bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Li4Ti5O12 As a High Power Anode Material in Li-Ion Capacitor (LIC),
Authors: Akintola Taofeek , Shellikeri Annadanesh , Akintola Tawakalt , Bolufawi Omonayo , Zheng Jim P. 
Published: February 2020

Li-ion capacitor (LIC) technology is an advanced energy storage device that helps bridge the massive gap between Li-ion batteries (LIBs) and electric double-layer capacitor (EDLC), by incorporating the inherent advantages of both devices. It uses a LIB material as an anode (e.g. hard carbon or graphite) and EDLC (e.g. activated carbon) as a cathode to improve the energy density, power density, and cycle life. However, there are some applications that need an extremely fast rate of charge and discharge (high rate performance) which the present LIB electrode material used in LIC cannot provide. This is due to various limitations of the LIB electrode material which are; structural damage of the material during high rate performance, the safety of the material, and the cyclability.
Lithium titanate oxide (Li4Ti5O12) is a material that can satisfy the requirements needed in high rate performance. This is because of its zero-strain insertion feature, very high safety, high efficiency, and excellent cyclability. However, it has an inherent problem of low electronic conductivity and poor ion diffusion. In order to address this issues, various approaches have been carried out by many researchers and it includes nano-structuring of the particle size to improve Li+ ion diffusion, surface coating with carbon, composting and many more.
In this work, investigation of Li4Ti5O12 as an anode material in LIC is done by using one synthesis method (sol-gel) to synthesize Li4Ti5O12 of different particle sizes. The effect of different particle sizes of the synthesized Li4Ti5O12 on its performance as an anode in LIC is studied in terms of energy density, power density, efficiency, and cycle life. Cathode to anode ratio effect in LIC performance is also carried out. Also, the study of different carbon coating thicknesses on the Li4Ti5O12 particles and how it affects its performance will also be carried out.
Electrochemical Characteristics of Vertically-Aligned Ti3C2 Nanosheet Electrode for High-Speed Charge/Discharge Supercapacitors
Authors: Hideshima Sho , Kawasaki Yusuke , Takimoto Daisuke , Gogotsi Yury , Sugimoto Wataru 
Published: February 2020

Two-dimensional titanium carbide (Ti3C2) nanosheets have recently received attention as a supercapacitor electrode material capable of achieving high capacity and rapid charge-discharge due to psudocapacitance associated with redox reaction on the surface1. To effectively use the surface of each single Ti3C2 nanosheet, nanosheet electrodes with well-controlled porous structures are necessary to increase ion and electron transfer pathway. Here, electrochemical performance of vertically-aligned Ti3C2 nanosheet electrodes, fabricated based on our proposed nanosheet vertical alignment method combined with electrophoretic deposition and freeze drying2, was examined.
To check the importance of the vertically aligned structure to improve electrochemical performance, a vertically-aligned and a horizontally-stacked nanosheet electrode were fabricated by using Ti3C2 nanosheets with lateral size of 200 nm. Cyclic voltammograms of the vertically-aligned electrode show redox peaks at approximately 1.0 V and 1.6 V versus Li/ Li+ at a scan rate of 2 mV s−1, whereas that of the horizontally-stacked electrode gives no significant peaks from Ti3C2 (Figure 1). The capacity obtained from the vertically-aligned electrode was larger than that obtained from horizontally-stacked electrode, suggesting that the vertically-aligned structure improved ion diffusion path to the surface. To investigate the effect of the sheet size on the electrochemical characteristics, vertically-aligned electrodes composed of three different-sized Ti3C2 nanosheets (100, 200 and 600 nm) were prepared and evaluated. It should be noted that the amount of the nanosheets loaded on each electrode was kept constant at 0.68-0.70 mg cm-2. The capacity reached approximately 153 (100 nm), 140 (200 nm) and 136 mAh g−1 (600 nm), at 0.2C current rate, respectively, suggesting that small Ti3C2 nanosheets could effectively improve Li ion accessibility to their active sites compared with large nanosheets. Thus the vertically-aligned Ti3C2 nanosheet electrode could be useful for supercapacitors with high capacity and high-speed charge/discharge ability.
This research was partly supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) (JPMJAL1008) from Japan Science and Technology Agency (JST).
References

M. Naguib, V. N. Mochalin, M. W. Barsoum and Y. Gogotsi, MXenes: A new family of two-dimensional materials, Adv. Mater., 26, 992 (2014).

