bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion Resistance in Acidic Solution of Ni-W Nanostructured Alloys
Authors: Creus Juan , Lagarde Mathieu , Shakibi NIA Niusha , Billard Alain , Pichon Luc , Feaugas Xavier , Savall Catherine
Published: February 2020

Nanocrystalline coatings were the scope of numerous studies due to their specific corrosion resistance and their particular mechanical, electrical and magnetic properties. The improvement of the corrosion resistance due to the reduction of the grain size, particularly at the nanometer scale, was not yet clearly established [1]. As grain size decreases, other metallurgical parameters that can affect the corrosion resistance like surface roughness, crystallographic orientation, chemical contamination, vacancy concentration, internal stresses at different scales … are also changed. The objective of our study is to better understand the influence of the microstructural parameters, mainly grain size and tungsten content, on the corrosion resistance in acidic solution of nanocrystalline coatings. It was previously observed that the deposition process strongly influences the defect density inside the coatings, so we have investigated two different deposition processes to obtain Ni-W alloys [2].

Electrodeposition by applying direct and pulse currents in an additive free citrate-ammonium bath and PVD magnetron sputtering were used for the elaboration of Ni-W coatings with different amounts of W. A multi-scale characterization of the metallurgical states of the nanocrystalline coatings using a combination of several microstructural techniques has permitted the characterization of the structural morphology, the grain size and the crystallographic texture [3,4].

Polarization curves were used to study the anodic behavior and the kinetics of the Hydrogen Evolution Reaction in acidic (H2SO4 1M, pH 3) deaerated solutions.

According to our results, the grain size refinement strongly depends on the elaboration parameters which also influence the light elements contamination (O, H, N, C) and/or the alloying addition. The analyses of the polarization curves in acidic media revealed that the tungsten addition considerably affects the stability of the protective passive film. It was suggested that the tungsten addition plays an important role on the electrochemical reactivity in both anodic and cathodic domains and that the other metallurgical parameters such as grain size only intervene at second order.

[1] K.D. Ralston, N. Birbilis and C.H.J. Davies, Scripta Materialia 63 (2010) 1201-1204.

[2] M. Lagarde, N. Shakibi Nia, J. Creus, X. Feaugas, C. Savall. Eurocorr Graz 2015, 6-10 sept.2015.

[3] C. Savall, A. Godon, J. Creus, X. Feaugas, Surface and Coatings Technology 206 (2012) 4394-4402.

[4] N. Shakibi Nia, J. Creus, X. Feaugas, C. Savall, Journal of Alloys and Compounds 609 (2014) 296-301.
(Invited) Doped Titania Oxide Nanotubes for Photoelectochemical Water Splitting
Authors: Liu Qiang , Ding Dongyan , Ning Congqin , Dong Zhenbiao
Published: February 2020

Extensive studies have been carried out on clean and renewable energy due to the pollution and depletion of fossil fuel. Ions doping is the efficient ways to enhance photocatalytic activity of titanium oxide (TiO2). Here we report photocatalytic activity of the Ni and Nb-doped TiO2 nanotube arrays photoanodes, respectively. The Ni-doped TiO2 nanotube arrays were fabricated through anodization of Ti50Ni alloys in electrolyte containing 5% ethylene glycol/glycerol containing (NH4)2SO4 and NH4F. Nb-doped TiO2 nanotube arrays were fabricated through anodization of Ti35Nb alloys in electrolytes of 1M NaH2PO4 containing 0.5 wt% HF. X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the doped TiO2 nanotubes photoanodes. The experimental results indicated that Nb and Ni doping could enhance the photocatalytic properties of the titanium oxide. The photocatalytic activity of Nb-doped TiO2 and Ni-doped TiO2 nanotube arrays photoanodes were 1.5 and 2 times as high as that of the undoped TiO2 nanotubes photoanodes, respectively. Density functional theory (DFT) calculations indicated that Ni-doping could narrow the band gap of undoped TiO2 through formation of impurity states and Nb doping could result in the valence band shift of the undoped TiO2. The doped TiO2 nanotube photoanode are promising for photoelectochemical water splitting application.
Degradation in Pmosfet during Off-State Stress
Authors: Park Segeun , Kim Ilgweon , Roh Yonghan
Published: February 2020

Degradation of P-channel MOSFET during off-state stress with ac bias has been experimentally investigated. Sub-threshold leakage increased after off-state with ac bias. It was caused by hot electron injection during off-state. With varying source voltage, the degradation during off-state stress with ac bias was more severe than off-state stress with dc bias. Degradation impact was the same as hot electron induced punch-through (HEIP) during on-state. It was observed that subthreshold leakage current of pMOSFET increased and standby current became serious. Gate length, tap width, doping concentration at source/drain extension, operation temperature and operation frequency, respectively, were evaluated and the degradation modeling has been introduced in our paper.

