bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Origin of Weak Points in Surface Oxides at the Atomic Scale on Cr-Containing Alloys
Authors: Marcus Philippe , Ma Li , Wiame Frédéric , Maurice Vincent
Published: February 2020

Stainless steels (SS) are widely used in various industrial sectors because they are protected against corrosion by an oxide film formed at the surface, only a few nanometers thick and strongly enriched in Cr(III).

Despite numerous studies of stainless steel passivity at the macroscopic scale, only recent surface analytical works have attempted to characterize the nature and elucidate the origin of sub-microscopic chemical and structural heterogeneities in surface oxide layers.

In this work, the topographic, structural and chemical alterations of a (100)-oriented model 304 austenitic stainless steel single crystalline surface have been investigated at the nanometer/ atomic scales during early stage oxidation by Scanning Tunneling Microscopy (STM) combined with X-ray Photoelectron Spectroscopy. The experiments were performed by exposing an oxide-free Fe-18Cr-13Ni(100) surface to oxygen.

The results presented first will be on the oxide-free alloy surface structure, with STM data revealing the presence of ordered vacancies under equilibrium conditions. Then the evidence of nucleation of chromium oxide at multi-atomic surface steps will be presented. A chromium pumping effect creates Cr enrichment in the oxide nuclei at the steps, and Cr-depleted zones at the border of the oxidized steps, allowing less protective iron oxide to be formed locally. Weak points in the surface oxide layers originate from this atomic scale surface process.

The further discussion of the presented data will emphasize the importance of this observation for the understanding of the role of the oxidation mechanisms in the nanoscale heterogeneity of the growing surface oxide on Cr-containing alloys such as stainless steel, providing a new insight into the mechanisms of pit initiation at weak points of passive films.

This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 741123, CIMNAS : Corrosion Initiation Mechanisms at Nanometric/Atomic Scale). Région Ïle-de- France is acknowledged for partial funding of the STM and XPS equipments. China Scholarship Council (CSC) is acknowledged for a scholarship to Li Ma (No. 201606380129).
(Invited) The Morphological Stability of Passive Oxide Films
Authors: Ramanathan Rohit , Voorhees Peter W
Published: February 2020

Understanding the kinetics of passive oxide formation and breakdown has been an ongoing problem for corrosion scientists for several decades. A model for the formation of a passive oxide film on a metal that is an extension of the Point Defect Model (PDM) will be presented. The potential description of the PDM is replaced with a boundary value problem that ensures Gauss' law is satisfied at the oxide-solution interface by considering the presence of the Helmholtz layer in solution. Our model predicts the observed linear variation of the steady-state film thickness with anode potential, and an increasing steady-state film thickness with increasing pH. A linear stability analysis of the moving metal-oxide and oxide-solution interfaces shows that, depending on the parameters, the passive film may be unstable to morphological perturbations of the film interfaces, leading to non-planar films and potentially the formation of a pit in the oxide. This also implies that one-dimensional models of oxide growth, that assume planar interfaces, can be inapplicable in broad classes of corrosion processes. The analysis shows that a morphological instability exists if the oxide dissolution mechanism is such that an increasing Helmholtz layer potential drop leads to an increasing dissolution rate. The instability behavior is consistent with the literature on breakdown of passivity in the presence of chloride ions. The theory provides insights on the initiation of passivity breakdown leading to pitting corrosion and the role that interfacial energy plays in determining stability.
(Invited) Rapid Cathodic Process on Anodized Metals By Fast Current-Controlled Polarization
Authors: Fujimoto Shinji , Kurokawa Tetsuya , Tsuchiya Hiroaki , Miyabe Sayaka
Published: February 2020

It is well known that oxygen reduction is one of the most important reactions in corrosion process. Therefore, oxygen reduction has been extensively studied on metals and alloys, the surface of which is covered with oxide film. In general, the oxygen reduction reaction during localized corrosion is considered to occur extremely fast, but such rapid cathodic process has not been reported. In the present work, we propose an approach to investigate rapid oxygen reduction reaction, so-called a fast current-controlled polarization, where a fast cathodic current transient is applied to metals and alloys covered with oxide film and from the resulting potential variation, the kinetics of the oxygen reduction on the surface is analyzed.

Materials examined were several valve metals such ad Ti, Al, and Zr. Anodic oxide films were produced by anodization on the metals in a phosphate buffer solution at various voltages. In the first current-controlled polarization, a triangle form of cathodic current was applied to the anodized metals, monitoring the resulting potential variation. The potential for all the anodized metals shifted in the less noble direction steeply and then recovered back gradually to the original potential. The potential variation was analyzed based on the assumption that the applied current was consumed as charge-discharge in the space charge layer in the oxide film and the oxygen reduction reaction. As a result, it was found that the oxygen reduction current was clearly different depending on the type of valve metal as well as anodization voltage. In this presentation, details on the fast current controlled polarization will be presented and the different reduction kinetics will be discussed.
A New Framework for Pit Growth Stability and Its Experimental Validation
Authors: Li Tianshu , Scully John R. , Frankel Gerald S.
Published: February 2020

A new framework has been developed in recent works to describe pit growth stability 1-4. In this framework, the concept of maximum pit dissolution current density, i
diss,max, was proposed to consider the competition between the dissolution and diffusion processes within a pit 2, 3, an issue that has not been satisfactorily addressed previously. The quantity i
diss,max is the rate of dissolution in a pit in the absence of a salt film. According to this new framework, the pit stability and salt film formation can be defined by the critical conditions of i
diss,max = i
diff,crit and i
diss,max = i
lim, respectively, where i
diff,crit and i
lim are diffusion current densities related to maintain critical and saturated pit concentration 3. Unifying sets of principal parameters for pit stability and salt film formation were developed based on these critical conditions: (T
crit, E
crit, r
crit) and (T
sat, E
sat, r
sat), respectively 3.