D. Mochizuki, R. Tanaka, Y. Ayato, S. Makino and W. Sugimoto, Vertically Aligned Reduced Graphite Oxide Nanosheet Film and its Application in a High-Speed Charge/Discharge Electrochemical Capacitor, ACS Appl. Energy Mater., 2, 1033 (2019).

Figure 1
(Invited) Intrinsically Stretchable Semiconductors and Electronics Enabled By Polymeric Nanostructures
Authors: Wang Sihong 
Published: February 2020

The vast amount of biological mysteries and biomedical challenges faced by human provide a prominent drive for seamlessly merging electronics with biological living systems (e.g. human bodies) to achieve long-term stable functions. Towards this trend, the main bottlenecks are the huge mechanical mismatch between the current form of rigid electronics and the soft biological tissues.
In this talk, I will describe a new form of electronics with skin-like softness and stretchability, which is built upon a new class of intrinsically stretchable polymer materials and a new set of fabrication technology. As the core material basis, intrinsically stretchable polymer semiconductors have been developed through the physical engineering of polymer chain dynamics and crystallization based on the nanoconfinement effect. This fundamentally-new and universally-applicable methodology enables conjugated polymers to possess both high electrical-performance and extraordinary stretchability.[1] Then, proceeding towards building electronics with this new class of polymer materials, the first polymer-applicable fabrication platform has been designed for large-scale intrinsically stretchable transistor arrays.[2] As a whole, these renovations in the material basis and technology foundation have led to the realization of circuit-level functionalities for the processing of biological signals, with unprecedented mechanical deformability and skin conformability. Equipping electronics with human-compatible form-factors has opened a new paradigm for wearable and implantable bio-electronic tools for biological studies, personal healthcare, medical diagnosis and therapeutics.[3]
References
[1] J. Xu#, S. Wang#, et al. Highly stretchable polymer semiconductor films through the nanoconfinement effect,
Science
, 2017, 355, 59-64.
[2] S. Wang, et al. Skin electronics from scalable fabrication of an intrinsically stretchable transistor array,
Nature
, 2018, 555, 83-88.
[3] S. Wang, J. Y. Oh, J. Xu, H. Tran, Z. Bao. Skin-inspired electronics: an emerging paradigm,
Accounts of Chemical Research
, 2018, 51, 1033–1045.
(Invited) Electrocatalysts for Lithium-Oxygen and Li-Sulfur Batteries
Authors: Lu Yi-Chun 
Published: February 2020

Electrocatalysis plays a critical role in metal-oxygen and metal-sulfur batteries. Rational catalyst design for nonaqueous oxygen evolution reaction (OER) in Li-O2 batteries and polysulfide reduction reaction in Li-S batteries is required to further improve the battery performances. In this presentation, we will discuss the catalyst effects and design strategies to improve the electrode kinetics and reversibility of Li-O2 and Li-S batteries. We will discuss promoting the fraction of the high-surface-energy facet of the catalyst is an effective approach to increase the Li-O2 OER activity. We designed and synthesized a series of chromium oxide (Cr2O3) with varying fractions of high-energy facet by inhibiting the growth of the low-energy facet, i.e. (012) of Cr2O3. We will discuss the correlation between the Li-O2 OER activity and the fraction of high-energy facet. Catalyst design consideration for polysulfide reduction to lithium sulfide will also be discussed. We will combine electrochemical characterizations and spectroscopic techniques to provide insights into the catalytic processes in these battery systems.
Acknowledgement:
This work was supported by two grants from the Research Grants Council (RGC) of the Hong Kong Special Administrative Region, China, under T23-601/17-R and NSFC/RGC Joint Research Scheme 2018/19 Project No. N_CUHK435/18.
Influence of Metal Dopants on MoS2 Crystallization Investigated through in Situ Electron Microscopy
Authors: Kondekar Neha , Boebinger Matthew G , Tian Mengkun , Kirmani Mohammad Hamza , McDowell Matthew T 
Published: February 2020

