bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Simulation Studies of Multilayer Electrode Coatings
Authors: Spotnitz Robert
Published: February 2020

The use of extrusion coating for lithium-ion battery electrodes enables the practical possibility of using multilayer coatings to improve battery performance.  The use of multilayer coatings of different materials, for example, a LiFePO4 coating next to a LiCoO2 coating, or a NMC coating next to a LiMn2O4 coating, has been experimentally tested in the literature [1-2] and modeling approaches [3-4] to optimize multilayer coatings presented.  In this presentation simulation results the effect segregating particles into discrete layers are presented for both high power and high energy cells.

References

J.F. Whitacre, K. Zaghib, W.C. West, B.V. Ratnakumar “Dual active material composite cathode structures for Li-ion batteries”, J. Power Sources 177 (2008) 528–536.

W.B. Chu, D-J. Liu, C.C. Chen. L.-C. Chen, S.-T. Tseng, S.H. Wen, C.R. Yang, U. S. Patent Application US 2014/0162118 A1, Jun. 12, 2014 “Electrode Structure of Lithium Ion Battery”.

V. Ramadesigan, R.N. Methekar, F. Latinwo, R.D. Braatz, V.R. Subramanian, “Optimal Porosity Distribution for Minmized Ohmic Drop across a Porous Electrode”, J. Electrochem. Soc. 157 (12) A1328-A1334 (2010).

S. Golmon,  K. Maute, M. Dunn, “A design optimization methodology for Li+ batteries” J. Power Sources 253 (2014) 239-250
(Invited) Computational Design of Electrolytes for Lithium-Ion Batteries
Authors: Ong Shyue Ping , Deng Zhi , Radhakrishnan Balachandran , Cheng Lei , Qu Xiaohui , Assary Rajeev , Jain Anubhav , Rajput Nav Nidhi , Persson Kristin A , Curtiss Larry
Published: February 2020

The electrolyte has today become a critical bottleneck in the drive toward high performance rechargeable lithium-ion batteries. Comprising organic solvents and LiPF6, current commercial electrolytes are flammable and have limited electrochemical windows of up to 4.5V. In this talk, we will discuss recent efforts in the application of first principles calculations to design novel solid and liquid electrolytes for lithium-ion batteries. We will show how first principles techniques can be used to predict important electrolyte design requirements such as ionic conductivity, electrochemical stability and phase stability. Such predictive capabilities may be used to guide the experimental realization of better performing electrolytes, for instance, by suggesting potential chemistry modifications or composition tuning strategies. The automation of these techniques in high-throughput leads to the development of multi-property electrolyte databases, which can then be screened for novel electrolyte candidates as well as mined for electrolyte design rules using machine learning techniques. Specific chemistries discussed will include the thiophosphate and anti-perovskite solid electrolytes, and quinoxaline-based molecules.
Dielectric Properties of Ethylene Carbonate and Propylene Carbonate Using Molecular Dynamics Simulations
Authors: You Xinli , Chaudhari Mangesh , Rempe Susan , Pratt Lawrence R
Published: February 2020

Ethylene carbonate (EC) and propylene carbonate (PC) are two widely used solvents in Li-ion batteries and supercapacitors. Ion diffusion in these solvents depends strongly on accurate predictions of solvent dielectric properties. We used all-atom molecular dynamics simulations of these pure solvents to calculate dielectric constants and dielectric relaxation times at various temperatures. The dielectric constant measures polarization of a material whereas dielectric relaxation measures the lag of the polarization in a dielectric medium in responding to a change in an applied field. Predicted values are compared with the available experimental results to validate the force field parameters (OPLS-AA) for these solvents. Current results for dielectric constant and dielectric relaxation time indicate that OPLS-AA force field produces reasonable agreement with experiment for both EC and PC.

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 Energys National Nuclear Security Administration under contract DE-AC04-94AL85000
Compare the Electronic Insulating Abilities of Inorganic Components in Solid Electrolyte Interphase (SEI): A First Principles Study
Authors: Lin Yuxiao , Qi Yue
Published: February 2020

Solid Electrolyte Interphase (SEI) can be formed by decomposed electrolytes or various coating materials. One of the functionalities of the SEI, especially its inorganic components, is to electrically passivate the electrode surface thus preventing further electrolyte decompositions, which leads to irreversible capacity loss, reduced columbic efficiency, and shortened cycle life in lithium ion batteries. However, due to the compositional and structural complexity of SEI, the electronic insulating mechanism of SEI still remains an open question. In this article, the electron tunneling barrier in SEI covered anodes was computed based on density function theory (DFT) calculations in order to evaluate the electronic insulating abilities of different SEI components. These SEI components include inorganic components commonly found in naturally formed SEI, such as LiF and Li2CO3; and other possible coating materials, such as Al2O3 and Li3PO4. Among them, Al2O3 can be further lithiated to LiAlO2. Therefore both the original coating material and its lithiated compound need to be considered. As the SEI thickness is at nanometer scales, the electron tunneling barriers vary greatly with film thickness, as a result of quantum size effect. This suggests that the electronic insulating mechanism of SEI will change during its growth as its thickness increases. Therefore, there is a difference between the early stage of the SEI formation and the late stage in SEI growth. Overall, by ranking the electron tunneling barriers and computing the electron tunneling probability, the critical thickness of SEI film required to block electron leakage from anode to electrolyte is estimated.

