bluuebunny/crossref_metadata_2025_split huggingface dataset:
Realization of Stable Cathode-Electrolyte Interfaces in DMSO Based Li-O2 Batteries: Experimental and Theoretical Perspectives
Authors: Noked Malachi , Schroeder Marshall A , Kumar Nitin , Pearse Alexander J , Leung Kevin , Lee Sang Bok , Rubloff Gary W 
Published: February 2020

One of the primary challenges impeding realization of the non-aqueous Li-O2 battery is finding a solvent that is chemically and electrochemically stable under cell operating conditions. Dimethyl sulfoxide (DMSO) is an attractive candidate for rechargeable Li-O2 battery studies; however, there is still significant controversy regarding its stability on the Li-O2 cathode surface.
We report here results from a model cathode system featuring various atomic layer deposited (ALD) catalysts including Ru, RuO2, and Pt on a mesoporous CNT sponge to study the OER/ORR behavior in DMSO-based Li-O2 cells. We performed multiple experiments (in-situ XPS, FTIR, Raman, and XRD) which assess the stability of the DMSO-Li2O2 interface and report perspectives on previously published studies. Our electrochemical experiments demonstrate long term, stable cycling of DMSO-based Li-O2 cells.
This work is complemented by density functional theory calculations of DMSO degradation pathways on Li2O2.
Both experimental and theoretical evidence strongly suggest that oxidation of DMSO on the surface of Li2O2 is very unlikely to spontaneously occur and will take place only under certain conditions and to a minor extent under controlled operating voltages and in cell environments free of acidic function groups (either in the electrolyte or porous scaffold).

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Nanostructured Electrodes Via Electrostatic Spray Deposition for Energy Storage System
Authors: Chen Chunhui , Wang Chunlei 
Published: February 2020

Energy storage system (such as Li-ion battery and supercapacitor) is an important technology that has been widely used for portable electronics, electric vehicles and renewable energy generations. Lots of research has focused on improving its performance, however, many crucial challenges need to be addressed to obtain high performance for further applications. Recently, an electrostatic spray deposition (ESD) technique could be one of the promising technique for electrode formation due to its many advantages, such as simplicity, cost-effective setup, non-vacuum, low temperature deposition conditions, good control for tailoring film composition and morphology, and high deposition efficiency. It provides a simple but versatile strategy for generating single or multi-component materials with varied morphologies, such as sponge-like, dense, porous and fractal, etc. Figure 1 shows the ESD set-up and some typical ESD derived electrode structures and performance. It is belived that controllable morphology, phase and crystalline structure is crucial for the optmization of electrochemical performance in terms of buffering volume change, increasing contact area, shorting ion diffusion passway, etc.. In this presentation, our recent research outcomes related to various ESD derived electrodes for Li-ion batteries and supercapacitors will be summarized and discussed.
Figure 1. (a-b) Schematic drawing and actual set-up of ESD; (c) CNT grow on C-MEMS structure; (d-e) porous Sn@carbon composites; (f) porous Li4Ti5O12; (g) NiO confined in cut-CNTs; (h) NiO/graphene composite; (i) cross section of rGO-CNT composite; (j) rate capability of ESD- Li4Ti5O12 electrode.

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High Energy Density Battery Electrodes with Low and Anisotropic Tortuosity
Authors: Amin Ruhul , Delattre Benjamin , Tomsia Antoni P , Chiang Yet-Ming 
Published: February 2020

The high inactive materials content (e.g., separators, current collectors, conductive additives, binder and packaging) of current nonaqueous battery designs contributes directly to high battery cost and reduces specific energy and energy density. Area specific capacity, which is perhaps the most objective measure of design performance, cannot be increased arbitrarily by increasing electrode thickness and/or density, due to kinetic limitations. In the limit of high density and large thickness, salt depletion within the electrolyte-filled porosity typically becomes rate-limiting. In order to reach higher usable energy at practical C-rates from thick, dense electrodes, it is essential to tailor the topology of the pore structure to reduce tortuosity anisotropy.
Here we report on the fabrication, characterization of tortuosity, and electrochemical testing of thick, dense electrodes made by the freeze-casting of aqueous suspensions followed by drying/sintering. This shaping technique allows design of oriented and interconnected structures that have tortuosity anisotropy, low absolute tortuosity, and high ionic transport. We report on the characterization of tortuosity of directionally fabricated electrodes with similar porosity while varying the solidification rate that resulted in different microstructural features. The electrochemical performance of the fabricated electrodes in half cells exhibits high areal capacity. Hybrid pulse power characterization (HPPC) and dynamic stress tests (DST) were also performed.
(Invited) Manipulating Electrical and Thermal Transport in Nanowire Based Nanocomposite through Doping for Thermoelectric Applications
Authors: Wu Yue 
Published: February 2020