Figure 1
BaTiO3 Film Grown by Water-Based Process
Authors: Alhasan Sarmad Fawzi Hamza , Abouelkhair Hussain , Peale Robert E. , Oladeji Isaiah O.
Published: February 2020

Self-assembled nano-crystalline BaTiO3 films on stainless steel foil substrates, were grown by the water based Streaming Process for Electrodeless Electrochemical Deposition (SPEED).  SPEED is an aqueous process that deposits self-assembled nanomaterial inorganic thin films over large areas, without a vacuum, providing a scalable and manufacturing friendly process to fabricate durable films.  Water-soluble compounds with complexing agents grow films by heterogeneous reaction on the substrate, with little wasteful homogeneous reaction.  Hydrophilic substrates bind hydroxyl ions (OH–), which are attachment sites for nucleation with density exceeding 1012 per square centimeter. The water based precursor, nebulized into 10 to 20 μm droplets (vapor phase SPEED, or VPSPEED), impinges on the substrate, which is at temperatures of ~300 ℃, giving growth rate exceeding 200 nm per minute.  The substrate heating provides the reaction activation energy, and decomposes/volatilizes reaction byproducts, but the required temperatures are well below those required for spray pyrolysis.  All films were subsequently annealed at 500 C for 1 hour.  The morphology of the ~1 mm thick films comprises single crystals of micron dimensions imbedded in a matrix of nanocrystals.  XRD confirms presence of BaTiO3 crystals of hexagonal phase.  Further annealing at 500 oC increases the hexagonal peak intensity.  Subsequent annealing at 600 oC for 1 hour causes a substantial transformation to the cubic phase.  Potential applications include dielectric layers, capacitors, waveguides, ferroelectric RAM, and pyroelectric infrared detectors and phosphors.  Characterization of pyroelectric properties and application to infrared detection will be presented.
(Invited) III-V Selective Area Growth and Epitaxial Functional Oxides on Si: From Electronic to Photonic Devices
Authors: Merckling Clement , Liu Ziyang , Hsu Mark , Hasan Samiul , Jiang Sijia , El Kazzi Salim , Boccardi Guillaume , Waldron Niamh , Wang Zhechao , Tian Bin , Pantouvaki Marianna , Van Campenhout Joris , Collaert Nadine , Heyns Marc , Van Thourhout Dries , Vandervorst Wilfried , Thean Aaron
Published: February 2020

Driven by fabrication cost reduction and device performance improvement, the Silicon semiconductor  industry continues its never-ending pursuit of new approaches for fabricating integrated circuits. In this context, the monolithic integration of III-V semiconductors epitaxially grown on Si substrate have been attracting much attention as building blocks for next-generation electronics and photonics due to their potential intrinsic properties.

Direct heteroepitaxy of III-V compound semiconductors on Si has traditionally represented a formidable challenge, due to the high material mismatch (lattice parameter, polarity, thermal coefficient, ...) between Si and III-V semiconductors generating high density of defect density during the epitaxial process. To overcome this, selective area growth of III-Vs in a pre-patterned Si substrate by Selective Area Metal-Organic Vapor Phase Epitaxy allow the possibility to obtain high quality and reduced defect density III-V based active layers onto standard Si(001) substrate.

 Using this approach we integrate III-V materials monolithically on Si while focusing on both ultimate trench widths (W < 20 nm) scaling as well as relaxed trench dimension in function of the targeted application. We report here on the heteroepitaxy of InP buffer on initiated from a <111> V-groove Si surface and discuss the unique relaxation mechanism of such compound with respect to Si substrate. We derived a fundamental understanding and theoretical modeling of the growth mechanisms in STI trenches as well as the determining role of the InP nucleation layer. The subsequent growth approach of InGaAs active layer, used for both nFET or Laser applications, is further studied.

Finally, III-V based electronic and photonic devices realized using selective area growth technique are presented and benchmarked to the current state of the art.
(Invited) Broadband Spectroscopic Characterization of Electrically Active Defects in Dielectrics: Monitoring the in-Service Evolution of Dialectics in Integrated System
Authors: Obeng Yaw S. , Okoro Chukwudi A , Amoah Papa K. , You Lin
Published: February 2020

Emerging nanoelectronics are been hindered by reliability challenges such as stress related failures. The stress buildup is due primarily to mismatch in the coefficient of thermal expansion (CTE) of the materials of construction which results in the generation of defects such as cracks, voids, delamination, plastic deformation, substrate warping and buckling. These types of damage ultimately lead to open or short circuits in the devices, resulting in catastrophic failure.  The chemistry and physics of the materials also play crucial roles in the changes in the stress over time, especially in low operating voltage devices. The process flows of such low voltages devices entail low temperatures processing, and the use of low temperature deposited dielectrics, such as low-k materials, plasma deposited and sub-atmospheric pressure deposited films derived from organometallic precursors as insulators between metal lines and layers. Unfortunately, these low-temperature-processed materials are metastable due the presence of reactive metastable intermediates from the cracking of the precursors, and incomplete reactions within the films that result in electrically active defects in the “as deposited” films. Metrology is thus needed for the accurate quantification of the reliability impact of stress evolution in such integrated systems.  Unfortunately, traditional spectroscopic tools, such as infra-red (FTIR), ellipsometry, electron spin resonance (ESR), solid state nuclear magnetic resonance (NMR), XRD, etc. which do not accommodate integrated devices.  Microwave (RF)-based metrology tools are uniquely suitable for studying the buried structures and interfaces inherent in such nanoelectronic devices.