Figure 1
(Invited) Understanding Lithiation Mechanisms in Silicon-Based Nanomaterials from First Principles
Authors: Hwang Gyeong S
Published: February 2020

Silicon-based alloys, composites and nanostructures have received great attention as a possible replacement of conventional carbon-based anodes due to their higher lithium storage capacity.  However, still fundamental aspects of lithiation processes and properties in Si-based nanomaterials remain largely ambiguous, despite their importance in overcoming many technical hurdles faced in practical use.  Using first principles-based atomistic modeling, we have explored lithiation mechanisms in various Si-based nanosystems including nanowires, composites, oxides, and alloys.  In this talk, I will present our recent progress in understanding the impacts of surfaces, interfaces and alloying elements on the properties and performance of Si-based anode materials for Li-ion batteries.  Our first principles study shows that the lithiation behavior of Si nanostructures and composites is considerably different from the case of bulk Si because of surface and interface effects.  For instance, the mobility of Li along the surface or interface tends to be significantly enhanced by several factors.  We also find that by alloying Si with certain metal (M) elements, the theoretical capacity is compromised slightly, but in return the Si-M network may help stabilize the lithiated host matrix and therefore contributes to the improved cycling performance.  I will also briefly touch on the importance of alloy composition and local atomic environment in determining the lithiation properties and performance.  The improved understanding can contribute to the rational design of Si-based anode materials to maximize capacity retention and rate performance.
Potential and Adsorbate Effects in Electrodeposition: Lessons Learned from Atomic-Scale in Situ and Operando Studies
Authors: Magnussen Olaf M.
Published: February 2020

Electrodeposition has become an important tool in nanoscience and -technology. Examples range from metallization processes in the microelectronics industry to self-organized growth of nanomaterials. Because the growth behavior and the resulting deposit morphology can be varied over a wide range by the electrochemical parameters and by suitably chosen additives, electrodeposition often provides superior control as compared to rivaling methods or even enables deposition of structures which are unobtainable by other means. On the other hand, precisely the strong dependence on potential and solution composition poses a problem as they are largely not understood. Development of electrodeposition or electroless plating processes therefore is still largely empirical, specifically for the deposition of structures with well-defined nanoscale morphology. For knowledge-based strategies better understanding of the atomic–scale processes is required. In particular, it is necessary to clarify how the potential-dependent interface structure and the presence of surface-active species influence processes such as diffusion on the planar surface and across steps, nucleation events, and the ion transfer itself.

Such data can be obtained by state-of-the-art surface-sensitive methods, which enable in situ studies of the interface structure and dynamics or even operando investigations at growth rates approaching those in technological processes. Together with ab initio theory calculations they provide first insights into the complex effects of potential and coadsorbates on the dynamics of species at the surface of the deposit during the growth (e.g. metal adatoms). I will specifically present studies of Cu and Au single crystal electrodes by synchrotron-based X-ray scattering techniques and high-speed scanning tunneling microscopy, focusing on the influence of halides on surface dynamics and metal growth. The obtained results reveal very pronounced and partially unexpected effects, which can lead to crossover between qualitatively different growth regimes. The relevance of these observations for electroplating, prospects for operando studies of technologically interesting cases, as well as remaining challenges and future directions will be discussed.
Electrodeposition of Nanowires and Nanostructures from Supercritical Fluids
Authors: Smith David Christopher
Published: February 2020

Supercritical fluids are potentially highly attractive media for the electrodeposition of metals and semiconductors into complex nanostructures [1].  Supercritical fluids readily penetrate porous and nanoporous structures because they have essentially zero surface tension.  They also have low viscosities and hence show enhanced mass transport rates.  Depending on the choice of electrolyte and solvent they can also have a wide electrochemical window. However these advantages do not come without several disadvantages; their generally low dielectric constants, and the necessity to work in sealed systems at elevated temperature and pressure.  For these reasons the field of electrodeposition from supercritical fluids is still relatively unexplored with very little published work on electrodeposition from single phase supercritical systems.

In order to explore the possibilities of using electrodeposition from supercritical fluids to make sub 20 nm nanostructures and nanostructured devices we have focused on the electrodeposition of a range of p-block elements (Ga, In, Ge, Sn, Pb, Sb, Bi, Se and Te) from supercritical difluoromethane [2]. In this lecture I will present results of our latest results on electrodeposition of these elements from supercritical difluoromenthane, the characterization of the electrodeposited materials, and work on the electrodeposition of sub-20 nm nanowires. I will discuss the experimental systems and novel reagents required to undertake this work, including the development of a simple high pressure, high temperature electrical feedthrough. I will also discuss our progress towards making transistors from supercritical fluid electrodeposited nanowires.

Acknowledgements:This is a contribution from the SCFED Project (www.scfed.net), a multidisciplinary collaboration between the Universities of Southampton, Nottingham and Warwick and is funded by a Program Grant from EPSRC (EP/I033394/1).

References

1. P. N. Bartlett, D. A. Cook, A. L. Hector, W. Levason, G. Reid, W. Zhang, M. W. George, J. Ke and D. C. Smith, “Electrodeposition from supercritical fluids”, Phys. Chem. Chem. Phys.,16(2014)9202-9219.