In this talk, we will discuss our work on how to use doping and porosity effects to manipulate the electrical and thermal properties in nanowire based bulk nanocomposites. Our success in increasing the efficiency of p-type BixSb2-xTe3 at higher temperatures can be largely explained by the increase in the optical band gap, according to the Burstein-Moss shift, due to doping, thus delaying the onset of bipolar conduction, which can shift the operation temperature to over 500K with a much improved ZT over 1. In addition, we will discuss the scalable synthesis of hollow nanostructures and the subsequent sintering of them into a highly porous thermoelectric nanocomposite. The as-sintered material has high porosity and holds a record low thermal conductivity, however, its zT is comparable to or even better than the state-of-the-art. The relative density leads to the less cost in raw material and better portability. We foresee that this large-scale approach can be extended to other types of thermoelectric materials and will inspire the utilization of hollow nanostructure in other fields.
(Invited) The Electrochemical Impedance Spectra of BiTe Thermoelectric Device
Authors: Lu Cian-Tong , Hsueh Kan-Lin , Li Wen-Jin , Liu Chia-Mei 
Published: February 2020

Thermoelectric material can be used for energy harvesting that converting thermal energy into electricity. It also can be used as solid cooler by passing electricity thought the element. Many TE array device were manufactured and their performance were tested. Some of the TE device property is not consisted with others. Performance degradation of TE devices was observed. Impedance spectrum was proposed as the non-invasive diagnostic tool.
The impedance measurement was carried out on a single semiconducting element of N-type or P-type. Impedance data was measured over a range of dc bias and they were fitted with an equivalent RC circuit. The parameter value of the RC circuit was calculated.
The EIS data were measured for three different TE array devices over bias voltage ranged from – 1.0 V to 1.0 V and temperature ranged from room temperature to 90 oC. An equivalent circuit Rs (CPE-C) (R1-C1) (R2-C2) was found that is capable of described the EIS data of these samples over the bias voltage and temperature ranges. Values of these parameters were calculated. The EIS technique can be used as an analytic tool for the diagnosis of TE array.
(Invited) Resistive States in Strontium Titanate Thin Films
Authors: Kubicek Markus 
Published: February 2020

Recently, resistive switching devices have attracted a lot of attention, especially for use as non-volatile memories being an alternative to classic transistor technology. Hysteretic I-V characteristics allow modulations between high and low resistive states with potential for fast switching speed, high scalability and low switching energies. Perovskite oxides are an interesting class of active switching materials: Their interplay of band structure, electronic and ionic defects, and interface effects control the switching process. The processes on the atomic scale (e.g. reordering of anions or cations) to accomplish the changes between resistive states require attention. Here, local high electric fields and/or locally elevated temperatures are enabling resistive switching. Studies on strontium titanate (SrTiO3) thin films deposited by pulsed laser deposition (PLD) are presented, focusing on understanding defect chemical and mechanistic implications and requirements of the switching process.
Defect chemical differences between the changes of resistive states at room temperature and at elevated temperatures were investigated. Here we use the temperature change to switch between two regimes in which oxygen vacancies are either mobile or immobile. By using combined electric DC and Electrical Impedance Spectroscopy (EIS) techniques we were able to develop and test a model which can explain different hysteretic I-V responses or pseudo-inductive loops found in impedance spectra as a consequence of the change of resistive states.
Also the influence of PLD parameters on the conductivity of SrTiO3 thin films as well as on their resistive switching behavior was studied in detail. By using microelectrodes, it was investigated how certain areas of a SrTiO3 thin film either required a forming process for reversible resistive switching or not. We propose critical defects distributed in the thin films to explain experiments with differently sized microelectrodes.
Additionally, the influence of the PLD process itself is critically discussed. For this purpose, we use a newly developed in-situ technique combining pulsed laser deposition and electrical DC or electrochemical impedance measurements. Recent results show that interactions with the plasma plume and/or the UV light has a strong impact on the electrical properties of oxide thin films. Interestingly, PLD interactions were even found to affect strontium titanate substrates used for deposition.
(Invited) The Non-Volatile Redox Transistor for Neuromorphic Computing
Authors: Talin Albert Alec 
Published: February 2020