This talk described experiments using 1D artificial pit electrodes that validate this new framework for pit stability. According to the model prediction, the critical potential for salt film formation (E
sat) should decrease with the log of pit depth. The results from experiments on 1D pits followed this relationship exactly, which provides strong support of the validity of the new model. Additionally, a critical pit concentration equal to 43% of the saturation concentration, C
sat, was determined, which is much lower than the critical concentration determined by others. Furthermore, i
diss,max values at fixed pit surface solution concentrations (100%C
sat and 70%C
sat) were determined using pits of varying depth. The Tafel slope was found to be about 116 mV in both environments. This is the first ever determination of pit dissolution kinetics in pit solutions of fixed concentration.

This new framework provides an opportunity to revisit several key topics of this field and generates new insights to interpret previous observations in a self-consistent way, such as to understand the effects of alloy composition, bulk chloride concentration, ohmic potential drop of the solution, etc.

Acknowledgments: This work was supported as part of the Center for Performance and Design of Nuclear Waste Forms and Containers, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0016584.

Reference

G. S. Frankel, T. Li and J. R. Scully, Journal of the Electrochemical Society
164, C180-C181 (2017).

T. Li, J. R. Scully and G. S. Frankel, Journal of The Electrochemical Society
165, C484-C491 (2018).

T. Li, J. R. Scully and G. S. Frankel, Journal of The Electrochemical Society
165, C762-C770 (2018).

T. Li, J. R. Scully and G. S. Frankel, Journal of The Electrochemical Society
166, C115-C124 (2019).
Effect of Copper on the Localized Corrosion and Stress Corrosion Resistance of High Strength Aluminum Alloys
Authors: Bhaskaran Ganesh , Singh Preet , Yuan Yudie , Mohanty Rashmi , Kamat Rajeev , Piroteala Tudor
Published: February 2020

High strength to weight ratio of the 7xxx aluminum alloys offer an exciting alternative to advanced high strength steels in automotive structural applications. Recently, Novelis has developed AdvanzTM 7000 series alloys that not only has higher strength to weight ratio but also improved localized corrosion resistance compared to conventional 7075. In this work, we have studied the effect of copper content on the stress corrosion cracking resistance of the AdvanzTM 7000 in peak-age (T6) conditions. ASTM G110 test showed pitting corrosion morphology in both low and high copper alloys compared to intergranular corrosion in 7075. Electrochemical polarization showed that increase in copper content increased the cathodic activity and pushed the free corrosion potential in noble direction. Slow strain rate tests were carried out according to ASTM G129 in ASTM D1384 solution containing hydrogen peroxide and in silicone oil. The fractured samples were subjected to scanning electron microscopy (SEM) and metallography cross section. These results indicated that the SCC cracks were initiated from the pitting corrosion sites in AdvanzTM 7000, while the intergranular corrosion site acted as crack nucleation site for 7075. The failure mechanism is discussed in terms of shift in corrosion morphology and the role of Al7Cu2Fe particles that had increased with the copper content of the alloys.
ICME Design of Corrosion Resistant High Entropy Alloys for Harsh Environments
Authors: Lu Pin , Olson Greg , Li Tianshu , Frankel Gerald S. , Gerard Angela Yu , Scully John R.
Published: February 2020

The integrated computational materials engineering approach is inherently suited to explore the vast, multi-dimensional high entropy alloy (HEA) compositional and processing space, and has been adopted in this work, coupled with empiricism, to design highly corrosion resistant HEAs. Using the combination of empirical and computational approaches, three non-equimolar HEA compositions were identified for their predicted ability to form a single-phase structure and to exhibit high corrosion resistance. Phase diagrams and E-pH Pourbaix diagrams for HEAs were calculated by CALPHAD. One of the HEAs, Ni38Cr21Fe20Ru13Mo6W2, has been successfully synthesized on the lab-scale and homogenized at 1250°C for 120 hours. Exceedingly high corrosion resistance of the Ni-rich HEA was demonstrated by electrochemical testing, including potentiodynamic polarization and electrochemical impedance spectroscopy, even in harsh acidic solutions. The successful validation of the computational design efforts with pre-set property goals shows that ICME is suitable for corrosion resistant HEA design, including complex non-equimolar HEAs.
A Chloride Susceptibility Index (CSI) : An Ab Initio Based Corrosion Resistance Indicator
Authors: Ke Huibin , Taylor Christopher
Published: February 2020

