bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroless UPD Monolayer Deposition - a Prelude to Highly Selective Electroless Atomic Layer Deposition Process
Authors: Solanki Dhavit , Wu Dongjun , Joi Aniruddha , Dordi Yezdi , Brankovic Stanko 
Published: February 2020

The improved understanding of nucleation kinetics has led to various discoveries in which the thin film growth was manipulated to enhance the evolution of atomically flat epitaxial overlayers. Exploiting some of these results has led to invention of several new methods and protocols for electrodeposition where underpotentially deposited (UPD) monolayer is used as a mediator, surfactant or sacrificial template. The one successful example is so called “deposition via surface limited redox replacement (SLRR) of UPD monolayer,” which gained a lot of applications for synthesis of noble metal thin films with different functionalities. This protocol/method represents the combination of the potential controlled step (formation of UPD monolayer) and the electroless step (SLRR of UPD monolayer by more noble metal ions, i.e., galvanic displacement). However, our studies show that there is still a lot of room left for improvements and further simplifications. These should expand application of this deposition protocol in many areas where traditional atomic layer deposition (ALD) process has been used.
In this talk we present results demonstrating an electroless ALD process in which a Pb UPD monolayer is used as a reducing agent and sacrificial material in SLRR reaction with noble metal ions such as Pt, Pd, and Ru and Cu. The full deposition cycle involves sequential exposure of the substrate such as Cu and Ru to the solution for electroless Pb UPD monolayer deposition and then to the solution for SLRR reaction and noble metal deposition. This results in an overall deposition of controlled amount of noble metal which is the function of the areal density of deposited Pb monolayer and stoichiometry of the SLRR reaction. Therefore, the process mimics, to a great extent, the standard ALD cycle where adsorption of the metal precursors and surface catalyzed reaction are replaced by electroless Pb UPD monolayer deposition and SLRR reaction. If the two-step SLRR cycle is repeated an arbitrary number of times, a highly compact, smooth, and conformal noble metal thin film can be grown. The deposition process is highly selective to the metal substrates at which Pb forms an UPD monolayer providing an advantage when certain integration requirements are considered. The process is designed for (but not limited to) aqueous solutions with fairly simple and stable chemistry that can be easily scaled up to any size and shape of the substrate surface. Results demonstrating details and underlying phenomena controlling this process will be discussed. In addition, an example of a high quality of Pt, Pd, Cu and Ru films grown on Cu and Ru substrate will be shown, as well as the applications of this process for metallization of structures relevant to semiconductor device fabrication.
(Invited) In-Situ Studies of Alloying and Alloy Surfaces in the Electrochemical Environment
Authors: Lucas Christopher , Grunder Yvonne , Fogg Joshua , Vasiljevic Natasa 
Published: February 2020

The development of new functional materials is transforming many technological areas of great interest from electronics and catalysis to detection and bio-sensing. Surface alloying and self-organization phenomena, driven by the surface stress and elastic interactions in metals, are key to these developments. While much has been done theoretically and explored experimentally in ultra-high vacuum (UHV), very little has been exploited in practical applications. Electrochemistry is the ideal science to exploit the physics and chemistry of such functional materials. Alloying between two components in general is driven by negative enthalpy of mixing and the lowering of surface free energy. However, when confined to a few surface layers, it can be observed even in systems that do not form alloys in the bulk phase (so called immiscible systems). UHV studies at elevated temperatures have found that the formation of immiscible surface alloys is a rather common phenomenon in systems with large lattice mismatch and that it is driven by surface stress relaxation and elastic energy.
In this talk in-situ surface x-ray scattering studies of alloy formation and alloy surfaces will be presented. This will include alloys prepared by UHV methods, in particular both bulk and surface Pt3Sn(111) alloys, and alloys prepared directly in the electrochemical environment, Pb-Au(111). For the Pt3Sn system, of interest in electrocatalysis due to its tolerance towards CO poisoning, the surface has been studied under UHV conditions and during the adsorption of water and the results are compared to measurements of bulk Pt3Sn alloys in 0.5 M H2SO4 electrolyte under potential control. For the Pb-Au(111) system, resonant x-ray scattering methods are used to identify the onset of surface alloying and correlate the changes in surface stress with the out-of-plane atomic structure.
(Invited) Interpretation of Certain Features of the Interface Stress Vs. Electrode Potential Curves of Gold with the Help of Dual Dynamic Voltammetry
Authors: Lang Gyözö G. , Kovacs Noemi , Dankhazi Zoltan , Vesztergom Soma , Ujvari Maria 
Published: February 2020