Inspired by the efficiency of the brain, CMOS-based neural architectures and memristors are being developed for pattern recognition and machine learning. However, the volatility, design complexity and high supply voltages for CMOS architectures, and the stochastic and energy-costly switching of memristors complicate the path to achieve the interconnectivity, information density, and energy efficiency of the brain using either approach. In my talk I will describe a non-volatile redox transistor (NVRT): a device with a resistance switching mechanism fundamentally different from existing memristors, based on the concept of reversible, electrochemical reduction/oxidation of a material to tune its electronic conductivity. The first type of NVRT that I will describe is based upon the intercalation of Li-ion dopants into a channel of Li1−xCoO2. This Li-ion synaptic transistor for analog computing (LISTA) switches at low voltage (mVs) and energy, displays hundreds of distinct, non-volatile conductance states within a 1V range, and achieves high classification accuracy when implemented in neural network simulations1. The second type of NVRT I will describe operates on a similar principle but is based on the polymer system PEDOT:PSS, and which we call the electrochemical neuromorphic organic device (ENODe)2. Plastic ENODes are fabricated on flexible substrates enabling the integration of neuromorphic functionality in stretchable electronic systems. Mechanical flexibility makes ENODes compatible with three-dimensional architectures, opening a path towards extreme interconnectivity comparable to the human brain.
(1) Fuller, E. J.; El Gabaly, F.; Leonard, F.; Agarwal, S.; Plimpton, S. J.; Jacobs-Gedrim, R. B.; James, C. D.; Marinella, M. J.; Talin, A. A. Li-Ion Synaptic Transistor for Low Power Analog Computing. Advanced Materials
2017, 29, 1604310.
(2) van de Burgt, Y.; Lubberman, E.; Fuller, E. J.; Keene, S. T.; Faria, G. C.; Agarwal, S.; Marinella, M. J.; Talin, A. A.; Salleo, A. A non-volatile organic electrochemical device as a low-voltage artificial synapse for neuromorphic computing. Nature Materials
2017, 16, 414.
This work was supported by the Sandia Laboratory Directed Research and Development (LDRD) Program. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
(Invited) Epitaxial Random Access Memory (epiRAM) Towards Large-Scale Synaptic Arrays
Authors: Kim Jeehwan 
Published: February 2020

Epitaxial random access memory (epiRAM) towards large-scale synaptic arrays

Shinhyun Choi, Scott Tan, Yunjo Kim, and Jeehwan Kim
Massachusetts Institute of Technology

Abstract

Neuromorphic computing has recently emerged as a non-Von Neuman computing method. Because its analog switching ability to represent multiple synaptic weights by varying conductance in the vertical filaments formed in the switching medium, a memristor has been considered as a suitable neuromorphic hardware platform. Conventional memristors typically utilize an defective amorphous solid as a switching medium for defect-mediated formation of conducting filaments. However, the imperfection of the switching medium also causes stochastic filament formation leading to spatial and temporal variation of the devices. In this talk, we introduce a silicon-based epitaxial random access memory (epiRAM), where we precisely confined the conducting paths in the single-crystalline films resulting in unprecedented device performances. MIT’s epiRAM exhibits extremely low temporal/spatial variation, linear synaptic weight update, high on/off ratio (250 for analog/10,000 for digital), great endurance (>109), long retention time (2 days at 85oC), and self-selectivity. This will allow large-scale neural network hardware, paving the way for computing beyond the conventional von Neumann architecture.
I-V Characteristics of NiO Nanowire Based Resistive Change Memory
Authors: Takase Kouichi , Aono Takashige , Sugawa Kosuke , Shimizu Tomohiro , Shingubara Shoso 
Published: February 2020