Few-layered MoS2 has electronic properties that can be tuned with the material thickness and crystal structure, making it attractive for a multitude of applications including next-generation optical and electronic devices. Doping MoS2 crystals through substitution or adsorption of transition metals has been shown to improve carrier concentration and mobility values while lowering the contact resistance. [1-3] Prior work has investigated the altered physicochemical properties caused by additions of metal atoms into the MoS2 lattice, but there is a significant lack of understanding and control of how dopants affect the crystallization and growth processes of the materials during synthesis. For manufacturing of highly-controlled MoS2 and related materials, improved knowledge of how to control the material structure during the growth process itself is essential. In this study, we combine in situ transmission electron microscopy (TEM) with ex situ investigation to determine how the addition of transition metal dopants influences the crystallization and growth of MoS2 materials from a solid-state amorphous precursor. Low concentrations of Ni are observed to cause significant differences in the MoS2 crystallization and growth process, leading to an increase in resulting MoS2 crystal size. This is likely a result of the observed altered mobility of interfaces between crystals in the presence of Ni, which is known to substitute at edge sites, during heating-induced growth. Addition of other metallic dopants, such as Cu, Fe and Co, did not result in similar increases in MoS2 crystallite size. Ongoing experiments building on the insights from this study aim to understand the influence of these metal atoms on the electronic and optical properties of few-layer MoS2 films. These findings demonstrate the important role of additional elements in controlling the evolution of TMDCs during synthesis, which should be considered when designing these materials for a variety of applications.

References

[1] Zhao, Y., Xu, K., Pan, F., Zhou, C., Zhou, F., & Chai, Y. Doping, Contact and Interface Engineering of Two-Dimensional Layered Transition Metal Dichalcogenides Transistors. Advanced Functional Materials, 2017, 27.
[2] Gao, J., Kim, Y. D., Liang, L., Idrobo, J. C., Chow, P., Tan, J., et. al. Transition-Metal Substitution Doping in Synthetic Atomically Thin Semiconductors. Advanced Materials, 2016, 28, 9735–9743.
[3] Lockhart De La Rosa, C. J., Arutchelvan, G., Leonhardt, A., Huyghebaert, C., Radu, I., Heyns, M., & De Gendt, S. (2018). Relation between Film Thickness and Surface Doping of MoS2 Based Field Effect Transistors. APL Materials,
2018, 6, 58301.
Analytical Model for the Breakdown Voltage in Punch-through IGBTs
Authors: Zhu Chen , Andrei Petru 
Published: February 2020

Insulated-gate bipolar-transistors (IGBTs) are becoming the main switching devices in medium- and high-power applications, such as switched-mode power supplies, power switches, variable frequency driver circuits, traction motors, and inducting heating. Although the switching speed of IGBTs is lower than in the case of metal-oxide-semiconductor field-effect-transistors (MOSFETs), the forward voltage drop is significantly lower, particularly in higher blocking voltage rated devices, which provides major advantage for using IGBTs in many applications. In addition, IGBTs have higher breakdown voltage and currant handling capacity than traditional bipolar-junction-transistors (BJTs), which makes them attractive for a variety of applications related to electric power switches.
In this presentation, we introduce two new analytical models for the breakdown voltage of the punch-through IGBTs. The models are based on the accurate analytical estimation of the ionization integral and the solution of the Poisson equation in the drift region, which lead to a nonlinear equation for the breakdown voltage as a function of the doping concentrations in the drift region, buffer layer, and gate and emitter junctions, as well as of the widths of these regions and junctions. In general, this equation does not have an analytical solution and needs to be solved numerically in order to compute the breakdown voltage. Analytical solutions can be found only in a number of particular cases that will be discussed at the conference. The numerical and analytical solutions of the breakdown voltages are compared to more accurate results obtained using Synopsys’s Sentaurus Device Simulator [1], which is a commercial-grade finite element semiconductor simulator. We observe a very good agreement between our models and the finite element simulations for a wide range doping concentration and geometric dimensions of the IGBTs. In addition, at the conference, we will also compare our analytical results with previous analytical results published in the literature [2].
The proposed analytical model provides an efficient way to design the geometry and doping concentration profiles in punch-through IGBTs and helps the optimization process of the breakdown voltage in these devices [3]. More details about the approximations used in our analytical calculations, the results of the comparison with the more precise finite element simulations, and the existing literature will be presented at the conference.
[1] 2016 Sentaurus Device Simulator User Manual, www.synopsys.com
[2] J. Baliga, Fundamentals of Power Semiconductor Devices: Springer, 2008.
[3] Zhu, C., & Andrei, P. (2017). Sensitivity of Breakdown Voltage of Power Transistors to Dopant Impurities. ECS Transactions, 80(7), 171-179.
Safe Operation of Maximum Temperature for Planar Gate SiC Mosfet under Avalanche Stress Shock
Authors: Li Xuan , Hou Zijie , Tong Xing , Deng Xiaochuan , Jiang Junning , Zhang Yourun , Zhang Bo 
Published: February 2020

