bluuebunny/crossref_metadata_2025 huggingface dataset:
Holistic Integrated Process Solutions for Patterning Phase Change Memory Devices
Authors: Hoang John , Shen Meihua , Lill Thorsten , Qian Danna , Routzahn Aaron , Chen Jack , Altieri Nick , Yu Anthony , Dulkin Alexander , Sims Jim , McKerrow Andrew , Dylewicz Rafal
Published: July 2021

Phase change materials (PCM) have emerged as the leading candidate for next generation non-volatile storage class memory as demonstrated by the commercialization of 3D Cross Point memory. More recently, PCM memories have been explored for non-von Neumann system architectures with potential applications in neuromorphic computing. To accelerate the widespread adoption of PCM technology, better understanding of the unit processes and its interactions is needed to cost effectively produce high fidelity PCM devices.

Challenges in creating cross point PCM architectures are significantly different from more dominant technologies such as DRAM and 3DNAND. From a device perspective, the PCM composition is sensitive to crystallization temperature, which translates to potentially large changes in the switching resistance for small changes in composition. From a material perspective, phase change chalcogenides readily etch in various plasma etch chemistries with the many etch chemistries exhibiting bulk composition changes. Furthermore, slight changes in the PCM composition can be removed by wet clean. In this regard, one of the main process challenges is to not etch chalcogenides laterally in order to maximizing the device volume. Finally, from a structural perspective, PCM are relatively soft with Young’s modulus that can be 3x smaller than materials found in DRAM/3DNAND stacks (e.g. Si, SiOx). Soft chalcogenides can lead to increased line bending, especially when the chalcogenide is at the bottom of the stack. As a result, post wet clean pattern collapse and line bending from film stress can be challenging to manage.

To meet the material and structural challenges, we developed an integrated system combining dry etch, wet clean, and deposition process modules. Comprehensive understanding of each process module as well as the interactions of different process modules has been obtained. We will present some holistic process solutions combining dry etch, wet clean, and deposition to deliver collapse free, high fidelity PCM structures.
Annealing Impact on the Evolution of Crystalline Phases and Emission in Si-Rich HfO2:Nd Films Obtained By Magnetron Sputtering
Authors: Vega-Macotela Leonardo Gabriel , Torchynska Tetyana , Rivero Dennis Dennis , Khomenkova Larysa , Gourbilleau Fabrice
Published: July 2021

Hafnium oxide ﬁlms doped with Si and Nd atoms have been produced by radio-frequency magnetron sputtering in pure argon plasma followed by an annealing in nitrogen atmosphere for 1-60 minutes at the temperature 1000 °C. The effect of post-deposition thermal annealing on the transformation of crystalline phases and photoluminescence spectra was investigated by the non-destructive methods (scanning electronic microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman scattering and photoluminescence(PL)). The XRD analysis of these samples demonstrate the phase separation process which depends on the time range and the annealing temperature. In the studed samples, the formation of the tetragonal HfO2, tetragonal SiO2 and cubic Si phases was observed by XRD and confirmed by the Raman study. Thermal annealing influents also on PL spectra where the main bands were detected at 380, 450, 550, 780 and 880 nm. The emission and excitation mechanisms for the Nd radiative defects, and the impact of phase transformation in studied films, are analyzed and discussed.
(Invited) Plasma Immersion Ion Implantation: Technology, Modelling, and Applications for Nanofabrication and 2D Materials
Authors: Bradley Michael P.
Published: July 2021

Plasma Immersion Ion Implantation (PIII) is an ion implantation technology in which the target to be implanted (i.e. a semiconductor wafer) is immersed in a plasma, and implanted with positive ions by the application of a high-voltage negative-bias pulse to the target. Because of the high plasma density achievable in modern plasma sources, large fluences can be implanted across large wafer areas, without beam scanning. PIII is well suited for a variety of nanofabrication applications. Because of its compatibility with ordinary silicon CMOS device processing, high fluence PIII is a versatile method for in situ fabrication of nanocrystals for integrated circuit applications. This talk will review the physics of energetic ions implanted into solid materials, and illustrate how post-implant thermal treatment can be used to form nanocrystals in the ion-implanted region. A number of potential applications of PIII as a materials synthesis technique will be discussed.
Mechanical and Optical Properties of Amorphous SiN-Based Films Prepared By ECR PECVD and CCP PECVD
Authors: Ahammou Brahim , Abdelal Aysegul , Levallois Christophe , Landesman Jean-Pierre , Mascher Peter
Published: July 2021

