bluuebunny/crossref_metadata_2025 huggingface dataset:
Supramolecular Assembly of Nitrogen-Containing Curved π-Conjugated Molecules to Polar Crystal
Authors: Hiroto Satoru , Wakita Mana
Published: August 2024

The chemistry of curved π-conjugated molecules has been extensively studied because of the development of their synthetic approach. Among the numerous studies, we have been engaged in nitrogen-containing curved π-conjugated molecules. These molecules have extended optical properties, redox-active behaviors, and electron-donating ability due to the electron-rich nature of nitrogen atoms. Recently, we have focused on the supramolecular assembling behavior of these compounds. For example, we have reported buckycatcher consisted of two azabuckybowls, providing two-photon absorbing host-guest complexes with fullerenes. In this presentation, we would like to show the packing behavior using π-extended azahelicenes and azabuckybowls. Our group has developed π-extended aza[5]helicene derivatives, showing brilliant emissive features. Recently, we succeeded in the synthesis of unsymmetrically substituted azahelicenes. We found that their stackings in the crystal were dependent on the substituent. X-ray diffraction analysis for all products showed π-stacked conformation with each other in the crystal (Figure 1b). In particular, azahelicenes with triisopropylsilyl groupswere found to align their dipole moments to form a one-dimensional columnar structure in the crystal. Polar crystals are expected to have applications in ferroelectric, piezoelectric, and nonlinear optical response materials. This is the first example of a polar crystal with helicenes, paving the way for novel piezoelectric organic materials.

The second topic is related to azabuckybowl. In the crystal, azabuckybowl forms a face-to-face dimer by concave-convex interaction. In this study, we prepared two types of azabuckybowl perylene bisimide (PBI) dyads connected with alkyne linkages. PBIs have also been reported to show columnar stacking in solution. We anticipated that the segregate stacking should be achieved by recognizing the difference in structures between the bowl and planar geometry. The UV/vis absorption spectra revealed the presence of intramolecular charge-transfer interaction. In addition, the concentration-dependent absorption spectra and 1H NMR spectra indicated PBI and azabuckybowl units stacked with each other independently in solution (Figure 1a). Here, we would like to discuss about the effect of the effect of molecular shape on the supramolecular assembly with the data obtained using these compounds.

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Charge-Transfer Spectroscopy and Electrochemistry of Transition-Metal Phthalocyanines
Authors: Nemykin Viktor , McNicholas Brendon
Published: August 2024

Charge-transfer spectroscopy of the selected transition-metal phthalocyanines will be discussed in conjunction with their electrochemical properties. Specifically, UV-Vis and magnetic circular dichroism (MCD) spectra of the PcFe(II)L2, PcRu(II)L2, PcMn(III)LX, and PcCr(III)LX (L is a neutral and X is a monoanionic ligand) will be discussed in terms of their metal-to-ligand (MLCT) and ligand-to-metal (LMCT) charge-transfer spectroscopy determined by the experimental UV-Vis and MCD as well as theoretical (time-dependent density functional theory) methods. Lever's EL scale was used to predict and correlate the MLCT and LMCT transitions in transition-metal phthalocyanines.
(Digital Presentation) Using Quantum Information Theory to Quantitatively Distinguish between Resonant Energy Transfer and Charge Transfer Interactions in Porphyrin Crystals
Authors: Malcioglu Baris , Pusuluk Onur
Published: August 2024

Quantum discord is a concept in quantum information theory that measures the quantum correlations between two subsystems in a system. Unlike traditional measures of quantum entanglement, quantum discord captures all types of quantum correlations, including those that do not necessarily involve entanglement. It quantifies the information that is lost when measuring one subsystem. The GW formalism is a powerful theoretical framework for calculating electronic excitation energies and quasiparticle properties in condensed matter systems. The GW formalism can be used to calculate a variety of electronic excitations, including quasiparticle band structures, optical excitations and plasmon excitations. Chemically relevant information from GW calculations can be accessed using Wannier orbitals which are a set of localized orbitals that describe the behavior of electrons in a periodic solid, and has the advantage of being a complete set. In this work, we propose the use of quantum discord concept to quantify different types of correlations between maximally localized Wannier orbitals obtained through GW calculations in order to infer whether an excitation is a resonant energy transfer excitation or a charge transfer excitation.
Method to Independently Measure the Electronic and Ionic Conductivity of Zinc Slurry Electrodes
Authors: Kathan Devadharshini , Mustain William Earl
Published: August 2024

Zn-MnO2 alkaline batteries are prevalent and reliable primary batteries due to their cost effectiveness, good safety characteristics, long shelf life and ability to deliver sustained power for continuous usage. This properties make alkaline batteries an ideal options to be used in remote controls, smoke detectors, wireless mice, toys and many portable electronic devices. Despite their advantages, the battery performance is constrained by the slurried Zinc anode. Because of this, researchers have prioritized the improvement of the anode, primarily aiming to enhance the capacity and stability of the active material. However, the actual behavior of the anode is limited by the ionic conductivity of Zinc slurry, which is several orders of magnitude lower than the electronic conductivity of the slurry. This causes the reacting front to begin at the anode-separator interface, leading to passivation of the anode, incomplete discharge and increased gassing.