The silicon carbide (SiC) metal-oxide-semiconductor-field-effect transistors (MOSFET) exhibits its superior dynamic characteristic due to significant shrink of chip size as a result of SiC wide band gap. This advantage transfers to the fast switching speed (i.e., higher dI/dt, dV/dt) of device, promoting high efficient and high power dense applications. When turn-off process, however, the sharp current variation may result in SiC MOSFET suffering avalanche stress. This shock becomes one of reliability issues for SiC MOSFET, influencing the reliability of the converter further. Recently, the avalanche related studies of SiC MOSFET raise extensive investigations and discussions. It is found that the achieved avalanche energy (E
av) of a specific SiC MOSFET is varied based on different load in the unclamped inductive switching (UIS) test and the underlying avalanche breakdown cause is relevant to thermal runaway. Therefore, it is of necessity to fully understand the role of temperature in the SiC MOSFET during avalanche mode. Meanwhile, a relatively direct and concise indicator to estimate the avalanche failure of SiC MOSFET is expected in practical scenario, even though various components are entangled inside the subject during avalanche shock. In this paper, avalanche capability of 1200V CREE SiC MOSFET characterizing planar gate structure is assessed using various load (3.6mH, 1.1mH, 0.3mH) UIS and heat induced avalanche failure is analyzed.
Through the SiC MOSFET suitable UIS test bench, the withstanding avalanche energy of 1200V rated CREE MOSFET (planar gate) under various avalanche shocks are achieved. Furthermore, verified by the experimentally calibrated TCAD simulation based-on the subject, the underlying mechanism for the avalanche breakdown is revealed. Through the investigation of temperature distribution inside device during UIS process, it confirms that the maximum temperature play predominant role in avalanche damage. When the temperature located at interface of Pbase/N drift region rises up to melting temperature of metal system of source, i.e., around 900K, it results in avalanche catastrophic failure of device. Based on this failure mechanism, accordingly we establish a maximum temperature limit (T
av(max)) of SiC MOSFET to guarantee safe operation in terms of avalanche shock. The indicator T
av(max) is defined as a critical limit of avalanche damage inside planar gate SiC MOSFET.
(Invited) Basic Ammonothermal Growth of Bulk GaN Single Crystal Using Sodium Mineralizers
Authors: Lee Young Kuk 
Published: February 2020

