bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Cycling Behavior of NMC532//Gr-Si Cell in Fluorinated Carbonates Electrolytes
Authors: Pupek Krzysztof Z.
Published: February 2020

In the quest to increase energy density of lithium-ion cells, silicon-containing negative electrodes have been extensively investigated. The long-term performance of these electrodes is limited due to the instability of the electrode-electrolyte interface that is continually disrupted during the lithation-delithiation cycles. Therefore, the development of an electrolyte formulation that enhances the stability of the interface would be a significant step forward.

We conducted a comparative study of several fluorinated carbonates like methyl 3,3,3-trifluoroethyl carbonate, bis(3,3,3-trifluoroethyl) carbonate, 3,3,3-trifluoropropylene carbonate, and mixtures thereof as solvents for NCM523//Gr-Si CR2032 cell electrolyte formulations.

Comprehensive data from rate study, impedance and cycle life evaluation tests will be presented and discussed.
Layered-to-Rock-Salt Transformation in Desodiated NaCrO2
Authors: Bo Shou-Hang , Li Xin , Toumar Alexandra J. , Ceder Gerbrand
Published: February 2020

O3 layered sodium transition metal oxides (i.e., NaMO2, M = Ti, V, Cr, Mn, Fe, Co or Ni) are a promising class of cathode materials for Na-ion battery applications. These materials, however, all suffer from severe capacity decay when a large amount of Na is extracted from the hosts. Understanding the causes of this capacity decay is the key to fully unlock the potential of these materials for battery applications.

In this work, we elaborate the capacity fading mechanism for one of the compounds in this class, i.e., NaCrO2. The (de)sodiation processes of NaCrO2 were first characterized by in situ XRD. Using a slow cycling rate (C/50), a phase diagram of NaxCrO2 close to thermodynamic equilibrium could be constructed. Ex situ synchrotron XRD and electron diffraction were then performed on samples that were charged to selected stages of charge. Through these and additional ab initio computation, we demonstrate that NaxCrO2 (0 < x < 1) remains in the layered structure framework without Cr migration up to a composition of Na0.4CrO2. Further removal of Na beyond this composition will trigger a layered to rock-salt transformation converting the P'3-Na0.4CrO2 to a rock-salt CrO­2 phase, which is responsible for the capacity fade of NaCrO2. This structural transformation proceeds via the formation of an intermediate O3-CrO2 phase that contains Cr in both Na and Cr slabs. It is intriguing to note that intercalation of alkaline ions (i.e., Na+ and Li+) into the rock-salt CrO2 is actually possible, albeit in a limited amount (~0.2 per formula).

Preventing the layered to rock-salt transformation is of uttermost importance to improve the cyclibility of NaCrO2. Possible strategies for circumventing this detrimental phase transition will be proposed. We believe insights obtained in this work can be potentially applied to other O3 type of Na and Li transition metal oxides, and can serve as strong basis for future materials design of NaCrO2 based cathodes.
A NiO-RuO2 Nanoparticle-Decorated Carbon Powder Cathode for Non-Aqueous Lithium-Oxygen Batteries
Authors: Tan Peng , Shyy Wei , Zhao Tianshou
Published: February 2020

Non-aqueous lithium-oxygen batteries have been considered as one of the most promising power sources for electric vehicles and portable devices, due to the high theoretical capacity (3.86×103 mAh g-1) and energy density (1.14×104 Wh kg-1) [1]. The electrochemical reactions in the discharge and charge processes involve the formation and decomposition of the solid product Li2O2 in the cathode. Carbon has been regarded as one of the most attractive cathode materials, due to its good conductivity, high specific area, proper pore volume, and low cost. However, it has been shown that both the highly oxidizing environment (O2
-) and Li2O2 can lead to the decomposition of carbon materials to form a thin Li2CO3 film at the carbon interface [2]. Besides, carbon can promote decomposition of the electrolyte to form side products (e.g. lithium carbonate and carboxylates) [3]. These irreversible side products accumulate on the cathode surface, leading to a high overpotential during charge, resulting in a short cycle life.

A new strategy to solve these issues is to promote the decomposition of side products. In this regard, we here developed a NiO-RuO2 nanoparticle-decorated carbon powder cathode. As NiO has been reported to have activity in the oxidation of carbonate and carboxylate species [4], we used NiO nanoparticles to decorate the carbon powder with two features: i) protect the surface defects, alleviating the decomposition of the electrolyte; and ii) promote the oxidation of side products, retaining the activate surfaces. To further lower the charge overpotential, we meanwhile decorated RuO2 nanoparticles on the carbon powder surface. As a result, this NiO-RuO2 nanoparticle-decorated carbon powder cathode can enable a non-aqueous lithium-oxygen battery with a low charge overpotential and long cycle life.

Further analysis and electrochemical characterizations will be presented at the meeting. The lithium-oxygen battery performance employing this type of cathode will also be presented at the meeting.

References

[1] G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson, W. Wilcke, Journal of Physical Chemistry Letters. 1 (2010) 2193-2203.

[2] B.D. McCloskey, A. Speidel, R. Scheffler, D.C. Miller, V. Viswanathan, J.S. Hummelshoj, J.K. Norskov, A.C. Luntz, Journal of Physical Chemistry Letters. 3 (2012) 997-1001.

[3] M.M. Ottakam Thotiyl, S.A. Freunberger, Z. Peng, P.G. Bruce, J. Am. Chem. Soc. 135 (2013) 494-500.

