bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accurate Estimation of Switching Losses in SiC Power MOSFET’s
Authors: Pozo Arribas Alejandro , Krishnamurthy Mahesh , Shenai Krishna 
Published: February 2020

The increasing reduction of the manufacturing costs of SiC devices and in particular SiC Power MOSFETs will soon make them cost competitive with other Si devices such as Si IGBTs. For the same voltage and current ratings, SiC Power MOSFETs offer better switching characteristics. Therefore, it is a matter of time that these new devices overtake the role of Si IGBTs in several applications.
Before that moment comes, there is still a lack of uniformity among SiC Power MOSFET manufacturers, especially in terms of the information related to the switching losses that is given in the Datasheet. If we take a look at the Datasheet information for Si Power MOSFETs, most of the manufacturers provide the transition times but not the switching losses. Besides those transition times are typically referred to resistive switching conditions.
Nevertheless, Si Power MOSFETs do not have the same voltage and current ratings as their SiC counterparts. Hence, they are typically used in different applications. Therefore, it makes more sense to compare SiC Power MOSFETs with their competence. These are Si IGBTs.
After analyzing Si IGBTs and their Datasheets we can notice that more information is given for the switching losses. In fact, many manufacturers choose to provide not only the switching times but also the switching losses. Besides, the switching losses are given under inductive switching conditions. For that purpose a freewheeling diode is required to provide a current path when the switch is turned on. This implies that the diode can affect switching performance of the device under test (MOSFETs or IGBT), especially during the turn on, due to the reverse recovery. To prevent from this, Schottky barrier diodes, with zero reverse recovery, are used as freewheeling diodes.
The question then is, is it correct to give the switching losses under inductive conditions? What is the impact of the freewheeling diode on the switching losses? Would a resistive switching test provide more accurate information.
Graphene Synthesis By Plasma Technique Toward Transparent Conductive Film Applications
Authors: Hasegawa Masataka , Kato Ryuichi , Okigawa Yuki , Isihara Masatou , Yamada Takatoshi 
Published: February 2020

We developed the large-area microwave plasma chemical vapor deposition (CVD) of graphene for transparent electrode applications. This technique has been successfully combined with the roll-to-roll process to synthesize graphene on Cu substrates. Nucleation density of plasma CVD of graphene crystal is too high, which suppresses two-dimensional growth of graphene and leads to graphene flakes of several nanometer stacks in multiple layers. This causes low electrical conductivity of the synthesized graphene. The low concentration of carbon source is effective to reduce the nucleation density and to enlarge the crystal size. In this study, we utilize small amount of carbon delivered from Cu foil and/or the ambient in the reaction chamber as extremely low-concentration of carbon source and perform the synthesis of graphene of higher crystalline quality.
The carbon atoms precipitate on the Cu surface by the heat treatment of the Cu foil for 15 minutes at about 800°C. Then the copper foil was exposed to the hydrogen plasma for about 30 seconds under 5Pa to synthesize graphene on the foil. We did not use any carbon-contained gas such as CH4. The crystalline quality of graphene was successfully improved by using carbon atoms contained in the Cu foil and/or the ambient in the reaction chamber.
The synthesized graphene on Cu foil was transferred to the quartz or silicon substrate. After that, the van der Pauw devices for Hall Effect measurements were fabricated using conventional photolithography, metal deposition and lift-off processes. The fabricated devices show that the mobility is estimated to be more than 1000 cm2/Vs, which was dramatically improved from the previous plasma CVD using CH4 as source gas.
This work was partially supported by the Basic research and development of high quality graphene funded by NEDO.
Fast Direct Growth of Self-Crystallized Graphene-from Controllable Growth to Material Characterization and Device Applications
Authors: Chueh Yu-Lun 
Published: February 2020