Hydrogenated amorphous silicon nitride (a-SiN:H) and silicon carbonitride (a-SiCN:H) films grown by plasma enhanced chemical vapor deposition (PECVD) are widely investigated for their interesting optical and electrical properties [1]. In this work, we discuss the effect of the deposition power on SiN-based films during plasma deposition. The influence on the optical and mechanical properties of the films was investigated. In order to study this issue on a broader basis, two types of plasmas were applied to deposit 0.5 to 1.5 μm a-SiN:H and a-SiCN:H films. First, a-SiN:H and a-SiCN:H films were deposited by electron cyclotron resonance (ECR) PECVD using the same deposition parameters for all films. During the deposition process, the carbon content in the a-SiCN:H thin films was introduced into the chamber through a pure CH4 gas source to avoid any perturbation on the deposition pressure. Second, a-SiN:H films were deposited by a capacitively coupled plasma reactor CCP PECVD using a SiH4/NH3/N2/Ar precursor mixture. In both deposition processes, the ion bombardment energy was tuned only by the deposition power. The mechanical properties of the films were determined ex-situ by profilometry to evaluate the residual stress using the wafer curvature method and by nanoindentation to determine Young’s modulus and hardness of the films. The thickness and the refractive index were measured by variable angle spectroscopic ellipsometry (VASE). It was observed that the evolution of the residual stress according to the deposition power in the ECR PECVD was different from the CCP PECVD. Besides, we notice a slight increase in the refractive index when the residual stress becomes more compressive as illustrated in figure 1 for a-SiN:H and a-SiCN:H films. Through this discussion, we try to have a better understanding of the different interactions taking place when the deposition power increases in terms of ion bombardment energy. Then, we will study the effect of ion bombardment on the film structure based on the composition and structure of the films and the hydrogen bond concentration measured by Fourier transmission infrared spectroscopy (FTIR). In addition, we have also investigated the influence of carbon incorporation on a-SiN:H thin film properties. We notice a decrease in the refractive index and an increase in the compressive residual stress caused by the carbon incorporation.

[1] A. Abdelal, Z. Khatami, and P. Mascher, “Optical and Electrical Properties of ECR-PECVD Grown SiCN Thin Films,” ECS Meet. Abstr., vol. MA2018-01, no. 17, p. 1189, Apr. 2018, doi: 10.1149/ma2018-01/17/1189.

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(Invited) Leveraging Reversible Chemistry for Materials Sustainability in Energy Storage
Authors: Chen Zheng
Published: July 2021

The development of next-generation energy storage devices and systems for electric vehicles (EVs) relies on materials with significantly improved performance and lower cost. The increasing amount of lithium-ion battery (LIBs) consumption will result in the resource shortage and price increase of lithium and precious transition metals (Co, Ni etc.); the wastes generated from disposal of used batteries can cause severe environment pollution. In this context, design of energy-efficient recycling and regeneration process for spent batteries is attracting growing interest. From a reversible chemistry point of view, this talk will introduce a potential strategy to directly recycle and regenerate spent LIBs using a “non-destructive” approach, which will lead to new electrode materials that can show the same level of performance as the native materials. Such a strategy combines fundamental understanding and process optimization for remanufacturing of energy materials. Therefore, it can potentially offer a sustainable solution for future energy storage.
(Invited) Nitrogen Fixation Using Non Thermal Atmospheric Plasma (over water) : Challenges and Perspectives
Authors: Maira Nicolas , Remy Antoine , Pattyn Cedric , Roy Nepal Chandra , Reniers François
Published: July 2021

Nitrogen fixation, i.e. the transformation of molecular nitrogen into nitrates or ammonia is a major industrial process. The Haber-Bosch and the Ostwald processes are at the origin of the massive increase of yield of food production, contributing to the development of modern agriculture. However, despite the fact that these processes are exothermic, the need to operate at high temperature for kinetic reasons, the necessity to start (most often) from natural gas as a source of hydrogen, and the industrial plants located far away from the end user, make these industrial processes huge producers of CO2.

Historically, the Birkeland-Eyde process, however, allow to fix nitrogen using arc plasma. The energy yield of this process being small, it was replaced by the Haber-Bosch process. With the development of low temperature, non thermal plasmas processes, there is nowadays a hope to develop local, low energy cost, nitrogen fixation reactors, with only air as reactant. For food and agriculture applications, especially for urban agriculture, a possible approach is to generate nitrates directly inside the water that feeds the plants. The talk will present a few non thermal atmospheric plasma setups than can be used for nitrogen fixation. In a first setup, nitrogen oxides are generated directly in a dielectric barrier discharge (DBD) filled with various proportions of nitrogen and oxygen. In a second setup, one of the dielectrics is replaced by water. In a third setup, a DC microplasma is lighted up between a metallic electrode and a water solution, containing an electrolyte. In this last setup, a counter electrode closes the electrical circuit, making it resembling a electrochemical cell. In this last setup, two configurations are tested, by changing the polarity of the two electrodes.

For all the setups, the amount of various nitrogen oxides formed in the gas phase as a function of the experimental parameters is studied using optical emission spectrometry, infrared spectrometry and mass spectrometry. Similarly, the composition of the liquid phase is analyzed using ionic chromatography and specific reagents tests. Correlations between a) the gas phase composition and b) the liquid phase composition are established. The role of OH radicals (in the gas phase) and hydrogen peroxide (in the liquid phase) on the relative amounts of nitrites and nitrates is evidenced. For the microplasma experiments, it is shown that inverting the polarity of the electrodes lead to drastic changes in the yields of the species produced. From all these results, potential mechanisms will be presented, and future challenges will be open to discussion.
(Invited) Silicon Nanosheets as Candidates for Silicon-Based Optoelectronics
Authors: Ryan Bradley J. , Diroll Benjamin T. , Guo Yuqi , Dolgos Carly J. , Wang Qing Hua , Roling Luke T. , Panthani Matthew G
Published: July 2021