2. P. N. Bartlett, D. C. Cook, M. W. George, J. Ke,  W. Levason, G. Reid, W. Su and W. Zhang, “Phase behaviour and conductivity study of electrolytes in supercritical hydrofluorocarbons”, Phys. Chem.Chem. Phys., 13(2011)190-198.

Figure 1
Electrodeposition of Cu-Ag Alloy Thin Films Directly on W Diffusion Barrier By Controlling Complexing Agents and Organic Additives
Authors: Kim Sunjung , Kim Kang O
Published: February 2020

Cu as an excellent electrical conductor has been used for interconnect in Si-based microelectronic devices. Recently Cu alloys instead of Cu have emerged as interconnect material for future microelectronic device fabrication because higher adhesion strength to foreign materials, larger resistance to electromigration, and improved electrical conductivity are required in very narrow interconnect lines. It is known that Cu-Ag alloy among Cu alloys has beneficial properties such as higher electrical conductivity, better formability, higher mechanical strength, and better resistance to electromigration than pure Cu.

In this research, we investigate the effect of electrodeposition parameters on the nucleation and growth of Cu-Ag alloy nano-nuclei and the formation of thin, smooth Cu-Ag alloy thin film. Cu-Ag alloys are electrodeposited directly on W diffusion barrier without employing a Cu seed layer. Area density, size, and morphology of Cu-Ag alloy nano-nuclei influence the microstructure, surface roughness, and thickness of Cu-Ag alloy thin film formed on the W diffusion barrier.

Sophisticated control of chemical equilibrium of electrolyte is carried out by managing the concentration and type of complexing agent and organic additives. Chelation behavior of Cu and Ag with complexing agent is also studied according to pH of electrolyte. Reduction rate and chemical composition of electrodeposited Cu-Ag alloy are controlled under diffusion-controlled deposition conditions.
Electrochemical Deposition of Hybrid Material Based on Polyindole and CdTe/CdS
Authors: Osial Magdalena E
Published: February 2020

The application of hybrid materials based on the organic and inorganic films in photovoltaic cells  offers significant advantages. Solar cells built this way are inexpensive to fabricate, can be used on flexible substrates and can be easily shaped. In this work the polyindole (PIN) was used as the matrix for deposition of inorganic semiconductor CdTe, which enables absorption of light in the visible region of solar spectrum, where the solar spectrum has the highest intensity. This feature is linked to the band gap energy of CdTe (Eg=1.4 eV) and high absorption coefficient. Widespread use of CdTe in photoelectrochemical solar cells is however limited by several factors such like susceptibility to photocorrosion in aqueous electrolytes, further hindering their application. The PIN matrix made as well-oriented wires was used to prevent CdTe against photocorrosion.

The results of the influence of electrochemical deposition conditions on the properties of hybrid material are presented. The polyindole was electrodeposited into the membranes to form well-oriented polymer matrix. The size of nanowires and their packing were varied by monomer concentration and time. The CdTe films were obtained electrochemically and chemically into and on the top of PIN nanowires. Initially, the polyindole properties such as electrochemical behavior in different solutions, wires morphology and structure were investigated by various techniques. After that, CdTe modification of the hybrid was studied by different techniques as well. The morphology was explored by Scanning Electron Microscopy, the chemical composition was investigated by Raman and IR spectroscopy. The UV-vis spectrometry was used to estimate the band gap energy of hybrid. It was found that size and packing of PIN nanowires determines the morphology of CdTe into and on the top wires. The chemical composition and doping type depends on the deposition parameters such as bath composition and ions concentration, deposition time and potential. The photoelectrochemical measurements carried out in polysulphide solution showed that application of polyindole layer improved the photostability of CdTe and increased the value of photocurrent.
Electrodeposition of Thick MnO2 Films on Restrictive Substrates
Authors: Timmermans Marina , Mattelaer Felix , Detavernier Christophe , Vereecken Philippe M
Published: February 2020

Lithiated electrolytic manganese dioxide (EMD or ƴ-MnO2) is considered to be a promising positive electrode material for rechargeable lithium ion batteries due to its relatively high specific capacity and long-term cyclability along with its low cost and low toxicity [1,2]. Conformal deposition of thick EMD material is needed for its application in 3D solid state batteries. However, during the anodic electrodeposition of manganese dioxide, the underlying current collector is oxidized at the same potential range as the EMD deposition, e.g. titanium nitride (TiN) or aluminum (Al) current collectors. In this work we investigate the use of thin coatings prepared by vapor phase of wet chemical deposition to protect the current collector from the undesirable oxidation and allow the deposition of thick MnO2 films with good adhesion properties. We show conformal deposition of MnO2 films up to 600 nm thick from aqueous bath on high aspect ratio silicon pillar arrays. Silicon pillars were covered with 20 nm TiN which acts as a diffusion barrier of Li ions into Si. Reversible insertion and extraction of Li+ into thick EMD is demonstrated on both planar and 3D substrates with an expected capacity increase associated with the surface area gain for 3D substrates. We also demonstrate the application of a thin coating to enhance the adhesion between the electrodeposited MnO2 cathode material and aluminum surface, including Al foil, opening doors towards its use in flexible batteries.