Graphene, one of the most attractive research topics in modern science owing to its fascinating electrical properties, has been attracted much attention. Its unique structure, two-dimensional honeycomb carbon lattice, enables high conductivity and transparency. This material is thus potentially expected to become a transparent conductive layer in optoelectrical applications and thus stimulates a lot of studies on the synthetic growth methods to requisitely develop high uniformity with high quality and simple process for industrial manufactory.
Common process for the synthesis of the graphene is typically based on heat chemical vapour deposition (CVD), for which carbon sources such as methane and acetylene are as precursors with metal-catalytic layers such as Cu or Ni foils. However, an additional complex transferred processes of the graphene layer on an insulator substrate from the metal-mediated layer are imperative steps for the device application, containing spinning coating of protective layer, etching of mediated layer, fishing of graphene layer, and removal of protective layer. Defects, such as cracks, wrinkles, and chemical residuals (Fe3+, polymer…etc.) can be readily formed during transferred processes, resulting in decease of electron mobility due to scattering behaviours by defects, thereby degrading device performance. Many transfer-free processes had been investigated to prevent these problems. The concept of back-side segregation by bulk or boundary diffusion had been applied to achieve the segregated graphene at interface between the substrate and the metal-mediated layer.
In this talk, a directly self-crystallized graphene layer with transfer-free process on arbitrary insulator by Ni vapor-assisted growth at growth temperatures between 950 to 1100 ºC via conventional chemical vapor deposition (CVD) system was developed and demonstrated. Domain sizes of graphene were confirmed by Raman spectra from ~12 nm at growth temperature of 1000 ºC to ~32 nm at growth temperature of 1100 ºC, respectively. Furthermore, the thickness of the graphene is controllable, depending on deposition time and growth temperature. In addition, we also develop a new method to synthesize graphene and highly oriented graphite via Ni-catalyzed solid phase segregation using amorphous carbon as a resource by the rapid microwave heating process (RMHP) in air. By controlling input powers of the microwave, the annealing temperature could be controlled, enabling this synthesis to dissolve the carbon atoms into catalyst layer. With annealing under an adequate temperature in air, the carbon solute in the Ni will retard the formation of the NiO film on the surface by reduction process.
Performance Improvement of Bulk Heterojunction Polymer Solar Cells with Metal Oxide Nanoparticles
Authors: Abdel-Fattah Tarek M , Younes Enas m , Namkoong Gon , El-Maghraby E. M. , Elsayed Adly , Abo Elazm A. H. 
Published: February 2020

Polymer solar cells (PSC) based on bulk heterojunction (BHJ) materials containing conjugated polymers and fullerene derivatives have large advantages of easy fabrication, and also have considerable potential in renewable energy resources [1–3]. The polymer solar cell efficiencies and their lifetimes can be improved by using metal oxides such as titanium suboxide TiOx or zinc oxide [4].
In this study, we fabricated polymer solar cells with two different bulk heterojunction (BHJ), thieno(3,4-b)-thiophene/ benzodithiophene copolymer,(6,6)-phenyl C71 butyric acid methyl ester (PTB7/PC71BM), poly (3- hexylthiophene) and [6,6]-phenylC71butyric acid methyl ester (P3HT/PC71BM). For the two PSC devices the TiOx interlayer was inserted between the active layer (BHJ) and metal electrode. The performance enhancement of the devices with and without interlayer was investigated. X-ray diffraction (XRD) and UV-VIS measurements were used to investigate structural and optical properties of samples. The current–voltage (J-V) curves of the polymer solar cells with active area of ~ 10 mm2 were measured. We found that the TiOx layer improved the efficiency and stability of the devices compared with the same devices without TiOx interlayer. Also we observed that the PTB7/PC71BM/TiOx solar cell was much stable compared with P3HT/PC71BM/TiOx solar cell.

