bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards Digital Twin Standards in Chemical Mechanical Planarization (CMP) for Advanced Packaging
Authors: Obeng Yaw 
Published: August 2024

A digital twin is an integrated multi-physics, multiscale, probabilistic simulation of a system that uses the best available physical models, sensor updates, process history, etc., to mimic and to predict the performance of the system. In the semiconductor industry, there is a need to establish such fundamental, mechanism-based, correlations between process conditions and observed process performance. Such understanding can lead to the creation of industry-wide technical standards, and digital twins (i.e., real time digital replicas of unit processes), that will enable inter-operability, ease process selection and integration, as well as help reduced cost of ownership.
In this paper, we revisit our decades old, but still relevant, quest for appropriate mechanism-based metrology to support the digitization of Chemical-Mechanical Polishing (CMP) for the back-end-of line (BEOL), with advanced packaging, specifically hybrid bonding for 3D interconnects, in mind. Here, we consider the digitization of the nanoscale tribological aspects of CMP. For example, many CMP processes use chemically unstable polyurethane pads in a variety of slurry formulations which make the process difficult to understand and to model. We had previously described how the chemical instability of the PU-pads affects the CMP process performance. Here we contextualize the historical performance data, identify data gaps, and propose some next steps towards digital twin CMP modules.
(Invited) Epitaxial Growth of Quasi-Low Dimensional Materials for Novel Thermoelectric Films
Authors: Nakamura Yoshiaki 
Published: August 2024

Thermoelectric conversion devices or modules with high performance have been expected for the electrical power generation from wasted heat. Then, thermoelectric materials with high dimensionless figure of merit zT at temperature T , described as S
2
σT/κ have been intensively sought, where S is Seebeck coefficient, σ is electrical conductivity, and κ is thermal conductivity. Therein, intercorrelation among three thermoelectric properties has been a big barrier against high zT. In conventional approach, the heavy elements such as rare metals are used because they inherently bring small κ in the materials. Now, ecofriendly ubiquitous element materials without toxic, rare, or high cost elements, showing high zT, are expected in the application view.
Introduction of nanostructures into materials is one of the promising ways to increase zT because of phonon scattering [1], quantum confinement effect in low dimensional materials and by energy filtering [2], and so on. Therein, structure design determines the properties, and then, this method can be expected to bring high zT in the ecofriendly and low-cost ubiquitous element materials. Furthermore, it is recently found that low dimensional materials and quasi-low dimensional materials such as layered materials with 2D structures in the unit cell show high zT values. Therefore, low and quasi-low dimensional materials for extraordinarily high zT values have been expected to be developed.
We have been developing a lot of kinds of well-controlled nanostructure films by SiO2 film technique. One of the examples: Si-based films including ultrasmall semiconductor nanodots with controlled interfaces, strains, crystal orientations, and compositions [3]. Furthermore, we have developed the epitaxial growth method of quasi-low dimensional material films composed of ecofriendly group IV elements on Si substrates: FeGeγ including 1D Ge helical structure and Ca-intercalated multi-layered silicene films. Here, we will introduce the epitaxial growth results of quasi-low dimensional material films. Epitaxial growth of FeGeγ films on Si were achieved by using Ge epitaxial nanodots as seed crystals[4]. In the case of Ca-intercalated multi-layered silicene, silicene bucked structure was found to be deformed. The deformation enhanced Seebeck coefficient. As a result, this sub-angstrom atomic displacement brought power factor enhancement while keeping high electrical conductivity [5]. In this talk, we will present the epitaxial growth process of quasi-low-dimensional material films on Si substrates for thermoelectric film devices composed of ecofriendly and low-cost thermoelectric materials .
[1] Y. Nakamura, et al., Nano Energy 12, 845 (2015).
[2] T. Ishibe, et al., ACS Appl. Mater. Inter. 10, 37709 (2018).
[3] Y. Nakamura, et al., Sci. Technol. Adv. Mater. 19, 31 (2018).
[4] T. Terada, Acta Materialia 236, 118130 (2022).
[4] T. Terada, et al., Adv. Mater. Inter. 9, 2101752 (2022).
Advancing Towards Commercialization with Enhanced Stability and Efficiency in Lithium Metal Batteries Using TTE as a Co-Solvent in Carbonate Electrolytes
Authors: Ha Chaeyeon , Kim Young-Jun 
Published: August 2024

