AlGaN/GaN recessed gate structure using ALE technology by O2/BCl3 multiple cycles of oxidation and etching [5]. After the recessed-gate process, the native oxide and carbon residue were removed by a wet cleaning process and O2 plasma treatment, and then the atom layer deposition (ALD) of about 12 nm thickness Al2O3 high-dielectric layer was also deposited. The backend process included gate field plate, SiNx passivation, and contact opening. Finally, the Ni/Au metal stack was deposited as pad electrodes, as shown in Fig. 1. The specific characteristics of the fabricated recessed MIS-HEMT were Lg of 3 μm, Lgs of 5 μm, Lgd of 10 μm, and Wg of 100 μm.Results and SignificanceIn Figure 2(a) and (b), TEM profiles of the recessed gate structure were presented. Following the ALE process for the recessed gate structure, the remaining thickness of AlGaN was approximately 5.1 nm and 5.6 nm for Slant A and Slant B, respectively. Although the thickness of AlGaN remaining was similar in both cases, the slant angle of the recessed gate structure differed, significantly. Specifically, Slant A had a 65-degree recessed gate structure, while Slant B had a 45-degree recessed gate structure. In order to analyze of operational characteristics of AlGaN/GaN MIS-HEMT with different slant-recessed gate structures (Slant A and Slant B), the three-terminal OFF-state breakdown voltage (BV) was measured, as shown in Fig. 3. Recessed gate MIS-HEMT feature design of Lg/Lgd/Lgd/Wg of 3/5/10/100 μm, and VG of -10 V was used as this BV measured condition. The Slant B structure demonstrated higher breakdown voltage (BV) performance compared to the Slant A structure. Specifically, the Slant B structure exhibited a BV of 470 V at 1 μA/mm and 750 V at 1 mA/mm, while the Slant A structure had a BV of only 70 V at 1 μA/mm and 140 V at 1 mA/mm. The reason for the superior BV performance of the Slant B structure (45-degree recessed gate structure) was attributed to the gradient of the AlGaN profile, which facilitates the thin film deposition process of materials such as Al2O3 and gate metal (Ni/Au). Additionally, the Slant B structure helps to reduce the high electric field effect between the gate and drain, further contributing to its improved BV performance.[1] Y. S. Lin, Y. W. Lain, and S. S. H. Hsu, "AlGaN/GaN HEMTs With Low Leakage Current and High On/Off Current Ratio," IEEE Electron Device Letters, vol. 31, no. 2, pp. 102-104, 2010.[2] Z. Tang et al., "600-V Normally Off SiNx/AlGaN/GaN MIS-HEMT With Large Gate Swing and Low Current Collapse," IEEE Electron Device Letters, vol. 34, no. 11, pp. 1373-1375, 2013.[3] T. H. Hung, P. S. Park, S. Krishnamoorthy, D. N. Nath, and S. Rajan, "Interface Charge Engineering for Enhancement-Mode GaN MISHEMTs," IEEE Electron Device Letters, vol. 35, no. 3, pp. 312-314, 2014.[4] T. Y. Yang et al., "A Normally-Off GaN MIS-HEMT Fabricated Using Atomic Layer Etching to Improve Device Performance Uniformity for High Power Applications," IEEE Electron Device Letters, vol. 43, no. 10, pp. 1629-1632, 2022.[5] I.-H. Hwang, H.-Y. Cha, and K.-S. Seo, "Low-Damage and Self-Limiting (Al)GaN Etching Process through Atomic Layer Etching Using O2 and BCl3 Plasma," Coatings, vol. 11, no. 3, p. 268, 2021. Figure 1

BUILDING HEAT SUPPLY SYSTEM BASED ON HYBRID SOLAR COLLECTORS

Increasing the efficiency of solar heat supply systems is one of the important problems of solar energy. The research presented in this article is aimed at improving the efficiency of hybrid solar collectors without a transparent coating for building heating systems. One of the key challenges in the field of solar energy is the development of new technologies to ensure high collection of solar energy and to integrate it into traditional heating and hot water systems. The study shows that hybrid solar collectors with the placement of heat carrier circulation circuit tubes above the heat absorber can increase the thermal efficiency factor with a certain change in the angle of inclination and the density of solar radiation. A nomogram was also developed that determines the dependence of this coefficient on the angles of arrival of solar radiation and its density.