References:

[1] Y. Lu, C. Alexander, Z. Xiao, Y. Yuan, R. Zhang and J. Huang, Nanotechnology, 23, 2012, 344007.
[2] H. Sun, J. Weickert, H. C. Hesse, L. S.-Mende, Solar Energy Materials & Solar Cells, 95, 2011, 3450–3454.
[3] A. R. b. M. Yusoff, H. P. Kim, J. Jang, Organic Electronics, 14, 2013, 858–861.
[4] J. K. Lee, N. E. Coates, S. Cho, N. S. Cho, D. Moses, G. C. Bazan, K. Lee, and A. J. Heeger, Appl. Phys. Lett, 92, 2008, 243308.
Elastic-Carbon Encapsulation: A Strategy Toward High-Performance Iron Pyrite (FeS2) Cathodes in Lithium Ion Battery Cathodes
Authors: Yoder Tara S. , Tussing Matthew , Cloud Jacqueline E. , Yang Yongan 
Published: February 2020

Iron pyrite (p-FeS2) has been widely utilized as a commercial cathode material for lithium ion batteries (LIBs) for 30+ years, due to its high charge capacity, natural abundance, low cost, and non-toxicity. Industrialized versions include both non-rechargeable Li/FeS2 batteries at ambient temperatures (-40 – 60 °C) and rechargeable Li/FeS2 batteries at high temperatures (400 – 450 °C). However, FeS2 cathodes suffer from very poor cyclability at room temperature. Four specific reasons have been identified for this problem: 1) Volume fluctuations during cycling, resulting in pulverization of large particles and a subsequent loss of contact to the current collector; 2) poor electrical conductivity of the lithiation product, lithium sulfide; 3) detrimental reactions between the electrolyte solution and the active materials (FeS2and its subsequent derivatives); 4) the loss of materials due to the formation of soluble lithium polysulfides.
In this presentation, we will outline our strategy to address all of the above challenges for FeS2 through the encapsulation of FeS2 nanoparticles in an elastic carbon (EC) matrix. Two carbon sources are explored to produce an ideal EC matrix, which is chemically and mechanically stable, elastic, and conductive. These unique properties allow accommodation of the volume fluctuation, enhance the charge transfer, and protect the FeS2 from damaging chemical reactions. The obtained FeS2@EC composites present significantly improved cyclability over bare FeS2 nanoparticles. Scanning electron microscopy, Raman spectroscopy, electrochemical impedance spectroscopy, and cyclability studies are utilized to confirm the structure-performance relationship.
Improving Performance of Li-Ion Battery Anodes with Polymeric Coating
Authors: Wu Nae-Lih , Li Fu-Sheng , Wu Yu-Shiang , Chou Jackey 
Published: February 2020

The properties of the interface between electrode active materials and electrolyte are known to have profound effects on the performance of Li-ion batteries (LIBs). A large amount of research has so far been devoted to modifying the surfaces of active materials in order to enhance the overall performance of the electrodes. Majority of the research has resorted to inorganic oxide coatings, presumably due to their chemical stability, and different beneficial effects have been claimed for both cathode and anode materials. Relatively far less progress has been reported for polymeric coating. Compared with the inorganic ones, the polymeric coatings typically require much lower processing temperature, and when used water as solvent, can be considered as more environmentally-friendly alternative. In addition, the rich chemistry of the polymeric coating intrinsically possess a greater flexibility for dealing with wide varieties of active materials and electrolytes for maximum performance.
For LIB anodes, there are two important issues to deal with for achieving high-energy and high-power performance. First, decomposition of electrolyte at the anode surface takes place at sufficient low potential leading to the formation of a passivation film, known as solid electrolyte interphase (SEI). Formation of the SEI consumes Li ion inventory and hence reduces the overall capacity of the battery cell. Therefore, the amount of the stable SEI layer should theoretically kept at a minimum. Secondly, the power densities for the state-of-the-art graphite electrodes remain insufficient.
In this presentation, we will report our progress in developing polymeric coatings for LIB anodes, particularly for graphite and graphite/Si composite. It is demonstrated that the properties of the anodes in different aspects, such as chemical/electrochemical, mechanical, and wetting behaviors, can be dramatically changed with the combination of polymer chemistry. In particular, it is shown that both the cycle life (Fig. 1) and even the power performance (Fig. 2) of the anodes can be remarkably enhanced by simple polymer coating.
Evidence for Continuous Transformation in Mixed Manganese Iron Olivines
Authors: Xiang Kai , Ravnsbaek Dorthe Bomholdt , Xing Wenting , Li Zheng , Chiang Yet-Ming 
Published: February 2020