1. Introduction
Resistive switching random access memory (ReRAM) has been expected to a next generation memory due to high-speed response, non-volatility, low power consumption [1]. However, poor reproducibility of a switching voltage hinders the practical application. According to a filament model, many kinds and number of filaments made at the soft breakdown of an insulator are thought to be the origin. In our previous studies, we employed anodic porous alumina (APA) with ordered nanoholes as the insulator of ReRAM because nanoholes are expected to inhibit the growth of conductive filaments spacially. In the result, we succeeded in suppression of the switching voltage variation [2].Looking at the top view of SEM image of APA (Fig. 1), we notice no restriction along the dashed lines. It means that there exist a division indicating a bulk property. In this study, a nanowire based insulator has been focused on to confine the filaments omnidirectionally.
2. Experiment
Nickel nanowires were buried into nanoholes of APA using electroplating method, where nickel sulfate was used as an electrolyte solution. The exposed Ni nanowires were obtained by chemical etching the alumina layer. The nanowires were oxidized by oxygen plasma for 1, 3, 5 min. The surface morphology of nanowires was investigated by a field emission scanning electron microscope (FE-SEM). For a contact preparation, Indium solder was used against the top electrode. The bottom electrode was a residual aluminum substrate. The I-Vcharacteristics of NiO nanowires were measured by a standard two-probe method at room temperature, where the current was limited to 1 mA in a SET process guard the device from a complete dielectric breakdown.
3. Results
Figure 2 (a) ~ (c) shows the cross-sectional SEM images of NiO nanowires. The typical diameter and the length were about 40 nm and 600 nm, respectively. Significant oxidation time dependence was not found in the shape. We can see clear switching behaviors for all samples. In case of 1 min oxidation, a relatively wide distribution of the switching voltage was measured. The distribution width became smaller in 3 min oxidation and widens again in 5 min oxidation. The relatively high current found in the RESET process in case of 3 min oxidation. It might be due to poor crystallinity of the NiO thin film because oxygen plasma is expected to make the film amorphous by the high kinetic energy of oxygen plasma. Longer oxidation time might help to formation of many filaments. So, this leads to widen the switching voltage distribution again in 5 min oxidation.
References
[1] M. J. Lee et al. Nano Lett. 9, 1475 (2009).
[2] Y. Tanimoto et al. Jpn. J. Appl. Phys 54, 06FH05(2015).

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(Invited) Critical Recent Advancement of GaN Technology and MMICs for Millimeter-Wave Applications
Authors: Chen Shuoqi , Witkowski Larry , Gu Xing 
Published: February 2020

In this paper, we will present the in-development of Qorvo’s 90nm GaN technology imbedded within Qorvo’s existing 3-Metal-Interconnect (3MI) MMIC process flow, to make active and passive devices fully compatible with state-of-the-art GaN MMIC process, for V- and W-band MMIC High Power Amplifier (HPA) applications. By applying an advanced epitaxial material structure, dedicated T-gate configuration and process refinement, as well as 50-mm SiC substrate with Individual Source Via (ISV) FET construction, this technology demonstrates GaN FET devices with >145GHz Ft and >850mS/mm Gm, enables circuit designers to utilize this technology to pursue millimeter-wave market opportunities. Using this technology, a Technology characterization vehicle (TCV) MMICs using 5-stage 85GHz GaN power amplifiers have been demonstrated through circuit design, fabrication and measurements. This MMIC achieves greater than 38 dB small signal gain at 85GHz (8dB small signal gain per stage), and greater than 30 dB small signal gain over 72 – 90 GHz bandwidth. Further test results for both FET device and MMIC, including DC, small signal and power characteristics, will be reported in conference. This emerging GaN on SiC transistor technology is well suited for next generation millimeter-wave HPA, wideband and multi-function MMIC applications and beyond.
This work was funded by ONR (Program Manager: Dr. Paul A. Maki, ONR N00014-13-C-0071).