A modified first-order plate theory of laminated piezoelectric plate actuators

Piezoelectric actuators with large output and high reliability are widely applied in electron device. In this paper, a modified first-order plate theory of laminated piezoelectric plates with upper and lower electrodes is presented. Then, based on the Mindlin first-order shear deformation theory, a quadratic function of electric potential across the thickness is used to describe the inverse piezoelectric effect. The laminated plate governing equations are derived in terms of the resultant force, moment and electric displacement. Further, supplementary equations are introduced through the continuity of electrical potential and the normal electric displacement across interface of each lamina, which are applied to solve the unknown electric functions in each lamina. The numerical results of displacement, deflection and electric potential are consistent with those obtained by the three-dimensional finite element method. Finally, with such a modified plate theory, regulation mechanisms of polarization direction and layer numbers are investigated on actuation properties of laminated piezoelectric actuators. It is shown that the polarization direction can change the driving displacement by an order of magnitude. It is expected that the modified theory can provide a more efficient and accurate approach for analysis of multilayer piezoelectric composite actuators.

Electronic Refrigerant Valves for Electric Vehicles

Electronic Refrigerant Valves for Electric Vehicles

An embedded microfluidic valve for dynamic control of cellular communication.

The communication between different cell populations is an important aspect of many natural phenomena that can be studied with microfluidics. Using microfluidic valves, these complex interactions can be studied with a higher level of control by placing a valve between physically separated populations. However, most current valve designs do not display the properties necessary for this type of system, such as providing variable flow rate when embedded inside a microfluidic device. While some valves have been shown to have such tunable behavior, they have not been used for dynamic, real-time outputs. We present an electric solenoid valve that can be fabricated completely outside of a cleanroom and placed into any microfluidic device to offer control of dynamic fluid flow rates and profiles. After characterizing the behavior of this valve under controlled test conditions, we developed a regression model to determine the required input electrical signal to provide the solenoid the ability to create a desired flow profile. With this model, we demonstrated that the valve could be controlled to replicate a desired, time-varying pattern for the interface position of a co-laminar fluid stream. Our approach can be performed by other investigators with their microfluidic devices to produce predictable, dynamic fluidic behavior. In addition to modulating fluid flows, this work will be impactful for controlling cellular communication between distinct populations or even chemical reactions occurring in microfluidic channels.

Study on Aerodynamic Drag Reduction by Plasma Jets for 600 km/h Vacuum Tube Train Sets

In order to break through the speed bottleneck, researchers envision using tubes to cover high-speed maglev trains and extract some of the air inside the tubes, creating a low-density environment on the ground, greatly reducing the aerodynamic drag of the trains, and in a relatively economical and feasible way, making high subsonic (600 km/h and above) and even supersonic ground transportation possible. The faster the running speed of high-speed trains, the greater the impact of aerodynamic drag on their energy consumption. Studying the aerodynamic characteristics of trains with a speed of 600 km/h can help optimize the aerodynamic shape of the train, reduce aerodynamic drag, and reduce energy consumption. This has positive implications for improving train energy efficiency, reducing energy consumption, and environmental impact. This paper adopts the numerical simulation method to study the drag reduction effect of the plasma arrangement and different excitation speeds on the train set in four positions when the incoming wind speed is 600 km/h, to analyze the mechanism of drag reduction, and then to analyze the combination of working conditions in order to investigate the drag reduction effect of plasma on the vacuum tube train set with an ambient pressure of 10,000 Pa. The findings demonstrate that the plasma induces the directional flow of the gas close to the wall to move the flow separation point backward and delay the separation of the flow, thereby reducing the front and rear differential pressure drag of the train set and lowering the aerodynamic drag coefficient of the entire train. The plasma arrangement is located at the rear of the flow separation point and in close proximity to the flow separation point. The pneumatic drag reduction effect peaks when the excitation speed reaches 0.2 times the train speed and the pneumatic drag reduction ratio is around 0.88%; the pneumatic drag reduction ratio of the rear car peaks when the excitation speed reaches 0.25 times the train speed and the pneumatic drag reduction ratio is 1.62%. The SDBD (Surface Dielectric Barrier Discharge) device is installed at the flow separation point around the nose tip of the rear car.