It is a widespread opinion that the electrochemical behavior of gold in aqueous media has been thoroughly studied, and the interface stress changes of gold can be explained by monolayer oxide formation/removal and adsorption phenomena. However, there are some peculiarities to consider. For instance, a sudden change in the slope of the interface stress vs. electrode potential curve recorded during the negative-going scan of the cyclic voltammogram can be observed in the oxide reduction region of gold in sulfuric acid solutions (Fig. 1).
The method of dual dynamic voltammetry, i.e. the simultaneous application of dynamic potential programs to the generator and the collector electrodes of a generator-collector system, is a promising new method for studying the mechanisms of electrochemical processes [1-3]. By applying this method to a gold/gold rotating ring-disk electrode (RRDE) it could be shown that the sharp change in the slope of the surface stress vs. potential curve recorded in the oxide reduction region of gold in sulfuric acid solutions [4] is accompanied by the formation of soluble, electrochemically reducible gold species which can be detected at the ring electrode.
References:
[1] S. Vesztergom, M. Ujvári, G.G. Láng, Electrochemistry Communications, 19, 1–4 (2012).
[2] N. Kovács, M. Ujvári, G.G. Láng, P. Broekmann, S. Vesztergom, Instrumentation Science and Technology, 43, 633–648 (2015).
[3] S. Vesztergom, N. Barankai, N. Kovács, M. Ujvári, P. Broekmann, H. Siegenthaler, G.G. Láng, Electrochemistry Communications, 68, 54–58 (2016).
[4] G.G. Láng, C.A. Barbero, „Laser Techniques for the Study of Electrode Processes”, Springer-Verlag, Berlin, Heidelberg, 2012.
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Figure 1
Superconformal Cobalt Fill through the Use of Sacrificial Oxidants
Authors: Rigsby Matthew , Brogan Lee , Doubina Natalia , Spurlin Tighe , Zhou Jian , Reid Jonathan 
Published: February 2020

As interconnect dimensions continue to decrease, the extendibility of conventional copper damascene processing becomes increasingly problematic. Small feature openings can lead to agglomeration of the thin seed that is required to avoid pinch-off, and this can then lead to poor nucleation during the electrodeposition process. Electromigration performance also suffers from the decrease in line dimensions. In addition, the increase in line resistance with shrinking dimensions means that the barrier is consuming valuable space within the feature. To address these extendibility issues, alternative metals, such as cobalt, are being actively explored.
Conventional damascene electroplating utilizes a combination of organic additives, namely, a suppressor, an accelerator, and a leveler, to achieve superconformal fill of interconnects. An alternative mechanism for superconformal cobalt fill is presented here. This mechanism, the Differential Current Efficiency Fill (DCEF) mechanism, utilizes sacrificial oxidants to achieve void-free superconformal fill. In the DCEF mechanism, the presence of a sacrificial oxidant promotes a difference in metal deposition rate between the field and the feature bottom. Addition of a single suppressor-type additive may assist in driving the plating rate differential. By appropriately selecting the sacrificial oxidant, the waveform, and the rotation rate, void-free superconformal fill can be achieved.
Figure 1 shows an example of the superconformal cobalt fill that can be achieved. Here, the rate and degree of fill are modulated by changing the rotation rate during the electrodeposition. Electrochemical polarization and current efficiency experiments are useful in determining appropriate process conditions, and these data will also be discussed.
The DCEF mechanism presents a new approach to achieving superconformal fill and will be important in extending electroplating to increasingly smaller interconnect dimensions. While the DCEF mechanism has been shown to work for superconformal cobalt fill, the concept may be applicable to other metals as well.
Figure 1: Superconformal cobalt fill: 1mA/cm2 240s, varied rotation rate