Many properties have been used to indicate the corrosion resistance of metallic materials. However, there is still no single property that can be used to compare across different alloy system and predict the corrosion resistance of metallic materials. Here, a universal scientifically based quantitative indicator called chloride susceptibility index (CSI) is introduced based on a multi-scale modeling framework. This framework can be applied to study the effect of different factors on corrosion resistance of alloys, including alloy composition, solution pH, Cl- concentration and temperature. Commonly used Ni-Cr-based alloys and stainless steels will be used as examples for this study. Firstly, ab initio modeling is used to study the adsorption energy of O and Cl to alloy surfaces with different solutes. Then, a Langmuir model is used to study the competitive adsorption of Cl vs. O under different conditions, from which CSI will be calculated. By connecting atomic scale properties with environmental conditions, CSI allows the predictable quantitative measurement of one aspect of the corrosion resistance of metallic materials, namely the sensitivity of the alloy surface to complexation with chloride versus oxide formation.
Bond Energy Models for Bond Energies in Alloys and Alloy Oxides
Authors: Chien Szu-Chia , Frankel Gerald S. , Windl Wolfgang
Published: February 2020

Fe-Cr (stainless steels) and Ni-Cr alloys are corrosion resistant because of the spontaneous formation of a passive film on the surface. One or more oxides may form based on the alloying elements. The current guide for alloy design based on resistance to localized corrosion is the pitting resistance equivalence number (PREN). PREN is an empirical model that based on a simple correlation of the elements in alloys to a parameter such as pitting potential or critical pitting temperature. There is no connection of PREN to basic material properties or fundamental mechanisms. With the goal of developing a scienced-based approach for alloy design including the ability to form a passivation layer and its subsequent stability in aggressive environments, we herein introduce new bond-energy models for both alloys and alloy oxides. The models were parameterized by density-functional theory (DFT) results for alloys having different crystal structures such as face-center cubic and body-center cubic as well as for alloy oxides with a corundum structure, which is one of the most common oxides structures for passive layers. Our study particularly focuses on metal cations that form the basis of stainless steels (Fe, Ni, Cr) and some common solutes (Mo, Ru, W, and Mn). Various metal-metal and metal-oxide bond strengths can be obtained from our models. This work provides new insights into the roles of alloying elements in strengthening and weakening effects on bond energies for corrosion applications.
(Invited) High-Performance 2D Tellurium Transistors Towards CMOS Logic Applications
Authors: Qiu Gang , Wang Yixiu , Wu Wenzhuo , Ye Peide D
Published: February 2020

The thirst for novel two-dimensional (2D) materials for ultra-scaled electronics keeps growing during the last decade as the downsizing trend of silicon-based conventional semiconductors is approaching its physical limit. An ideal paradigm of 2D materials suitable for logic device applications should possess high carrier mobility for both type of carriers, good air-stability, controllable doping scheme and a reasonable bandgap.

Recently reported hydrothermal growth technique of 2D tellurium (Te) thin films, which meet all the above criteria, offers a new option for 2D material-based CMOS applications. Tellurium is a narrow bandgap p-type semiconductor (0.35 eV) with nearly symmetric mobilities for both electrons and holes of around 700 cm2/Vs at room temperature. It has one-dimensional chiral crystal structure and can be grown into 2D films under right conditions. Just like other 2D materials, these 2D facets of Te also contain no dangling bonds and therefore the 2D films can preserve the material properties and have great potential for miniaturizing device geometry in principle. Here we first report systematic investigation of 2D Te p-type transistor performance approaching atomic-thin limit. The device key parameters, such as field-effect mobility, on/off ratio and stability were thoroughly studied as a function of film thickness. The device performance was then optimized through contact and dielectric engineering, and large drive current over 1 A/mm was achieved. We further employed photo-current mapping method to show that rare accumulation-type ohmic contacts were formed using high work function metal (palladium). Finally, we present an atomic layer deposited (ALD) dielectric doping technique to effectively dope the intrinsically p-type channel into n-type with almost symmetric operations for both NMOS and PMOS. Prototypical inverters based on Te CMOS demonstrate great potential of constructing Te-based high-speed CMOS logic circuits. Our work not only established a comprehensive guideline for designing and optimizing 2D Te based CMOS devices, but also provided a device platform to explore versatility of 2D Te from many other perspectives, such as condensed matter physics and thermoelectronics.
(Invited) Mid-Infrared Colloidal Quantum Dot Based Nanoelectronics and Nano-Optoelectronics
Authors: Hafiz Shihab Bin , Scimeca Michael R. , Sahu Ayaskanta , Ko Dong-Kyun
Published: February 2020