Toward optimized operation of freshwater generator using computer vision, and its economic and environmental benefits

Sufficient quantities of fresh water (FW) must be maintained for the operation of ships and fresh water generators (FWGs), used to produce FW on ships tend to be suboptimal because of work schedules and low-skilled marine crew. Therefore, a system that optimally and automatically operates the discharge valve of an FWG distillate pump by recognizing the FW condition through a sight glass using computer vision technology was developed. Three deep-learning models were trained using videos of FW flowing and filling the sight glass. An optimal model structure was selected in the pre-test phase, which consisted of (i) a test using a camera and a monitor showing the validation videos, and (ii) a test based on data. In the real-test phase, an electrical valve and stepper valve were used as optimization valves, and the flow rates of the fuel oil for the generator engine (G/E) and FW for the FWG were recorded for 10 experimental conditions. The stepper valve operated in a more stable manner than the electrical valve, and its prediction performance with CNN-LSTM was superior. Finally, the economic and environmental impacts were evaluated based on the flow rates of fuel oil for the G/E and FW for the FWG.

Kinetic Theory of Expansion of Two-Component Plasma in a Plane Vacuum Diode

Kinetic Theory of Expansion of Two-Component Plasma in a Plane Vacuum Diode

IEEE Transactions on Electron Devices Table of Contents

IEEE Transactions on Electron Devices Table of Contents

Topology Study of Milking Machine Based Parametric Modeling

The large market for cow's milk makes the order capacity for cow's milk high and will increase the milking process. In the production process, especially the milking process, people still manually use their hands, so fatigue often occurs, especially in people with more than 2 livestock. This causes the production process to be ineffective and the production results are also limited. Creating an automatic milking machine equipped with a milk can, a vacuum tube and a hose. Besides, a topology study will also be carried out based on the model of the machine. The three-unit component will affect the performance of the Milking Machine, especially the milk collector and milk can. Their size needs to be analyzed to get the optimum one. Optimization results for the topology of the milk collector bore diameter showed that the milk flow rate in the milk collector at a bore diameter of 9mm was 6,154 ltr/min, at a bore diameter of 14 mm was 26,566 ltr/min and at a bore diameter of 19mm was 66,128 ltr/min (conditions without being connected to hose). The shape of a milk can with a reduction of 30% from the initial weight, which is 3,358 kg to 2,350 kg, is owned by a milk can with the most optimal cone-dome tube shape. The difference in weight with the tube is generally 1,008 kg. The quantity flow when installed with a 2m long hose is 6,729 ltr/min

Advanced Thermal Interface Materials: Assembly and Integration for System in Package

Power dissipation is perhaps the greatest challenge facing modern electron devices. It has limited the performance of Si integrated circuits for nearly two decades, and is also limiting the performance of (high-power) GaN discrete devices. As such, many information technologies (ITs) have an urgent need for power dissipation solutions at the hardware level. The most feasible solution is via the device packaging, since self-heating of the device is deeply rooted in fundamental aspects of electron transport in imperfect semiconductors at normal temperatures. This packaging solution often occurs at the die attachment, whereby a thermal interface material (TIM) couples the device to the board. The interface/bulk thermal conductivity of this TIM determines the temperature rise of the device at a given operating power. Today, most TIMs rely on the thermal conductivity of metals, and are rapidly becoming a bottleneck for power dissipation in advanced ITs. This talk will discuss the limitations of metallic TIMs, and integration/characterization challenges for new materials that may extend the performance scaling of high-power devices.