The utilization of Zinc in the slurry anode can be increased by bringing the values of ionic conductivity and electronic conductivity closer together. Unfortunately, due to the redox electrolyte mechanism that moves electrons through the anode [1], the literature does not have an established method that is able to independently measure the ionic and electronic conductivity of the slurry. Before methods can be proposed to improve ionic conductivity of slurry, a method must first be devised that is able to truly measure the ionic conductivity in isolation.

In this study, a novel methodology is reported to quantify both the ionic and electronic conductivity of the slurried anode. This innovative approach aims to provide a deeper understanding of the complex interconnection between electronic and ionic conductivities of the Zinc slurry. By addressing this critical aspect, the research contributes to advancing the fundamental understanding of Zn-MnO2 alkaline batteries, potentially paving the way for significant improvements in their performance and reliability for a wide array of applications.

References

[1] E. Faegh, T. Omasta, M. Hull, S. Ferrin, S. Shrestha, J. Lechman, D. Bolintineanu, M. Zuraw and W.E. Mustain, “Understanding the Dynamics of Primary Zn-MnO2 Alkaline Battery Gassing with Operando Visualization and Pressure Cells”, J. Electrochem. Soc., 165 (2018) A2528-A2535
Investigating the Influence of Sintering Temperature and Ascertaining Hopping Path in Sodium Superionic Conducting Electrolytes for Sodium-Ion Batteries
Authors: Tiwari Anurag , Kumar Singh Rajendra Kumar
Published: August 2024

Recently, sodium super-ionic conducting (NASICON) type solid electrolytes have gained significant interest as potential candidates for next-generation batteries due to their exceptional properties such as high ionic conductivity, affordability, and remarkable chemical and electrochemical stability. Therefore, NASICON type solid electrolyte (Na3Zr2Si2PO12) is synthesized by solution assisted-solid state reaction (SA-SSR) method and sintered at three different temperatures, 1200 ℃, 1250 ℃ and 1300 ℃. Various experimental techniques are used to characterize and optimize the sintered electrolytes. The Rietveld refinement of X-ray diffraction pattern of prepared electrolytes revealed the monoclinic crystal structure having 3-dimension hopping channel for sodium ion migration through triangular bottleneck area. Complex impedance spectroscopy revealed, the highest bulk and grain boundary conductivity are found, 4.05 mS cm-1 and 0.31 mS cm-1, respectively, for the sample sintered at 1250 ℃. Using optimized electrolyte, sodium half-cell is demonstrated with Na3V2P3O12 (NVP) as cathode. The assembled cell delivers maximum discharge capacity 101.6 and 84.45 mAh g-1 at the current density 10 and 40 mA g-1, respectively with good capacity retention (~95.02%) upto 50 cycles.

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Aligned Semiconducting Carbon Nanotubes for Commercial Logic and RF Electronics
Authors: Jinkins Katherine , Arnold Michael S. , Foradori Sean
Published: August 2024

Carbon nanotubes are exceptional semiconductors that offer larger current densities and faster switching than conventional Si and GaAs devices, making nanotubes promising for meeting the performance and energy efficiency needs of next-generation electronics. However, the successful commercialization of carbon nanotubes necessitates the control over semiconducting purity, alignment, packing density, and scalability. The simultaneous control of these characteristics has been a major challenge preventing the integration of nanotubes in industrial electronics and the full exploitation of their electronic properties. This talk will present an overview of recent technological developments and methods that progress towards these goals.

In these methods, semiconducting (purity of >99.99%) carbon nanotubes are deposited on target substrates via scalable alignment methods at room temperatures. These individual methods separately enable the deposition of quasi-aligned (±28°) nanotube arrays (~50 nanotubes µm-1) demonstrated across 100 mm substrates, highly-aligned (±6°) nanotube arrays (~100 nanotubes µm-1) demonstrated across 100 mm substrates, and the selective-area deposition of highly-aligned nanotube (±7°) arrays (~up to 250 nanotubes µm-1). The nanotube arrays with high packing density (~250 nanotubes μm-1) yield exceptional current densities of 2 mA μm-1 and transconductances of 1 mS μm-1 at VD of -0.6V. Importantly, due to the low-temperature nature of the deposition processes, these techniques offer a direct path towards the alignment of carbon nanotubes directly on Si and other materials, such as GaN or plastics, to enable high-performance 3D integrated circuits.
Unlocking the Capability of the Lithium Metal Battery Anode through Organofluorine Additives
Authors: Fukuda Ryuichi , Maniyanganam Ahamed Irshad , Prakash G. K. Surya G. K. , Narayan Sri
Published: August 2024

Metallic lithium as the anode material in batteries offer extraordinarily high specific capacity and low electrochemical potential, allowing lithium metal batteries (LMBs) to achieve gravimetric energy densities unobtainable by traditional intercalation-based chemistry. However, one must control the morphology and composition of its solid electrolyte interphase (SEI) in order to suppress the growth of separator-piercing Li dendrites and combat electrolyte depletion. Here, we find the usage of small amounts of organofluorine additives to the commercial ethylene carbonate and diethyl carbonate (EC-DEC) electrolyte mixture improves the specific capacity and capacity retention (>99% over 100 cycles at C/3 rate) of LiNi8.15Co1.5Al0.35O2 (NCA) LMB cells. Esters, carboxylic acids, and ketoesters with various degrees of fluorination were explored as potential electrolyte additives.