Colloidal Group IV nanomaterials (Si, Ge, Sn and their alloys) are of great interest due to their potential to offer broadly tunable optical properties. By manipulating composition, size, or surface chemistry Group IV nanomaterials have potential to serve as nontoxic, earth abundant phosphors or semiconductors that can be used for optoelectronic applications that span the ultraviolet to the mid-infrared spectral ranges. The synthesis of colloidal Group IV nanostructures is challenging due to the highly covalent character of Si and Ge, and typically require temperatures in excess of 400°C to form crystalline particles. We have recently reported new synthetic methods for Si and Ge nanomaterials derived from precursors synthesized in the solid-state, including suboxides and Zintl phases. In each of these cases, colloidal nanostructures can be accessed by selectively removing unwanted components from the solid-state precursor, liberating nanostructures that are terminated with atomic or molecular species such as hydrogen atoms or methyl groups. We also characterize the structural properties of the Group IV nanostructures that we synthesized using a combination of infrared spectroscopy, solid-state NMR, and pair distribution function analysis to confirm the structure and order. In the case of Si and Ge, single-atom thick nanosheets were synthesized, their stability and decomposition at elevated temperatures were characterized. The optical properties of Group IV nanomaterials have sparked debate over the past few decades. We found that Si nanosheets exhibit fast (nanosecond) photoluminescence lifetime, which is several orders of magnitude greater than Si nanocrystals, and offer potential explanations for the observed difference. Finally we show that Si and Ge nanocrystals and nanosheets can be used for sensing applications, including infrared photodetectors and ionophore-based sensing schemes.
(Invited) Synthesis and Optoelectronic Applications of Colloidal Nanorod Heterostructures
Authors: Shim Moonsub
Published: July 2021

Engineering band structure and heterointerfaces has been and continues to be critical for advances in electronics, optoelectronics, photovoltaics, and displays among many high-tech applications. Achieving atomic precision through widely-accessible and cost-effective means would allow rapid advances in these critical areas. The evolution of colloidal semiconductor nanocrystals from single-composition, “spherical” particles to complex heterostructures of diverse shapes provides many opportunities for precision band structure engineering through scalable solution synthesis. With anisotropic shapes that can be exploited for assembly, charge carrier manipulation and optical anisotropy, etc., incorporating heterojunctions and other functional interfaces into colloidal nanorod heterostructures represents an especially promising direction. In this talk, general challenges to the synthesis of complex-yet-well-defined colloidal nanorod heterostructures will first be discussed. Approaches such as spatially selective solution epitaxy, catalytic growth, cation exchange and combinations thereof can be exploited to achieve unique heterostructures with useful properties. Examples of colloidal nanorod heterostructures of II-VI as well as I-III-VI semiconductors will be discussed. In addition, light-emitting diodes (LEDs) incorporating these materials are shown to not only radically improve existing function but also impart new capabilities without adding complexity in manufacturing.
(Keynote) Nanocrystal Design and Self-Assembly in Service of Heterogeneous Catalysis
Authors: Murray Christopher B. , Rosen Daniel , Lee Jennifer D , Elbert Katherine C. , Hammel Benjanin
Published: July 2021

Colloidal nanocrystals (NCs) with tunable electronic, optical, properties and rich opportunities for surface functionalization are impacting many areas of heterogeneous catalysis. In this talk, I will briefly outline the current state of the art in synthesis, purification, and integration of single-phase NCs and core-shell (heterostructures) and heterodimer nanocrystals (Janus) NCs emphasizing the design of semiconductor building blocks with tunable shapes (spheres, roads, cubes, discs, octahedral in combination with transition metal NCs. Complimentary NC sizes and shapes will be used to create binary, ternary NC superlattices providing a scalable route to the production of multi-functional catalytic films. The modular assembly of these NCs allows the desirable features of the underlying quantum phenomena to be retained and enhanced even as the interactions between the NCs allow new photocatalytic applications and enhanced electrocatalytic behavior to emerge. Synergies in the electronic and optical coupling between NCs will be emphasized. The programing of metal and metal oxide NC architectures using dendron based surface ligands will be explored as a route to create new organic/inorganic hybrid materials that preserve accessibility for small reactants to active NC surface sites while the chemical affinity if the organic pocket in which the NC sits is modified.
(Keynote) Charge Transfer-Mediated Sensitization of Lanthanide Ions By a Perovskite Quantum Dot Host
Authors: Chang Woo Je , Irgen-Gioro Shawn , Weiss Emily A.
Published: July 2021

Lanthanides are narrow-linewidth sources of intense emission, and their complex electronic structure allow for non-linear processes such as quantum cutting. Their extinction coefficients are however extremely low, so their emission needs to be sensitized by a neighboring chromophore or host matrix. This talk describes a mechanism for photosensitization of lanthanide ions (Ln3+) substitutionally doped into CsPbCl3 colloidal quantum dots (QDs). This mechanism involves a charge transfer intermediate state, QD+-Ln2+, resulting from photoinduced electron transfer from the excitonic state of the QD to Ln3+. Transient absorption spectroscopy helps to confirm this mechanism and obtain rate constants for the various photophysical processes within these systems.
(Invited) Heating-up Synthesis of Lead Free, Perovskite-Related Colloidal Nanocrystals
Authors: Paik Taejong , Lee Minji , Lee Donguk
Published: July 2021