In past two decades, tremendous research efforts have been devoted to understanding the phase transformation behavior of olivine type cathode materials, especially LiFePO4 (LFP). It is well known now that insertion/extraction of lithium in LFP is accompanied by a first-order phase transition between lithiated and delithiated states. Various reports have shown that there is 20~30mV voltage gap between charge and discharge within two-phase range. This voltage hysteresis is attributed to the energy barrier to form intermediate compositions on the single particle level and sequential particle-by-particle transition behavior on the multi-particle level. [1-8]
In comparison, LiMnyFe1-yPO4 (LMFP), which is isostructural to LFP, shows strikingly different phase transition behavior. Recent operando Synchrotron Radiation Powder X-Ray Diffraction (SR-PXD) study from our group revealed the formation of metastable solid solutions covering an extended composition range in LiMnyFe1-yPO4 (LMFP, y=0.1, 0.2, 0.4), indicating continuous transition behavior on single particle level and simultaneous transition behavior on multi-particle level. Under this scenario, the voltage hysteresis should be vanishingly small, if not zero. [9, 10]
In order to determine voltage hysteresis (or zero-current gap), the open-circuit voltage (OCV) of LMFP within the Fe(II)/Fe(III) phase transition region was measured after charging and after discharging to the same composition. The zero-current gap is the difference in OCV under these two conditions. We found that there is no zero-current gap or thermodynamic hysteresis in LMFP (y=0.1, 0.2, 0.4), as shown in Figure 1. This result indicates that the energy barrier for LMFP to accommodate intermediate composition on single particle level is negligible, resulting in continuous phase transition behavior despite the fact that the composition is well within the two-phase field. Also this result supports the hypothesis that phase transition in LMFP (y=0.1, 0.2, 0.4) takes place in many particles simultaneously.
This result may be correlated with the observation that LMFP (y<0.6) has better rate capability than LFP at high rates. Under extremely high rates, surface reaction/transport rather than bulk transport/transition may become rate-limiting. For similar materials, the exchange current density should be similar, hence reaction rate may be correlated with the effective surface area. With the phase transition taking place simultaneously in many particles, LMFP (y<0.6) should have higher active surface area and thus superior rate capability under high rates.
Electrochemical Properties of DLC Coated LiNi0.8Co0.15Al0.05O2 Cathode Material of All-Solid-State Lithium Ion Battery
Authors: Visbal Heidy , Aihara Yuichi , Park Youngsin , Doo Seokgwang 
Published: February 2020

The surface of LiNi0.8Co0.15Al0.05O2 (NCA) cathode material was coated with diamond like carbon (DLC) by chemical vapor deposition method, in order to prevent the side reaction at the interface for sulfide based all-solid state lithium-ion batteries. The DLC coated material showed a higher capacity with good cyclability and high rate performance. The interface resistance between the cathode active material and the solid electrolyte significantly decreases by DLC coating onto the NCA powder. The discharge capacity of DLC coated sample at 0.05C was 113 mAhg−1 while that of bared one was about 102 mAhg−1. The charge and discharge cut off potentials were 4.0 and 2.8 V, respectively. The thickness of the DLC coated layer was verified by transmission electron microscope (TEM), and was about 3`5 nm. The sp2 bonding ratio of the DLC coated LiNi0.8Co0.15Al0.05O2 powder was estimated from the C-KELNES spectra to be 50`55%. DLC coating could avoid formation of an inactive layer when surface impurities of NCA react with the sulfide electrolyte to form at irreversible passivation byproduct. This layer of impurities obstructs the Li-ion transport at the interface, and therefore increases the interfacial resistance and decreases the rate capability for bare samples.
In this work, the diamond like carbon (DLC) coating were proposed for the first time as buffer coating layers for all-solid state battery. We demonstrated that the buffer layer is not needed to have a lithium conductivity to reduce the interface resistance between cathode material and sulfide based electrolyte.
Evaluation of Electrochemical Performance of Recovery Silicon from Waste Silicon Sludge As Lithium Ion Battery
Authors: Jin Yun Ho , Park Kyung-Soo , Jung Hang Chul 
Published: February 2020