On the Application of Thévenin Equivalent Circuits to the Analysis of Vacuum Tube Circuits

In this paper, we express Thévenin equivalent circuits seen looking into the terminals of the small-signal model of the vacuum tube triode in terms of the Thévenin equivalent circuits seen looking out of the other terminals and apply them to the analysis of the common-cathode, common-plate, and common-grid single-tube amplifier configurations, as well as a differential pair amplifier. This is an adaptation of equivalent circuit techniques for transistor circuits pioneered by Marshall Leach. The use of equivalent circuits can yield intuitive solutions that avoid solving sets of equations.

Regulating Phase Separation Kinetics for High-Efficiency and Mechanically Robust All-Polymer Solar Cells.

All-polymer solar cells (all-PSCs) possess excellent operation stability and mechanical robustness than other types of organic solar cells, thereby attracting considerable attention for wearable flexible electron devices. However, the power conversion efficiencies (PCEs) of all-PSCs are still lagging behind those of small-molecule-acceptor-based systems owing to the limitation of photoactive materials and unsatisfactory blend morphology. In this work, a novel terpolymer, denoted as PBDB-TFCl (poly4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b″]dithiophene-1,3-bis(2-ethylhexyl)-5,7-di(thiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c″]dithiophene-4,8-dione-4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene), is used as an electron donor coupled with a ternary strategy to optimize the performance of all-PSCs. The addition of PBDB-TCl unit deepens the highest occupied molecular orbital energy level, reducing voltage losses. Moreover, the introduction of the guest donor (D18-Cl) effectively regulates the phase-transition kinetics of PBDB-TFCl:D18-Cl:PY-IT during the film formation, leading to ideal size of aggregations and enhanced crystallinity. PBDB-TFCl:D18-Cl:PY-IT devices exhibit a PCE of 18.6% (certified as 18.3%), judged as the highest value so far obtained with all-PSCs. Besides, based on the ternary active layer, the manufactured 36 cm2 flexible modules exhibit a PCE of 15.1%. Meanwhile, the ternary PSCs exhibit superior photostability and mechanical stability. In summary, the proposed strategy, based on molecular design and the ternary strategy, allows optimization of the all-polymer blend morphology and improvement of the photovoltaic performance for stable large-scale flexible PSCs.

Morphometric and immuno-biochemical markers of placenta in patients with uterine eclampsia

Purpose: to study the segmentation of organometric and immuno-biochemical digital indicators in ewes with ESO at the end of gestation.Materials and methods. The experiment involved three flocks of Tsygai, Volgograd and Stavropol breeds, each with 700 suyag sheep. Placental tissue samples were taken from clinically healthy and sick pregnant ewes, which were placed in 10% neutral formalin. Using a Cytadel 2000 histoprocessor (Shendon), the obtained samples were clarified in chloroform and enclosed in a Histomix paraffin medium (Biovitrum). Histosections were prepared on a rotary microtome (MICROM HM340E). Using the AxioScope.A1 (ZEISS) microscope, histopreparations were photographed and processed using the ZENpro 2012 (ZEISS) program. According to Schmidt and Thannhauser, the RNA content was determined using a two-wave spectrophotometer in UV. The activity of the G-6-Phase was studied by Swanson. In vacuum tubes Vacuette ™ (Austria), blood samples were taken in the morning before feeding, from the jugular vein. Results. In sheep with eclampsia, a decrease in the total mass of the placenta, its cotiledons, as well as an increase in the length of the umbilical cord, in which stroma sclerosis is noted in the vascular wall, was observed. Small calcification foci were found in the tissues of the afterbirth, and small terminal villi are located around the stem villi near the vascular membrane, tightly adjacent to them. The proportion of syncytiotrophoblast of crypts of carbuncles and villi of the chorion of cotyledons of mature syncytium decreases in comparison with physiologically occurring severity. The content of RNA in its subcellular fractions is mainly concentrated in the microsomal fraction, 18% - in mitochondria and 7% - in the nuclear fraction. Albumins in pregnant ewes with eclampsia were reduced by 1.35 times. BASC and phagocytic activity of leukocytes in queens with eclampsia of pregnant sheep is reduced 15 days before lambing, which poses a threat to the reproductive health of the mother and the viability of newborn lambs.