[4] M. Hong, H.C. Choi, H.R. Byon, Chemistry of Materials. 27 (2015) 2234-2241.
Engineering Metal Nano-Composite As Anode in High-Performance Li-Ion Batteries
Authors: Niu Junjie
Published: February 2020

Due to a high theoretical capacity and an excellent Li+/e- conductivity, the worldwide available metals such as Tin and Aluminum anticipates attractive applications in energy storage. Unfortunately the battery performance is limited because of the pulverization and oxidation. In order to prevent these, here we present a metal nano-composite, which is constructed by a pure metal nanoparticle and a “breathing” thin shell with a flexible interspace, using an in situ chemical redox.  This new configuration can effectively avoid the loss of pulverized active material while providing a fast pathway for Li+/e- transport. In parallel, the controllable void inside can accommodate the large volume expansion to ensure a sufficient adhesion to the shell, leading to a high cyclability and an excellent rate capability. The current facile, low-cost approach to metal nano-composite will open an avenue in next-generation Li-ion batteries in replacing graphite anode electrode.
The Role of Composite Binder on Mechanics and Performance of Lithium Ion Battery Electrodes
Authors: Grillet Anne M. , Humplik Thomas , Stirrup Emily K. , Barringer David , Mendoza Hector , Roberts Scott A. , Snyder Chelsea Marie , Apblett Christopher A. , Fenton Kyle R , Long Kevin N.
Published: February 2020

Battery electrodes are complex multiphase composites which must provide efficient bicontinuous networks for transport of electrons (through the particle phase) and positive lithium ions (through the electrolyte filled pores of the electrode). A crucial but often neglected element of battery electrodes is the binder, typically a mixture of polyvinylidene fluoride (PVDF) and carbon black.  The binder has two primary roles – to provide mechanical integrity and to improve electrical conduction of the electrodes.  Migration of the binder has also been implicated as a potential mechanism of capacity fade in rechargeable lithium ion batteries.

We will present experimental characterization of the polymer binder for battery applications.  Mechanical properties of the composite binder will be shown for both dry films and also binder swollen with carbonate electrolytes used in rechargeable lithium batteries.  The electrical properties are strongly dependent on the applied stress and more modestly on the strain rate.  The evolution of mechanical and electrical properties of the binder after repeated cycling will be shown.

Mesoscale simulations will be presented using experimentally determined three dimensional structures of battery cathodes.  Using these realistic microstructures, the role of polymer binder properties on the effective modulus of the electrode will be examined.  The complex particle scale geometry results in a heterogeneous stress distribution with the binder between particle contacts experiencing high localized stresses.  Implications for battery internal resistance and cycling stability will be discussed.

Sandia National Laboratories is a multi-program 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. SAND2015-10738 A
Electrodeposition and Stacking to Form 3D Hierarchically Porous Structures
Authors: Robinson David B. , Garcia Gail F. , Nishimoto Ryan K. , Bartsch Michael S. , Arrington Christian L. , Buffleben George M. , Jones Christopher G.
Published: February 2020

Rapid transport between fluid and solid phases can yield high power density in electrochemical energy storage systems, and efficient chemical separations in chromatography.  Transport is often slower in the solid phase, and in long, narrow channels of the fluid phase. Careful architecture can lead to significant improvement of overall transport rates.  A known architectural theme that can achieve this is hierarchical porosity, where there are a few long, wide channels connecting to many shorter, narrower channels that provide greater access to the solid phase.

We have fabricated and tested hierarchically porous metal hydride electrodes and chromatography columns with overall dimensions in the millimeter range. The fluid channels are tens or hundreds of micrometers wide.  The solid layers are tens of micrometers thick, and penetrated by pores that are about 10 nanometers wide. We achieve this through electrodeposition of thick layers of block copolymer-templated nanoporous palladium onto a fine wire mesh or photoresist-patterned wafer.  Pieces of these materials are then stacked and fixed in place to form a defined geometry that is macroscopic in three dimensions. Palladium forms a hydride under mild chemical or electrochemical conditions.  We have measured hydrogen transport rates into or out of these structures electrochemically and by mass spectrometry. Transport rates are significantly faster than for cases where one or both scales of porosity are absent. We expect that similar improvements could be demonstrated for other multiphase chemical systems, such as electrodes that store lithium ions, or organic solutes for chemical separations.

Sandia National Laboratories is a multi-program 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. SAND2015-10657A
Locomotive Studies on Electrodeposited Bimetallic Microtubular Motors for pH Sensing
Authors: Moo James Guo Sheng , Wang Hong , Pumera Martin
Published: February 2020

In order to harness the potential of self-propelled miniaturized machines, there has been a sustained effort to increase locomotion in chemically-powered micromotors. Catalytic microdevices, propelled by hydrogen peroxide decomposition to oxygen bubbles, has been the most ubiquitous of them all. The microtubular motors were achieved through a templated-electrodeposition approach with a silver-sputtered polycarbonate membrane, serving as a working electrode in a three-electrode setup. Bimetallic components were accomplished with the sequential electrodeposition of copper, followed by platinum, which serves as the inner catalytic lining. The use of pH to alter the mobility of micromotors is demonstrated in this work through the manipulation of hydrogen peroxide chemistry in different acidity/alkalinity. The addition of sodium hydroxide to increase the pH of the solution led to a consequent increase in activity of micromotors. Meanwhile, introduction of hydrochloric acid led to corrosion of the microstructures, culminating in locomotive changes. Such dramatic changes in activity and velocities of the micromotors allow the usage of this behavior for pH detection. This concept was illustrated in the electrosynthesized tubular bimetallic Cu/Pt micromotors. Alteration of pH shall serve as a useful general strategy for manipulating hydrogen peroxide decomposition in oxygen-bubble propelled catalytic micromotors.
Investigation on Process Parameters on the Adhesion of Electroless Ni-P Film on Silane Compound Modified Si Wafer
Authors: Hsu Chin Wei , Wang Wei-Yan , Wei Tzu Chien
Published: February 2020