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Synthesis and Modular Engineering of Porous Graphene Nanoarchitectures
Authors: Mugarza Aitor
Published: August 2024

Bottom-up nanoarchitectonics has demonstrated the capability to control structural parameters of nanomaterials with atomic precision. The surface-assisted synthesis of graphene-based one-dimensional nanostructures à la carte distinctly illustrates the power of this concept. However, despite impressive advances in the synthesis of 1D homostructures, advancing in structural complexity faces major challenges. However, despite impressive advances in the synthesis of 1D homostructures, advancing in structural complexity faces major challenges. The functionalization of edges in nanorib-bons, an effective strategy to tailor their electronic properties and chemical interactions, is a clear example. The concept of inserting the desired functional groups or dopants in the molecular precursor often fails due to their lack of stability during the reaction path. The fabrication of heterostructures is a second example, where the challenge lies on the control of the size and distribution of their com-ponents. A third one is extending the on-surface strategy to two-dimensional structures, where examples of long-range ordered nanoarchitectures are very limited.

In this talk I will present different strategies that we have developed to overcome each one of this challenges. I will show introducing our method to synthesize a 2D nanoporous graphene, where the long-range order is achieved by the sequential growth of 1D building blocks and their posterior coupling [1]. I will continue presenting two modular strategies that lead to more complex nanoporous structures. The first consist on the molecular engineering of the coupling bridges. I will show an example where the introduction of phenyl groups in the bridges brings tunability of the quantum electronic coupling and the corresponding in-plane electronic anisotropy [2]. In a final example I will focus on intercalating different 1D ribbon components in periodic arrays for the formation of lateral heterostructure superlattices where the junction is defined with atomic precision [3]. One of the components being a N-doped ribbon, the heterostructure can also be seen as a nanoporous graphene sheet bearing N-doped pores.

References:

Moreno et al., Science 360, 199–203 (2018).

Moreno et al., J. Am. Chem. Soc. 145, 16, 8988–8995 (2023).

Tenorio et al., Adv. Mater. 2110099 (2022).
Engineering Topological States in Nanographenes
Authors: Fischer Felix Raoul
Published: August 2024

Our research focuses on the rational design, deterministic assembly, and detailed investigation of the physical phenomena emerging from quantum confinement effects in graphene nanomaterials. We pursue a highly integrated multidisciplinary program, founded on synthetic bottom-up approaches toward functional materials with precisely defined structure. We control their assembly into hierarchically ordered architectures and evaluate inherent physical properties using modern scanning probe techniques cross multiple length, time, and energy scales. We recently demonstrated the rational design and experimental realization of a graphene nanoribbon (GNR) superlattices that hosts a 1D array of symmetry-protected topological states, thus generating otherwise inaccessible electronic structure.1 This new class of materials can be thought of as an extended form of poly-acetylene wherein highly localized half-filled topological states replace the familiar single occupied p-orbitals along a conjugated π-system. Experimental results and first-principles calculations reveal that the frontier band structure of these GNR superlattices is defined purely by the coupling between adjacent topological interface states and can be tuned all the way from a semiconductor and a metal.2,3 This novel manifestation of 1D topological phases presents an entirely new route to band engineering in 1D materials based on precise control of their electronic topology and is a promising new platform for future studies of 1D quantum spin physics and metallicity in low dimensional carbon nanomaterials. 1. Topological Band Engineering of Graphene Nanoribbons. Rizzo, D. J.; Veber, G.; Cao, T.; Bronner, C.; Chen, T.; Zhao, F.; Rodriguez, H.; Louie, S. G.; Crommie, M. F.; Fischer, F. R. Nature
2018, 560, 204-206. 2. Inducing Metallicity in Graphene Nanoribbons via Zero-Mode Superlattices. Rizzo, D. J.; Veber, G.; Jiang, J.; McCurdy, R.; Cao, T.; Bronner, C.; Chen, T.; Louie, S. G.; Fischer, F. R.; Crommie, M. F. Science
2020, 369, 1597-1603. 3. Robust Metallic Zero-Mode States in Olympicene Graphene Nanoribbons. McCurdy, R. D.; Delgado, A.; Jiang, J.; Zhu, J.; Wen, E. C. H.; Blackwell, R. E.; Veber, G. C.; Wang, S.; Louie, S. G.; Fischer, F. R. J. Am. Chem. Soc.
2023, 145, 15162-15170.
Understanding the Kinetics of Cation Insertion-Coupled Electron Transfer in Thin Film Electrodes from Cyclic Voltammetry
Authors: Chagnot Matthew , Abello Sofia , Wang Ruocun , Dawlaty Jahan M , Rodriguez Lopez Joaquin , Zhang Chao , Augustyn Veronica
Published: August 2024