Colloidal nanocrystals are widely used in various applications such electronic devices, phosphors, lasers, magnets, and catalysts. The synthesis of highly uniform nanomaterials with controlled size, shape, and compositions is paramount to precisely understand their size-, shape-, and composition-dependent physical and chemical properties. Here, I will describe novel materials chemistry to synthesize lead-free perovskite-related nanocrystals with precise control of their compositions. The synthesis of nanocrystals is performed via injection-free, heating-up method in the presence of a solvent mixture with a high boiling point. We present synthetic method to systematically tailor structure and composition of highly uniform and phase-pure perovskite-related nanocrystals and investigate photoluminescence properties depending on their structure and compositions.
(Invited) Controlling Synthesis and Functionalization of Anisotropic Gold Nanoparticles for Applications in Biology
Authors: Fabris Laura
Published: July 2021

Anisotropic gold nanoparticles, such as, for instance, nanorods and nanostars, have been integrated in many areas of biomedical research, including, but not limited to, imaging, sensing, and therapy. While the use of gold has remained relatively consistent due to, primarily, its biocompatibility, the choice of morphology to employ has depended on the intended application. Regardless of the application, attention must be paid toward the definition of best practices for the synthesis, functionalization, and characterization of nanoparticles, especially when they need to be interfaced with the biological milieu.

In my talk, I will report on our recent observations concerning the design of gold nanostars to target the biologically transparent window of the electromagnetic spectrum, the optimization of synthetic monodispersity to improve single cell applicability, and the careful control of relevant bioconjugation steps that need to be implemented to realize functional intracellular biosensors. I will focus in particular on the synthesis of highly monodispersed gold nanostars with resonant bands extending up to 2000 nm, on the use of surfactant free nanostars for the design of surface enhanced Raman spectroscopy (SERS) nanoprobes for the stratification of prostate cancer patients, and the use of tunable silica shell to increase stability of the nanostars while also enhancing their SERS response. I will also report on the effect of the protein corona on the performance of fluorescent flares and SERS beacons for the identification and quantification of influenza A virus (IAV) RNA both in buffer and in individual intact cells.

Despite the broad applicability of anisotropic gold nanoparticles, often a complete understanding of their properties and the steps needed to reproducibly and accurately achieve them is lacking. Due to the intrinsic complexity of the biological milieu, the consistency of the probes used to understand it is even more imperative and thus requires even more synthetic control. I will therefore, in conclusion, present some tips and guidelines that will hopefully stimulate an interactive conversation on the topic.
(Invited) Effects of Coordination Structure of Silicon Ions on Electrodeposition Process of Silicon in Fluoride Melts
Authors: Suzuki Yuta , Fukunaka Yasuhiro , Goto Takuya
Published: July 2021

Silicon electrodeposition in molten salts is a key technology for fabricating silicon films, as a material for solar cells, by environmentally friendly and inexpensive processes. We have already reported the electrodeposition of silicon films from SiO2 in fluoride melts. However, there are only few studies about the effects of ions in fluoride melts, such as O2- anion, and Li+/Na+/K+ cations, on silicon electrodeposition processes. In particular, it is important to understand the coordination structure of silicon ions for controlling the nucleation and growth processes between solid metal substrates and fluoride melts interface.

In this study, we investigated the electrodeposition of silicon from SiO2 in LiF-NaF-KF melts mixed with Li2O as a source of O2- anion at 873 K, and binary LiF-KF, LiF-NaF, and NaF-KF melts. The results of the in-situ Raman spectroscopy and DFT calculations indicated that the O2− anions could cleave the Si-O-Si bonds of SiO2 or silicate ions such as [Si2O5]2−; consequently, the formation of tetrahedron [SiO3F]3− species was promoted. Furthermore, the reduction currents, attributed to the reduction of Si ions, increased significantly by the addition of Li2O; moreover, the thickness and current efficiency of the electrodeposited polycrystalline Si layer prepared by potentiostatic electrolysis was improved. This study suggested the design of the molten salts bath was significant for controlling interfacial phenomena at electrode/molten salts to fabricate high-quality Si layers.
(Invited) Surfactant Mediated Electrochemical Deposition: Principles and Extensions
Authors: Moffat Thomas , Braun Trevor Michael , Josell Daniel
Published: July 2021

Historically speaking, and to the present day, the commercial success of thin films has much to do with the ability of surfactants to yield smooth bright surfaces. The microelectronics industry has provided significant motivation for the development of a more fundamental understanding the role electrolyte additives in electrochemical deposition, one obvious example being the innovations related to superconformal growth for 3-D Cu interconnects. This talk will provide an overview of the combined use of electroanalytical and surface science techniques to gain insights into surfactant mediated growth processes. Going further still, the knowledge garnered from investigations, that were originally focused on understanding Cu electrodeposition for interconnects, have been, and continue to be, extended to other metals and chemical systems with important applications ranging from microsystems to batteries to electrocatalysis.
Alternative Metals for Advanced Interconnects: Cobalt and Beyond
Authors: Rigsby Matthew A. , Spurlin Tighe A. , Reid Jonathan D.
Published: July 2021