We previously reported a novel polyvinyl alcohol-capped palladium colloids (PVA-Pd) as the catalyst for the electroless plating of nickel-phosphorous (ELP-Ni-P) film on 3-2-(2-aminoethylamino) ethylamino propyl trimethoxysilane (ETAS)-modified Si surface [1]. It was found the interaction between PVA-Pd and amino-moiety on ETAS is the root cause of the superior adhesion of ELP-Ni-P film without the need of post annealing. The adhesion of ELP-Ni-P film catalyzed by PVA-Pd on ETAS-modified Si surface is significantly improved from 4.63 MPa to 10.83MPa when compared with it made via traditional Sn/Pd process.

In this study, the effect of process parameters in this method including annealing temperature, annealing time, ETAS dipping time, PVA-Pd concentration and PVA-Pd dipping time are systematically investigated by means of design of experiments (DOE). From the analysis of variance (ANOVA) table, it is found the annealing temperature, annealing time and ETAS-dipping time have main effects on the adhesion of ELP-Ni-P film. Surprisingly, SEM cross-sectional image of the ELP-Ni-P film made by this method reveals that imperfect self-assembly monolayer (SAM) formation of ETAS aids the formation of nickel-silicide intermetallic (IMC) layer, rendering an even better adhesion before annealing. On the contrary, the adhesion of ELP-Ni-P film deposited on perfect ETAS monolayer becomes worse after post annealing. We speculate that silane-compound may play as a barrier layer for the IMC formation, which may jeopardize the original function of Ni-P film as the barrier layer for the subsequent copper layer in semiconductor industry.

Reference:

[1] T.-C. Wei, T.-C. Pan, C.-M. Chen, K.-C. Lai, and C.-H. Wu, "Annealing-free adhesive electroless deposition of a nickel/phosphorous layer on a silane-compound-modified Si wafer," Electrochemistry Communications, vol. 54, pp. 6-9, 2015.

Figure 1
Electrochemical Fluorination of Uranium to UF6
Authors: Martinez-Rodriguez Michael Joe , Olson Luke Christopher , Gray Joshua R. , Garcia-Diaz Brenda Lee
Published: February 2020

The development of efficient and environmentally benign methods to reprocess used nuclear fuel will be enabling technologies for the nuclear renaissance.  The primary large scale method for processing used nuclear fuel is aqueous and generates large volumes of high level radioactive waste.  The use of electrochemical and fluorination methods for reprocessing used nuclear fuel have been proposed and researched by various groups, but combinations of electrochemical and fluorination methods have not been investigated.  Fluorinating agents are extremely potent oxidizers and may electrochemically fluorinate metallic used nuclear fuel with no input of electricity. A galvano-fluorination process has been developed at Savannah River National Laboratory. This electrochemical non-aqueous process enables efficient gas phase uranium recovery while allowing for control of the reaction. Thermodynamic modeling of the electrochemical fluorination process has shown UF6 to be the first gaseous fission product produced during fluorination. Further thermodynamic modeling was used to determine the feasibility of oxide reduction required for oxide fuel before electrochemical fluorination and for experiments.  A chemical reactor system for electrochemical fluorination of U with NF3 in a fluoride molten salt was constructed along with vessels for product collection and analysis. This work has proven that an electrochemical reaction happens between U and NF3 which confirms the feasibility of electrochemical fluorination and the development of a processing scheme.
Nickel Electrodeposits As a Model Material to Study Abrasive Waterjet Machining
Authors: Mieszala Maxime , Lozano Torrubia Pablo , Mischler Stefano , Axinte Dragos A. , Michler Johann , Philippe Laetitia
Published: February 2020

Understanding the erosion mechanism during abrasive waterjet machining is essential to manufacture parts with the desired dimensions, surface finish and mechanical properties. Numerous models1–3exist to predict the effect of the process parameters on the profile of the waterjet footprint. In these models the material properties are either not explicitly considered or taken as homogeneous. In addition, the effect of the original microstructure as well as the microstructural changes during abrasive waterjet machining are usually ignored. Therefore there is a need for a model material with tunable grain size in order to gain better insights into the abrasive wear mechanisms of metals.

Electrodeposition of nickel allows to vary the grain structure and thereby the mechanical properties in a fast, reproducible and inexpensive way. Varying the grain size without changing the composition from nanocrystalline to microcrystalline is highly desirable to perform systematic study. In this poster Ni electrodeposition is used as a tool to study erosion mechanisms during abrasive waterjet milling. By milling trenches in nickel samples with different grain sizes, it was observed that the microstructure has little effect on the erosion rate. Microstructural and mechanical characterization revealed surface nanocrystallization in the microcrystalline nickel specimens due to severe plastic deformation. The surface being altered, the mechanical properties are changed and the erosion rate reduced.