[1] M. Thackeray, Prog. Solid St. Chem., 25, 1997

[2] A. Etman, A. Radisic, M. Emara, C. Huyghebaert, P.Vereecken, J. Phys. Chem. C, 118 (19), 2014

Figure 1
Electrodeposition of Cu on Nickel Seed Layer/p-Si in Buft Cell
Authors: Priyadarshani Divya , Goradia Prerna , Contractor Aliasgar , Gouk Roman , Verhaverbeke Steven , Visser Robert
Published: February 2020

This paper describes the electrochemical deposition of Cu by galvanostatic method on p-Si with high deposition rate. To prevent the diffusion of Cu into Si, a thin layer of Ni is used as a diffusion barrier. A novel bath i.e., high pH Nickel sulphate bath without reducing agent was used for the galvanic reaction to form a Ni seed layer. The SEM images show the thickness of smooth and dense Ni film is in the range of 190-200 nm. Resistance of the Ni-pSi was found to be ~0.28 Ω/sq by four point probe which is lower than the resistance of Si i.e, ~108 Ω/sq. Copper was deposited on this seed layer of Ni by applying a high electric field across the wafer by placing it between a copper plating bath and an acid electrolyte. A high DC voltage was applied between a copper sheet placed in the copper bath and a platinum sheet placed in the acid electrolyte. A deposition rate of about 3.85 um/min of Cu on Ni-pSi was achieved and the film showed good adhesion. This electrochemical reaction involves silicon dissolution from one face and simultaneous copper deposition on the other. SEM images show the compact and smooth Cu film having ~3.85 um thicknesses. This experimental value of the thickness is in agreement with the theoretical value expected for 100% current efficiency. The resistance of electroplated Cu film on Ni/p-Si was measured by four point probe and found to be 0.07 Ω/sq.

Fig: a and b: SEM image (Surface and Cross sectional) of Ni/p-Si

       c and d: SEM image (Surface and Cross sectional) of Cu on Ni-pSi

References:

(1) Chengkun,*Xi Zhang, King-Ning Tu, and Yahong Xie., Journal of The Electrochemical Society
2007,
154 3, D170.

(2) Daisuke Niwa*, Takayuki Homma* and Tetsuya Osaka**,J. Electrochem. Soc.
2005, 152, C54.

Figure 1
Reaction Dependent Transport of Carbonate and Bicarbonate through Anion Exchange Membranes in Electrolysis and Fuel Cell Operations
Authors: Rigdon William A. , Omasta Travis J , Lewis Connor A , Mustain William E
Published: February 2020

Developments in alkaline anion exchange membranes have seen recent success for their use in new and exciting electrochemical applications.  Historically, the use of carbon dioxide in alkaline cells plagued performance by carbonating the electrolyte.  However, advances have allowed for use of polymer membranes that permit transport of carbonate and bicarbonate species 1.  This results in a mixed anionic conductivity of these materials which presents new applications for their use in low temperature electrochemical reactions.  For example, carbon dioxide can be separated and compressed from a gas stream in electrolysis (pumping) mode 2.  Furthermore, carbonate species could also be used for conversion of fuels in the anode 3,4.  Therefore, exploring the transport properties of these materials under differing half-reactions can elucidate limitations and possibilities for future use.

A correlation can be made between the current applied in electrolyzer mode or drawn in fuel cell mode and the measured cell products, especially the evolution of carbon dioxide from the anode.  Carbon dioxide is first reduced along with oxygen in the cathode to form carbonate or bicarbonate anions.  This occurs through either indirect reactions which include a bicarbonate step or else they can be converted directly to carbonate.  In the fuel cell, hydrogen oxidation results in carbon dioxide without the oxygen evolution reaction by proceeding through a bicarbonate pathway.  Due to the contribution of different reactions, transport is typically mixed through the membrane.  Cell potential and resulting half-cell reactions will therefore determine the amounts of carbonate and bicarbonate in addition to hydroxide anions transported.  The measured ratio of electrons to moles of carbon dioxide is indicative of the overall exchange mechanisms occurring.  In this study, a careful evaluation of electrolysis and fuel cells is coupled with product analysis by spectroscopic and chromatographic methods of gaseous products from the anode to understand how the operating mode influences the carbonate/bicarbonate transport balance in the electrochemical anion exchange cells.

References:

1. J. R. Varcoe et al., Energy Environ. Sci., 7, 3135–3191 (2014)

2. J. Landon and J. R. Kitchin, J. Electrochem. Soc., 157, B1149 (2010)

3. W. E. Mustain, J. A. Vega, and N. S. Spinner,  Patent US2012/0193222 A1 (2012).

4. N. Spinner and W. E. Mustain, J. Electrochem. Soc., 160, F1275–F1281 (2013)
Simultaneous Recovery of Potassium, Chloride and Removal of COD from Landfill Leachate Concentrates Using a Combination of Cation-Exchange Membrane Electrolysis
Authors: Li Xinyang
Published: February 2020

Nanofiltration (NF) and reverse osmosis (RO) filtration system are widely used in landfill sites as polishing step for advanced treatment of landfill leachates. The membrane systems always generate large amount  of  concentrates containing high level of refractory organic compounds, potassium, chloride and other inorganics, which hardly be treated via conventional biological process. Thus, a proper disposal of these concentrates from or RO systems is critically important.The advanced oxidation processes (e.g, electrochemical oxidation, Fenton oxidation and ozone oxidation) are generally used in treatment of the concentrates. However, the potential resource such as K+and chloride in concentrates are not efficiently recycled but discharged to environment. In present study, we explore innovative and environmentally sustainable treatment processes, a combined cation-exchange membrane electrolysis (CEME)/magnesium potassium phosphate (MPP) crystallization process, for treating NF concentrate, which include (a) contaminant removal: organic pollutant and ammoniacal-nitrogen removal; (b) recycling and onsite reuse of chloride ions in the form of gaseous chlorine; (c) separation and beneficial recovery of potassium from NF concentrates.