Cyclic voltammetry is a powerful technique for probing the electrochemical kinetics of energy storage materials. However, interpretation of the cyclic voltammetry kinetics of such materials has been limited by the application of analytical solutions initially developed for ion blocking electrodes, whereby mass transport is limited to semi-infinite diffusion in the electrolyte medium. Here, we utilize established numerical simulation models for finite diffusion coupled with experimental results of a model insertion electrode to demonstrate the relationship between solid-state diffusion and cyclic voltammetry current, peak potential, and capacity. This simulation is publicly available.1 We show that the cyclic voltammetry response of thin film electrode materials undergoing solid-solution ion insertion without significant Ohmic polarization can be explained with finite diffusion. Specifically, we investigate the kinetic behavior of Li+ insertion-coupled electron transfer into thin films of orthorhombic Nb2O5. We observe a general trend in the b-value, a descriptive parameter derived from the relation ip=avb between peak current ip and scan rate v. We find that both in simulation and experiment, we can tune the b-value response between the theoretically limiting values of 0.5 and 1 based on the solid-state diffusion characteristics of the thin film and the experimental timescale. We also show that b-values below 0.5 are possible, and arise due to a combined effect of the potential window of the experiment and confined diffusion. Our findings show the power of a simple 1D finite-diffusion model for predicting the kinetic response of an electrode undergoing ion-coupled electron transfer, and help to inform on how the scan rate selection in voltammetry experiments affects the observed kinetic behavior.

https://github.com/mchagnot/Numerical_CV_Sim_1D_Diffusion
Developing Online ICP-MS Methodology for Examining Catalyst Degradation Dynamics during Electrochemical CO2 Reduction
Authors: Yan Katherine , Hannagan Ryan T. , Lee Sang-Won , Matthews Jesse E , Yap Kyra M. K. , Kamat Gaurav A. , Lee Dong Un (Daniel) , Stevens Michaela Burke , Nielander Adam C. , Jaramillo Thomas F.
Published: August 2024

The electrochemical CO2 reduction reaction (CO2RR) provides a path towards sustainable production of carbon-based fuels and chemicals, using renewable electricity to drive the conversion of CO2 into products such as ethylene, ethanol, and methane. A challenge limiting the implementation of CO2RR is catalyst stability during operation, and greater fundamental understanding is needed to uncover the governing physical, chemical, and electrochemical factors, as well as degradation mechanisms, operative under reducing conditions. One tool that can be used for conducting such fundamental studies is online inductively coupled plasma mass spectrometry (ICP-MS). In this study, an experimental framework was developed for using online ICP-MS for time-resolved degradation studies during CO2RR conditions. Using a customized flow cell setup, we coupled an ICP-MS to a potentiostat to simultaneously apply a potential or current while evaluating dynamics and degradation for both Au and Cu catalysts. Both ionic dissolution and degradation in the form of nanoparticle detachment can be detected and analyzed. The presence of nanoparticles is indicated by spikes in ICP-MS data. The intensity of the spikes is directly related to particle size. We used ICP-MS to determine particle mass, size distribution, and cumulative mass loss over time. We found the use of ICP-MS to obtain particle size distribution gave comparable results to transmission electron microscopy (TEM) determination of particle size distribution.

Au foil as the CO2 reduction catalyst was used as a model system for detecting and quantifying degradation in situ using ICP-MS. We found Au degradation to occur in the form of nanoparticle detachment, with increasingly negative applied potential (0 V vs RHE to -1 V vs. RHE) in the presence of CO2 leading to increased number of nanoparticles in the electrolyte; however, no ionic dissolution was observed. In comparison, when the electrolyte was saturated with N2, nanoparticles detached from the electrode at a lower rate than in CO2-saturated conditions. We also examined Cu degradation under the same conditions as the Au system. Cu degradation occurs as both ionic dissolution and nanoparticle detachment, but under all conditions, Cu has less nanoparticle detachment and cumulative mass loss due to nanoparticles than Au. The developed experimental framework in this study would be translatable to a variety of electrocatalytic reactions and environments. Examination of catalyst degradation behavior in situ, including non-traditional degradation mechanisms such as nanoparticle detachment from bulk materials, can be used to obtain greater fundamental understanding of degradation mechanisms and rational design of materials with improved stability.
Multimodal Characterization of AM316 Crevice Corrosion
Authors: Hangarter Carlos M , Geltmacher Andrew B , Tailleart Nicole R. , Callahan Patrick G , Watring Dillon , Olig Scott M.
Published: August 2024

Non-destructive 3D characterization techniques are particularly important for materials synthesized by advanced manufacturing techniques that display disparity from their namesake identifiers (e.g. UNS S31600 or SS316). This is a particular concern for non-equilibrium materials, such as additively manufactured (AM) alloys, that often contain porosity, surface roughness, phases, microstructures and internal stress not exhibited in wrought or cast counterparts. This work examines chemical, electrochemical and microstructural evolution of AM and wrought SS316 under a crevice corrosion configuration. These results include chronoamperometric signatures, potentiometric sensors to track pH and X-ray computed micro-tomography 3D reconstructions during crevice corrosion. In-situ measurements are combined with initial and post-mortem SEM and EDS to better understand two AM316 materials that exhibit ennobled and more active behavior relative to wrought SS316. Local composition and phase heterogeneity at different length scales is shown to be a primary driver for contrasting crevice corrosion performance.
Comparing the Corrosion Behavior and Microstructure of a WE43 Mg Alloy in Simulated Body Fluids Under Different CO2 Conditions
Authors: Yang Chen-Hsun , Chang Hung-Ying , Chu Peng-Wei
Published: August 2024

With the low density and high specific strength, magnesium (Mg) alloys are lightweight alloys with various applications. In addition, combined with biocompatibility, similar mechanical properties to human bones, and unique biodegradability, Mg alloys are promising biodegradable implant materials for orthopedic surgeries. However, the degradation rates of Mg alloys are too fast in physiological environments, which limits the clinical applications of Mg implants. Therefore, understanding the corrosion behavior in physiological environments is crucial for developing biodegradable Mg alloys.