PSVII-26 Effects of an Electrolyte Drinking Solution on Performance and Physiological Responses of Preconditioning Beef Calves

Abstract Weaning and transport are the major stressor events for beef cattle production. Strategies to mitigate weaning stress responses and promote quick recovery of homeostasis are always warranted to improve welfare and productivity of beef cattle. This study evaluated the effects of an electrolyte drinking solution on the performance and physiological responses of pre-conditioning beef calves. Forty Angus × Hereford steers [230.4 ± 4.8 kg body weight (BW), 195 ± 30 days of age] were sorted into 20 pens (2 calves/pen) immediately after weaning for a 45-d preconditioning period. Pens were randomly assigned to two treatments: 1) control: water; and 2) electrolyte solution: water and electrolyte drinking solution on one additional trough per pen. A total of 10% of the estimated daily water intake of calves was fortified with the electrolyte solution on the ratio of 31.6 g/L of water. The electrolyte composition contained calcium, phosphorus, salt, magnesium, potassium, and a mix of carbohydrates. Treatments were provided from d 1 to 14, and thereafter electrolyte supplementation was ceased. Assigning weaning as day 0, calf BW was recorded and blood samples were collected via jugular vein puncture into commercial heparinized vacuum tubes on d 0, 1, 3, 7, 14, 21, 44 of the experiment. Plasma samples were analyzed for haptoglobin, ceruloplasmin and cortisol. Variables were analyzed considering pen as the experimental unit and pen(treatment) as a random effect. Blood parameters were evaluated as repeated measurements and effects of treatment, day, and treatment and day interaction were analyzed with the MIXED procedure of SAS. Significance was set at P ≤ 0.05. Calves consumed 700 mL of electrolyte solution daily which consisted of 20% of the offered. No effects (P = 0.61) were observed on ADG (0.82 kg, SEM: 0.050) or final BW (P = 0.81; 267 kg SEM: 5.36). No differences in cortisol (P = 0.64; 2.30 ng/mL SEM: 0.147), ceruloplasmin (P = 0.29; 26.9 mg/mL SEM: 0.659) and haptoglobin (P = 0.57; 0.64 µg/mL SEM: 0.029) concentrations were observed. Electrolyte solution supplementation during preconditioning did not improve performance or influenced acute response markers of beef calves.

Kinetic Theory of Expansion of Two-Component Plasma in a Plane Vacuum Diode

The results of study of the initial stage of expansion of a collisionless plasma with the electric current into a plane vacuum gap on the basis of kinetic equations for electrons and ions and the Poisson equation for the electric field are given. Self-consistent dynamics of a two-component plasma and electric field are theoretically modeled and the fundamental mechanism for establishing superthermal velocities of charged particles is described in detail. The parameters of anode-directed flows of positive ions in the cathode plume plasma are calculated. The expansion velocities of the cathode plume plasma observed in vacuum arcs at the level of (1−5) × 106 cm/s can be explained within the framework of the proposed collisionless mechanism.

IEEE Transactions on Electron Devices Table of Contents

IEEE Transactions on Electron Devices Table of Contents