 This study shows the potential for using metal electrodeposition to produce model materials to study engineering issues. The range of microstructure offered by electrodeposition enabled us to screen the effect of the microstructure during abrasive waterjet machining. Similar approach could be extended to other machining and finishing processes.

References

1 J. Billingham, C.B. Miron, D. A. Axinte, and M.C. Kong, Int. J. Mach. Tools Manuf. 68, 30 (2013).

2 S. Anwar, D. A. Axinte, and A. A. Becker, Proc. Inst. Mech. Eng. Part J J. Eng. Tribol. 225, 821 (2011).

3 P. Lozano Torrubia, D. A. Axinte, and J. Billingham, Int. J. Mach. Tools Manuf. 95, 39 (2015).
High Dopant Activation and Diffusion Suppression of Phosphorus in Ge Crystal with High-Temperature Implantation By Two-Step Microwave Annealing
Authors: Shih Tzu-Lang , Lee Wen-Hsi
Published: February 2020

In this paper, high-temperature ion implantation and low-temperature microwave annealing were employed to achieve maximum n-type active concentration, which can be fully activated in germanium. To use the characteristic of microwave annealing more effectively, two-step microwave annealing was also employed. In the first step annealing, a high-power (1200 W; 425 °C) microwave was used to achieve solid-state epitaxial regrowth (SPER) and enhance microwave absorption. In the second step of annealing, unlike in conventional thermal annealing, which requires a higher energy to activate the dopant, a low-power (900W;375 °C) microwave was used to achieve lowest sheet resistance 78Ω/□ and maximum active concentration 1.025×10
20
P/cm
3
, which close to its solid solubility limit of 2×10
20
P/cm
3
.

Figure 1
(Invited) Heterogeneous Integration of III-V Semiconductors on Silicon for Electronics
Authors: Lee Rinus
Published: February 2020

Silicon has been the material of choice to fabricate integrated circuit chips, which are now ubiquitously used in almost all electronic products.  However, today’s market demands electronic chips that are more power efficient and diverse in functionalities.  To meet these demands, one potential solution is to use III-V semiconductors (including GaN). The ability to tailor the electronic and optical properties of III-V semiconductors seamlessly will allow for lower power and greater functionality in future electronics. However, it is critical that III-V semiconductors are heterogeneously integrated onto silicon to enable the technology to be economically viable.

In this invited talk, we highlight the opportunities and review the most recent progress in heterogeneous integration of III-V semiconductors onto silicon. We will also address the most critical issues that remain to be overcome before III-V semiconductors is adopted for high volume manufacturing in silicon environments. This includes gate dielectric and metal contact interfaces as well as cross-contamination and safety issues of III-V processing in state-of-the-art foundries.
(Invited) Effects of Off-State Stress Voltage and Time on the Recovery of on-Resistance (Ron) of AlGaN/GaN MIS-Hemts
Authors: Chyi Jen-Inn , Shiue Ching-Chuan
Published: February 2020

Dynamic resistance of AlGaN/GaN Metal-Insulator-Semiconductor- High Electron Mobility Transistors (MIS-HEMTs) has been extensively investigated lately because of its great impact to the energy efficiency of the devices. There have been many reports on the observation of degradation of dynamic on-resistance (Ron) after an off-state stress. Lots of efforts have also been devoted to the understanding of this phenomenon. To date, charge trapping in the buffer layer and surface states are considered the two major mechanisms for the degradation. However, a clear physical model for the degradation remains to be sought. In this study, the degradation and recovery of Ron after various stress voltage and time are investigated and correlated to the charge trapping and detrapping near the channel region.
Electrochemical Characterization of Surface States at the GaN/Electrolyte Interface
Authors: Winnerl Andrea , Garrido Jose A. , Stutzmann Martin
Published: February 2020

In recent years, III-nitride materials – traditionally used in light-emitting diodes, high power and high temperature electronic devices and short-wavelength photodetectors - have attracted considerable interest in photo-electrochemistry and photocatalysis due to the very favorable energy position of its band edges with respect to many redox levels in liquid electrolytes.

Understanding the mechanisms governing charge transfer across the semiconductor/electrolyte interface is important for a quantitative analysis of cyclic voltammetry and impedance spectroscopy. In previous work [1], by combining contact potential difference and photocurrent measurements, we could show that localized surface defect states play a crucial role in the kinetics of photo-generated charges. As a next step, the influence of these electrically active states located in the semiconductor bandgap on the charge transfer to the electrolyte is investigated.

Here, we present a systematic electrochemical study of MOCVD grown n-type GaN in aqueous electrolytes. Cyclic voltammetry and impedance spectroscopy measurements are performed over a wide range of potentials and frequencies to determine the energy positions of GaN charge transfer states and to investigate the electron transfer kinetics between GaN and redox molecules. Furthermore, the surface states are changed by applying different surface treatments and the influence of these on the details of charge transfer is investigated.