During Mg alloy degradation, hydroxide (OH-) ions are generated, and the pH near the alloy surface increases. Since carbonate-bicarbonate (CO3
2--HCO3
-) is a vital pH buffer system in the human body, the corrosion behavior of Mg alloys would be affected by the CO2 concentrations of the test environments. In this study, we performed electrochemical and corrosion tests of a solution heat-treated WE43 (Mg-4 wt%Y-3 wt%Nd) alloy in Hanks’ balanced salt solutions (HBSS) at 37°C. By performing the tests in air and in an incubator maintained at 5% CO2, the effect of carbonate-bicarbonate pH buffering on the corrosion behavior and corrosion microstructure of the WE43 Mg alloy was investigated.

When testing the WE43 Mg alloy in air, a general corrosion morphology was observed during the 24-hour immersion. In contrast, WE43 Mg alloy tested in the incubator shows a more active surface potential and localized corrosion initiates on the alloy surface in the early stages of immersion. Electrochemical impedance spectroscopy (EIS) analysis shows that WE43 Mg alloy tested in air has better corrosion resistance than in the incubator. Furthermore, the corrosion resistance of the alloy tested in air increases with immersion time but decreases when tested in the incubator. Potentiodynamic polarization curves after 24-hour immersion confirm that the corrosion current density (i
corr) of the WE43 Mg alloy tested in the incubator is higher than that when tested in air. The difference in corrosion behavior is owing to the carbonate-bicarbonate pH buffering effect and will be discussed based on corrosion microstructure characterizations.

Figure 1
(Invited) Battery Safety and Self-Quenching Battery Pack Concept: D3 (Dissipate, Direct, and Douse Heat and Fire)
Authors: Pannala Sreekanth , Li Tingwen
Published: August 2024

Battery pack safety following an individual cell runaway is an important aspect to address as we pack more energy into a small volume and mass. Thermal runaway incidents are extremely rare but can be catastrophic. The runaway can be triggered by local overcharge, thermal or mechanical abuse.

In this talk, we will first go into the details of thermal runaway initiation and propagation. Second, solution to quench the thermal runaway from propagating within the cell through a novel and passive detection of incipient thermal runaway temperature via thermoplastics will be introduced; and that is followed by discussion on the coolant release trigger to quench the runaway. In addition, this solution prevents propagation from cell-to-cell and reduce the chance for secondary combustion. This solution also leverages the fast thermal conductivity that is offered by the Cu and Al current collectors within the cell. The role of current collectors in relaying the information from the source of thermal runaway to the surface of the new format cell will be discussed.

The solution proposed here is chemistry agnostic and can be adapted to applications such as in transportation of cells and packs, grid energy storage, and mobility. The talk concludes by describing the next steps and value chain partnerships to make this safer solution a reality.

Below is an image that shows the self-quenching battery concept.

Figure 1
Chemistry and Formation of Solid-Electrolyte Interphase (SEI) at Li-Metal Potential
Authors: Yu Weilai , Cui Yi , Bao Zhenan
Published: August 2024

Li metal batteries (LMBs) have long been considered a solution to address the energy density limitations of Li-ion batteries. However, the widespread adoption of LMBs has faced challenges due to operational issues, notably safety concerns arising from the formation of Li dendrites and uncontrolled reactivity at the interfaces, leading to continuous consumption of the electrolyte. To enhance the reversibility of the Li-metal anode (LMA), a promising approach has emerged involving the development of a novel liquid electrolyte comprising an ether solvent and LiFSI salt. Notably, this electrolyte formulation has achieved impressive Coulombic efficiency (CE) values surpassing 99.5%. Despite this progress, the underlying causes of Coulombic inefficiency (CI) and its connection with the formation of a solid-electrolyte interphase (SEI) on the Li metal surface remain inadequately understood.

Gaining fundamental insights into these essential processes occurring during continuous cycling of the LMA can provide valuable guidance for optimizing CE more effectively. This presentation focuses on recent advancements that systematically unravel the underlying chemistry and formation of SEI derived from FSI anions at the interface of the Li metal anode in contact with various liquid electrolytes. By employing a non-washing protocol and a Cu current collector, we successfully captured and identified crucial reaction intermediates from SEI chemistry, enabling precise determination of the decomposition pathway for FSI anions. Our discoveries unveil a dynamic scenario at the electrode/electrolyte interface, where these reaction byproducts can significantly dissolve into the liquid layer, and their relative solubility dictates their role in passivating the electrode surface. Furthermore, we demonstrate a strong correlation between faster interfacial passivation in higher-performing electrolytes and the reduced solubility of diverse inorganic species within the liquid electrolyte. These fresh insights into SEI chemistry and formation open new avenues for enhancing LMA performance by mitigating undesired side reactions at the interface.
(Invited) Metal Corrosion Mitigation in Fine Geometries during Chemical Mechanical Planarization
Authors: Tseng Wei-Tsu , Motoyama Emiko , Chu Pinlei , Malley Matthew , Canaperi Donald
Published: August 2024

In the Si semiconductor industry, aggressive device geometry scaling has given rise to new processing challenges to each new technology nodes over the past 6 decades. When the feature size shrinks to nanometer regime, new phenomenon emerges whereby significant loss in metal vias and lines can be observed after CMP.