GaN is a promising semiconductor of wide band gap of 3.4 eV at room temperature and can be used as a substrate material for blue/green/UV light-emitting diode (LED) and laser diode (LD) [1]. Sapphire has been the most widely used substrate for manufacturing GaN-based LEDs. However, GaN films grown on sapphire substrates include many critical defects owing to the large lattice mismatch (~15%) and large difference of thermal expansion coefficients (~25%) between GaN and sapphire. Thus, GaN substrates are needed for fabrication of the high power LEDs and LDs.
Two typical routes, ammono-basic and ammono-acidic, have been studied in the ammonothermal growth of GaN crystals. Addition of alkali (Li, Na, and K) elements to ammonia typically results in a basic ammonia solution, whereas addition of halogens (F, Cl, Br, and I) to ammonia typically results in an acidic ammonia solution. The acidic ammonothermal method has a fast crystal growth rate but requires installation of Pt liner due to the corrosive environment. Thus, the basic ammonothermal method is regarded as more appropriate for mass production of GaN crystals [2].
Only a few types of basic mineralizer including NaNH2 [3] and KNH2 [4] have been used previously for the crystal growth of GaN. The reports of comparison with other sodium-based mineralizers for ammonothermally grown GaN crystals have not to be achieved. Potassium mineralizers were not included in this study because they are more sensitive to oxygen and moisture and corrosive to autoclave compared to sodium mineralizers.
In this study, we demonstrate the growth rate, crystal quality, and surface morphology of the as-grown GaN single crystals according to sodium amide, sodium azide, and sodium metal as mineralizer. Also, we describe the morphology and properties of approximately 2 inch GaN crystals grown by ammonothermal method using sodium metal mineralizer.
Reference
[1] S. Nakamura, G. Fosol, The Blue Laser Diode, Springer, Berlin, 1997, chap. 1.
[2] R. Dwilinski, R. Doradzinski, J. Garczynski, L. P. Sierzputowski, A. Puchalski, Y. Kanbara, K. Yagi, H. Minakuchi, H. Hayashi, J. Cryst. Growth 311 (2009) 3015.
[3] T. Hashimoto, F. Wu, J. S. Speck, S. Nakamura, J. Cryst. Growth 310 (2008) 3907.
[4] R. Dwilinski, R. Doradzinski, J. Garczynski, L. P. Sierzputowski, A. Puchalski, Y. Kanbara, K. Yagi, H. Minakuchi, H. Hayashi, J. Cryst. Growth 310 (2008) 3911.
Band Offsets of Insulating & Semiconducting Oxides on (AlxGa1-x)O3
Authors: Fares Chaker , Kneiss Max , von Wenckstern Holger , Grundmann Marius , Tadjer Marko J , Ren Fan , Hays David , Gila Brent P , Pearton Stephen J. 
Published: February 2020

β-Ga2O3 is a wide bandgap semiconductor (~4.8 eV) with properties suited to power electronics, truly solar-blind UV detection, and extreme environment applications. Additional bandgap tunability can be achieved through incorporation of Al into β-Ga2O3, leading to β-(Al,Ga)2O3 monoclinic phase alloys with the bandgap tuned from 4.8- 6 eV. This enables heterostructure designs such as modulation-doped electron channels, quantum wells, and superlattices.
Out of these possible structures, β-(AlxGa1-x)2O3/Ga2O3 heterostructure field-effect transistors (HFETs) have shown impressive and improving performance compared to Ga2O3 based metal semiconductor field effect transistor (MESFETs). For these heterostructures, other wide bandgap oxides can be used as gates dielectrics, and narrow energy bandgap conductive oxides can be utilized to reduce contact resistance between the ohmic contacts and semiconductor surface. For gate dielectrics on (AlxGa1-x)2O3, one must utilize oxide materials with a bandgap of 7 eV of higher to have adequate offsets in both the conduction and valence bands. In this study, we utilize x-ray photoelectron spectroscopy (XPS) to report on the determination of the band alignment of various insulating and semiconducting dielectrics onto (AlxGa1-x)2O3 at various aluminum concentrations. The dielectrics were deposited using atomic layer deposition (ALD) or sputtering. For SiO2 and Al2O3, there are differences of up to 1 eV in band alignments on single crystal (AlxGa1-x)2O3, depending on whether they are deposited by sputtering or ALD. For the conductive oxides, AZO/ β-(AlxGa1-x)2O3 and ITO/ β-(AlxGa1-x)2O3 heterojunctions have a nested gap (type I) band offset. The valence and conduction band offsets are negative in both cases and can be used to enhance carrier transport across the heterointerface.