Lithium metal batteries are considered ideal anode materials for next-generation battery systems due to their high theoretical specific capacity (3,860 mAh g-1) and low negative electrochemical potential (−3.040 V vs. the standard hydrogen electrode), which are essential for high energy density. However, the fatal dendritic growth on the lithium metal surface, which occurs during repetitive cycling, acts as a significant barrier to commercially successful lithium metal battery application. Therefore, regulating the morphology of lithium plating in commercial carbonate-based electrolytes is a critical challenge for the stable operation of lithium metal batteries. Additionally, this leads to the formation of inhomogeneous lithium dendrites in carbonate-based electrolytes, manifesting as uneven current density and lithium-ion concentration gradients. The uneven current leads to inconsistent charging/discharging rates in the corresponding Ni-rich cathode, which in turn causes overpotentials and deteriorates cell safety, culminating in a reduction of capacity. this has been clarified through Kelvin probe force microscopy analysis to demonstrate an uneven state of charge distribution in the Ni-rich cathode.
In this work, we propose a new strategy for high-performance lithium metal batteries, utilizing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a co-solvent with carbonate electrolytes. By using TTE as a co-solvent, we observed a reduction in the viscosity of the electrolyte, leading to improved ionic conductivity and a decrease in the overpotential during the lithium plating/stripping process via in-situ electrochemical atomic force microscopy. This resulted in more uniform Li deposition compared to conventional carbonate-based electrolytes, forming a dense and stable Li metal layer. Furthermore, by leveraging our control over stable lithium plating morphologies via TTE co-solvent system, we observed long-term cycling stability (capacity retention of 78% at 300 cycles) with the use of an ultra-thin Li layer (40 µm). Through these results, we have effectively enhanced the stability and efficiency of high-energy-density (380 Wh kg-1) electrodes based on carbonate electrolytes, and we believe that this study can contribute to the commercialization of lithium metal batteries.

Figure 1
(Invited) Ultrahigh Efficiency Excitonic Micro-LEDs
Authors: Mi Zetian 
Published: August 2024

To date, it has remained challenging to achieve high efficiency micro-LEDs, which are desired for next generation displays and virtual/augmented reality. The performance degradation with reducing dimensions for conventional LEDs has been largely attributed to the plasma damage induced on the mesa sidewalls. Here, we show such a fundamental challenge can be overcome by developing nanowire excitonic LEDs. In this study, InGaN/GaN nanowire LED heterostructures were grown on N-polar GaN-on-sapphire substrates utilizing selective area epitaxy. Studies have shown that the exciton binding energy in strain-relaxed InGaN nanostructures can be dramatically enhanced. Due to the strong Coulombic interaction between electrons and holes, the impact of nonradiative SRH recombination on the performance of an excitonic LED is significantly reduced. By exploiting the large exciton oscillator strength of quantum-confined nanostructures, we have achieved an external quantum efficiency (EQE) exceeding 25% for a green-emitting device with lateral dimensions less than 1 micrometer, which is the highest value reported for any LEDs of this size to the best of our knowledge. It is further observed that the EQE and output power of the excitonic LED show a significantly faster rising trend with current injection, compared to conventional devices. We have identified several important factors for achieving high efficiency excitonic LEDs, including the epitaxy of nanostructures to achieve strain relaxation and reduced dislocation densities and the formation of three-dimensional quantum-confinement to enhance electron-hole wavefunction overlap. We have further investigated the effect of Mg incorporation in p-GaN layer on the device performance. We found out that an optimized Mg dopant incorporation in nanowire structures can contribute significantly to the efficiency of micro-LEDs. We have measured significantly enhanced performance by optimizing Mg dopant incorporation, which leads to reduced leakage current and improved EQE. For example, for a red-emitting micro-LED, a peak external quantum efficiency of >8% was measured for a device with a lateral dimension less than one micrometer by optimizing Mg-dopant incorporation. Through these studies, we show that by harnessing the exciton oscillator strength of nearly dislocation-free nanostructures, together with a careful optimization of p-doping in the contact layer, the efficiency bottleneck of micro-LEDs can be addressed.
Conflict of interest: Some IP related to this work has been licensed to NS Nanotech, Inc., which was co-founded by Z. Mi. The University of Michigan and Mi have a financial interest in the company.
Development of a Thin-Film NMC System for the Investigation and Suppression of Harmful Reactions Occurring on the Surface of Cathode Materials in Li-Ion Batteries
Authors: Rodrigues Sameer R.J. , De Taeye Louis , Vereecken Philippe M. 
Published: August 2024

Materials with the stoichiometry Li(NixMnyCoz)O2 (NMC) have emerged as promising candidates for use as cathodes in Li-ion batteries for electric vehicles. This is primarily due to their high capacity, which increases with the nickel content (Ni-rich NMC). However, the increase in nickel also leads to a decrease in the stability of the material, hindering market introduction [1]. Much of these stability issues emanate from the surface of the material and move subsurface towards the bulk during battery operation [2]. The internal electrode architecture of traditional composite battery cathodes, containing active materials, carbon additives, and binders, complicates the study of the surface reactions. For this reason, we developed a thin-film model system of Ni-rich NMC with a high surface area-to-volume ratio to exacerbate the effect of the surface reactions, enabling easier characterization of the surface without influence of the bulk.
The interfacial reactions occurring when NMC is exposed to air was investigated using the thin-film system. These experiments were supported by thermodynamic calculations to propose a mechanism of what reactions occur on the surface. Our study showed that the surface of NMC is stable in inert environments, however, when exposed to air (in particular H2O and CO2) the active material at the surface reacts to form Li2CO3, coinciding with loss of Li2O and protonation of the material, forming transition metal oxyhydroxides. We found that this phenomenon can be reversed by performing a heat treatment, moving Li2O back into the film. However, during the annealing process, an additional reaction between the film and substrate takes place. This, once again, leads to the active material being deficient in Li2O. To compensate for this deficiency, Li2CO3 was deposited onto NMC prior to annealing. The thermodynamical properties of each film were approximated from their electrochemical behavior. It was found that the film treated with Li2CO3 before annealing was thermodynamically similar to what is expected for an NMC cathode. These results contribute to the understanding of the interfacial reactions that take place on the surface of NMC cathodes. Additionally, the study proposes strategies to mitigate and compensate for these reactions.
References:
[1] Noh et al. Journal of Power Sources 233 (2013)
[2] Lin et al. Nat Commun 5, 3529 (2014)
Dynamic Coupling of Internal Strain Field and Lithium Pathway within Individual Battery Particles in Solid State Batteries
Authors: Chung Jinkyu , Bae Junho , Choi Hanbi , Nam Chihyun , Lee Danwon , Koo Bonho , Kim Namdong , Lim Jongwoo 
Published: August 2024