Recently, in terms of Lithium ion battery market has been widely growing up from mobile IT devices into Electrical Vehicle market. The battery is the most important part in xEV than any other parts. Anode materials in lithium ion battery, those price evaluated about 10 % in composition of typical lithium ion battery. However, the price of anode parts including carbon or silicon materialss were very unstable. It absolutely relies on importation in korea. The silicon which has superior theoretical specific capacity than commercial anode materials (Si = 4200 mAh/g, Carbon = 372 mAh/g), To develop silicon based anode materials for lithium ion battery, raw material of silicon should be priceless and stable supply chain.
To figure out these unstable raw material market, we had been focused on waste silicon sludge which were gathered by process for silicon wafer back grinding. The waste silicon sludge were discarded over 2000 ton/year, all of them are currently buried in korea.
Waste silicon sludge were consists of wafer grinding materials, silicon, and water/oils. Herein, we recovered the silicon from waste silicon sludge and purified the silicon for lithium ion battery anode starting materials. Not only recovred silicon, also recovery silicon had been pulverized to nano-sized by beads-milling. these nano-sized recovery silicon induced that shorten lithium ion paths and large surface area. Malic acid was a chosen media for carbon coating on nano-sized recovery silicon surface. We analyzed among recovered silicon properties and its electrochemical performance.
Building Ionic/Electronic Three-Dimensional Conductive Framework to Enhance the Electrochemical Performance of LiVPO4f Cathode for Lithium Ion Batteries
Authors: Wang Jiexi , Li Xinhai , Guo Huajun , Wang Zhixing , Huang Bin 
Published: February 2020

LiVPO4F has high charge-discharge plateau and good safety, making it a promising high-voltage cathode material for lithium ion batteries (LIBs).1
,
2 Nevertheless, LiVPO4F suffers low electronic and ionic conductivity, which brings poor rate capability as well as cycle performance. Moreover, the reaction at the electrode/electrolyte interface at high voltage with high oxidative V4+ causes low cycle property and low initial coulombic efficiency.3 Therefore, mastering the electrode/electrolyte interface is of great significance for application of LiVPO4F. Surface coating and bulk doping are usually used to overcome these issues in some well-known electrode materials. Coating with highly disperse graphene is able to effectively improve the electronic conductivity of the materials.4
,
5 Li3PO4 is a fast ionic conductor and is also used as inorganic coating material to enhance the ionic transmission of the electrode materials for LIBs.6 Also, Li3PO4 is expected to act as a barrier that restrains the side reaction at the electrode/electrolyte interface at high voltage.7 In this report, we construct the ionic/electronic 3D conductive framework to enhance the comprehensive performance of LiVPO4F. As shown in the schematic diagram (Fig. 1), in this ideal architecture, the nano Li3PO4 are dispersed in the space of thin graphene layers, and the LiVPO4F particles are well wrapped by graphene. We expect the Li3PO4 and graphene co-coated LiVPO4F to deliver impressive electrochemical performance, including superior cycle performance, good rate capability, and high initial coulombic efficiency.

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66,168 (2012).