bluuebunny/crossref_metadata_2025_split huggingface dataset:
Invited: Investigation of the Solid Electrolyte Interface (SEI) on Silicon Nano-Particle Anodes
Authors: Lucht Brett L. , Nie Mengyun , Nguyen Cao Cuong 
Published: February 2020

The surface reactions of electrolytes with a silicon anode in lithium ion cells have been investigated. The investigation utilizes two novel techniques that are enabled by the use of binder-free silicon (BF-Si) nanoparticle anodes. The first method, transmission electron microscopy with energyndispersive X-ray spectroscopy, allows straightforward analysis of the BF-Si solid electrolyte interphase (SEI). The second method utilizes multi-nuclear magnetic resonance spectroscopy of D2O extracts from the cycled anodes. The TEM and NMR data are complemented by XPS and FTIR data, which are routinely used for SEI studies. Coin cells (BF-Si/Li) were cycled in electrolytes containing LiPF6 salt and ethylene carbonate or fluoroethylene carbonate solvent. Capacity retention was significantly better for cells cycled with LiPF6/FEC electrolyte than for cells cycled with LiPF6/EC electrolyte. Our unique combination of techniques establishes that for LiPF6/EC electrolyte the BF-Si SEI continuously grows during the first 20 cycles and the SEI becomes integrated with the BF-Si nanoparticles. The SEI predominantly contains lithium ethylene dicarbonate, LiF, and LixSiOy. BF-Si electrodes cycled with LiPF6/FEC electrolyte have a different behavior; the BF-Si nanoparticles remain relatively distinct from the SEI. The SEI predominantly contains LiF, LixSiOy, and an insoluble polymeric species. The depth dependence of structure of the SEI was further investigated by Hard X-ray photoelectron spectroscopy (HAXPES). Finally, the effect of different binders including PVDF, CMC, and PAA on the surface of silicon nanoparticles and on the structure of the SEI will be discussed.
We gratefully acknowledge funding from Department of Energy office of Basic Energy Sciences EPSCoR Implementation award (DE-SC0007074).
In-Operando X-ray Tomography Studies of Dendrite Formation in Zinc-Air Batteries
Authors: Yufit Vladimir , Tariq Farid , Wu Billy , Biton Moshiel , Merla Yu , Eastwood David , Lee Peter , Brandon Nigel P. 
Published: February 2020

Rechargeable aqueous zinc-air systems are remarkably attractive power sources because of high specific energy, safety, environmental compatibility and low cost. However these systems are still under development and suffer from sufficiently short cycle life that prohibits their use for large electrical storage applications requiring several thousand cycles. One of the key factors responsible is dendritic growth when the system is recharged. Dendrites can grow sufficiently wide to penetrate the separator between the anode and the cathode and cause an internal short-circuit. Despite the substantial work accomplished in studying of zinc dendrite formation there are only few reports available on real time imaging of dendrite growth.
Recent developments in X-ray micro/nano tomography have demonstrated the great advantage of the technique for non-destructive ex- and in-situ characterisation of materials and devices for electrochemical energy storage and generation. We used synchrotron x-ray tomography to investigate the mechanism and kinetics of dendrite formation during zinc-air system operation. The dendrite growth was analysed in-operando in radiography mode while three-dimensional image of dendrites covering the electrode surface was reconstructed from multiple tomographic projections ( Figure 1).
Invited: Surface Modification of Positive Electrode and its Effect to Bulk
Authors: Sakaebe Hikari , Taguchi Noboru , Akita Tomoki , Tatsumi Kuniaki , Ogumi Zempachi 
Published: February 2020