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1D Core-Shell Nanostructures Formed By Electrodeposition of Metals and Metalloids in Anodic TiO2 Nanotubes
Authors: Kowalski Damian 
Published: February 2020

The anodizing is a high-voltage electrochemical conversion process that forms barrier-type or nanoporous/nanotubular oxides on valve metals and alloys, mainly depending on the composition of electrolyte used.[1] The key to achieve the ordered nanoporous/nanotubular structures is a displacement of the film material above the original surface position due to synergistic effect of pits generation (field assisted oxide dissolution), stress generated at the metal-oxide interface including electrostriction and plastic oxide flow switching the growth of the barrier-film to nanotube/nanopore. Typically, the TiO2nanotube array formed in organic electrolytes such as glycerol, dimethyl sulfoxide, ethylene-glycol is obtained in the form of close packed structure in which the nanotubes nearly stick together with the tube walls. A fundamentally different nanostructure from that is obtained in diethylene-glycol electrolyte. The nanostructure is characterized by free standing nanotubes separated by an interconnecting space much bigger than the thickness of nanotube wall. [2,3] Such geometry gives possibility for deposition of secondary materials using electrochemical processes in view of improved wetting behavior of the nanostructure. [4] Herein we report on how to control the electrodeposition process to achieve unique core-shell geometries. We discuss on wetting behavior and nucleation-growth on such porous structures, a key points to achieve controlled electrodeposition. An examples of composites formed between oxide layer and Si, CdSe, Au, Pt will be demonstrated.
References:
[1] D. Kowalski, D. Kim and P. Schmuki, Nano Today, 8(2013) 235.
[2] D. Kowalski, J. Mallet, J. Michel, and M. Molinari, J.Mater.Chem.A
3(2015) 6655.
[3] D. Kowalski, J. Mallet, S. Thomas, J. Rysz, B. Bercu, J. Michel and M. Molinari, Electrochim. Acta, 204(2016) 187.
[4] D. Kowalski, and P. Schmuki, Chem. Comm., 46(2010) 8585.
Fig. 1 Core-shell structures formed by means of electrodeposition of Si and Au. STEM image (left) shows 60nm thick silicon layer electrodeposited from ionic liquid electrolyte on the outer-shell of TiO2 nanotube. Back scattering electron image (right) shows gold electrodeposited in-between the bottoms of TiO2 nanotubes.

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Cost of Renewable Energy
Authors: Newman John 
Published: February 2020

To switch from conventional fossil fuels to renewable energy is a huge undertaking. Before starting this costly exercise, the community should assess what is involved, how much it will cost, and by how much the standard of living will be reduced.
It is not complete to focus on efficiency, and certainly not reversible energy efficiency. In one example, emphasizing minimizing overall energy efficiency leads one to conclude that building a photovoltaic device and an electrolyzer in a single unit is the correct approach. However, this raises the total cost significantly over what could be accomplished when the photovoltaic and the electrolyzer can be kept separate and each optimized separately. Then the PV can be run at its maximum power, and the electrolyzer can be run at a different temperature and at a significantly higher current density, at the optimum governed by a trade-off between capital and operating costs.
To bring a new product to market requires careful planning to insure that the product is useful and at an attractive price. Even more so when you are contemplating changing the whole energy infrastructure.
Perhaps cheaper than clean renewable energy like wind, geothermal, or solar would be to continue to burn fossil fuels but to capture and sequester the carbon dioxide produced and thereby mitigate climate change. It surprised me how much more attractive this method could be.
Ruthenium Electrodeposition from Deep Eutectic Solvents
Authors: Bernasconi Roberto , Magagnin Luca 
Published: February 2020