Electronic and optoelectronic devices fabricated from colloidal quantum dots (CQD) provide a promising path toward realizing low-cost devices with greatly simplified device fabrication procedure, owing to their solution-processability. The impact that CQD technology would bring is expected to be significant, especially in the mid-infrared application areas, which is currently dominated by epitaxial semiconductor technologies. In this work, we introduce a new generation of infrared CQDs, namely Ag2Se CQDs, which has been recently uncovered to show distinct optical absorption in the mid-infrared. We report on the fabrication of solution-processed photoconductive photodetectors and discuss our analyses on the electronic and optoelectronic characteristics of our devices. We also demonstrate the feasibility of mid-infrared photodetection with a measured peak responsivity of 0.16 mA/W at 4 μm under room temperature operation.
Data-Driven Modeling of Dielectric Breakdown Phenomena in Polymers
Authors: Shetty Pranav , Chen Lihua , Batra Rohit , Wu Chao , Li Zongze , Cao Yang , Ramprasad Rampi
Published: February 2020

Polymers are widely used as dielectrics in devices ranging from capacitors to multi-layered IC’s and as insulation for high voltage cables. In these applications, the dielectric breakdown strength is a critical parameter affecting device performance [1]. In this work, we study the dielectric breakdown properties of common polymers using machine learning. The complex nature of the dielectric breakdown process makes it analytically intractable for real systems and thus ideal for application of machine learning.

The input to the machine learning model consists of material property values and the model outputs dielectric breakdown. For our training data, dielectric breakdown of polymer thin films is experimentally measured using small area breakdown measurements [2] at multiple temperatures ranging from -100 °C to 100 °C. The input to our model are property data that are known to influence dielectric breakdown. Selecting a subset of our original feature space using variable selection algorithms, we train a machine learning model using gaussian process regression.

We test our model on unseen experimental data and find that it predicts dielectric breakdown of unseen polymers accurate to the experimental error of measurement. In addition we find that the underlying physics of the temperature dependence of dielectric breakdown is captured well in the training domain. Our model can be used to systematically search polymer spaces to accelerate discovery of high breakdown strength polymers.

References

[1] Zulkifli Ahmad (October 3rd 2012). Polymer Dielectric Materials, Dielectric Material, Marius Alexandru Silaghi, IntechOpen, DOI:10.5772/50638

[2] Rytoluoto, I., et al. ”Large-area dielectric breakdown performance of polymer films-part i: measurement method evaluation and statistical considerations on area-dependence.” IEEE Transactions on Dielectrics and Electrical Insulation 22.2 (2015): 689-700.
A Dielectric and Vibrational Spectroscopy Study of the Confinement Effects on Ion Dynamics in a Methacrylate Based Polymerized Ionic Liquid within Nanoporous Silica Membranes
Authors: Kinsey Thomas , Glynn Kaitlin , Cosby James Tyler , Sangoro Joshua R
Published: February 2020

In this study, the structures and dynamics of a low molecular weight ionomer confined at length-scales below which solvation layers have been shown to form for ionic liquids within nanoporous silica are investigated using broadband dielectric spectroscopy, Raman spectroscopy and 1H NMR. Silica membranes having 7nm unidirectional pores were prepared using well-defined electrochemical etching procedures in a 1:1 volume fraction ethanol:hydrofluoric acid electrolyte solution. In situ free radical polymerization of the low molecular weight ionic liquid polymer, poly-[(methacryloyloxy)ethyl]dimethylammonium bis[(trifluoromethyl)-sulfonyl]imide, was performed monitored with Raman spectroscopy to observe changes in ion coordination and anion conformational fluctuations with monomer conversion in bulk and within nanoporous silica. The free radical polymerization reaction kinetics were observed to be increased under confinement compared to bulk as previously reported, and resulted in a 5kg/mol polymer with narrow molecular weight distribution. From the dielectric spectra, the dc conductivities of the polymer under confinement were determined to be increased compared to the polymer in the bulk. Using a simple model accounting for porosity within the membranes, a calculated adsorbed layer at the interface of the pore wall with the ionic liquid was determined to decrease with polymerization, effectively counteracting the effects of immobilization of ions within the polymer backbone. Furthermore, the possible changes in free volume under confinement and with polymerization are discussed through detailed observation of the Raman spectra regarding anion conformational changes. These changes in free volume are shown to correlate to increased ion dynamics. The ion dynamics in these materials are further described in terms of the current understanding of interfacial electrostatic interactions of ionic liquids with solid surfaces and in conjunction with the effects of polymer dynamics under confinement.
Appraising the Extensibility of Optics-Based Metrology for Emerging Materials
Authors: Barnes Bryan M , Henn Mark-Alexander , Sohn M Y , Zhou Hui , Silver Richard M
Published: February 2020

Over the last decade, our group at the National Institute of Standards and Technology (NIST) has explored novel ways to overcome the perceived limitations of applying optical scattering and imaging in the characterization of small silicon features. As a result, we were able to both qualitatively and quantitatively characterize features that are well-below the resolution limit, namely small groupings of well-ordered, periodic nanoscale features. This was achieved by specifying a limited number of parameters to describe these structures and comparing the measurements to extensive electromagnetic simulations with varying parameters. Such imaging simulations, which have yielded quantitative measurements of features less than λ/30 in size, require a priori knowledge of the nominal geometry, number of features, and optical constants of these materials; quantitative information from another tool set can augment such optical parametric fitting through “hybrid metrology,” pioneered by our group at NIST.