Concerns about the extendibility of copper as an interconnect conductor for future technology nodes have resulted in increasing interest in alternative conductor metals.1 With ever-decreasing interconnect dimensions, alternative metals bring hope of improved resistivity and reliability through more favorable electron scattering and cohesive energy and the possibility of improved scaling through barrier layer removal.2,3 Cobalt, in particular, has been the subject of several recent studies and has already found its way into at least one major semiconductor manufacturer’s scheme as a replacement for tungsten in trench contacts.4 Considerable work has focused on understanding the cobalt electrofill process to enable its implementation in current interconnect technology.5–8 While conventional copper damascene plating uses a three-additive system, cobalt superfill can be achieved while using only one organic component, with the hydrogen evolution reaction having been shown to also play a role.5,7,8 Recently, we have demonstrated that boric acid is also an important component of cobalt plating baths.6 As shown in Figure 1, boric acid forms a series of polyborate species in solution as a function of both concentration and pH. Presence of the polyborates is correlated with pH buffering under typical cobalt electroplating conditions, preventing precipitation of cobalt hydroxide and improving nucleation within the features. Just as the cobalt electrofill process represents a departure from the established damascene copper plating techniques, development of processes for other alternative metals for future technology nodes will require new and creative formulations and methods to overcome electroplating challenges for these metals.

K. Lin, M. Chandhok, and M. Reshotko, in 2018 IEEE International Interconnect Technology Conference (IITC), p. 2–3, IEEE, Santa Clara, CA, USA (2018) https://ieeexplore.ieee.org/document/8430404/.

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M. A. Rigsby, T. A. Spurlin, and J. D. Reid, J. Electrochem. Soc., 167, 112507 (2020).

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C. H. Lee, J. E. Bonevich, J. E. Davies, and T. P. Moffat, J. Electrochem. Soc., 156, D301 (2009).

Figure 1: Raman spectra showing speciation of (a) 10 g/L and (b) 40 g/L boric acid in water as a function of pH.6

Figure 1
Mapping Adsorbates with Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy to Understand Rapid Superconformal Filling of Cu Trenches
Authors: Raciti David , Hight Walker Angela , Moffat Thomas
Published: July 2021

Additive adsorbates are widely used as surfactants to guide morphological and microstructural evolution during electrochemical deposition of thin films. Even though this strategy has been employed for several decades understanding of the mechanisms at play on the interface remain limited. Modern spectroelectrochemical methods, from surface-enhanced Raman spectroscopy (SERS) to surface-enhanced infrared spectroscopy (SEIRAS) and non-linear optical methods like sum frequency generation (SFG) can provide significant insight into the composition, structure, and dynamics of the surfactant adsorbates through their vibrational signatures. on nominally static surfaces. Each strategy is limited to specimen geometry; SERS is closely linked to the use of rough, plasmonically-active surfaces while SEIRAS measurements are constrained to thin, IR-transparent, metallic films. In the last decade, a significant advance was the introduction of nanoparticle reporters, based largely on silica coated Au nanoparticles, that enable Raman spectroscopy studies on well-defined, single-crystal surfaces whereby the nanoparticle serves to channel the plasmonic energy to the nanoparticle-substrate interface. The silica or alternative coating materials are designed to be inert with respect to the chemistry of the adsorbate species under study while remaining thin enough to allow effective focusing of the optical energy. This approach has been adopted by several researchers interested in understanding molecular adsorption on well-defined, single-crystal surfaces, the electrical double layer, and numerous aspects of reactivity related to catalysis, batteries, electrodeposition, etc. The present work demonstrates the use of Au@SiO2 (core-shell) nanoparticles, also known as SHINERS (Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy), to enable in situ vibrational spectroscopic measurements during electroplating of comparatively smooth, rapidly advancing, surfaces. In particular, the ability of the reporters to float on an advancing surface while responding to area change is used to reveal important, area-driven changes in adsorbate coverage. This study also opens a new avenue for exploring the intersection of analytical surface chemistry and composite electroplating.

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Understanding the Relationship between State-of-Charge and Structural Fragility in Ni-Rich Layered Materials for Lithium Batteries
Authors: Waters Crystal K. , Lin Feng
Published: July 2021

Lithium batteries are at the frontier of energy storage. Co-free, Ni-rich layered transition metal oxide (TMO) materials have gained interest within the past decade due to their low cost and increased practical capacity. The challenge with employing these layered oxide cathodes is their inherent structural fragility, facilitated by metal cation migration and lattice oxygen loss. Upon charging, the redox center becomes oxidized, generating thermodynamically favorable electron transfer pathways between the electrolyte and the layered oxide. This transfer pathway is mainly due to the TM3d-O2p orbital hybridization perturbation during battery charging.

Surface reconstruction and the structural reordering that accompanies it can undesirably influence the cathode – electrolyte interphase, leading to enhanced electrolyte degradation pathways that can minimize Coulombic efficiency. Electrolyte decomposition occurs at the oxide cathode surface, but can lead to bulk electronic and structural changes of the layered oxide, chemomechanical breakdown, and irreversible phase transformations.

In this study, we focus on understanding the interplay between bulk phase transitions and surface instability with respect to electrolyte chemical decomposition. We use novel galvanostatic cycling parameters, extensive electron microscopy, and synchrotron X-ray techniques to decouple chemical and electrochemical electrolyte decomposition pathways to understand their role in Co-free, Ni-rich oxide cathode degradation. This work allows us to decouple surface and bulk chemistries at the cathode – electrolyte interphase to inform further insight into optimal Ni-rich oxide cathode design.
(Invited) Towards Model-Based Predictive Battery Electrode Design
Authors: Krewer Ulrike , Witt Daniel , Schmidt Oke , Röder Fridolin
Published: July 2021

Lithium ion batteries contain porous electrodes, whose design determines battery performance, cost and life-time.