Findings from our previous studies suggest just a few nanometers of metal loss imposes serious yield loss in sub-5nm technology nodes MOL and BEOL metallization. Post CMP clean process can be responsible for ~ 50% of the metal loss after CMP. The phenomenon was observed with W, Co, and Cu alike. It affects conductors as well as liner/barrier metals, and exhibits strong dependence on pattern density, feature size, and even underlying layer. [1, 2]. Properly formulated slurries and post CMP clean chemicals can modulate the amount of metal loss and partially alleviate the issue.

In this study, we continue to assess how post CMP clean chemicals and modified de-ionized water can influence the amount of metal loss for Cu interconnects. As a starter, blanket wafers resembling several different Cu/liner/low-k stacks were evaluated. The were subjected to polish with the same alkaline slurry followed by various alkaline post clean chemicals (Clean 1, pH ~ 10.2; Clean 2, pH 9.8). It was observed on the attached figure that brush clean only process with DIW alone can induce small amount of Cu loss. For wafers with polish and post clean, on a comparison basis, Clean1 resulted in slightly more Cu loss than Clean2. However, when dilute NH4OH solution (pH ~ 9.6) was introduced to replace DIW during brush clean with Clean1, the amount of Cu loss is reduced, on par with that of Clean2. The observation suggests NH4OH-treated DIW can help alleviate part of Cu loss during post CMP clean process. Patterned wafers with various combination of liner stacks will be subjected to clean process with various combinations of chemistries and/or NH4OH-treated DIW. The amount of Cu or liner loss will be characterized.

References:

[1] R. Patllola et al., “Copper Metal Loss in Nanometer Fine Features during Chemical-mechanical Planarization”, ICPT (2022).

[2] W.-T. Tseng et al., “Nano-scale Metal Loss during Chemical-mechanical Planarization”, ICPT (2023).

Figure 1
Electrochemical Cell Design and Operation for Copper Recovery from Chemical Mechanical Polishing Slurries
Authors: Landon James , Rassoolkhani Alan , Dunn Collin , Rentschler Jeffrey , Lippert Cameron , Caridi Adam T. , Keleher Jason J.
Published: August 2024

Copper (Cu) removal from chemical mechanical polishing (CMP) waste is critical to maintaining discharge compliance with local municipalities and the Environmental Protection Agency (EPA). Typical treatment of this waste stream has followed two conventions: either coagulant-based precipitation or ion exchange (IX).1 Many industries use iron-based coagulants for metal removal from wastewater to meet discharge compliance. However, the process is often cumbersome, requires long settling times and significant chemical utilization, and results in a sludge stream that must be shipped and disposed of properly, eliminating the possibility for metal recovery. Since the concentrations for Cu removal from CMP waste streams is normally low (<100 ppm), IX has generally been the preferred treatment method. Nevertheless, IX also has some negatives associated with the process. Hydrogen peroxide can and will damage the IX media, resulting in premature replacement. The industry has dealt with this impact by employing one-time use media, but this adjustment means that media is only used once before being shipped offsite for regeneration. This results in operational impacts due to the need for oversight of media replacement and also eliminates the ability for Cu to be recovered at the originating process site.

In this talk, electrochemical methods to recover Cu from CMP wastewaters will be described. Electrochemical cell design and operation will be shown to provide Cu removal across wide ranges of concentration, and the depth of Cu separation (<2 ppm) and efficiency of the process will be discussed. The presence of hydrogen peroxide and its influence on the process will be evaluated. The removal and recovery of Cu will be shown in a complete cycle, demonstrating the ability to recover and reuse Cu directly at a process site. The impact of (1) pH, (2) chelator type, and (3) abrasive (SiO2) will also all be reviewed. Changes to the slurry, as analyzed pre- and post-electrochemical separation, will be characterized to determine possibilities for the reuse of the CMP slurry itself. Ultimately, the ability to design process systems using electrical input and minimal chemical additives to treat wastewater to municipal and EPA specifications while maximizing recycling efforts will be evaluated and presented.

References:

E. Speed, Environmental Aspects of Planarization Processes, S. Babu (Ed.), Advances in Chemical Mechanical Planarization (CMP), Woodhead Publishing, 229-269 (2016).