In the next decade, as the nanoelectronics industry further expands its palette of key emerging materials, it is critical to accurately establish their optical properties. Similar challenges exist for other optics-based, deep-subwavelength measurements, e.g., thickness determination via ellipsometry and parametric fitting via scatterometry. Specifically, the model-based metrology often employed for optics-based methods is challenged by the anisotropy and eventual thickness dependence of the dielectric tensor for two-dimensional materials and ultrathin films. Proper characterization of this tensor empirically or computationally will grow in importance as dimensions continue to decrease. The required steps, known limitations, and potential benefits of atomistic density-functional theory (DFT) simulations are discussed with respect to determining the macroscopic optical response due to feature dimensions only a few atoms in width.
(Invited) Plasma Etching at Ultra-Low Temp, Pressure and Radical Conditions for Next Generation Nano Chip Fabrication
Authors: Park Jongchul
Published: February 2020

The memory and logic chips are essential for the expansion of big data processing and AI related technologies in the near futrure.

The needs for high density cell and high aspect ratio cell structure and even EUV patterning for the next generation memory and logic chips are increasing more and more.

The conventional etching technologies cannot porvide the appropriate solutions for the next generation nano chip fabrication anymore.

I researched some innovative new etching technologies recently.

- ultra low pressure plasma ( < 1mTorr)

- ultra low temperature ESC ( < -100 degree)

- ultra low radical plasma (Ion beam etch)

The above new technologies will give the breakthrough against current process limitations on the nano chip fabrication.
(Invited) Characterization of Isotropic Thermal ALE of Oxide Films in Nanometer-Size Structures
Authors: Fischer Andreas , Routzahn Aaron , Lill Thorsten
Published: February 2020

Isotropic atomic layer etching (ALE) is increasingly becoming an option and even a necessity for modern chip manufacturing. Especially for application such as 3D-NAND memory, the ability to perform isotropic etches will be a critical addition to the established suite of reactive ion etching.

In this work, we have characterized the reaction of aluminum oxide (Al2O3) via the vapor-based DMAC ligand exchange mechanism in nanometer-size structures in which the oxide is buried below a silicon nitride mask. In the oxide, we measured vertical and horizontal etch rates and found that the etch showed some residual anisotropy even though all elements of the etch itself (flow, no plasma) were none-directional.

We applied a simple Monte-Carlo simulation to show that anisotropy is caused by a delay in the onset of the horizontal etch beneath the mask and by molecular scattering effects in the vapor phase above the nano-structures.

We are contrasting these results with experimental findings in structures without an anisotropy of the etch.
Precise Control of Poly-Silicon Height by Plasma Etching in FinFET Technology Node
Authors: Wang Yan , Zhang Dongping , Zhang Haiyang
Published: February 2020

The FinFET technology was brought to mass production for several years to replace the planar transistor structures. Critical process control is highly required for better device and yield performance.[1] When IC scale shrinks, the device performance becomes more and more sensitive to its physical dimension, in which the gate height is included.

In the HKMG era, the metal gate height control can be traced back to the poly-silicon height control, including the wafer-level uniformity, wafer to wafer, and lot to lot. Our work is focused on the poly-silicon height control with plasma etch process. The gate height uniformity control was already reported in 2017 by inductively coupled plasma (ICP) etching process.[2]

In this report, a precise control method from the point view of local height variation within die, surface induced polish process stability and advanced process control of the poly height planarization is discussed by plasma etching process. With an insertion of cap layer, the local poly-silicon height variation can be improved over 40%. A plasma treatment post the cap layer etch-back can reduce the break-through time of poly-silicon process, and thus improve the stability of CMP process as well as the CMP uniformity. An advanced process control of poly-silicon etch back process is implemented. Dynamic process time is dependent on the poly-silicon height post CMP process, which is due to the normal process variation, and 1% of the poly-silicon height variation after poly-silicon etch back is finally realized.

This work was partially sponsored by Shanghai Rising-Star Program (B type). The authors would like to thank Tongxun Guo from Lam research for the support of constructive discussion.

Reference:

[1] C. Auth et al., “A 22 nm high performance and low-power CMOS technology featuring fully-depleted tri-gate transistors, self-aligned contacts and high density MIM capacitors,” in VLSI Symp. Tech. Dig., pp. 131–132, 2012.

[2] Y. Wang et al., “Poly-Si Planarization by ICP Plasma Etch at FinFET Technology”, ECS Trans. 77(3), 71-76, 2017.
(Invited) Nitrogen Functionalization and Doping of Conductive Carbons By Means of Low Temperature Plasmas
Authors: Kovacevic Eva , Boulmer-Leborgne Chantal , Strunskus Thomas , Hussain Shahzad , Jagodar Andrea , von Wahl Erik , Sciaqua Dario , Tatarova Elena , Dias Ana , Cvelbar Uros , Berndt Johannes
Published: February 2020

Nanomaterials, such as nanocomposites, nanorods, nanotubes and graphenes, are nowadays almost past the title “novel materials”, they have been widely investigated and used as either promising or already proven materials for various applications ranging from electronics and black body coatings to fuel cells and supercapacitors. Such advanced nanomaterials, independently of their chemical composition, are also used for the delivery of therapeutic agents, including biomolecules targeting disease sites, for bioimaging, or in general for biomedical engineering.