[1] A. Winnerl, R. N. Pereira, and M. Stutzmann, Phys. Rev. B 91, 075316 (2015)
TiO2 Compact Layer-Free TiO2 Nanotubes Films Prepared By Anodizing of Ti Grade 2 Immersed in Aqueous Electrolyte
Authors: Ortega-Díaz David , Godinez Mora-Tovar Luis Arturo , Sepúlveda Selene , Manríquez Juan
Published: February 2020

TiO2 nanotubes (TiO2-NTs) films have been traditionally prepared by electrochemical anodizing of highly pure Ti foils (Ti>99.999%) in aqueous or organic electrolytes. In this sense, since the oxygen content in pure Ti foils could be considered as traces, all the oxygen employed to promoting the growth of TiO2-NTs on this Ti substrates, must be transported from the electrolyte. Therefore, organic solvents such as polyalcohols have been preferred for preparing the electrolytes utilized during Ti anodizing. In this investigation we proposed that industrial grade Ti foils having intercalated oxygen in their crystallographic networks, can be utilized for promoting the formation of TiO2-NTs films in aqueous medium and in the absence of polyol type solvents. Our results confirmed that Ti grade 2 foils were successfully anodized by applying 20V in a two-electrode cell containing a 0.1M NaF + 0.5M H3PO4 aqueous solution an a Pt foil as cathode.  Anodizing times were varied at 2, 3 and 4h. The as-prepared TiO2-TNTs films were characterized by scanning electron microscopy (SEM), UV-Vis diffuse reflectance spectroscopy, dispersive Raman spectroscopy (DRS) and X-ray diffraction (XRD).

Before any thermal treatment, SEM images were obtained from the anodized Ti substrates, thus revealing the formation of pristine TiO2-TNTs having averages of 800nm-length, 115nm-internal diameter, and 24nm-wall thickness. Furthermore, the same SEM images revealed the presence of a TiO2 compact layer on the top of all TiO2-TNTs films, whose thicknesses increased as function of anodizing time. In order to remove this compact layer, an ultrasonic field of 42 kHz was applied for 20, 40 and 60s to all the anodized Ti foils. A complete removal of the compact layer was achieved only for the case of the TiO2-TNTs films growth after 3h of Ti anodizing. Finally, a reproducible crystallographic composition of anatase and rutile, were obtained after the thermal treatment of the TiO2-NTs films in good agreement with the literature. Finally, TiO2-TNTs films obtained after 3h of Ti anodizing and 40s of ultrasonic treatment (i.e. TiO2 compact layer-free TiO2-TNTs) were tested as photoanodes of porphyrin-sensitized solar cells having an open-circuit potential of 0.40V, and fill factor of 0.43 under polychromatic illumination. At first sight, these results suggest a promising application of these electrodes into the field of the solar energy conversion devices.
Role of Defects in Enhancing the Electrochemical Properties of Transition Metal Oxide
Authors: Chakrapani Vidhya , Wang Qi
Published: February 2020

Transition metal oxides are an important class of materials that are valued for their catalytic, ferroelectric, superconducting, and optical properties, and hence they find uses in diverse applications such as heterogeneous catalysts, sensors, solar cells, and high temperature superconductors.  Such rich properties of metal oxide are partly enabled by their complex surface chemistry and the presence of lattice vacancies that significantly perturb the electronic structure of the material.  Hence, an in-depth understanding of the origin and nature of these defect states is important for further expanding the scope of oxide-based systems for various applications. The focus of this presentation is on elucidating the nature of interaction of various chemicals with defects in metal oxide.  The chemical-structure-property correlations developed in this work can enable rational engineering of a new type of nanoscale, low temperature catalysts having tailored functionality and selectivity that can significantly reduce the energy cost and carbon footprint of many important chemical reactions.
Formation and Characterization of Copper Oxide Nanowires through Thermal Oxidation
Authors: Hsu Hsiu-Ming , Lu Kuo-Chang
Published: February 2020

In this work, cupric and cuprous oxide nanowires were successfully synthesized through thermal oxidation of copper substrates in a three zone horizontal tube furnace over temperatures ranging from 300 to 800℃. Processing parameters, including temperature, pressure, heating time, type of gas and flow rate, were varied and investigated in terms of their influence on the morphology, aspect ratio, composition and density of the nanowires. Scanning electron microscopy studies show that these nanowires controllably ranged in diameter from 40 to 400 nm with lengths of up to 60 µm and the varying density was a function of the growth temperature and reaction time. High resolution transmission electron microscopy and x-ray diffraction studies were conducted to further identify the chemical composition, crystal structure and growth direction of the nanowires. Additionally, the growth mechanism has been proposed. This study with physical property measurements demonstrates that copper oxide nanowires are attractive choices for future applications in lithium-copper oxide batteries and optoelectronics at nanoscale.
The Integration of Functional Oxide Thin Film with GaAs By Laser Molecular Beam Epitaxy
Authors: Wen Huang
Published: February 2020

Integration of crystalline oxide thin films with semiconductors has attracted considerable attention in recent years. Compared to Si, GaAs have a higher saturated electron velocity and electron mobility, transistors based on GaAs can function at a much higher frequencies. In this talk, SrTiO3 films were grown on GaAs (100) substrates as an intermediate buffer layer for the epitaxial growth of oxide thin films including ferroelectric BaTiO3 and semiconductor ZnO by laser molecular beam epitaxy (LMBE). The properties of the multilayers in terms of growth modes, strain and interface structures were characterized by the insitu reflective high energy electron diffraction (RHEED) pattern. The crystalline quality and surface morphology of the oxide/GaAs heterostructure were investigated respectively by a combination of Xray diffraction (XRD) and atomic force microscopy (AFM). These heterostructure exhibit good functional properties such as ferrelectrisity and resistive switching. Furthermore, the fundamental interface properties of these heterostructure with an emphasis on the strain effect were discussed in relation with the electrical properties. The results provide an understanding of the integration of oxide/GaAs heterostructure with full control over the interface structure at the atomic scale.
Effect of Ba Co-Doping on Sr5(PO4)3Cl:Ce3+ Blue Emitting Phosphor Application for White Light Emitting Diodes
Authors: Deressa Gemechu
Published: February 2020