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Surface Analysis of AlGaN Channel Hemts
Authors: Douglas Erica A. , Brumbach Michael , Klein Brianna , Baca Albert G. , Allerman Andrew A. 
Published: February 2020

High electron mobility transistors (HEMTs) with AlGaN channels are excellent candidates for high-power applications due to increased bandgap and electric field as compared to GaN channel HEMTs. An increase in critical electric field is achieved by increasing the Al mole fraction of both the barrier and channel layer of the HEMT to AlyGa1-yN/AlxGa1-xN, where y>x≥0.3. However, the effects of the fabrication process on the surface of high Al content AlGaN has yet to be studied.
As AlyGa1-yN/AlxGa1-xN HEMTs gain interest for a variety of applications, unintended modifications to the surface of the AlGaN can have unintended consequences to device performance. X-ray photoelectron spectroscopy (XPS) was performed on Al0.45Ga0.55N/Al0.3Ga0.7N heterostructure. XPS indicated that native surface oxidation of Al0.45Ga0.55N occurs in as-grown material stored at ambient of approximately 8 atomic %. A standard low power microwave O2 ash is a standard process performed to remove organic contamination and descum after photolithography. Though an Al0.45Ga0.55N sample exposed to an O2 ash indicated a slight decrease in C, an increase in the surface oxidation from approximately 8 atomic % (as grown) to approximately 20 atomic % after O2 plasma was observed (Fig. 1). XPS spectra show that after exposure to an O2 ash, oxygen is binding to both Ga and Al. This has substantial implications for device performance and integration schemes for heterostructures with increasing Al content. As the presence of an oxide interlayer can have large implications to Schottky contacts, the effect of an HCl clean to remove the native oxide was investigated. Even after exposure to a 35% HCl dilute in H2O, the O atomic % decreased from 8% to only 6%. Presuming that lower oxygen surface content is desirable, the HCl clean offers a tangible benefit for the surface of Al0.45Ga0.55N/Al0.3Ga0.7N heterostructures.
This work was supported by the Laboratory Directed Research and Development (LDRD) program at Sandia. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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(Invited) Advances in SiC and GaN Power Device Development and Future Directions
Authors: Anderson Travis J , Hobart Karl D , Hite Jennifer K , Luna Lunet E , Kub Francis J 
Published: February 2020

As wide bandgap semiconductors, devices based on SiC and GaN represent critical next-generation medium voltage and high voltage power switch technology. SiC device technology has matured rapidly over the past two decades, owing to advances in substrate quality, a fundamental understanding of epitaxial growth to characterize defects and identify and eliminate performance-limiting defects such as basal plane dislocations, and device breakthroughs such as the junction barrier Schottky (JBS) diode and DMOSFET. While lateral GaN-based HEMT technology has been highly successful for RF power amplifiers and is well-positioned to supersede GaAs-based MMICs, advances in vertical power device technology has been limited due to the lack of high quality native substrates. As large area substrates have become available by hydride vapor phase epitaxy (HVPE) and ammonothermal growth, several fundamental vertical power devices have recently been realized, including Schottky diodes with edge termination, trench MOSFETs, and CAVETs. However, significant fundamental materials challenges currently limit device performance, specifically the realization of repeatable thick drift layers with low background doping as well as a reliable selective area planar process for p-type doping.
In this presentation, an overview of SiC and GaN device development at the U.S. Naval Research Laboratory will be summarized, first looking at SiC devices including the development of novel materials characterization techniques to understand the role of defects on device performance, reliability and failure analysis of devices, including BPD kinetics in PiN and MPS diodes, and novel device designs including grayscale termination processes, temperature compensated PiN diodes, and hybrid Si/SiC modules. Recent developments in GaN vertical device technology will also be presented, including the development of an ion implanted p-type doping process and preliminary materials characterization to understand the relationship between substrate quality, epitaxial layer quality, and device performance. Future directions for GaN device development enabled by the availability of bulk substrates will also be discussed, including implications for lateral devices, novel lateral device designs, and fundamental materials work based on the lessons learned from SiC.