This study demonstrated that the proposed combined process can effectively remove 82%, 99%, 34%, 99% of organic matter, ammoniacal-nitrogen, total nitrogen, and chloride ions, respectively. And the recovered gaseous chlorine was reused on site as a decolorizing agent for synthetic dye (RhB) containing wastewater and complete decolorization was also achieved. The potassium ions were recovered  via magnesium potassium phosphate crystallization . Additionly, about 53% of the potassium (from 2762 mg/L to 1389 mg/L) was removed via formation of magnesium potassium phosphate(MgKPO4·6H2O) precipitate.

A combination of membrane electrolysis process is demonstrated to be an effective method for the convenient recycling of NF concentrates generated from a landfill plant. This combined process achieves effective removal of organic pollutants in the concentrates and complete removal of NH3-N via an active chlorine-mediated reaction. The combined process also simultaneously enables highly efficient recycling of chloride and potassium ions from NF concentrates as beneficial products (gaseous chlorine and MgKPO4·6H2O buffered fertilizer, respectively). Additionally, we have demonstrated that the recovered gaseous chlorine could be reused on site as a decolorizing agent for treating colored wastewater (i.e., RhB solution), and that complete decolorization could be achieved. The results indicates that recycling of NF concentrate via the combination  process is feasible.

Figure 1
(Invited) Vacuum Ultraviolet Photochemical Atomic Layer Deposition of Alumina and Titania Films
Authors: Chalker Paul Raymond , Marshall Paul A , Dawson Karl , Sutcliffe Christopher J , Brunell Ian F , Sedghi Naser , Hall Stephen , Potter Richard J
Published: February 2020

Conventional atomic layer deposition (ALD) is a thermo-chemical process where co-reagents are sequentially pulsed in cycles onto a heated substrate. As an alternative to substrate heating, various forms of other “energy – enhanced” ALD processes are being investigated. Herein, the photochemical atomic layer deposition of Al2O3 and TiO2thin films at 60°C is reported using a shuttered vacuum ultraviolet (VUV) light source to excite molecular oxygen as a co-reagent with the metal precursors. The growth mechanisms using trimethyl aluminium (TMA) and titanium isopropoxide precursors, are investigated using in-situ quartz crystal microbalance (QCM) and post-deposition ellipsometric measurements.

The figure below illustrates the mass gain / loss processes during a series of ALD cycles of TMA with O2/ UV excitation from a VUV lamp with peak emissions at 125 nm (9.9 eV) and 160 nm (7.7 eV). Further, the figure shows the growth per cycle (GPC) derived from the QCM data and also separately from single wavelength (633 nm) ellipsometry measurements made on silicon (100) samples exposed to the same growth conditions. Both data sets indicate that as the VUV illumination time is extended beyond 5 s to 10 s the overall mass gain per cycle saturates and becomes approximately constant, which is consistent with other self limiting ALD processes. The photochemical process is exploited to achieve area-selective film deposition. Selective area deposition was achieved by projecting the VUV light through a metalized magnesium fluoride photolithographic mask. The selectivity of deposition is a function of the UV exposure time and the mask – substrate separation.

The photochemical atomic layer deposition of TiO2 thin films from titanium isopropoxide exhibits similar growth characteristics to the Al2O3 photochemical process, however subtle differences in the growth mechanisms are attributed to the different reactions of the excited oxygen species (O(
3P)) with the Al-CH3 and Ti-OCH(CH3)2 bonds.

Figure 1
(Invited) Metallic Nanocoatings on Optical Fibers as a Sensor Platform
Authors: Mandia David J. , Zhou Wenjun , Wells Adam , Albert Jacques , Barry Sean Thomas
Published: February 2020

Optical fibres are excellent platforms on which to build a sensor: they substrate is inexpensive, and produced in tonnes per year. The technology effectively couples light and materials, and employs inexpensive (telecommunication) tools to interrogate the results. We are working on a tilted fibre Bragg grating (TFBG) sensor using atomic layer deposition (ALD) to modify the surface interface (Figure 1).

By printing a FBG into the core of an optical fibre, light “modes" that were confined to the core can be directed to the cladding interface. These light modes can then sense changes in this interface, and these changes can be read if the light is directed back into the core. Depositing nanoparticulate films onto the cladding surface alters the effect on these cladding modes. They undergo a wavelength shift and a "peak-to-peak" amplitude change that is significantly different than is seen in uncoated fibres. We have been exploring the deposition of copper, silver, and gold metal films on optical fibre surfaces and investigating the changes in the light modes.

The changes in the light modes that interact at the fibre metal interface are sensitive to the surrounding index of refraction. So, by using a high-permittivity dielectric material between the fibre and the metal coating, the sensitivity can be changed.

Thus, the sensor platform that will be discussed consists of an optical fibre coated in a high-K dielectric material, and then further decorated with metal nanoparticles. The dielectric material is typically deposited by ALD, and the metal is typically deposited by either chemical vapour deposition or atomic layer deposition.