This contribution presents several examples of plasma synthesized and plasma functionalized carbon based nanomaterials (nanostructures), CBNs, which nowadays play an important role for biomedical engineering, and in particular for the development of novel biosensors. The examples presented in this paper concern materials which are synthesized in low pressure RF plasmas from hydrocarbon precursors, like ethylene, with or without nitrogen presence during their growth. Most of the examples are vertically aligned graphene flakes. The post-treatment of these materials is performed in low pressure radio frequency capacitively coupled plasma and microwave plasma. In this contribution we will focus on surface treatment by nitrogen and ammonia plasma. The goal of such surface treatments with nitrogen containing plasma is doping and functionalization, very often simultaneously obtained. Plasmas were controlled by means of mass spectroscopy.

The method of choice for the analysis of the bonding situation of the materials before and after treatment in this presentation is near edge X-ray absorption fine structure spectroscopy (NEXAFS), and X ray photoemission spectroscopy (XPS) performed on HESGM beamline, HBZ Bessy II Germany.

Acknowledgments

The authors would like to acknowledge the support obtained by French National Research Agency via projects ANR PlasBioSens and PlasmaBond, APR Apropore, French Regionals support by APR Capt’Eau, and PIVOT. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 730872 (CALYPSO plus for the work at the HZB BESSY II synchrotron, Berlin, Germany) and grant agreement No766894 (FET-OPEN project PEGASUS).
(Electrodeposition Division Research Award) Electrodeposition of Semiconductor Films: Where Are We After Three Decades?
Authors: Rajeshwar Krishnan
Published: February 2020

This perspective talk focuses on the history and status of electrodeposition for preparing thin films of inorganic and organic semiconductors, metal/semiconductor junctions, or even nanocomposite materials containing different phases. The use of light brings an added dimension and versatility to the preparative strategy. Variants on the basic cathodic or anodic deposition protocols will be elaborated as are approaches that rely on the initial deposition and stripping of a precursor layer. Another topic is operando compositional analysis of the depositing layers using a combination of electrochemical techniques with other complementary probes such as spectroelectrochemistry, electrochemical quart crystal microgravimetry (EQCM), and AC impedance spectroscopy. Finally, state-of-the art and future challenges will be discussed using examples drawn from the author’s and collaborators’ laboratories.
(Invited) Electrophoretic Deposition of Energy Storage Metal Oxides
Authors: Penner Reginald
Published: February 2020

Electrodeposition is an attractive tool for synthesizing energy storage materials - such as transition metal oxides (TMOs) - for batteries and capacitors. A key advantage of electrodeposition is that the material of interest is synthesized directly on a metal or carbon current collector promoting an intimate, low resistance contact between the deposited material and the current collector. But electrodeposition methods have limited reach if a soluble form of the metal ion does not exist. LixNb2O5 is one technologically important TMO that falls into this category.

The electrophoretic deposition (EPD) process we have developed produces nanoporous, phase pure T-Nb2O5 films 38 nm to 144 nm in thickness. These films exhibit unusually high specific capacities, Csp (units: mAh/g). For example, films of 60 nm thickness produce Csp = 420 mAh/g at 5 A/g and 220 mAh/g at 50 A/g which is to be compared with a theoretical Faradaic capacity of 202 mAh/g. T-Nb2O5 films also produce impressive energy and power with specific energy from 770 - 486 Wh/kg, and specific power in the range from 9-90 kW/kg. It is important to add here that the accuracy of all of these mass-normalized metrics is insured by directly measuring the mass of these films using quartz crystal microbalance (QCM) gravimetry. Our investigation of T-Nb2O5 is still in its early stages, but the exceptional performance seen for these EPD T-Nb2O5 films is very encouraging. Our hypothesis is that EPD provides a general method for the synthesis of energy storage materials with signicant advantages relative to competing methods, including the ability to impart a controllable porosity and the ability to facilitate the enhancement of mechanical and electrical properties via compositing.

In this presentation, I will discuss this EPD process and our recent investigations of the mechanisms of degradation operating in the T-Nb2O5 films prepared using this process. Gold@T-Nb2O5 core@shall nanowires can also be obtained by EPD and the properties of these systems for electrical energy storage will be compared with those of T-Nb2O5 films. Finally, the lithiation/potential-dependent electrical conductivity of solid (non core-shell) T-Nb2O5 nanowires prepared by has been measured for the first time, in-situ. These data, showing variations in electrical conductivity by three orders of magnitude with lithiation state, will also be discussed.
(Invited) Electrodeposited Metallic Nanowires for Bioanalytic Nanofluidic Devices
Authors: Park Sunggook , Podlaha Elizabeth J. , Beheshti Mohammad , Choi Junseo , Li Deyang , Geng Xiaohua
Published: February 2020

Electrodeposited metallic nanowires have been demonstrated as electrode or sensing materials in many applications such as optoelectronic devices, energy devices, and biosensors due to their excellent electrical and optical properties. However, most of previous demonstrations utilized the metallic nanowires in the form of percolating networks. Individual nanowires also have potential as nanoscale electrodes or nanoscale sensing materials for the applications where electrical signals need to be extracted from nanoscale components of the device. In this sense, metallic nanowires are suitable electrode or sensing materials for bioanalytic nanofluidic devices where electrical signals from nanoscale single molecules need to be interrogated in a device with nanoscale components.