Improvement technique of the life of Li-ion batteries has been intensively studied. Modification of the surface of positive electrode material including coating is effective to this purpose. In that process, it is very important to compare the bulk and surface structure of the positive electrode with/without surface modification to understand this effect.
For basic information concerning the effect of surface modification, authors have applied Transmission Electron Microscopy (TEM) to visualize the structural distribution inside the positive electrode particles after degradation [1]. As a model material, we synthesized sub-micron size particle of positive electrode such as LiCoO2 by Pechini sol-gel method [2, 3] that could provide the suitable sample for TEM observation without damages from sample preparation like ion-milling or FIB. Analytical TEM measurements by scanning transmission microscopy (STEM) with electron energy-loss spectroscopy (EELS) equipped with monochromator were applied. Li-K EELS peak around 62 eV was clearly found and this peak intensity changed with Li charge-discharge state. The EELS mapping from the spectrum imaging method using this Li-K region spectra showed a distribution of Li in the particle or among particles during the charge discharge cycle. We discuss precisely the change of chemical states at the surface and Li ion distribution inside particles of positive electrode material with/without surface modification using Si, Zr, Al, Mg oxide during charge-discharge cycle.
References
[1] N. Taguchi, T. Akita, H. Sakaebe, K. Tatsumi, Z. Ogumi, J. Electrochem. Soc., 160, A2293 (2013).
[2] Y. Sun, I. Oh, S. Hong, J. Mat. Sci., 31, 3617 (1996).
A Critique of Wide Bandgap (WBG) Power Semiconductor Datasheets
Authors: Shenai Krishna 
Published: February 2020

Power switching devices made using wide bandgap (WBG) semiconductors such as Silicon Carbide (SiC) and Gallium Nitride (GaN) have the potential to make transformative impact on electrical energy generation, transmission, distribution and conditioning [1]. Although SiC power diodes and power MOSFETs are commercially available for voltage ratings up to 1,700 volts, a careful review of the datasheets suggests severe shortcomings and the need for improved consistency, parameter definition and standardization in order for application engineers to adapt this new technology with trust and confidence. This paper will provide a critique of WBG datasheets with recommendations for specific improvements.
[1] K. Shenai et al, “Current status and emerging trends in wide bandgap (WBG) semiconductor power devices,” ECS J. Solid State Sci. and Tech.
2(8), N3055-N3063, Jul 2013
Workforce Development for Electric Power Engineers
Authors: Guo Liping 
Published: February 2020

Due to the rapid growth of renewable energy technology such as solar and wind power, the nation will have a shortage of skilled power engineers; however, an ample supply of these engineers is critical in making the nation’s energy system greener and smarter. This presentation will address how to increase knowledge of renewable energy and power engineering amongst college and pre-college (middle and high school) students. The presented project is funded by the National Science Foundation (NSF) Transforming Undergraduate Education in STEM program from 2012 to 2015.
This project uses a progressive approach as participants from different levels – high and middle school students, college students, teachers and faculty engage in collaborative learning about renewable energy. We are developing enabling teaching materials and courses to engage participants. This will enable students and faculty to research renewable energy technology and how these can solve environmental and societal issues. A broad-based advisory group representing industry has been used to identify areas of need in energy and the workforce related knowledge and skills needed in the enhancement of the curriculum. The curricular enhancements focus on authentic problems in renewable energy in ways in which students will be engaged in problem-based learning. In particular, we are developing and using sun tracking solar power systems as an enabling tool to create innovative teaching materials including demonstrations, hands-on experiments, and course modules. The progressive, scaffolding approach used in building content knowledge throughout the curriculum prepares graduates with strong content and research skills needed to advance the field of renewable energy. We are seeking to attract more students, especially women and under-represented groups, into power engineering, through outreach activities, open houses, lab tours and seminars.
Full Epitaxial Trench Type Buried Grid SiC JBS Diodes
Authors: Reshanov Sergey A. , Schöner Adolf , Kaplan Wlodek , Zhang Andy , Lim Jang-Kwon , Bakowski Mietek 
Published: February 2020