This presentation will cover an overview of the chemistry of the precursor compounds for thin film deposition, the film deposition processes, and an interpretation of the resulting sensing ability of the cladding light modes. The wavelength shift is stronger when the device experiences a higher surrounding refractive index (SRI). This happens at low thicknesses, and can be exploited as an SRI detector. Interestingly, there is a significant difference in the spectra for a monolayer of discrete nanoparticles compared to a connected metallic film, also making these devices useful for detecting conductive film deposition.

Figure 1
Evaluation of InGaAs and InP Compatibility with Alkaline Photoresist Stripping Formulations
Authors: Westwood Glenn
Published: February 2020

III-V semiconductors, such as InGaAs, are leading contenders to replace Si as high-mobility channel materials for sub-10 nm finFETs.(1,2) Implementation of these high-mobility materials into FEOL processes faces many challenges because of the chemical sensitivity and complex nature of these materials relative to the conventional Si channel.  In particular, damage from wet cleaning solutions is a major concern that needs to be understood and controlled when designing new cleaning formulations for use in the manufacture of III-V based devices.  Herein, we will describe our work at understanding InGaAs and InP compatibility with formulated alkaline photoresist strippers with a focus on the impact of solvent and alkaline component selection.

Initial studies focused on etch rates of InGaAs and InP in  a series of proprietary cleaning chemistries.  InGaAs films (500 Å) on InP – as well as bulk InP – wafers were used for this study.  Etch rates were determined by energy-dispersive X-ray spectroscopy (EDX) as well as by gallium and arsenic leaching via ICP-MS.  While acidic chemistries in general showed excellent compatibility,  alkaline- and amine-based chemistries displayed varying levels of compatibility with InGaAs.

Because of the range of compatibilities observed in alkaline chemistries, we explored the impact of solvent and alkali selection as well as water content on selectivity.  Specifically, we evaluated a series of non-proprietary solutions using a selection of solvent types, alkaline components, and water content (semi-aqueous vs. non-aqueous).   The impacts of these components will be discussed and compared to results previously presented for GaAs etched in these same chemistries.(3)

For the strippers that are reported to be highly compatible with InGaAs and InP, a more thorough analysis of surface changes will be reported including changes in roughness (AFM) and composition (XPS).  The results and key learnings from this study will be discussed in relation to how InGaAs and InP may be cleaned with limited surface damage.

1)       International Technology Roadmap for Semiconductors, see www.itrs.net

2)       J. A. del Alomo, Nature, 479, 317 (2011).

3)       G. Westwood, SEMATECH Surface Preparation and Cleaning Conference, Austin, TX, 2012.
(Invited) Material and Device Integration for Hybrid III-V/SiGe CMOS Technology
Authors: Deshpande Veeresh Vidyadhar , Djara Vladimir , Caimi Daniele , O'Connor Eamon , Sousa Marilyne , Czornomaz Lukas , Fompeyrine Jean
Published: February 2020

Continuous scaling of CMOS technology has revolutionized our society. Although the microelectronic industry has benefited economically from the constant scaling of MOSFET dimensions, serious technical challenges have now emerged that could become show-stoppers. Pure lithographic scaling is no longer sufficient to bring about expected benefits as both performance and power consumption metrics degrade owing to short channel effects. As the overall industry is shifting towards ‘mobile and connected devices’, the need for reducing power consumption is becoming a very critical requirement for sub-14 nm nodes. Besides this, the demand for integrating multiple functionalities on chip (Systems-on-Chip) is also growing. In the past decade, considerable efforts have been made for innovation-driven scaling by introduction of novel materials (high-k/metal gate) and new device architectures (strained silicon, FDSOI, FinFETs etc.). These have helped us reap performance benefits of reduced MOSFET dimensions. As we go to sub-14 nm nodes, limitations in lithography and silicon material properties are becoming more serious than ever. In order to continue scaling, innovations in channel materials and integration is required. High-mobility channel materials such as Ge, SiGe and III-V compound semiconductors are envisaged to provide necessary power-performance benefits in these nodes. In order to provide a robust, manufacturable CMOS technology these will need to be co-integrated on the same platform. Various challenges have to be tackled for achieving high-mobility CMOS technology. These range from material integration aspect to device fabrication. In this paper we will first detail various methods of integrating the III-V materials which could provide a scalable and manufacturable platform. Based on these, we will then review the various III-V device architecture and processing methods (high-k/III-V interface, source/drain contacts, III-V MOSFETs) that can enable high performance MOSFETs. We will further discuss challenges and strategies to develop a scaled hybrid III-V/SiGe CMOS platform in various architectures (2D vs 3D monolithic) and demonstrate hybrid circuit results.
(Invited) Scavenging Kinetics of Interfacial SiO2 in HfO2/SiO2/Si Gate Stacks
Authors: Toriumi Akira , Li Xiuyan
Published: February 2020

SiO2-interface layer (IL) “scavenging” in high-k gate stacks needs to be understood for the interface control as well as for further EOT scaling. A simple model that the oxygen vacancy (Vo) was involved in the scavenging was proposed, but further details have not been elucidated well.

We have studied the SiO2-IL scavenging in HfO2/SiO2/Si gate stacks in UHV condition in place of metal electrode scavenging. This method has enabled us to study the diffusion and reaction in this system from the top surface without a metal gate.