Spectral broadening of blue apatite phosphors (Sr, Ba)5(PO4)3Cl:Ce3+ was achieved by changing Sr-Ba cation combinations. Their blue emission colors come from the 5d1-4f1 transition of Ce3+ ions, and their excitation bands are ranged from 250 nm to 400 nm. The substitution of Ba2+ for Sr2+ ions was confirmed by Raman spectra. The broadest Raman width in Sr2.45Ba2.45(PO4)3Cl:Ce3+ phosphor supported its highest disorder of the host lattice, leading to the emission spectral broadening with a half width of 95.5 nm due to the larger variation in crystal filed strength. The thermal quenching behavior showed the blue emission maintenance of 80 % around 100°C. Finally, the 400 nm-pumped white-LED was optically simulated so as to achieve an excellent color-rendering index (Ra) of 90 at white color point.
(invited) 2-Dimensional Layered Materials for Si Technology
Authors: Shin Hyeon-Jin
Published: February 2020

Two dimensional (2D) layered materials are crystalline materials with layered structures, including Graphene, h-BN, and Transition Metal Di-chalcogenides (TMD’s). Each of their layers is consisting of one or a few atomic layers and they form van der Waals interactions with neighboring layers. Recently, they have been studied intensively due to their extraordinary properties, such as, flexibility and transparency. In addition, they have exceptional electronic, optoelectronic, chemical and mechanical properties. For example, Graphene has high electron mobility, chemical inertness, and thermal conductivity, while TMD has high photo responsivity. Based on their properties, many potential applications were proposed and demonstrated.

We have been investigated 2D layered materials for Si technology, but not for the active materials. We have focused 2D layered materials as interface materials due to the chemical inertness and their atomically thin nature. Especially, Graphene has been suggested as a promising material for future interconnects because of its unique electrical and chemical properties. For instance, they are good candidates for diffusion barrier.[1]

Also, they are good candidates for interface materials between metal and Si to reduce the schottky barrier heights and contact resistance in source and drain, which is one of the most critical issues for scaling down.[2]

In this talk, we will cover and discuss the possibility of Graphene and other 2D layered materials for interconnects and contact resistance reducer in Si technology. In addition, we will also cover other potential applications based on 2D layered materials’ unique properties, such as, chemical inertness and atomic thick nature.

[1] L.Li et al., “Verticle and lateral copper transport through graphene layer”, ACS Nano, 9(8), pp. 8361-8367 (2015)

[2] K.-E. Byun et al., “Graphene for true ohmic contact at metal-semiconductor junctions”, Nano Letters, 13 (9), pp. 4001-4005 (2013)
(Invited) TMD Materials Challenges: Defects, Impurities, Passivation and Interfaces
Authors: Wallace Robert M
Published: February 2020

Layered Transition Metal Dichalcogenides are under scrutiny for potential applications in electronics,  catalysis, sensing, photonics, and other technologies.  For many applications, superior control of the materials quality and the resultant interface is essential for practical, reliable device applications.  This talk will describe our recent studies investigating TMD materials surfaces using in-situ and ex-situ analysis to establish the quality of both geological and synthesized TMDs, and the challenges associated with enabling useful device technologies.

This work was supported in part by the Center for Low Energy Systems Technology (LEAST), one of the six SRC STARnet Centers, sponsored by MARCO and DARPA, by the SWAN Center, a SRC center sponsored by the Nanoelectronics Research Initiative and NIST, and the US/Ireland R&D Partnership (UNITE) under the NSF award ECCS-1407765.
(Invited) Contacts to and Contact-Less Characterization of Transition Metal Dichalcogenides: Challenges Abound
Authors: Bartels Ludwig
Published: February 2020

Transition metal dichalcogenides (TMD) such as MoS2 or WSe2 have often been billed as the semiconducting counterpart – or even successor - of graphene. While the semiconducting nature of the corresponding bulk materials is beyond doubt, the understanding of what semiconducting means for a 2 dimensional material is emerging only slowly. In this presentation I will talk about the formation of contacts to TMD materials and the associate shift of the Fermi level. Experimental techniques used to obtain the data includes  X-ray photoelectron spectroscopy and transport measurements. The results shed light on fundamental challenges of transport and devices utilizing these materials. In addition, I will also talk about surface acoustic wave measurements that reveal photogenerated carrier concentrations in TMD materials. These measurements can be performed without the need for metal contacts and, thus, do conceptually not suffer from the limitations described above.
Novel Iron Bismuth Oxychloride Nanosheets for Lithium Ion Batteries
Authors: Myung Yoon , Choi Jaewon , Wu Fei , Banerjee Sriya , Majzoub Eric , Banerjee Parag
Published: February 2020