In this paper, we discuss the use of broadband radio waves (RF) (with frequencies up to 20 GHz) to detect, characterize and monitor the evolution of active defect in low-temperature processed dielectric films as a result of deliberate thermal exposure.  The impact of thermal anneal on the behavior of the electrical defects shed light on the chemical changes occurring within the dielectric films that lead to changes in stress buildup.
3-D Extension of Chemical Mechanical Polishing for Nano-Structuring Applications on Alternative Technologies
Authors: Ozdemir Zeynep , Basim G. Bahar
Published: February 2020

Chemical mechanical polishing has long been adopted as a technique to enable global planarization for semiconductor applications.  The main functional requirements such as selectivity, enhanced material removal rates and minimal defectivity are achieved through advanced slurry formulations and process set up.  In this study we tune the CMP process to generate controlled nanostructures to benefit from the synergy it enables on metallic surfaces namely; (i) formation of a protective metal oxide film during polishing and (ii) ability to tune the root mean square surface roughness from nano to micro scale.

The first application is on titanium surfaces to modulate the surface structure of the implantable biomaterials.  We have demonstrated earlier that the CMP application on dental implants have improved the in-vitro biocompatibility with 3-D applications being developed [1].  The application we propose in this study is the application of the CMP induced nano-structuring for the lime-scale prevention on the heating elements. Lime scale formation by the hard water often causes numerous technical and economic problems in industrial and house-hold equipment. In scope of the work bare stainless steel and alternative coating materials were characterized for surface roughness, surface energy and wettability responses in order to observe the CMP induced nanostructure levels on the CaCO3 attachment behavior. Surface topography was evaluated through atomic force microscopy (AFM) on all the materials after CMP process was conducted. Accelerated lime scale formation tests were performed on these surfaces and the affect of random nanostructures and their thermal expansion abilities as live nanostructures were evaluated on the exfoliation of the lime scale. From the experimental work surface total energy was observed to be one of the main indicators for the lime scale adhesion prevention [2].  Figure 1 shows the calcination removal performances of the alternative coating elements as compared to the steel after the heat cycle the heating elements are exposed to..                     

References

Ozdemir Z., Orhan O., Bebek O., Basim G. B., Development of 3-D Chemical Mechanical Polishing Process for Nanostructuring of Bioimplant Surfaces, ECS Transactions, 2014, 61, 21-26.

Basim G.B.,Chemical Mechanical Polishing Induced Live Nano-Structures for Lime-Scale Prevention on Heating Elements. International Patent Office Application No: PCT/TR2013/000378, Application Date: 31.12.2013.

Figure 1
(Invited) Plasma-Based Technology for Mass Production of Graphene and Other 2D Layered Materials
Authors: Keidar Michael
Published: February 2020

Arc discharge plasma is as one of the most practical and efficient methods to synthesize various carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene with minimal defects and large yield. This is achieved due to the relatively high synthesis temperature and eco-friendly growth mechanism. Moreover, by introducing a magnetic field during synthesis process, large-scale graphene and high-purity SWCNT can be obtained in one step. In addition, the yield of graphene can be controlled by external parameters, such as the type and pressure of buffer gas, the temperature of substrate, and plasma density and temperature. Bulk graphene (graphene platelets, flakes) is usually characterized by several layer (2-20 nm) graphene pieces having characteristics sizes of about microns to ten microns. Currently, the main method for synthesis of bulk graphene is chemical exfoliation, where chemicals are utilized to separate the graphene sheets from the piece of graphite. Current production capability are quite limited and estimated to be around several tens of tons of material annually worldwide. This work is focused on development of novel highly efficient and low cost plasma-based method for graphene production in industrial quantities characterized by exceptional product properties. The synthesis is based on utilization of arc discharge supported by ablation of anode material at atmospheric pressures. Pure carbon anode (several millimeters in diameter) and arc current in the range 50-100A were utilized for the synthesis. The graphene was synthesized on the metal substrate and was mechanically remove using metallic brush immediately after the synthesis. The synthesized samples were characterized using SEM, TEM and Raman spectroscopy. Typical size of the graphene platelets was found to be about several microns. The graphene platelets down to ~2 layers were obtained. We present state-of-the-art experimental data on various attempts to employ the arc plasma technique for the graphene synthesis and consider growth mechanisms including precipitation, surface-catalyzed processes and a substrate-independent approach. The potential of arc synthesis for the growth of other types of 2D materials and future prospects are discussed.
(Invited) Nanostructures Growth By Oxidation of Metallic Alloy Thin Films with Atmospheric Pressure Remote Plasma
Authors: Imam Abdallah , Gries Thomas , Hussein Khaled , Amati Mateo , Belmonte Thierry
Published: February 2020

During the last decade, research on metal oxide nanostructures has led to the emergence of new materials with unique physical and chemical properties. In this work, we report on a process based on an atmospheric pressure micro-afterglow to synthesize oxide nanostructures of copper-iron alloy thin films deposited by magnetron sputtering. In plasma afterglow processes, active species like oxygen atoms or metastable states of oxygen are available. They are more active than ground state oxygen at low temperature because of the extra amount of energy coming from dissociation or excitation. Oxidation of metals in these conditions promotes the growth of oxide nanostructures.