This talk will present strategies and technical challenges to be resolved in applying individual metallic nanowires in bioanalytic nanofluidic devices. While high rate synthesis of metallic nanowires can be achieved via electrodeposition in a nanoporous template, the main challenges to produce nanofluidic devices with individual nanowire electrodes include position and aligning the nanowires at designated locations and cover-plate bonding in the presence of electrode structures. Also, the efforts on device fabrication need to be combined with the effort on engineering nanowires with both sufficient mechanical strength and improved electrical conductivity, so that the nanowires are compatible with both the fabrication and operational protocols. This work is a part of the effort from the NIH Center for BioModular Multiscale Systems for Precision Medicine (CBM2) where the center goal is to design, produce and deliver to the medical community mixed-scale tools for analyzing circulating biomarkers for disease management for precision medicine
Electrodeposition of Bismuth Telluride from a Weakly Coordinating, Non-Aqueous Solution
Authors: Meng Lingcong , Cicvaric Katarina , Bartlett Philip N. , Han Yisong , Hussein Haytham , Sweeney Francis , Kashtiban Reza , Macpherson Julie , Hector Andrew L , Reid Gill , Smith David , Beanland Richard , Groot K.
Published: February 2020

Thermoelectric materials are of interest for converting waste heat to electricity and could be useful in applications such as power generation.1 Currently, bulk bismuth telluride (Bi2Te3) is the most commonly used material for thermoelectric coolers and waste heat recovery. However, theoretical calculation2 predicts that the thermoelectric performance of Bi2Te3 can be dramatically improved by confining its dimensions to the nanometre scale.

Electrodeposition provides a bottom-up technique compared to conventional coating methods, such as physical vapor deposition (PVD). It is of advantage in the efficient use of the starting material and can be used to plate curved surfaces and even inside of topologically demanding surfaces.3 The use of electrodeposition to fill nano-structures is also achievable, which is exploited in the Damascene process to grow 20 nm diameter Cu wire.4

In electrochemical experiments water is the most commonly used solvent but its limitation includes narrow potential window, which is crucial in electrodeposition as water reduction will be a competing process for metal reduction/deposition and introduces complexity to experiments. Here we employ an electrolyte system based on tetrabutylammonium chlorometallate metal sources with compatible tetraalkyl halide supporting electrolytes in non-aqueous, weakly coordinating solvents,5,6 which provides the ability to deposit alloys with desired structures and properties.

In this work we report the deposition of Bi2Te3 films from dichloromethane. Bi2Te3 is a narrow band gap layered semi-conductor and it is demonstrated that the composition and structure of the BiTe films can be controlled by tuning the electrochemical parameters, such as the electrolyte concentration and deposition potential (Figure 1).7 We then investigate Bi2Te3 nucleation and growth using transmission electron microscopy (TEM) with a boron doped diamond electrode, acting as the electron transparent substrate.8 We observe the initial stage of Bi, Te and BiTe nuclei after electrodeposition (from individual atoms to atom arrays and nanocrystals)

This work is conducted as part of the ADEPT project funded by EPSRC (EP/N035437/1).

[1] Materials 7.4 (2014): 2577-2592. [2] Physical review B 47.24 (1993): 16631. [3] Proceedings of the National Academy of Sciences 106.35 (2009): 14768-14772. [4] IBM Journal of Research and Development 42.5 (1998): 567-574. [5] Chemistry-A European Journal 22.1 (2016): 302-309. [6] RSC Advances 3.36 (2013): 15645-15654. [7] Journal of Electroanalytical Chemistry 839 (2019): 134-140. [8] ACS nano 12.7 (2018), 7388-7396

Figure 1
(Invited) The Electrodeposition of Porous Catalysts for CO2 Reduction
Authors: Ambrozik Stephen , Raciti David , Moffat Thomas P.
Published: February 2020

Electrocatalytic carbon dioxide reduction exhibits promise as way to combat anthropogenic climate change and convert CO2 into fuels and chemical feedstocks. The efficient reduction of CO2 requires a catalyst that operates at low overpotential, high turnover frequency and high selectivity. Recent trends in state-of-the-art CO2 reduction catalysis involve the utilization of high surface area porous and/or oxide derived catalysts to promote the reduction of CO2 to multi-carbon products. The activity and selectivity of these catalysts has been attributed to a variety of different structural, electronic and geometric aspects ranging from the presence of high energy grain boundaries following oxide reduction1, and residual subsurface oxygen2,3, to cascading reactions coupled with mass transport through the porous catalyst networks4,5,6. This work is focused on examining the effect of high surface area porous catalysts on CO2 reduction. The electrodeposition of high surface area catalysts with well-defined interconnected porosity will be demonstrated and CO2 reduction activity and selectivity will be tested with respect to the catalysts composition, thickness, and pore and ligament size.