Ruthenium is one of the most promising materials for the realization of barrier/seed layers in low-k copper interconnects technology. It is a possible candidate for the substitution of materials like Ta/TaN or TiN. This metal presents interesting properties like a reasonably low resistivity (7.1 µΩcm in bulk), a high melting point and high mechanical properties. Moreover, it presents almost no solubility with copper, preventing thus interdiffusion [1]. Finally, ruthenium can be directly plated with copper [2], avoiding the deposition of seed layers.
Ruthenium can be easily PVD deposited on Si, obtaining ultrathin barrier layers suitable for the most advanced patterning techniques. However, PVD deposition presents some major disadvantages like high cost, limited productivity and a significant difficulty in uniformly plating vias and trenches having high aspect ratio (this effect is known as shadowing). Alternative techniques, including wet metallization, can overcome these limitations. Electrodeposition in particular proved to be able to provide uniform metallization even in very high aspect ratio features, like in the case of copper superfilling [3].
Ruthenium tends to oxidize in aqueous solution, and for this reason electrodeposition from standard electrolytes can present technological problems. Alternative solvents have been proposed in the past to solve this issue, the most notable being ionic liquids like BMIPF6 [4]. Another possible alternative are deep eutectic solvents, which are characterized by interesting properties like water stability, high conductivity and the absence of harmful chemicals (which make them suitable also for employment in the green chemistry field).
The present work describes the electrodeposition of ruthenium thin films for microelectronic applications from a deep eutectic solvent. Metallic layers are deposited and characterized from the electrical and morphological point of view to evaluate their possible use as barrier layers in microelectronics industry.
[1] R. Chan, T. N. Arunagiri, Y. Zhang, O. Chyan, R. M. Wallace, M. J. Kim and T. Q. Hurd, Electrochem. Solid-State Lett., 7, G154 (2004)
[2] Y. Zhang, L. Huang, T. N. Arunagiri, O. Oieda, S. Flores, O. Chyan, and R. M. Wallace, Electrochem. Solid-State Lett., 7, C107 (2004)
[3] D. Josell, D. Wheeler and T. P. Moffat, Electrochem. Solid-State Lett., 5, C49 (2002)
[4] O. Raz, G. Cohn,W. Freyland, O. Mann, Y. Ein-Eli, Electrochim. Acta, 59, 6042 (2009)
Experimental and Modeling Studies of Neodymium Electrodeposition from High-Temperature Chloride-Based Molten Salts
Authors: Shen Dai , Akolkar Rohan 
Published: February 2020

Electrowinning and electrorefining of rare earth lanthanides using molten salt electrolytes is of interest because these technologies offer the potential for energy-efficient and low-cost recovery and reuse of these strategically important elements. However, efficient electrochemical processing of rare earth elements such as neodymium (Nd) is hindered by its multivalent nature. Specifically, the existence of Nd3+ and Nd2+ redox-active species can substantially lower the overall current efficiency of Nd electrorefining [1]. In the present talk, we will report on experimental and modeling investigations into the electrodeposition of Nd metal from NdCl3-containing halide melts (eutectic LiCl-KCl). We will discuss how cyclic voltammetry studies and diffusion-reaction modeling help unravel the thermodynamic, kinetic and mass transport properties associated with the multivalent redox transitions prevalent during Nd electrodeposition. Furthermore, we will discuss how these properties can be used to design efficient Nd electrowinning and electrorefining processes. The broad applicability of our design approach will be discussed in the context of electrodeposition of other multivalent rare earth metals and alloys.
1. L. Feng, C. Guo, and D. Tang, J. Alloys Compd., 234, 183 (1996).

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Electrochemical Nucleation and Growth of Metals in Molten Salts
Authors: Suzuki Yuta , Yokota Masayuki , Sakanaka Yoshihide , Fukunaka Yasuhiro , Goto Takuya 
Published: February 2020

Investigation of electrochemical nucleation and growth mechanism is of great significance for controlling morphology of elctrodeposited metals on substrate. However, information concerning nucleation and growth mechanism in molten salts has not been sufficient, although it is necessary to understand growth processes of electrodeposition of metals in molten salt for realizing practical process. In particular, investigation of electrodeposited metals at early stage is expected to give us new information about morphogenetic process during electrolysis in molten salts.
From the background, molten chloride salts containing silicon ions was used for studying electrochemical nucleation and growth mechanism of metallic silicon by using electrochemical techniques combined with micro-spectroscopic techniques. After conducing electrolysis for one second, hemispherical nucleated Si was observed by SEM, and process of agglomeration was also observed as time proceeded. The effect of time evolution on growth process has been also studied by conduction potentiostatic electrolysis. The growth mechanisum from the experiments will be presented at the symposium.
Effect of Magnetic Field on Al Electrodeposition in Ionic Liquid
Authors: Takahashi Hitomi , Matsushima Hisayoshi , Ueda Mikito 
Published: February 2020