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(Dielectric Science and Technology Division Poster Award, 1st Place) Effects of Gas Dissolved Water for Ceria Nanoparticles on the SiO2 Film Surface in Post-CMP Cleaning
Authors: Park Kihong , Jeon Wookyung , Liu Pengzhan , Jeon Sanghcuk , Park Sanghyun , Kim Taesung
Published: August 2024

In the semiconductor industry, there is a growing trend of using smaller ceria nanoparticles (CNPs) during the Swallow Trench Isolation (STI) CMP process. However, the use of these CNPs has made it more difficult to clean residual particles from the SiO2 film surface after CMP. This study aimed to investigate the effects of gas-dissolved water (GDW) on CNP surfaces and the mechanical cleaning effects of nucleated bubbles applying megasonic conditions. The study found that CNP surface was reduced by H2 GDW and CO2 GDW, but oxidized by O2 GDW. The concentration of Ce3+ ions on CNP surfaces changed from 18.64% to 19.48%, from 20.31% to 21.94%, and from 21.27% to 19.22% when CNPs were respectively immersed in H2 GDW, CO2 GDW, and O2 GDW for 3 to 12 hours. Adhesion energy between CNPs and SiO2 particle surface, following immersion of CNPs in H2 GDW, CO2 GDW, and O2 GDW for 6 hours, was found to be 6.06E-16 J, 6.18E-16 J, and 4.83E-16 J, respectively. After cleaning with GDW and applying megasonic, residual Ce ion concentrations on the SiO2 film surface were found to be 0.06 ppb, 0.41 ppb, and 0.10 ppb for H2 GDW, CO2 GDW, and O2 GDW, respectively.
(Invited) Design of Reduced Shear Force Cu Cleaning Processes Via α-β-Unsaturated Chemistries for Enhanced BTA Residue Removal
Authors: Caridi Adam T. , Dudek Abigail , Cahue Tatiana R. , Keleher Jason J.
Published: August 2024

As integrated circuit and logic devices continue to decrease, limiting induced defectivity during Chemical Mechanical Planarization (CMP) processes (polishing and substrate cleaning) is imperative. Defects resulting from the CMP process can be classified as mechanical (i.e., scratching), chemical (i.e., corrosion), or physiochemical (i.e., adsorbed contaminants) according to the mechanism of formation. Traditionally, a contact cleaning method implements a polyvinyl alcohol (PVA) brush to transfer cleaning chemistry to the substrate of interest and provides the necessary mechanical energy for defect removal. While this process effectively removes contaminants, its reliance on shear forces can induce secondary defect modes, such as scratching. One major challenge for the post-CMP cleaning of Cu substrates is the polymeric residue film comprised of BTA-Cu+ complexes that propagate during the CMP polishing process. The current and most effective mode to mitigate this “residue defect” is coupling brush-induced shear force with additives that promote interfacial redox reactions to remove residues through an undercutting mechanism. This work focuses on developing a “softer” and additive structure-based approach that drives less aggressive interfacial shear between the brush and wafer substrate. More specifically, α-β-unsaturated additives with diverse functionality (i.e., -unsaturated carboxylic acids, carboxylic acids, and unsaturated benzaldehydes) will be tested to evaluate their efficacy to “overcut” the organic residue via a proposed aza-Michael addition reaction pathway. This “overcutting” mechanism relies on additional modes of interaction (i.e., p-stacking, H-bonding, conformational relationships, etc.) with the BTA- Cu+ polymeric residue film. A suite of dynamic techniques (i.e., Tafel analysis, OCP vs. time, contact angle, additive diffusion analysis, and shear force) will attempt to correlate the additive structure and reaction mechanism to organic residue removal efficiency and measured interfacial shear forces. Initial results have shown that implementing an “overcutting” mechanism will decrease the overall shear force and significantly reduce the generation of secondary defects without sacrificing overall defect removal efficiency.
Total Holographic Characterization of Large Particle Contaminants in Chemical Mechanical Polishing (CMP) Slurries
Authors: Philips Laura A , Cheong Fook Chiong
Published: August 2024

Nanoparticle slurries are widely used in semiconductor CMP processing. Accurately evaluating quality attributes of CMP slurries can be challenging for standard optical methods. Ceria slurries can be too optically dense and inhomogeneous for most optical measurements. Diluting the slurry can induce agglomeration or break up the agglomerates already present in the slurry. Previous studies of silica CMP slurries demonstrated that Total Holographic Characterization (THC) is effective for monitoring agglomeration in slurries. THC uses particle holograms to determine particle size and composition. Ceria nanoparticles have higher refractive indexes than silica nanoparticles, and produce more scattered light, which can reduce the signal of measurements of agglomerates, making accurate, reproducible measurements more challenging. Ceria slurry was successfully analyzed at concentrations typically used in semiconductor processing. Effective-medium theory is used to understand the variation in refractive index of large particle contaminants as compared to native slurry nanoparticles and other contaminants such as pad debris.
Overview and Potential Solutions of Current and Future Challenges in CMP
Authors: Dandu Veera , Amanapu Hari Prasad , Penigalapati Dinesh , Chiuchiarelli Pietro
Published: August 2024

This talk is dedicated to the special session in honor of Prof. Babu

Shrink of critical dimensions and stringent technology specifications are posing several planarization challenges in technology development (TD) and high-volume manufacturing (HVM) phases of current and advanced technology nodes. In this talk, we will focus on process challenges related to achieving (a) minimum defects (b) high planarization efficiency with less than 1nm dishing (c) tighter WIW and WID uniformities (d) ultra-smooth post-CMP surface roughness in the order of sub-nanometer. In addition, identifying appropriate endpoint control techniques combined with advanced process control strategies to provide good process margin will also be discussed. Addressing the above challenges in a cost-effective manner is vital for HVM. Root cause analysis and probable working models will be discussed for high-risk process challenges. Based on our understanding, a jist shall be provided about challenges associated with future technology nodes in logic and memory industries, with focus on how (a) technical understanding, (b) change in CMP ecosystem, and (c) AI can help solving technology development and high-volume manufacturing problems.
Dielectric Property Tuning via Electric Field Alignment in Mxene (Ti3C2)-Based Polymer Nanocomposites
Authors: Likhi Farzana , Singh Maninderjeet , Karim Alamgir , Cao Thomas
Published: August 2024