In this talk, we particularly focus on the following three steps in the scavenging process.  

(1)   VO diffusion kinetics in scavenging

This has been studied by controlling as-deposited HfO2 stoichiometry by changing the deposition conditions.

(2)   Substrate effect on scavenging

Various types of substrates with a same gate stack have been used for the scavenging experiment.

(3)   Si diffusion kinetics in scavenging

Si out-diffusion from HfO2/SiO2/Si gate stacks has been investigated through the mass spectroscopy.

We present experimental results in each step. In particular, we notice that SiO2/Si interaction may be involved in this process, as well as that the scavenging causes SiO2-IL reduction. Furthermore, we propose an analytical model for the SiO2-IL scavenging. Interestingly, it looks like the Deal-Grove model for Si oxidation, but coefficients are related to each other in the scavenging.  

These results are important not only for scavenging SiO2-IL in HfO2/SiO2/Si stacks but also for establishing the oxide electronics, because understanding of both cation and anion kinetics in oxides is critical to control the hetero-interface characteristics.
Investigation of Conversion Positive Electrode Active Materials for the Aluminum Rechargeable Battery
Authors: Chiku Masanobu , Kunisawa Takeshi , Higuchi Eiji , Inoue Hiroshi
Published: February 2020

Introduction

 As a post lithium ion battery, new rechargeable batteries with metal negative electrodes which form multivalent cations during discharging are actively being investigated because they are expected to have high specific power, high energy density and low cost. Mg is the most popular materials for the multivalent cation battery because it shows higher energy density (3837 mAh cm-3) than Li (2062 mAh cm-3). Al is two times as large in energy density (8043 mAh cm-3) as Mg. Thus Al rechargeable battery is a promising next generation power source.

 To construct the Al rechargeable battery, investigation of the positive electrode material is necessary. Preciously, we reported the Al rechargeable battery using V­­2O5 positive electrode and its specific capacity was about 200 mAh g-1, however this battery can only be charged/discharged with 1/10 ~ 1/40 C rate and it is too low charging/discharging rate for practical application.1)

 In this study, we have developed the Al rechargeable battery using CuF2 as the positive electrode to increase the high rate dischargeability. This battery can be operated with high charging/discharging rate, however, XRD data suggested that in the process of conversion reaction, CuCl and CuCl2 was produced by substitution of F- with Cl-supplied from the electrolyte. So, we also investigated transition chlorides (CuCl, CuCl2 CoCl2, FeCl2) as the conversion positive electrode active material for the Al rechargeable battery to increase specific power and energy density.

Experimental

 All electrochemical measurements were performed with a glass cell. The electrolyte was a mixture of aluminum chloride, dipropylsulfone and toluene with the mole ratio of 1:10:5. An Al plate with diameter of 14 mm was used as counter and reference electrodes for all experiments. A glass fiber filter was used as separator.

 44 mg of transition Chlorides and 5 mg of Ketjen black powders were mixed, and 1-Methyl-2-pyrrolidone and 4 mg of polyimide were added to the mixture to prepare a paste. The positive electrode was prepared by casting the paste onto a molybdenum current collector and drying at 230 °C.

Results and discussions

 Figure 1 shows CVs of CuF2, CuCl and CuCl2 positive electrodes. Almost the same oxidation and reduction peaks were observed. This suggests that CuF2 was converted to CuCl or CuCl2 by substitution of F- with Cl-during charge-discharge reactions.

 An Al rechargeable battery using CuCl and CuCl2 as cathode material was fabricated and subjected to charge-discharge tests (Figure. 2). For the initial 15 cycles, discharge capacity was higher than 150 mAh g-1, suggesting CuCl and CuCl2 was a new positive electrode material for Al rechargeable battery.

 CoCl2 and FeCl2 positive electrodes showed oxidation and reduction peaks. However, their capacities were less than that of CuCl and CuCl2.

Reference

1) M. Chiku et al. 224thECS Meeting # 521

Figure 1
High Performance P2-Type Na2/3(Mn1/2Fe1/4Co1/4)O2 Cathode Material with Superior Rate Capability for Na-Ion Batteries
Authors: Liu Lei , Li Xin , Bo Shou-Hang , Wang Yan , Chen Hailong , Twu Nancy , Wu Di , Ceder Gerbrand
Published: February 2020

We designed a new P2 type cathode material, P2-Na2/3(Mn1/2Fe1/4Co1/4)O2, by mixing transition metals in the TM layer in P2 type layered oxide to prevent the long range ordering of Na or transition metals and create a large single phase region which is conductive to good Na+ transport. Futhermore, we suppressed the undesirable monoclinic transition commonly observed in Mn-containing layered oxides by introducing the Co2+/3+ redox couple. As a result, P2-Na2/3(Mn1/2Fe1/4Co1/4)O2 shows so far the largest single phase region and the highest rate performance among layered oxide cathode materials. We believe this work has opened the door for the application of sodium ion batteries in high power energy storage devices.
New Carbon Materials with Large Closed Pore Volume As Anode for High Energy Na-Ion Batteries
Authors: Kano Akira , Hojo Nobuhiko , Ito Shuji , Fujimoto Masahisa , Nakura Kensuke
Published: February 2020