The effect of the addition of copper to iron (and vice versa) is investigated by creating either alloys single layers or stacks of copper and zinc layers with different thicknesses on a glass substrate. The experimental device consists in using an Ar-O2 microwave plasma. Active species exit the reactor through a tiny hole (500 µm in diameter) and react with the copper-iron film to perform the direct synthesis of oxide nanostructures in a single step without any template or surfactant. The morphology, shape and size distribution can be controlled by varying the experimental parameters such as the amount of oxygen injected in the plasma, the microwave power, the treatment time or the alloy composition. It appears possible to synthesize different kinds of nanostructures with good reproducibility in a single-step process: nanowires, nanowalls or nanoblades. Various characterization means, including SEM, SIMS, TEM and XRD were used to determine the composition of the nanostructures. Besides, XPS microscopy experiments were carried out with the SPEM at the spectroscopy for chemical analysis (ESCA) microscopy beamline at the Elettra synchrotron facility in Trieste. We show that both oxides, CuO and Fe2O3, can be formed on the same spot (see figure). Furthermore, by controlling the composition of the alloy, we show that very thin CuO nanowires (with diameters as small as 5 nm) can be grown. Ultra-thin nanoblades of Fe2O3 can be formed. They are so thin than their edge is submitted to grow instabilities and become serrated.

The formation mechanism of these structures was investigated. The role of the addition of a new element on the growth mechanism, together with the way it is distributed within the stack, will be discussed. The role of stress on grain size, grain boundaries and outward diffusion of metallic ions will be discussed. Results will be compared to those obtained by different groups via thermal oxidation. Finally, a growth model will be proposed to explain the synthesis of the as-grown nanostructures.

Figure 1
Plasma Etching Chemistry for Smoothening Ofultrananocrystalline Diamond Films
Authors: Sunkara Mahendra Kumar , Jaramillo-Cabanzo Daniel Felipe , Willing Gerold
Published: February 2020

Ultrananocrystalline diamond (UNCD) is characterized by the dimensions of its ultra-nanoscale grains and is typically synthesized under high nucleation conditions using an argon-rich hydrogen/methane/argon gas mixture. UNCD films consist of crystalline grains of at least 95% sp3-bonded carbon that are 2-10 nm in size with a surface roughness ranging between 20 and 40 nm. UNCD films exhibit most of the outstanding properties of diamond such as an exceptional hardness, high mechanical strength, extremely low friction coefﬁcient, chemical inertness, thermal stability and high electrical conductivity at room temperature when doped with nitrogen. While all these properties are intrinsic of the material, the required roughness scale of the UNCD film needs to be carefully tailored and customized on an application-by-application basis. For instance, a low roughness is key to manufacturing adequate micro-electromechanical systems (MEMS), wear-resistant low friction coatings, X-ray lithography masks and biomedical devices where stringent tolerance and topological precision are of utmost importance.

Here, a new process for controlled smoothening of ultrananocrystalline diamond films using H2/O2 plasma is presented. Diamond films were exposed to oxygen, hydrogen and hydrogen/oxygen mixture (19:1) plasmas. Evolution of morphology and thickness were monitored ex-situ using scanning electron microscopy (SEM) while roughness was measured using atomic force microscopy (AFM). Neither pure oxygen nor pure hydrogen plasmas were found suitable for smoothening the films. The H2/O2 mixture plasma exposure resulted in a constant roughness decrement of 0.043 nm/min with a slow etching rate (0.07 µm/h) allowing for the control of the final film roughness without sacrificing too much of the material thickness.
Growth of Vertically Aligned Al-Doped ZnO Nanorod-Nanowalls Via Chemical Bath Deposition
Authors: Chu Sheng-Yuan , Tang Jian-Fu
Published: February 2020

Nanostructured ZnO materials have received considerable interest from scientists due to their remarkable performance in electronics, optics and photonics.In recent years, ZnO nanostructures with one-dimensional (1D) and two-dimensional (2D) morphologies, such as nanorods, nanobelts, nanowalls and nanoflowers, have been synthesized. Previous research has suggested that providing multiple types of nanostructures is significantly better than just a single type. In this paper, we used Al layers of various thicknesses as a reaction layer to synthesize an array of vertical nanorods and nanowalls on a ZnO-coated substrate. Previous studies reported that Al undergoes chemical reactions under alkaline conditions in the presence of amines (hexamethylenetetramine: HMTA). Our findings indicate that an increase in the Al3+ ion concentration in the precursor solution leads to a morphological evolution from nanorods to nanowalls. Measurements of cathodoluminescence (CL), X-ray diffractometry (XRD), and SEM-EDS confirm that the resulting structures are pure ZnO with good crystallinity. We also investigated the optical properties of these ZnO nanostructures and propose a possible growth mechanism.

Figure 1
Recent Attempts to Improve the Capabilities of Commercial CFx to Enhance the Efficiency of Li/CFx Batteries
Authors: Meshri Dayal T. , Shembel Elena M , Meshri Sanjay D. , Adams Robert L. , Mathur N.C. , Pinnapareddy Devender , Redko Vlad I , Maksyuta Irina M , Markevich Alexandr V
Published: February 2020

Lithium/CFx batteries have long storage life and have wide applications in various fields from space exploration to medical electronics. Lithium/CFx battery shows highest theoretical capacity when compared to other primary batteries such as Li/SOCl2 and Li/MnO2 batteries. However, Li/ CFx batteries suffers from voltage delay, show lower open circuit voltage during initial discharge and do not perform well in high rate applications which may be due to intrinsically poor electronic conductivity of CFx cathode material Historically, while making the cathode, addition of carbon is done to improve the material conductivity and get a better performance but it decreases the discharge capacity.

Recently, many attempts have been made to improve efficiency of Li/CFx batteries by modifying CFx properties through various physical and chemical means from coating carbon on CFx surface to mechanochemical and chemical treatment. Use of some of these modified CFx   resulted in improved battery performance that included no voltage delays, better operating voltage and higher rate capabilities in comparison to standard Li/ CFx batteries.