The modern SiC Schottky barrier diodes utilize JBS concept that gives surge current capability. However, in planar structures the protection of the Schottky areas from high electric field is not sufficient thus resulting in high leakage currents.
It has been demonstrated that buried grid technology (implanted or epitaxial) gives extremely low leakage currents even at high temperature operation due to superior shielding [1-2]. But the manufacturing complexity limits this technology to niche markets.
Less complicated trench concept of implanted JBS diodes was utilized in [3]. It also enables to improve both the forward voltage drop and the leakage current.
In this paper we present the new concept of fully epitaxial trench JBS diodes. Simulations [3] revealed better trade off of forward and blocking behavior of epitaxial buried grid technology. Epitaxially grown p-n junctions result in increased bipolar injection at high current densities and thus lead to improved surge current capabilities.
The concept of fully epitaxial trench JBS diodes enables cost-efficient manufacturing. Implantation and high temperature annealing steps are replaced with one epi re-growth step that can be performed in multi wafer epi reactors. The re-growth step utilizes Ascatron’s 3D-SiC core technology based on embedded epitaxial growth techniques like presented in [4]. Ring type edge termination is formed simultaneously with the active area grid. The cross section of the epitaxial trench type buried grid JBS device is shown in Fig.1. To optimize the JBS performance the grid spacing is set below 2µm and the n channel has higher doping than the n- drift region.
Fig. 2 shows cross section of the device after p+ epi re-growth in the trenches.
Cross section of the active area of fabricated JBS device is shown in Fig. 3.
Fabricated devices are rated for 20A / 1200V and have leakage currents below 0.1µA at 1000V blocking voltage.
References
1. M. Bakowski, J-K. Lim, W. Kaplan, and A. Schöner, ECS Trans., 41 (8), p. 155 (2011).
2. M. Bakowski, J-K. Lim, W. Kaplan, ECS Trans., 50 (3), p. 415 (2013).
3. M. Aketa, Y. Yokotsuji, M. Miura, and T. Nakamura, Materials Science Forum, 717-720, p. 933 (2012).
4. A. Schöner, N. Sugiyama, Y. Takeuchi, and R.K. Malhan, Materials Science Forum, 600-603, p. 175 (2009).
Optimal BaTiO3 BaTiO3 Cluster Formation for High Performance Piezoelectric Nanogenerators
Authors: Shin Sung-Ho , Lee Min Hyung , Nah Junghyo 
Published: February 2020

Several piezoelectric materials, including ZnO, BaTiO3, and PZT, have been widely investigated to develop high performance piezoelectric nanogenerators (NGs).1-3 In particular, the NGs based on BaTiO3 (BTO) nanoparticles (NPs) are of interest due to their excelling piezoelectric properties and environmentally safe nature. However, the performance of the NGs largely depends on how well BTO NPs can be distributed in the active piezoelectric generation layer. To this end, we report BTO composite thin film formation method using rapid solvent evaporation process, where BTO cluster is formed by cementing NPs with P(VDF-HFP).4 By optimizing the process, the optimal BTO composite thin film, having high density of spherical BTO clusters on the composite film, is obtained and adopted for the NG fabrication. Our NGs show output voltage and current over 110 V and 22 mA, corresponding power density of 0.48Wcm-3, which is one of the highest value reported up to date.

References

1. Z. L. Wang, J. H. Song, Science, 2006, 312, 242–246.
2. J. H. Jung, M. Lee, J.-I. Hong, Y. Ding, C.-Y. Chen, L.-J. Chou, Z. L. Wang, ACS Nano, 2011, 5, 10041–10046.
3. Luo, Y. et al., Appl. Phys. Lett. 2003, 83, 440–442.
4. S.-H. Shin, Y.-H. Kim, M. H. Lee, J.-Y. Jung, J. Nah, ACS Nano, 2014, 8, 2766−2773.
Challenging Issues for Terabit-Level Perpendicular STT-MRAM
Authors: Park Jea-Gun 
Published: February 2020