Orientation control is crucial for fine-tuning the functional properties of two-dimensional (2D) nanomaterials. MXene (Ti3C2) alignment has drawn significant attention lately as the targeted properties can be controlled by manipulating the structural anisotropy. However, controlled MXene nanosheet orientation inside the polymer matrix is a complex and less understood mechanism. In this study, we applied an in-plane electric field to align the MXene nanosheets vertically inside the semicrystalline polyvinylidene fluoride (PVDF) (Tg⁓ -35°C) matrix in situ, where the amorphous phase assisted the electric field alignment at room temperature. These vertical orientations of the nanosheets were confirmed directly using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Our study reveals a significant correlation between MXene-orientation and dielectric property enhancement. PVDF- 5 wt.% MXene demonstrated the highest dielectric permittivity increase of ⁓500% because of the maximum surface polarization of the nano-capacitors inside the matrix. Interestingly, the loss value shows a sharp jump after the 5 wt. % MXene concentration, demonstrating a percolative network formation. Notably, our nanocomposite exhibited a low loss before (0.07) and after (0.66) applying the electric field, even at a high MXene concentration (20wt.%). Finally, to understand the effect of polymer domain structure on the electric field-induced orientation effect, we conducted a comparative study between non-ferroelectric poly vinyl alcohol (PVA) and ferroelectric (PVDF) polymer-based MXene nanocomposites. Interestingly, we observed a synergistic effect of the polymer chain and MXene orientation on the permittivity enhancement in the ferroelectric polymer-based nanocomposites at both high and low frequencies. This study provides fundamental insights for designing hybrid solid-state dielectric films for next-generation flexible electronics.
(Invited) Bulk Traps in Layered 2D Gate Dielectrics
Authors: Shin Jaemin , Pathan Tyafur , Zhou Guanyu , Hinkle Christopher L.
Published: August 2024

Ultra-thin ferromagnets, when coupled with magnetoelectric or multiferroic materials, could potentially enable highly energy-efficient electric field control of the magnet for use in nanoelectronic memories. Substitutional doping of magnetic impurities in monolayer transition metal dichalcogenides (TMDs) may be a promising way to create 2D ferromagnets but, according to theoretical calculations, require high doping levels (10-20 %) to achieve above room temperature (RT) Curie temperature. Room-temperature ferromagnetism has been reported for very low doping levels (0.1-1%), in conflict with the theoretical calculations, and always in the presence of high concentrations of defects, making it unclear if the dopants alone are responsible for this ferromagnetism. In this work, we use a combination of molecular beam epitaxy (MBE), plan-view TEM, XRD, XPS, Raman, and magnetometry to study iron and vanadium doping in monolayer WSe2. We show that optimally grown monolayers with up to 35% doping and low defect density show no ferromagnetism. Interestingly, ferromagnetism is observed when these monolayers contain a significant amount of selenium vacancies (Sevac), intentionally created via a post-growth heat treatment process, and magnetism is seen to scale with heating time/vacancy concentration. Moreover, even undoped WSe2 shows similar ferromagnetism for Sevac > 1014 cm-2. This ferromagnetism can later be quenched by filling these vacancies via Se annealing. For films with low Se vacancy concentration, TEM analysis reveals significant clustering of the V and Fe dopants which likely suppresses the ferromagnetism predicted by theory - a problem that has previously plagued III-V based dilute magnetic semiconductors as well. We go so far as to claim that all of the above room-temperature ferromagnetism reports in the literature thus far are due to Se vacancies and not magnetic doping.
(Invited) CdS/Ti-Si-O Composite Photoanode for Photoelectrochemical Hydrogen Generation
Authors: Feng Weilong , Ding Dongyan , Chen Zhi
Published: August 2024

Advancements in clean energy drive socio-economic development and foster a sustainable future by restructuring energy systems and promoting low-carbon development. In this paper, we presented a comprehensive investigation on the design and performance characterization of CdS/Ti-Si-O composite photoanodes for photoelectrochemical (PEC) hydrogen generation. Silicon-doped TiO2 nanotube arrays were fabricated through anodization of Ti-5Si alloy, followed by the deposition of CdS using the SILAR (successive ionic layer adsorption and reaction) process, resulting in nanostructured Ti-Si-O photoanodes modified with CdS. The composite photoanodes were characterized in terms of their composition, microstructure, optical properties and photoelectrochemical hydrogen production performance. The composite photoanodes revealed a notable enhancement in PEC hydrogen generation properties with a photocurrent density of 7.86 mA/cm2，which was 19.15 times and 9.59 times to those of the undoped TiO2 photoanode and Ti-Si-O photoanode, respectively. The Si-doping mechanism of the photoanodes was elucidated through Density Functional Theory (DFT) calculations. The synergistic combination of Si-doping and CdS modification represents a novel and promising approach for the design of efficient nanostructured photoanodes.