In this paper, development of CFx from historical perspective to the present day will be briefly discussed. We shall also present a short review on  the recent attempts made by us and various other groups to modify properties of CFx for Li/CFx batteries. Use of modified CFx  looks very promising for improving the efficiency of Li/CFx batteries.
Modelling Li-S Cells: Mechanisms behind Voltage- and Capacity-Drop during Discharge
Authors: Zhang Teng , Marinescu Monica , Wild Mark , O'Neill Laura , Offer Greg
Published: February 2020

The lithium-sulphur (Li-S) cell could provide the next step-change in battery technology with a promising practical energy density of 500-600 Wh/kg. However, a lack of understanding of the complex electrochemical, transport, and phase-change phenomena in Li-S cells is arguably holding back development. Acquiring this knowledge requires experimental characterizations in tandem with mechanistic modelling. In this presentation, we point out that existing Li-S models do not sufficiently capture the voltage- and capacity-drop mechanisms of Li-S cells during discharge. We first demonstrate that introducing a concentration dependence of the electrolyte conductivity is necessary to retrieve the experimentally documented trends in electrolyte resistance, which contributes to a major voltage-loss mechanism for high-energy density Li-S cells. We further illustrate the existence of an often overlooked potential drop mechanism – the ‘precipitation overpotential’ – which originates from the limited rate of lithium sulphide precipitation. In addition, we propose that the rate capability of high energy-density Li-S cells is mainly limited by the slow transport of ionic species, as is evident from the good agreement between experimental and model-predicted capacity loss at high discharge currents as well as a cell capacity recovery phenomenon that we report for the first time.

References:

T. Zhang, M. Marinescu, M. Wild, L. O’Neill, and G. Offer, Phys. Chem. Chem. Phys.
17, 22581 (2015).

M. Marinescu, T. Zhang, G. Offer, Phys. Chem. Chem. Phys., 2015, advance article.
Utilising Shiners for the Study of Oxygen Electrochemistry in the Lithium-Oxygen Battery
Authors: Galloway Tom , Ball Sarah , Copley Mark , Hardwick Laurence J
Published: February 2020

Understanding the fundamental reaction mechanisms in the lithium oxygen battery is a key step in the development of a stable electrolyte. Surface enhanced Raman spectroscopy (SERS) is a non-destructive and non-invasive technique; it can be used to investigate the chemical bonding of surface species, making it a very valuable technique to study in situ the oxygen reduction and evolution reactions taking place at the liquid-solid interface. However the Raman signal is inherently weak. The signal can be enhanced by roughening the cathode surface, using an electrochemical oxidation/reduction cycle (ORC)1. By studying the oxidation reduction/evolution reaction within dimethyl sulfoxide based electrolytes on SERS active gold; the presence of both superoxide (O2
-) and lithium peroxide (Li2O2) has been observed at the interface2. SERS however is limited to precious metal surfaces.

 Unlike SERS the use of SHINERs (shell isolated nanoparticles for enhanced Raman spectroscopy3) (figure 1) is not restricted to precious metal surfaces.  Adding a near-monolayer of SHINERS can enhance the Raman signal by ca. 108. The gold nanoparticle has a strong electromagnetic field which enhances the Raman signal, whilst the SiO2 shell inhibits any catalytic effect from the gold core. SHINERs can therefore enhance a variety of surfaces, such as carbon, which have been previously very challenging to analyse.

   In situ studies with SHINERS without the presence of lithium have been able to track the reaction mechanism on planar, glassy carbon, gold, palladium and platinum surfaces, with the reduction and oxidation of free O2
- observed. Further studies on glassy carbon in the presence of lithium have detected lithium superoxide (LiO2) and lithium peroxide (Li2O2) species in MeCN and DMSO electrolyte media’s. We are continuing to further develop this technique within non-aqueous electrolytes on a wider range electrode surfaces.

Figure 1
Spark Plasma Sintering Study on the Super Ionic Glass Ceramic Conductor: Li7P3S11
Authors: Nguyen Han , Hy Sunny , Chu Iek-Heng , Ong Shyue Ping , Meng Ying Shirley
Published: February 2020

Solid-state electrolytes that can perform on par with conventional liquid electrolytes are highly sought after for use in all solid-state batteries. An all solid-state battery promises to operate without the possibility of catastrophic failure and have substantially longer self-life than conventional batteries. The Li7P3S11 glass-ceramic is one class of solid electrolytes that could meet the sought after power and reliable performances. We demonstrate a rapid synthesis and densification of the supersonic conductor electrolyte Li7P3S11via spark plasma sintering (SPS) technique. Dense solid-state electrolytes have been formed with a room temperature ionic conductivity is comparable to conventional liquid electrolyte.

Hayashi, A., Ishikawa, Y., Hama, S., Minami, T. & Tatsumisago, M. Fast Lithium-Ion Conducting Glass-Ceramics in the System Li[sub 2]S-SiS[sub 2]-P[sub 2]S[sub 5]. Electrochem. Solid-State Lett.
6, A47 (2003).

Seino, Y., Ota, T. & Takada, K. A sulphide lithium super ion conductor is superior to liquid ion conductors for use in rechargeable batteries. Energy …
7, 627 (2014).