Recently demand for Li-ion batteries is growing as power sources for various applications such as electric vehicles and electric energy storage systems, because their high energy density and light weight properties are suitable for these applications. However, lithium resources may be insufficient to meet the increasing demand for these applications. Na-ion batteries could be a promising alternative to Li-ion batteries thanks to the natural abundance and lower cost of sodium. Non-graphitized carbon materials such as hard carbon are well-studied as high capacity anode materials for Na-ion batteries. The discharge capacity of 200 - 300 mAh/g, which is lower than conventional graphite anode materials for Li-ion batteries, has been reported [1,2]. In addition, the insertion mechanism of Na-ion into non-graphitized carbon materials is proposed that Na-ions are first inserted between stacked graphene layers in the voltage range from 2.0 V to 0.2 V (vs. Na metal), and then inserted into nano-pores in the voltage range from 0.2 V to 0.0 V (vs. Na metal) [2]. In this study, we focused on the pore structure of carbon materials and investigated the relationship between the carbon structures and electrochemical properties to clarify the optimum pore structure and propose a new carbon material as anode for high energy Na-ion batteries.

 Non-graphitized carbon samples were synthesized by heating various raw materials at between 1000 and 2600 °C under flowing argon. The pore structure of the synthesized carbon samples was characterized by using argon and nitrogen adsorption measurement and helium gas densitometry. Electrochemical properties were evaluated by using laminate-type cell with Na metals as the counter electrode and the reference electrode.

  Open and closed pore volumes of the synthesized carbons were calculated and the relationship between the reversible capacity and pore volume was investigated. As seen in Figure 1, an almost linear relationship between the reversible capacity in the voltage range from 0.2 to 0.0 V (vs. Na metal) and the closed pore volume was confirmed. Some carbon materials with large closed pore volume on the basis of this relationship were designed and successfully synthesized. Figure 2 shows charge/discharge curves of one of synthesized carbon samples. This carbon sample had the closed pore volume of 0.37 cc/g and its discharge capacity reached 413 mAh/g. This result suggests that Na-ion could be inserted reversibly in the closed pore and non-graphitized carbons with large closed pore volume may be promising for high capacity anode materials for Na-ion batteries.

[1] D. A. Stevens et al, J. Electrochem. Soc., 148 (2001) A803

[2] S.Komaba et al, ACS Appl. Mater. Interfaces, 3 (2011) 4165

Figure 1
Morphology Progression of Electrodeposited Li2O2 during Charging of Li/O2 Batteries
Authors: Griffith Lucas Daniel , Sleightholme Alice , Siegel Donald J , Monroe Charles W
Published: February 2020

Non-aqueous Li/O2 batteries could achieve much higher specific energies than lithium-ion (3-5x)1, making battery powered electric vehicles more competitive with traditional combustion vehicles.2 Realizing this promise however requires significant improvement in cycle life and cycling efficiency. Understanding the charge mechanism is crucial to lowering the charging overpotential, which in turn would increase efficiency. Observing the process of deposition and dissolution of electrodeposited Li2O2 in Li/O2 cells can shed light on the charging mechanism.

During charge, the amount of energy necessary to decompose Li2O2 likely depends on the morphology of the Li2O2 particles deposited3-5: higher surface energy morphologies should require less energy. The morphology formed on discharge depends heavily on cell potential with higher energy particles formed at higher overpotentials.4,5 Observing how Li2O2  is consumed during charge could further explain the relationship between cell overpotentials and Li2O2 morphology, as well as probe any differences in the discharge and charge mechanisms.

In this talk we will show how the morphology of electrochemically deposited Li2O2 changes at intermediate states of charge in a Li/O2 cell. Cells are discharged and charged at constant rate of 0.5 mAcm–2 as described in a previous report.5 After discharge is complete, various intermediate states of charge are sampled by stopping the charge at cell potentials of 3, 3.375, 3.75, 4.125, and 4.5 V. Partially cycled electrodes are harvested from the cell and imaged with scanning electron microscopy.

 Figure 1 shows a typical discharge charge curve, with an image of a control electrode and the morphologies observed for a fully discharged cell and a cell charged to 4.5 V (coincidentally corresponding to about half of the discharge current). From this it is clear that Li2O2 is not consumed uniformly throughout the electrode during charge. The implications of the non-uniform consumption of Li2O2 for electron and O2 transport in the electrode during charge will be discussed.

Figure 1
Synergy Between Different Graphene Structures in Layer-By-Layer Assembly for Li-Air Battery Cathodes
Authors: Kim Jangwoo , Joo Yong Lak
Published: February 2020

Lithium-air or lithium-oxygen batteries widely known for its high energy density stand in the spotlight of world with an expectation that it could promote electric vehicles or high grid energy storages to the next level. Studies on the interface between carbon and catalyst or the reaction properties of each with respect to oxygen and electrolyte are underway. However, a few was reported on the structural characteristic of a cathode coated with two different carbons without a catalyst. In the current study, a sandwich-structured cathode was manufactured by successively alternating two different carbons in a layer-by-layer assembly manner onto a gas diffusion substrate. With a constant amount of total carbon but with a different number of layers a clear synergic effect was demonstrated in terms of both increasing the specific capacity and reducing charge overpotential. The results strongly indicate that the structural variance of cathode controlled by different carbon morphologies affects the overall performance of lithium-air batteries, not to mention their surface properties.

Figure 1