Recently, many researchers have intensively studied p-STT MRAM as an alternative terra-bit-integration nonvolatile memory since current Si-based dynamic-random-access-memory has a physical scaling limit of less than 20 nm. p-STT MRAM has demonstrated a fast write time of ~10 ns, non-volatile memory operation, and extremely low power consumption. However, for satisfying a commercial specification as a terra-bit-integration nonvolatile memory, perpendicular magnetic tunneling junction (p-MTJ) of p-STT MRAM essentially needs to satisfy critical device performances for p-MTJ spin-valves such as a high TMR ratio of 150 %, a high Jex of > 0.7 erg/cm2, a good Ku of 1x107 erg/cm3, a good ¢ of ~ 74,and a low critical writing current (JC0) of 13.4 MA/cm2, which should satisfy the thermal stability such as an ex-situ annealing above 400 °C. In general, a CoFeB based p-MTJ spin-valve in p-STT-MRAM has been fabricated with the stacked structure of bottom electrode/ amorphous Ta seed layer/amorphous CoFeB free layer/MgO tunneling barrier/amorphous CoFeB pinned layer/capping layer/buffer layer/ synthetic anti-ferromagnetic layer (SyAF) /top electrode. In particular, nano-scale thick amorphous CoFeB layer has been applied for free and pinned layer. However, the mechanism by which the perpendicular magnetic anisotropy (PMA) characteristic for amorphous CoFeB based p-MTJ using amorphous Ta seed layer could be achieved has not been clarified. In our study, we will review its mechanism and the thermal stability limit for amorphous CoFeB based p-MTJ using amorphous Ta seed layer. In addition, we will present the thermal stability enhancement for amorphous CoFeB based p-MTJ using bcc crystalline seed layer and its mechanism. For amorphous CoFeB based p-MTJ using amorphous Ta seed layer, the B atoms were segregated at the interface between the MgO tunneling barrier and the CoFeB free and pined layer after the ex-situ annealing of 275 °C, producing interface-PMA (i-PMA), as shown in Fig. 1(a). However, the PMA characteristics for amorphous CoFeB based p-MTJ using amorphous Ta seed layer was rapidly degraded as the ex-situ annealing temperature increased above 400 °C, which the mechanism was not proved yet. Surprisingly, the crystalline structure of both CoFeB free layer and pinned layer sustained at the amorphous structure although the p-MTJ was ex-tu annealed at 275 °C, as shown in Fig. 2.
In order to enhance the thermal stability of amorphous CoFeB based p-MTJ, a bcc crystalline seed layer is essentially necessary rather than amorphous Ta seed layer. During ex-situ annealing at 400 °C, the bcc crystalline seed layer could texture the amorphous CoFeB free and pinned layer into the bcc crystalline CoFe free layer, MgO tunneling, and CoFeB pinned layer, as shown in Fig. 3. As a result, amorphous CoFeB based p-MTJ could achieve the TMR of ~135 %, as shown in Fig. 4. In this presentation, I will challenging material issues for p-STT MRAM in the view of the perfect crystalline linearity for free layer, MgO tunneling barrier, and pinned layer, and SyAF layer.
Photon-Assisted Electrochemical Construction of <0001>-n-ZnO/<111>-p-Cu2O Photovoltaic Devices with Intermediate TiO2 Layer
Authors: Mohd Zamzuri Mohammad Zain , Sasano Junji , Binti Mohamad Fariza , Izaki Masanobu 
Published: February 2020

The Cu2O/ZnO photovoltaic (PV) device is a realistic candidate for next generation thin film solar cell. The conversion efficiency for the electrodeposited super-straight type PV device was lower than that for the thermally prepared substrate-type PV cell. We developed a photon-assisted electrochemical process to construct the substrate-type PV device without the reduction of the Cu2O.1 Here, we show the photon-assisted electrochemical process to construct the substrate type Cu2O/ZnO PV device with a photovoltaic performance.
The Cu2O layer was prepared by heteroepitaxial electrodeposition on <111>Au/Si wafer substrate in an alkaline solution containing copper acetate and lactic acid. The ZnO layer was stacked on the Cu2O layer by elecrodeposition in a zinc nitrate solution with light irradiation. The PV device was fabricated by stacking the top Al electrode by evaporation.
The light irradiation was needed to grow the <0001>-ZnO layer having the columnar grain morphology and 3.3 eV bandgap energy on the Cu2O layer without the reduction to metallic Cu. The thickness increased with the deposition time up to 30 min and then decreased. And the pores could be observed for the ZnO layer at the deposition time over 30　min. The <0001>-ZnO/<111>-Cu2O PV device showed a photovoltaic performance under AM1.5 illumination, and the performance changed depending on the deposition time, which strongly affected the structure of the resultant ZnO layer. The best photovoltaic performance with short-circuit current density of 2.93 mAcm2 could be obtained for the substrate-type <0001>-ZnO/<111>-Cu2O PV device prepared at 30 min for the ZnO deposition.

Ref. 1. B. M. Fariza, M. Izaki, et al., Thin Solid Films, 520(2012), 2261.
High-Performance Sb-Based III-V Nanowires Synthesized on Amorphous Substrates: From the Formation Mechanism to p-Channel Transistor Applications
Authors: Ho Johnny C 
Published: February 2020