Hayashi, A., Minami, K., Mizuno, F. & Tatsumisago, M. Formation of Li+ superionic crystals from the Li 2S-P2S5 melt-quenched glasses. J. Mater. Sci.
43, 1885–1889 (2008).

Minami, K., Hayashi, A. & Tatsumisago, M. Crystallization Process for Superionic Li7P3S11 Glass-Ceramic Electrolytes. J. Am. Ceram. Soc.
94, 1779–1783 (2011).

Minami, K., Hayashi, A. & Tatsumisago, M. Crystallization Process for Superionic Li7P3S11 Glass-Ceramic Electrolytes. J. Am. Ceram. Soc.
94, 1779–1783 (2011).

Eom, M., Kim, J., Noh, S. & Shin, D. Crystallization kinetics of Li2S–P2S5 solid electrolyte and its effect on electrochemical performance. J. Power Sources
284, 44–48 (2015).

Acknowledgments

This work was supported by the National Science Foundation under grant number  ACI-1053575.
Improvement of Cycling Performance of Silicon-Graphite Composite Anode Using Blended Electrolyte Additives
Authors: Jo Hyuntak , Tran Xuan Minh , Nguyen Dan Thien , Jeon Do-Man , Yang A-Reum , Song Seung-Wan
Published: February 2020

Silicon-graphite composite anode materials are potential alternatives to graphite anode material for high-energy density Li-ion batteries, as the theoretical specific capacity of silicon is ten-fold larger than that of commercialized graphite.1,2 However, the major drawback of silicon-based anode material is a short cycle life caused by large volume change,  low electrical conductivity and mechanical disintegration of particles. To overcome those issues, a variety of methods for improving cycle performance of silicon-based anodes have been researched, such as the use of composite with larger fraction of graphite,3,4 modification of surface property of silicon,4 and the use of new binder, nanostructured silicon, and functional electrolyte additives.3 Recently, the batteries with composite material containing very low fraction of silicon are being commercialized, which can accommodate the large volume change of silicon and obtain reasonable electrical conductivity. Another promising approach is the control of electrode-electrolyte interfacial reaction for the formation of a stable solid electrolyte interphase (SEI) utilizing functional electrolyte additives, which has to be based on a basic understanding of interfacial phenomena. In this presentation, we report the improved cycle performance and the interfacial phenomena of silicon-graphite composite anodes under the condition of various blended additives.

Acknowledgements

This research was supported by the Korean Ministry of Trade, Industry & Energy (10049609), National Research Foundation (2012026203), and Nano-Material Technology Development Program by the Ministry of Science, ICT and Future Planning (2009-0082580).

References

1. B. A. Boukamp, G. C. Lesh and R. A. Huggins, J. Electrochem. Soc., 128, 725 (1981).

2. R. A. Sharma and R. N. Seefurth, J. Electrochem.
Soc., 123, 1763 (1976).

3. S. Hong, M.-H. Choo, Y. H. Kwon, J. Y. Kim and S.-W. Song, J. Electrochem.
Soc., 161, A1851 (2014).

4. J.-S. Kim, C. C. Nguyen, H.-J. Kim and S.-W. Song, RSC Adv.,
4, 12878 (2014).
Structrual Stabilization of Layered NaxMO2
Authors: Matsui Masaki , Mizukoshi Fumikazu , Imanishi Nobuyuki
Published: February 2020

In recent years, Na-ion batteries are expected as a potential post Li-ion battery system because of the abundant resources.  A lot of layered materials: NaxMO2 (M=Cr, Mn, Fe, Co, Ni) has been investigated as candidate positive electrode materials for Na-ion batteries.  Substitution of the transition metal in NaxMO2 is common strategy for the improvement of their cycling performances.  On the other hand, an elemental substitution of Na sites has never been investigated because the substituted atoms easily hinder the smooth diffusion of Na+ in the active materials. In the present study, we intentionally substituted the Na+ sites in the P2-type NaxCoO2 with Ca2+ and investigated how it affected to the electrochemical properties. 

The XRD study showed that the calcium substitution suppressed the lattice mismatch of the co-existing two phases with some shrinkage of the lattice constant along c-axis.  The several voltage steps observed at the peculiar compositions of the NaxCoO2 were eliminated by the calcium substitution.  We suspect the calcium should have hindered the sodium ions and the vacancies to take the ordered form.  As a consequence the most of the biphasic regions in the voltage profile were disappeared.  The suppression of the phase transformation during the charging-discharging process improved the cycling performance of the NaxCoO2 especially at high charging-discharging rate as shown in Fig.1.  The XRD patterns after the cycling test showed that the NaxCoO2 formed a sodium poor phase, while the substituted calcium ion mostly suppressed the phase separation.  The results showed that the cycleability of the layered NaxMO2 could be improved not only by the materials design of MO2 slab, but the sodium ion layer ordering.