Iron Bismuth Oxychloride nanosheets were successfully synthesized by facile hydrolysis method. The X-ray photoelectron spectroscopy (XPS) shows composition was uniformly controlled as Fe0.3Bi0.7OCl. UV-Vis spectra and cyclic voltammetry (CV) results show the band gap of nanosheets correspondingly decreased from 3.4 eV for BiOCl to 2.08 eV for Fe0.3Bi0.7OCl due to raising of the valence band edge. Activation energy for electrical conductivity reduced from 862 meV to 796 meV for BiOCl and Fe0.3Bi0.7OCl, respectively. Density functional theory calculations predict changes to the valence band and decrease in the Fermi level toward the valence band edge for the Fe0.3Bi0.7OCl nanosheets - in accordance with experimental data. Correspondingly the Li ion capacities increased from 215 mAh/g for BiOCl to 542 mAh/g for Fe0.3Bi0.7OCl after 50 cycles at the current density of 100 mA/g.
(Invited) Mechanical Energy Harvesting Using Triboelectric/Piezoelectric Properties from Two-Dimensional Materials
Authors: Kim Sang-Woo
Published: February 2020

Graphene has not been used as an active material in energy harvesting devices and systems. Recently, a new type of power-generating device that converts mechanical energy into electricity using triboelectricity was intensively studied. The triboelectric effect depends on various factors, such as the electron affinity, work function, friction, chemical structure, pressure, surface roughness, and humidity. A number of theoretical studies on the electrostatic behavior of graphene have been reported, and it has been concluded that graphene can store an electric charge for a period of time, which adds to its suitability for triboelectric nanogenerators. We designed and fabricated flexible transparent triboelectric nanogenerators by using monolayer, bilayer, trilayer, and quadlayer graphene. The dependence of the power output performance of the graphene triboelectric nanogenerators on the number of graphene layers is also discussed in detail in terms of the work function and friction, which arises due to different electronic relations between randomly and regularly stacked graphene layers. Furthermore, this talk will introduce a direct observation of the directional dependent piezoelectric effect in CVD grown monolayer MoS2 using lateral piezoresponse force microscopy measurements and the piezoelectric power output from piezoelectric nanogenerators fabricated with monolayer MoS2.
(Invited) 2D Materials for Electrochemical Applications
Authors: Chhowalla Manish
Published: February 2020

Two dimensional (2D) transition metal dichalcogenides (TMDs) are being studied for devices that utilize electrochemistry. Examples include hydrogen evolution reaction catalysis and energy storage. Typical semiconducting 2D TMDs are not well suited for catalysis or energy storage because they are not sufficiently electrically conducting. To circumvent this issue, metallic edges of TMDs have been used to increase the catalytic performance. Increasing strain in 2D materials generally leads to an increase in the density of states at the Fermi level and therefore the electrical conductivity. In addition to increasing the fraction of edges and strain, it is also possible to introduce semiconduction to metallic phase transformation in 2D TMDs by chemistry. The metallic TMDs exhibit exceptional electrochemical properties as catalysts for evolving hydrogen and storing charge in supercapacitors. In this talk, I will highlight the fundamental structural properties of 2D TMDs and correlate them to mechanisms responsible for the electrochemical behavior of 2D TMDs.
(Invited) 2D Materials for Wearable Electronics
Authors: Ahn Jong-Hyun
Published: February 2020

Tactile sensors, in the form of conformal and embedded devices, have attracted intense research interest because of their diverse applications, from electronic skin (E-skin) for robotics to health care monitoring systems. Much effort has been made to develop large- area and high-performance tactile sensors with good sensitivity and mechanical flexibility. MoS2 semiconductors have recently attracted attention because of their outstanding mechanical and optical transmittance, high gauge factor, and tunable band gap. However, there is no report on multi-cell devices for practical applications that transcend the fabrication of a single cell. In this talk, I present an ultrathin conformal, MoS2-based tactile sensing array covering an area of 2.2 cm ´ 2.2 cm. We integrated the sensor with a graphene electrode and interconnect to achieve good mechanical flexibility and optical transmittance in the visible color range (Figure 1). This sensor shows high sensitivity, good uniformity, and linearity even after 1000 loading cycles. In addition, it provides excellent mechanical flexibility over strain of 1.98% and better than 80% transparency.

Figure 1.
MoS2 tactile sensor transferred on the fingertip. a-b) Optical and SEM images of the MoS2 tactile sensor on a fingertip. c) Colorized SEM images of the MoS2 strain gauge (left, yellow) and graphene electrode (right, blue). d) Pressure map detected by the MoS2 tactile sensor from contact with pens of different diameters (7 and 5 mm). e) Calculated crosstalk isolation of the MoS2 sensor array with different pen-tip sizes (D : 7,5 and 2 mm).

Figure 1
Electrochemical and Mechanical Properties of a Newly Designed Anode Supported SOFC
Authors: Guan Wanbing , Wang Jianxin , Yu Rong , Zhou Xiao-Dong
Published: February 2020

In an SOFC stack, the interface between the cathode and the interconnect plays an important role on the measured performance of a single cell. A contact between cathode/interconnect and cathode/current collecting cathode was designed to investigate mechanism of cathodic current collector on cell performance. The cell covered with Ag paste on the cathode side exhibits slightly higher power density than that of the cell partially covered with Ag paste. The Ag paste was applied on the cathode side at the corresponding position in contact with the punctuate structure of the interconnect as current-collecting layer. The difference in power densities between the two unit cells was mainly due to the electron transverse transfer on the cathode surface. When the structure of the interconnect was changed from a convex punctuate structure to contentious liner strips. It is found that the cell performance is driven by both gas flow and electron transverse transfer. The effect of electron transverse transfer on cell performance was more significant than that of gas flow rate. The cumulative effect of the transverse electron cannot be neglected. Furthermore, we will report a newly cell structure, so-called “hollow symmetric anode-supported planar solid oxide fuel cell”. The cell remains flat before and after reduction. The pressure of anti-failure load was about 20 times larger than that of conventional anode supported substrates. Meantime, its performance is nearly identical as that of the traditional anode-supported cell. The designed cell can be scaled easily and is cost effective.
Development of Solid Oxide Fuel Cells at Versa Power Systems & FuelCell Energy
Authors: Torabi Alireza , Barton Joseph , Willman Carl , Ghezel-Ayagh Hossein , Tang Eric , Pastula Michael
Published: February 2020