1.Introduction
Aluminum is a very important material because of its distinctive features of a bright silvery appearance, light weight and high corrosion resistance. Also, it is used as a base in light-emitting diodes owing to its high reflectance of more than 90% in the visible light region. We have previously carried out Al electrodeposition with additives and reported a shiny coating under the control of a stirred flow [1]. In that work, the surface roughness and glossiness was drastically improved by increasing the stirring rate.
To pursue a novel convection method, we consider that the superimposition of a magnetic field, B, is a possible solution. Lorentz force occurs when a magnetic field is applied perpendicular to current, and a convection caused by the power is called MHD convection [2]. Therefore in an ionic liquid which consists of only ion species, the MHD convection can expect to act more effectively as compared with an aqueous solution system. In this report, Al films were electrodeposited in EMIC-AlCl3 ionic liquid under a uniform magnetic field, whereupon their morphology and crystal orientation were analyzed by scanning electron microscopy and X-ray diffractometry.
2.Experimental
Electrodeposition was carried out with a three-electrode system. The electrolyte used was EMIC-AlCl3 (1:2). The cathode was a Cu plate and the anode was an Al plate. All experiments were conducted in a glove box purged using by Ar gas at 60°C. The Al electrodeposition was conducted galvanostatically until the amount of electrical charge reached 29 C cm−2, which corresponds to a deposition 10 µm thick. A static and uniform magnetic field of 0.3 T was applied parallel to the electrode surface. The surface morphology of the electrodeposited Al films was observed using SEM, while the crystal orientation was measured by XRD using the Cu-Kα line.
3.Results and discussion
In the galvanostatic electrolysis experiment, potential shifted to the noble direction by applying a magnetic field, and when current density was enlarged, the difference appeared more notably. The magnetic field also affected the orientation of deposition, and a (200) plane orientated priority. These are considered that the stirring effect by a MHD convection is involving. The SEM images show that the crystal grains change remarkably in the presence of a magnetic field, where a typical morphological variation is shown in Fig. 1. Fig. 1(a) shows angular deposits around 1.0 µm in size, and a surface covered with fine irregular grains. The application of magnetic field, however, created large grains with tabular-facet planes 2–4 µm in size (Fig. 1 (b)), although no additives were used in the present experiments.
[1] H. Takahashi, C. Namekata, T. Kikuchi, H. Matsushima and M. Ueda, Journal of the Surface Finishing Society of Japan, 68, 208 (2017).
[2] A. Bund, S. Koehler, H. H. Kuehnlein and W. Plieth, Electrochimica Acta, 49, 147 (2003).

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Improving Li/Solid Electrolyte Interfacial Contact and Performance By Evaporating a Conformal Lithium Layer
Authors: Frisco Sarah , Whitacre Jay 
Published: February 2020

In solid polymer electrolyte/lithium metal based batteries, the interfacial integrity of the lithium metal/polymer interface is critical, and the imperfect, non-uniform initial contact of lithium foil pressed into electrolyte worsens with cycling. This leads to increased impedence at the interface and declining cell performance. To address this issue, we are assessing the impact of depositng a conformal layer of lithium via evaporation onto the electrolyte surface prior to the application of a lithium foil bulk electrode. This approach yields initially enhanced interfacial area due to the improved contact from this conformal coating, which should lead to improved cycling behavior. Electrochemical data in the form of galvanostatic cycling and electrochemical impedence spectroscopy will be discussed in the context of nano-resolution X-ray radiographs and SEM. Data from commercial and lab created solid electrolytes, including PEO and other polymer electrolytes will be shown. Discussed will be the relative performance of solid-state lithium metal cells with a simple lithium foil anode versus a combined lithium evaporated layer/lithium foil anode. Furthermore, the propensity for dendritic failures in PEO electrolyte systems will be examined.