Figure 1
Chemical Stability of Li7La3Zr2O12 garnet Solid-State Electrolyte
Authors: Sharafi Asma , Meyer Harry M , Nanda Jagjit , Chi Miaofang , Yu Seungho , Dudney Nancy J , Siegel Donald J , Sakamoto Jeff
Published: February 2020

Li-ion battery technology has advanced significantly in the last two decades. However, future energy storage demands will require safer, cheaper and higher performance electrochemical energy storage. The development of advanced energy storage batteries such as solid-state and Li – S batteries, could enable a significant increase in energy density compared to Li-ion batteries. While the primary strategy for improving performance has focused on state-of-the-art Li-ion components, this work seeks to develop solid-state batteries employing Li metal anodes. One approach entails the replacement of a liquid with a solid electrolyte. Recently, the ceramic electrolyte, Li7La3Zr2O12 (LLZO) cubic garnet, has shown promise owing to its unique combination of properties such as high Li-ion conductivity (~1 mS/cm at room temperature) and electrochemical stability between 0-6 V vs. Li/Li+. The purpose of this work was to characterize the LLZO interface stability upon air exposure and its effect on the Li-LLZO interface charge transfer resistance. Specific attention was given to LLZO phase purity, and relative density. The LLZO was densified using a rapid densification process achieving > 97% relative density, with < 10% grain boundary resistance; effectively consisting of an ensemble of single LLZO crystals. Furthermore, the LLZO interface-charge-transfer has been related to the LLZO surface preparation by Electrochemical Impedance Spectroscopy (EIS) with equivalent modeling to understand the conduction mechanism at the Li-LLZO interface. X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Raman Spectroscopy were used in a concerted effort to determine the reaction pathways that govern chemical reactions between LLZO and ambient air. It will be shown that while several days of exposure to air results in high Li-LLZO interface charge transfer resistance, 24 hours of exposure to air (50 % relative humidity) had a negligible effect on interface resistance.
Surface Analysis of Composite Cathodes in Li-Ion Batteries: SEI Composition As a Function of Spatial Origin and Cycling Protocol
Authors: Schulz Natalia , Hausbrand René , Jaegermann Wolfram
Published: February 2020

With respect to stationary applications the demand of suitable storage technologies for electrical energy originates from discontinuous renewable primary energy sources has increased the interest in Li-ion batteries. In order to develop long lasting and cost efficient energy storage systems a comprehensive understanding of battery degradation mechanisms plays a fundamental role. Particularly the formation (and properties) of the cathodic solid electrolyte interface (SEI) under specific cycling conditions and its consequences on the mechanical fatigue has not been fully understood yet. Among the reasons are the limited number of studies published concerning the rudimentary analysis of composite electrodes. In this connection the analysis of the SEI layer on particles inside the electrode has not been performed yet. The main purpose of this work is a surface analysis of particles on the top and inside of the composite cathode after electrochemical cycling following a specific protocol.

This work deals with post mortem analysis of LiCoO2-composite cathodes by X-ray photoelectron spectroscopy (XPS). The electrodes were taken from 18650 type Li-ion cells, which were galvanostatically cycled under specific protocols. Analysis was performed of the top surface of the cathode and of material buried inside the cathode. To analyze the surfaces of buried material the top part of the cathodes has been mechanically removed. To improve the assignment of the XP-spectral features we used reference materials like LiCoO2 and SEI related components. We also performed experiments with pure LiCoO2-cathodes to analyze the SEI layer on the active material without interference from layers formed on other constituents of a composite cathode.

The surface analysis of electrochemically treated LiCoO2-composite cathodes showed a lower SEI thickness on buried material than on the top layer of the cathode. In both investigated locations of the electrode the same organic and inorganic (e.g. LixPOyFz-type) surface compounds were observed. We could determine that the proportion of the species in the SEI depends on the applied cycling protocol. Furthermore, the evaluated LiCoO2 of the composite showed changes in the electronic structure compared to the XP-spectral feature of the LiCoO2-reference material.
Systematic Variation of Sulfur Cathode Chemistry and Its Effects on Cell Performance
Authors: Perdue Brian Robert , Height Hannah E. , McBrayer Josefine , Apblett Christopher A.
Published: February 2020

In recent years, tremendous effort has been invested into researching energy storage chemistries that will replace lithium ion.  New strategies with higher capacities must be considered, such as a chemical conversion cathode. The lithium sulfur chemistry is a promising candidate as it uses earth abundant, inexpensive, high capacity sulfur as its cathode.  Conversion cathodes like sulfur are much more challenging as a secondary battery, and behave differently than intercalation cathodes.  Because of this, different design criteria must be applied to conversion cathodes to maximize power and capacity.  The interplay of conductive network, insulating active cathode, and binder all give rise to differences in performance for the dissolution and precipitation of the cathode material.  This work attempts to identify key design criteria for sulfur cathodes by systemically varying the basic components of cathode chemistry and structure.  A matrix of ~110 different cathode formulations were fabricated by varying conducting carbon, % active material, binder system, and sulfur loading.  Performance of these cathodes was evaluated by means of 2032 coin cell tests under constant current and pulsed loads.   First discharge capacity, capacity retention, coulombic efficiency, impedance, cathode surface area, and cathode porosity are utilized to gauge the effectiveness of the cathode and explain trends observed in cycling tests.  The effects of cathode rheology on porosity surface area and overall cathode utilization was also investigated.  Observed differences in performance between different electronically conductive elements and different cathode support elements were observed, with nuanced changes in morphology resulting in significant performance changes.

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.