Fuel Cell Energy, inc (FCE) and its wholly-owned subsidiary Versa Power Systems (VPS) are advancing the current state of Solid Oxide Fuel Cell (SOFC) technology towards commercial deployment for efficient and nonpolluting generation of electric power from natural gas and other fuels such as coal. 

SOFC technology represents an important opportunity to utilize fossil fuels in an efficient and environmentally-friendly manner. SOFCs are scalable, efficient (not subject to Carnot cycle limitations), and produce low emissions (e.g. nitrogen oxides) compared to combustion-based electrical power generation technologies (due to lower operating temperatures). SOFC power systems have the potential to achieve greater than 60 percent efficiency (based on higher  heating value of fuel) and more than 97 percent carbon capture at a cost-of-electricity that is projected to be approximately 40 percent below that presently available through integrated gasification fuel cell (IGFC) systems with carbon capture.  An attractive pathway to deployment of either IGFC or natural gas-fueled fuel cell (NGFC) systems is through near-term market opportunities in natural gas fueled distributed generation (DG) applications. 

The recent advancements in the base technology include:

Reduced anode thickness from 1 mm to 0.6 mm

Demonstration of steady-state cell operation at 500 mA/cm2 for over 2 years with less than 0.35% per 1000 hour degradation rate

Demonstration of stable cell operation in high cathode gas humidity environment
The Fabrication of Garnet-Type Li7La3Zr2O12 Solid Electrolyte Materials
Authors: Zhang Xingxing , Fergus Jeff W.
Published: February 2020

The use of solid electrolytes rather than currently used organic carbonate liquid solutions can improve battery safety. The implementation of solid electrolytes requires improvement in the lithium ion conductivity of the electrolyte materials.  In this research, garnet-type Li7La3Zr2O12 (LLZO) is investigated. One of the challenges in the synthesis of LLZO is producing the desired cubic phase, because low-temperature processing can lead to formation of the tetragonal phase, while high-temperature processing can lead to loss of lithium.  In this work, results on processing of garnet-type LLZO powders and ceramics are presented.
(Invited) Ion Conducting Oxides for Electrochemical Energy Conversion and Storage
Authors: Wachsman Eric D.
Published: February 2020

Research in functional materials has progressed from those materials exhibiting structural to electronic functionality.  The study of ion conducting ceramics ushers in a new era of "chemically functional materials."  This chemical functionality arises out of the defect equilibria of these materials, and results in the ability to transport chemical species and actively participate in chemical reactions at their surface.  Moreover, this chemical functionality provides a promise for the future whereby the harnessing of our natural hydrocarbon energy resources can shift from inefficient and polluting combustion - mechanical methods to direct electrochemical conversion.

The unique properties of these materials and their applications will be described.  The focus will be on the application of ion conducting ceramics to energy conversion and storage, chemical sensors, chemical separation and conversion, and life support systems.  Results presented will include development of record high conductivity solid-state battery and fuel cell electrolytes, record high power density (3 kW/kg) solid oxide fuel cells, NOx/CO species selective solid-state sensors, high yield membrane reactors, and regenerative life support systems that reduce CO2 to O2 and solid C.
Effect of Co/Fe Ratio and Microstructural Design on the Structural and Electrical Properties of Mixed Conducting BaSrCo1-XFexO3-X
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Ni Chung-Ta , Lo Shang-Yi , Chen Ta-Te
Published: February 2020

Sr-doped LaMnO3, is commonly used as the cathode for SOFC applications due to its superior electronic conducting properties. With enhancement of ionic conduction, mixed conducting perovskites, such as BaSrCo1-xFexO3-x, may also be used as the SOFC cathode and ion transport membranes for gas separation.

However, the structural /electrical properties of BaSrCo1-xFexO3-x are not only highly dependent upon the Co/Fe ratio but also on the microstructural design.

In this study, Ba0.5Sr0.5Co1-xFexO3-x, is first fabricated by using carbonates/oxides as raw materials. Secondly, a BaSrCo1-xFexO3-x thin film is deposited on a porous BaSrCo1-xFexO3-x substrate by electrophoretic deposition technique. As a result, with high Co/Fe ratio, Ba0.5Sr0.5Co1-xFexO3-x exhibits hexagonal distortion of perovskite structure. With low Co/Fe ratio, Ba0.5Sr0.5Co1-xFexO3-x exhibits cubic perovskite structure. The structure evolution is rationalized based on XRD and XPS analysis in addition to the consideration of cationic valence and radii. The mixed conduction behaviors of Ba0.5Sr0.5Co1-xFexO3-x is rationalized based on the defect types and charge compensation mechanism. The sintering and densification of Ba0.5Sr0.5Co1-xFexO3-x is examined as a function of Co/Fe ratio. The microstructure of catalytic layers were also investigated. Finally, the enhancement of oxygen permeation through thin-film membrane is demonstrated as well.