Yet, we are far from knowing what is the best structure, and it is prohibitively time- and resource-consuming

to do experimental trial and error production, as there are too many parameters in the production process and in the electrode itself.

This motivates to use physico-chemical models that yield insight into performance and limitations of given electrode structures as well as

allow optimal design. The need for models that allow structure optimisation, i.e. rapid evaluation of many design variants, basically excludes large 3-dimensional models with complex inhomogeneous structures. On the other hand, homogeneous pseudo-two-dimensional models face limitations regarding the prediction of new electrode designs as the crucial influence of conducting additives and binder are not considered sufficiently.

This talk will elucidate a pathway that allows model-based predictive battery design.

It shows the application of microstructure models to identify the effective electric and ionic conductivity and electroactive area of

electrode structures containing additives, and the transfer of this knowledge via surrogate models into electrochemical P2D models to evaluate the respective electrochemical performance. The effect of additive and active material content and distribution is demonstrated at the example of Li ion battery cathode and all solid state Li battery electrodes. The models are applicable to predict the performance of electrodes in cells. We further elucidate how uncertainties in the production process of electrodes lead to distributed electrode design parameters and performance.

Finally, we show and compare two pathways of identifying optimal electrode designs at the example of dual layer electrodes: a coarse-grained scanning of thousands of design variants using 8 parameters reveals strongly different designs for optimal charge and discharge, whereas a high resolution optimisation of two design parameters shows flat performance plateaus.

Model-based design optimization without extensive experimental studies will reduce costs and experimental efforts in the development of next-generation batteries.
(Invited) Graphene-Based Materials for Sensing Applications
Authors: Merkoci Arben
Published: July 2021

Graphene-related materials (GRM) such as graphene oxide (GO) and graphene quantum dots (GQDs) display advantageous characteristics with interest for building innovative biosensing platforms and even smart devices such as nano/micromotors for a myriad of uses including sensing. Quenching of the fluorescence induced by GO or photoluminescence of GQDs can easily operate in synergy with various other nanomaterials and platforms opening the way to several unprecedented biosensing strategies and unique nanomotor technologies. Taking advantage of GRMs we are developing simple, sensitive, selective and rapid biosensing platforms that include: a) GO – based microarray & laterals flow technologies taking advantages of high quenching efficiency of GO. A “turn ON by a pathogen” device will be shown as a highly sensitive detection system using plastics or paper/nanopaper substrates; b) GQDs–based sensors for contaminants detection based on the use of multifunctional composite materials that enable rapid, simple and sensitive platforms in connection to smartphone; c) electroluminescent-based approaches d) A water activated GO transfer technology using wax printed membranes for fast patterning of a touch sensitive device with interest for electronic devices including sensing as well as for a cost-efficient nanomotor building technology for several applications. This work is supported by EU (Graphene Flagship), CERCA Programme / Generalitat de Catalunya.
Electrodeionization of Organic Acids Using Porous Bipolar Resin Wafers
Authors: Jordan Matthew Leo , Palakkal Varada Menon , Lin Yupo , Arges Christopher G. , Valentino Lauren
Published: July 2021

Organic acids are valuable precursors for synthesizing specialty chemicals and monomers for bio-degradable plastics. These chemicals often originate in complex bio-oil and fermentation mixtures making capture of these species challenging. This talk presents material innovations of the porous ion-exchange resin wafers used in electrodeionization (EDI) for targeted removal and purification of organic acids. The new porous conductors consisted of anion- or cation-exchange resins that were immobilized in a wafer format with anion- or cation-exchange ionomer binders. The adoption of ionomer binders over the conventional polyethylene binder enhanced ionic conductivity of the resin wafers. Interestingly, differences in ionic conductivity between the porous anion and cation resin wafers were ascribed to the ratio of ionic mobility values of the counterions they transferred. With the new materials in-hand, single anion and cation-conducting resin wafers were appended together with a water dissociation catalyst at the interface. These layered resin wafers constituted a Janus bipolar resin wafer; and when deployed in EDI, they were able to raise the diluate stream’s pH value by 3 to 4 units while also removing other anions. Raising the pH above the pKA of organic acids ionizes these species making them susceptible for transport under applied electric fields and purification in resin-wafer EDI. Overall, the new porous, Janus bipolar resin wafers are promising materials for extracting organic acids from liquid streams that have a low concentration of total dissolved solids (i.e., other ionic species).

Figure 1
Heuristic Strategy for Achieving Long-Term Cycle Stability for Ni-Rich Layered Cathodes at Full Start of Charge
Authors: Kim Un-Hyuck , Sun Yang-Kook
Published: July 2021

The demand for energy sources with high energy densities continues to push the limits of Ni-rich layered oxides that are currently the most promising cathode materials in Li-ion batteries.1-3 Although most current research is focused on extending battery’s cycle life using Ni-rich layered cathodes,4 long-term cycling stability using a practical full cell is yet to be demonstrated. Here, we introduce Li[Ni0.90Co0.09Ta0.01]O2 which maintains 90% capacity retention after 2,000 cycles at full state of charge (SOC) with an energy density > 850 Wh kg−1. In contrast, the currently most sought-after Li[Ni0.90Co0.09Al0.01]O2 cathode loses ~40% of its initial capacity within 500 cycles at full SOC. Cycling stability is achieved by radially aligned primary particles with crystallographic texture toward the particle surface that effectively dissipate the internal strain occurring in the deeply charged state,5,6 while the substitution of Ni3+ withhigher valence ions induces ordered occupation of Ni ions in the Li slab and stabilizes the delithiated structure.

