bluuebunny/crossref_metadata_2025_split huggingface dataset:
(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