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(Invited) Emerging Ferroelectric Devices
Authors: Gruverman Alexei
Published: February 2020

Ferroelectrics comprise a class of polar materials with an electrically switchable spontaneous polarization allowing their use as binary data storage media in nonvolatile ferroelectric random access memories (FeRAMs). Currently available FeRAMs utilize a destructive read process of stored information, which requires the memory cells to be re-written by a relatively high voltage, increases the read time and limits the scalability. An alternative approach to the read operation is based on the polarization-driven resistive switching, known as the tunneling electroresistance (TER) effect. If the ferroelectric film is sufficiently thin (of the order of several nanometers), conduction electrons can quantum-mechanically tunnel through the ferroelectric barrier. By flipping the polarization of the ferroelectric barrier it is possible to change an internal electronic potential profile and, hence, alter the transmission probability and produce the TER effect. Using this effect, reading of the polarization state can be performed in a non-destructive manner by measuring the resistance of the memory cell to a relatively low voltage. Since TER does not depend on the amount of the stored charge it allows a much better scalability. In addition to being highly relevant to technological applications, the TER effect concerns the fundamental issues of the critical behavior and switching dynamics in ultrathin ferroelectric films, role of structural defects and interfacial properties in the transport behavior. Maintaining a stable polarization in ultrathin ferroelectric films is essential for exploiting the functionality of these materials in nonvolatile memory applications.

            This talk will focus on investigation of the polarization-controlled tunneling conductance in the FTJ devices that incorporate both ferroelectric films and 2D transition metal dichalcogenides (TMD). In addition, the in-plane transport of the TMD conducting channel in the ferroelectric field effect transistor (FE-FET) devices modulated by polarization reversal will be discussed. We show that interface engineering in these hybrid TMD-FE systems provides a possibility of successfully addressing the most serious challenges relevant to ferroelectric device performance, such as ON/OFF ratio, lifetime, operation endurance and reliability.
A Thermal Method to Reduce the Polysilicon Resistance for Deep Submicron Integration Process
Authors: Li Xiang , Liu Shi Xiang , Liu Xu Li , Foong Mun Loong , Ye Wei qiang
Published: February 2020

In the ultra-large-scale integration (ULSI) technologies, polysilicon resistors are usually employed in the integrated circuits as a precise analog resistor element for a variety of applications, such as DAC (digital resistor give the solution of the linearity and Rs concerns to analog converter) in analogue circuits [1-3]. Conventionally the polysilicon resistance can be adjusted by ion implantation and post annealing process [4]. For the self-aligned implantation process, the dosage changes which are always utilized to adjust the resistance are feasible to induce the MOS characteristics changes, especially in the submicron process whose short-channel effects (SCE) are much more sensitive to the dosages [5]. In this work, we propose a new inner anneal process in N2ambient after polysilicon re-oxidation to reduce the polysilicon resistance by changing the polysilicon grain size.

    The test patterns are manufactured on 300mm-diameter wafer by 65-nm 1-poly 7-metal standard CMOS technology. After polysilicon re-oxidation to form oxide film on polysilicon surface, the wafers are annealed at 800oC, 900oC, 950oC and 1000oC in N2ambient, respectively. Fig. 1 shows the process flow and annealing process steps in the flow. After anneal, the polysilicon grain size is measured by X-ray powder diffraction (XRD). And the electric characteristics for NMOS, PMOS and polysilicon resistance are tested.

    Fig. 2 shows the poly resistance reduction proportion and poly grain size after anneal at 800oC, 900oC, and 1000oC for 5min, and 950oC for 20min in N2 ambient, respectively. Only after annealing at 950oC or above for 5min, the resistance can be obviously reduced, due to the poly grain size increasing. Fig. 3 shows threshold voltages (Vt) variation proportions of NMOS and PMOS owning gate length of 65nm and width 0.12µm after utilizing annealing process at different temperatures. PMOS is more sensitive to the anneal process than NMOS. But after anneal at 950oC or below, the threshold variation for both NMOS and PMOS is less than 5%, which is acceptable for the integration process manufacturing.

    A new anneal process at N2 ambient to adjust the polysilicon resistance has been proposed. It has been verified that utilizing anneal process at 950oC or below, the 65nm MOS performances can be maintained almost same as before. Consequently, it is considered that the anneal method can be to be applied to the deep submicron integration process.

References

[1] C. D. Parikh, and R. M. Patrikar, Solid-state Electronics, 43, 683 (1999).

[2] R. Murii, and M. J. Deen,, IEEE Trans. Electron Devices, 49, 187 (2002).

[3] C. Uang, H. Chuang, S. Tsai, K. Thei, P. Lai, S. Fu, Y. Tsai, W. Liu, IWJT, 293 (2004).

[4] S. Gupta, J. Electrochem. Soc. 149, G271 (2002).

[5] R. H. Dennard, F. J. Gasensslen, H. M. Yu, V. L. Rideout, E. Bassous, A. R. Leblanc,  Solid-state Circuits Soc Mag. IEEE, 87, 668 (1999).

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GaN Based Vertical Transistors on GaN Substrates
Authors: Zhang Anping , Lu Xing , Lei Lei , Zhang Yong , Yang Song , Yu Kun , Makhdoom Shahid , Wang Xuhui , Zhou Ting
Published: February 2020

GaN based power transistors have attracted intensive interest for highly efficient, high-frequency and high-temperature switching applications. Compared with GaN lateral devices, GaN based vertical devices can provide higher current density and higher breakdown voltage. In combination with low defect density offered by GaN substrates, GaN vertical transistors will fully exploit the great potential of GaN technology. We will present the recent developments in GaN vertical trench-gate MOSFETs and current aperture vertical electron transistors, with emphasis on our efforts to tackle some key challenges in MOS interface and leakage current. The performance of GaN vertical devices on GaN substrates will also be compared with that of GaN vertical devices on Si substrates.