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Park, K.-J. et al. Adv. Energy Mater.
8, 1801202 (2018).

Ryu, H.-H. et al. Materials Today
36, 73–82 (2020).
High-Energy Density W-Doped Ni 95% Layered NCA Cathodes for Next-Generation Lithium-Ion Batteries
Authors: PARK Jeonghyeon , Kim Un-Hyuck , Sun Yang-Kook
Published: July 2021

The Li[Ni0.8Co0.15Al0.05]O2 (NCA) cathode has become commercialized because it provides high capacity with long cycle life. To further increase the capacity of existing NCA cathodes, the content of Ni in the NCA cathode has been progressively increased; however, this approach is limited by the capacity fading and safety concerns.1-4 Here, we report fundamental electrochemical performances of W-doped Li[Ni0.95Co0.04Al0.01]O2 cathode (W-NCA95) with columnar grains by introducing “W”.5 The microstructure-modified W-NCA95 delivers a high initial capacity of 242 mAh g–1 (0.1 C) and retains 77.4% of its initial capacity after 1000 cycles, compared to 14.5% for Li[Ni0.95Co0.04Al0.01]O2 cathode (NCA95). The outstanding cycling performances of the W-NCA95 cathode are attributed to the reduction of the anisotropic volume change and the unique long rod-shaped primary particles morphology. The proposed W-NCA95 cathode paves the way for the development of Ni-rich layered cathodes that can exhibit high capacity, superior cycling stability, and improved thermal stability.

H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources 233 (2013) 121-130.

Watanabe, M. Kinoshita, T. Hosokawa, K. Morigaki, K. Nakura, J. Power Sources 258 (2014) 210-217.

S. Yoon, H.-H Ryu, G.-T. Park, J.-H. Kim, K.-H. Kim, Y.-K. Sun, J. Mater. Chem. A 6 (2018) 4126-4132.

J.-H. Kim, S. J. Kim, T. Yuk, J. Kim, C. S. Yoon, Y.-K. Sun, ACS Energy Lett. 3 (2018)

U.-H. Kim, D.-W. Jun, K.-J. Park, Q. Zhang, P. Kaghazchi, D. Aurbach, D. T. Major, G. Goobes, M. Dixit, N. Leifer, C. M. Wang, P. Yan, D. Ahn, K.-H. Kim, C. S. Yoon, Y.-K. Sun, Energy Environ. Sci. 11 (2018) 1271-1279.
Anodic Stability of Electrolyte Solvents and Additives at the Ni-Rich NMC Cathode-Electrolyte Interface in Li-Ion Batteries
Authors: Dose Wesley M. , Allen Jennifer P. , O'Keefe Christopher A. , Temprano Israel , Björklund Erik , Weatherup Robert S. , Grey Clare P. , De Volder Michael F. L.
Published: July 2021

One of the key challenges facing Li-ion batteries with Ni-rich layered cathodes is the poor interfacial stability at both electrodes. Several recent reports have investigated the reactivity of the electrolyte at the surface of LiNixMnyCo1-x-yO2 (NMC) as a function of Ni content and electrolyte composition,1,2 but many of the complex processes taking place are not fully understood. In this work, we use a rapid electrochemical-based screening protocol3 to quantify the anodic stability of single-solvent electrolytes and additive-containing electrolyte solutions with respect to the fraction of Ni in the NMC cathode. The current that flows during a high voltage hold at 4.6 V vs Li/Li+ is found to be sensitive to the NMC surface chemistry, the degree of delithiation, and the composition of the electrolyte. Post-test XPS, solution NMR, and online electrochemical mass spectroscopy (OEMS) are combined to study the electrode- and electrolyte-dependent degradation products that are insoluble on the surface of the electrode, soluble in the electrolyte, and released as gas. The insights from quantification of the electrolyte anodic stability and the degradation signatures identified through this work highlight the importance of developing unique solutions to lower the interfacial reactivity of Ni-rich cathodes, which is a critical step to prolong the cycle life of high-energy Li-ion batteries.

References

Y. Zhang, Y. Katayama, R. Tatara, L. Giordano, Y. Yu, D. Fraggedakis, J. G. Sun, F. Maglia, R. Jung, M. Z. Bazant, Y. Shao-Horn, Energy Environ. Sci., 13, 183, 2020.

J. Wandt, A. T. S. Freiberg, A. Ogrodnik, H. A. Gasteiger, Mater. Today, 21, 825, 2018.

A. Tornheim, S. E. Trask, Z. Zhang, J. Electrochem. Soc., 163, A1717, 2016.
Optimization of 2-D Spatial Distributions of Pore Sizes, Platinum Content, and Nafion Amount in PEMFC
Authors: Lamb James , Andrei Petru
Published: July 2021

Proton exchange membrane fuel cells (PEMFCs) provide a key technology to enable the transition to a zero-emission economy. In transportation applications, PEMFCs allow high-efficiency conversion of fuel to electricity, long range, and rapid refueling, all without pollution, noise, or other undesirable effects. However, cost remains one of the largest barriers to widespread adoption of PEMFC technologies. The goal of our research is to reduce PEMFC cost by optimizing the performance of the cell.