Abstract:
In recent years, due to the narrow direct bandgap and outstanding carrier mobility, Sb-base nanowires (NWs), such as GaSb, have been extensively explored for high-performance electronics and optoelectronics. Importantly, these p-channel nanowires can be potentially integrated with n-type InSb, InAs or InGaAs NW devices via different NW transfer techniques to facilitate the III-V CMOS technology. However, there are still very few works till now focusing on the electronic transport properties of GaSb NWs. Here, we successfully demonstrate the synthesis of crystalline, stoichiometric and dense GaSb NWs on amorphous substrates, instead of the commonly used III-V crystalline substrates, InAs or GaAs NW stems as others reported. The obtained NWs are found to grow via the VLS mechanism with a narrow distribution of diameter uniformly along the entire NW length with minimal tapering and surface coating. Notably, when configured into FETs, the NWs exhibit impressive electrical characteristics with the peak hole mobility of ~200 cm2V-1s-1. All these have illustrated the promising potency of such NWs directly grown on amorphous substrates for various technological applications, as compared with the conventional MOCVD grown GaSb NWs.
Reference:

Yang Z., Wang F.Y., Han N., Lin H., Cheung H.Y., Fang M., Yip S.P., Hung T.F., Wong C.Y., Ho J.C. "Crystalline GaSb nanowires synthesized on amorphous substrates: from the formation mechanism to p-channel transistor applications", ACS Applied Materials & Interfaces, 5, 10946-10952, 2013.

Yang Z., Han N., Wang F.Y., Cheung H.Y., Shi X., Yip S.P., Hung T.F., Lee M.H., Wong C.Y., Ho J.C. "Carbon doping of InSb nanowires for high-performance p-channel field-effect-transistors", Nanoscale, 5, 9671-9676, 2013.
Investigation on Metal-Induced Crystallization of Amorphous Silicon Using Xenon Flash-Lamp
Authors: Mudgal Tarun , Reepmeyer Christopher , Cormier Denis , Manley Robert G. , Hirschman Karl D 
Published: February 2020

Flash-lamp annealing (FLA) is an alternative technique for crystallization of amorphous silicon which can be scaled to large substrates. A process using FLA may have significantly reduced process complexity and time; however published results that demonstrate potential for use in flat panel displays have been limited [1]. This work investigates FLA in combination with metal-induced crystallization (MIC). The FLA system used in this work is a NovaCentrix PulseForge 3300, which anneals the material using a series of short but intense bursts of broad spectrum light from xenon flash lamps. High peak power over microseconds time scale can provide control over the depth of heating to avoid damage when processing on substrates such as glass or plastic. Input factors to the FLA system included lamp intensity, pulse width, number of pulses and repetition rate. Since samples are not in thermal equilibrium during FLA, power/time/flash-count combinations that deliver the same energy produce very different results. Additional factors included use of an anti-reflective SiO2 layer, and substrate heating (steady-state). Performing FLA on samples with trace amounts of nickel has demonstrated effective crystallization with single-pulse exposures delivering energy of ~ 5 J/cm2. Experiments which investigate the influence of both MIC and FLA process parameters on the material properties and electrical characteristics of TFTs will be presented.
[1] S. Saxena, D. C. Kim, J. H. Park, and J. Jang, "Polycrystalline silicon thin-film transistor using Xe flash-lamp annealing," IEEE Electron Device Letters, vol. 31, pp. 1242-1244, 2010
Effects of the Bombardment of Negative Oxygen Ions on Gate Bias Stability of InGaZnO Thin Film Transistors
Authors: Kim Doohyun , Yoon Soobok , Hong MunPyo 
Published: February 2020

Amorphous InGaZnO (α-IGZO) thin-film transistors (TFTs) are very promising due to their potential use in thin film electronics and display drivers. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs applications. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability. Nomura et al. reported that these deep defects are located in the surface layer of the α-IGZO channel. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process. It is well known that these defect states can influence on the performances and stabilities of α-IGZO TFTs. Nevertheless, it has not been reported how these defects are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by a self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films and can create the defects of α-IGZO thin films. The a-IGZO TFTs have been fabricated with different dc biases (200 V, 300V, and 400V). Figure 1 shows that the transfer characteristics of the a-IGZO TFTs with a positive bias stress (PBS in (a)), a negative bias stress (NBS in (b)), and a negative bias illumination stress (NBIS in (c)). It is observed that the changes of the transfer characteristics with PBS, and NBS are not depended on different dc biases. However, a huge shift of a threshold voltage on a-IGZO TFTs is observed under NIBS condition.
In this study, we have investigated that the NOIs accelerated by dc self-bias were one of the dominant causes of instability in α-IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process to prevent the NOIs bombardment effects and present how much to be improved the instability of α-IGZO TFTs by this new deposition method.