References:

1.) Kanan, M. W., Nature
508, 504-507 (2014)

2.) Cuenya, B. R. al, Nature Comm.
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3.) Nilsson, A. al, J. Phys Chem. Lett., 8, 285-290 (2017)

4.) Surendranath, Y. al, J. Am. Chem. Soc.,
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5.) Broekmann, P. al, ACS Catal., 7, 5431-5437 (2017)

6.)Wang, C. al, Catal. Sci. Technol., 8, 2364-2369 (2018)
Room Temperature Chloroaluminate Deep Eutectic Solvents As an Electrolyte in Aluminium Rechargeable Batteries.
Authors: Ryder Karl S , Zaleski Christopher , Efimov Igor , Purnell Tomas
Published: February 2020

Novel chemistry of Deep Eutectic Solvents (DES) is a matter of current interest as the unusual properties of these solvents make them a versatile medium for a variety of reactions. In particular, they provide media with a wide potential window and high ionic strength for the redox chemistry of metals. A wide range of type II DES (Metal halide (MX) + Hydrogen Bond Donor (HBD)) with AlCl3 (MX) have been synthesised, where hydrogen bond donors (HBD) included acetamide, methyl-, dimethyl-, trimehylacetamide, urea, di- and tetramethylurea. The ratio of AlCl3 - HBD was maintained at 1.5:1 throughout. Viscosity and conductivity of these novel DES, have been related to the melting point of HBD as well as to the availability of proton exchanging groups. Mechanisms of aluminium deposition/dissolution from room temperature chloroaluminate melts were studied in order to elucidate the effects of amines type on the properties of these novel electrolytes. Mass transport and speciation were investigated by means of Electrochemical Quartz Crystal Microbalance (in dispersive mode), UV-Vis and NMR. It was found that although the higher deposition rate was proportional to the higher conductivity of the respective DES, the rate of the stripping process was related to the type of HBD used. Creation of an aluminium based battery requires a balance between current efficiency and deposition rate and this can be achieved by a choice of suitable HBD. The influence of surface tension of DES on their electrochemical properties, and ultimately availability of proton exchanging groups to participate in liquid formation is currently under investigation.

Figure 1
(Invited) From the Lab to Technical Scale—Aluminum Electroplating from Ionic Liquids
Authors: Gollas Bernhard
Published: February 2020

After several decades of intense research, room temperature chloroaluminate ionic liquids can now be considered a viable alternative to organic solvent-based alkyl-aluminum electrolytes for the commercial electroplating of aluminum [1]. While their possible use also includes electrochemical energy storage in secondary batteries [2], the development of chloroaluminate ionic liquid electrolytes was initially aimed at surface finishing [3], mainly for corrosion protection of steel. The properties of various combinations of Lewis acidic aluminum halogenides and Lewis basic organic halogenide salts have been established in numerous studies and the reaction mechanism of aluminum electrodeposition and dissolution has been explored, also by modeling [4]. In order to compete with the established SIGAL process [5], various aspects regarding the properties of the electroplated aluminum layers as well as practical issues of the plating process from chloroaluminate ionic liquids have to be addressed.

The morphology and structure of the aluminum layers correlate with their chemical and mechanical properties and must therefore be tailored to the respective application. Here, the current density and bath additives play a major role. Keeping in mind that the Lewis acidity of the electrolyte on the cathode surface has to be maintained, the limiting current can be maximized by adjusting the viscosity through co-solvents or temperature and by agitation of the bath. However, co-solvents as well as increased temperature might compromise the electrolyte stability [6]. Additives can be used as levelers, grain refiners, and/or brighteners. However, the highly reactive Lewis acidic mixture can severely limit their persistence and efficiency [7]. The pre-treatment of the substrate surface must be compatible with the water sensitive electrolyte and directly affects the adhesion of the electroplated layers. In addition, the post-treatment has to be adjusted to the reactive ionic liquid in order to maximize the layer quality.

These issues will be addressed in the talk showing examples from own work. Further aspects such as drag-out loss, bath maintenance, recycling, disposal, and cost, all relevant for a scale-up of the process, will be discussed.

[1] T. Tsuda, G. R. Stafford, and C. L. Hussey, J. .Electrochem. Soc., 164, H5007 (2017).

[2] G.A. Elia, K. Marquardt, K. Hoeppner, S. Fantini, R. Lin, E. Knipping, W. Peters, J.‐F. Drillet, S. Passerini, and R. Hahn, Adv. Mater, 28, 7564 (2016).

[3] F. H. Hurley and T. P. Wier, Jr., J. Electrochem. Soc., 98, 207 (1951).

[4] S. Schaltin, M. Ganapathi, K. Binnemans, and J. Fransaer, J. Electrochem. Soc., 158, D634 (2011).

[5] Y. Zhao and T. J. VanderNoot, Electrochim. Acta, 42, 3 (1997).

[6] P. Kosmus, O. Steiner, W. Goessler, and B. Gollas, Electrophoresis, 35, 1334 (2014)

[7] P. Kosmus, O. Steiner, W. Goessler, B. Gollas, and G. Fauler, Electrophoresis
37, 1095 (2016).