In this presentation we focus on the numerical optimization of the microstructure of the anode and cathode catalyst and gas diffusion layers in low-temperature PEMFCs. Our approach consists of discretizing realistic PEMFC structures numerically and solving the following optimization problem on a finite element grid [1]:

max
V(μPt, μN, μC, μ∈)

μPt(r), μN(r),

μC(r), μ∈(r)

where V is the voltage of the cell at a specified current density, μPt, μN, μC, and μ∈ are the two-dimensional spatial distributions of the platinum, nafion, and carbon contents, and porosity, respectively. The above problem is solved using a modified steepest descent method in which the gradients of the cell voltage with respect to the local values of the platinum, nafion, carbon, and porosity distributions are computed efficiently using an adjoint method [2, 3]. The numerical algorithm is implemented in our finite element simulator, RandFlux [4], in which the derivatives of transport equations with respect to the state variables and the adjoint operator are computed efficiently using automatic differentiation.

The figures present the optimized distribution of the platinum, nafion, pore fraction, and carbon as a function of the location in the cathode catalyst layer for a standard PEMFC with a membrane thickness of 25 mm, GDL thicknesses of 250 mm, and catalyst layer thicknesses of 15 mm. The 2-dimensional PEMFC is symmetric with respect to y=0.5 mm, has the opening between y=0.25 mm and 0.75 mm; the membrane is toward the left side of each figure, the gas diffusion layer (GDL) is toward the right side. The optimization was performed in order to increase the polarization of the cell at a current density of 0.5 A/cm2. We observe that it is optimum to increase the density of the platinum particles and the amount of the electrolyte near the membrane side of the catalyst layer and, in the same time, increase the porosity and carbon fraction near the gas diffusion layer. More results about the technique, the numerical implementation, and a number of fully optimized cells will be presented at the meeting.

References

Lamb and P. Andrei, ECS Transactions, 98, 67 (2020).

J. Lamb, G. Mixon and P. Andrei, Journal of The Electrochemical Society, 164, E3232 (2017).

J. Lamb and P. Andrei, ECS Transactions, 97, 671 (2020).

RandFlux, Florida A&M University and Florida State University, http://www.eng.famu.fsu.edu/ms/RandFlux.

Figure 1
Molecular Dynamics of Electrostatic Channeling on the Surface of Malate Dehydrogenase-Citrate Synthase
Authors: Xie Yan , Calabrese Barton Scott
Published: July 2021

Multi-enzyme catalytic cascade reactions exist in many metabolic pathways in nature; the benefits of these reactions include high efficiency and reduced time and labor costs [1].The design and application of efficient cascade reactions in biofuel cells, sensors, and chemical conversion requires an understanding of intermediate channeling between adjacent cascade active sites. Electrostatic channeling, for example, utilizes electrostatic force to control the direct transfer of charged intermediates [2]. Here, we study the electrostatic channeling of an oxaloacetate (OAA) intermediate between malate dehydrogenase (MDH) and citrate synthase (CS) active sites within the tricarboxylic acid (TCA) cycle.

The MDH-CS supramolecular assembly includes a positively charged surface between neighboring active sites that guides the movement of the negatively charged oxaloacetate, thus improving the transfer efficiency [3].To study the interaction between OAA and the charged enzyme surface and identify OAA’s transfer pathways, we simulated this system using molecular dynamics (MD). Specifically, since both MDH and CS have two identical subunits and thus two active sites, we ran 50 MD simulations for 10 ns near each of the four active sites, resulting in 200 parallel runs of simulations. Then we analyzed the resulting MD dataset with a Markov State Model (MSM) [4].We identified multiple energy basins in MSM, including four active site basins, a desorption basin, and an intermediate basin. MSM successfully predicted the the transition rates between those energy basins and identified the dominant transport pathways of OAA from MDH to CS. The visualization demonstrates that the dominant transport pathway crosses Arg65, providing further support for the experimental observation that Arg65 plays an critical role in the electrostatic transport process of OAA [3].This study improves the field’s understanding of natural substrate channeling mechanisms and can help with the design of artificial cascade reactions.

References

K. C. Nicolaou, D. J. Edmonds, and P. G. Bulger, Angew. Chemie - Int. Ed., 45, 7134–7186 (2006). doi:10.1002/anie.200601872.

I. Wheeldon, S. D. Minteer, S. Banta, S. Calabrese Barton, P. Atanassov, and M. Sigman, Nat. Chem (2016). doi:10.1038/NCHEM.2459

B. Bulutoglu, K. E. Garcia, F. Wu, S. D. Minteer, and S. Banta, ACS Chem. Biol., 11, 2847–2853 (2016). doi:10.1021/acschembio.6b00523

F. Noé, C. Schütte, E. Vanden-Eijnden, L. Reich, and T. R. Weikl, Proc. Natl. Acad. Sci. U. S. A., 106, 19011–19016 (2009). doi:10.1073/pnas.0905466106

Figure 1