In all-solid-state batteries (ASSBs), (electro)chemo-mechanical aspects such as uneven interfaces, cathode-electrolyte interphase formation, delamination, fracture, defects, etc., are the major factors in capacity fade but remain largely unknown.
Nonhomogeneous transfer of lithium ions can cause significant variations in strain and stress within battery electrodes, leading to degradation in battery performance. In all-solid-state batteries (ASSBs), the lithium pathway and the associated strain/stress field become more intricate due to the (electro)chemo-mechanical reaction at the electrode-electrolyte interfaces. The dynamic volume change in active particles are heavily influencing by strength of the solid electrolyte and interfacial conformality. This can continually alter the lithium pathway and the internal stress field, leading to recurrent redefinitions of (electro)chemo-mechanical environment.
Here, we have developed an operando coherent X-ray imaging platform and associated analysis methodologies. This technology can track the nanoscale transport of lithium and the strain evolution of individual electrode particles in ASSBs. With this platform, we gained a comprehensive electrochemical and mechanical understanding of the cycling properties of single electrode particles in ASSBs.
(Invited) Developing Periodically-Aligned Fibrous Structures to Suppress Lithium Dendrites for Anode-Free Batteries
Authors: Kim Jae Chul 
Published: August 2024

We have developed electrospinning-based manufacturing capability for dendrite-free anode-free and anode-less batteries. Electrospinning is a widely used, feasible manufacturing approach to create nano- and micro-porous layers of functional fibers. By tailoring fiber compositions, the electrospun layers can afford a wide variety of functionalities applicable to biomedical templates, separation membranes, and energy storage. Its manufacturing capability is, however, limited to producing randomly oriented fibrous structures. Topology and tortuosity of the electrospun fibrous layers are poorly controlled, making it difficult to systematically investigate structure-property relationships for any given applications, especially electrochemical systems.
In this presentation, we will demonstrate how to improve the controllability of fiber construction geometry by electrospinning. Unlike conventional electrospinning, our approach employs a mobile stage that allows precise alignment of fibers. Produced fibrous structures will be used to construct current collectors of the anode-free batteries, one of the proposed beyond-lithium (Li)-ion battery systems for high energy density. While direct, yet reversible, Li plating and stripping on and from the current collector has proven difficult due to uncontrolled dendrite growth, we found that the flat copper foil reinforced by the three-dimensional fibrous structure can enhance Li storage efficiency over an extended number of cycles, outperforming the planar case. We will discuss the effect of fiber compositions and controlled geometrical configurations on stabilizing Li plating and stripping morphologies to suppress Li dendrite growth and provide a fundamental design principle to construct anode-free and anode-less battery cells. Battery manufacturing advanced by this work will offer a systematic strategy to develop next-generation energy storage systems for a sustainable energy future.
An Integrated New Method for the Characterisation of Thickness Changes in Battery Active Materials during Cyclisation Under Pressure
Authors: Bugenhagen Bernhard Eberhard Christian , Baumann Annika 
Published: August 2024

Measuring thickness-changes in a battery stack (dilation) during cyclisation is paramount for the characterisation of chemo-mechanical properties of battery materials. A variety of approaches to achieve these measurements is available, either for measuring the whole stack or individual active materials. Another topic of great interest is the cyclisation of batteries under an applied pressure. These pressures range from a few kPa to hundreds of MPa. Especially the research of solid-state battery materials requires measurements of electrochemical properties under pressure.
In light of this, characterising chemo-mechanical properties under an applied pressure is a natural demand. However, to the best of our knowledge, no commercially available integrated solution to measure the dilation in a battery stack under any significant amount of applied pressure has been reported yet.
We therefore present a convenient and reproducible method to derive thickness changes of a whole cell stack under defined pressures during cycling. For that, the commercially available PAT-Cell-Force was used (Image 1, left). The PAT-Cell-Force allows the application of a force of up to 1500 N on a cell stack of a diameter of 18 mm. This translates to a pressure of up to ~6 MPa. Additionally, the PAT-Cell-Force is equipped with a strain gauge sensor, allowing the measurement of the force during the experiment. While cycling, periodic fluctuations in the force signal are observed that are correlated to the cell voltage (Image 1, right).
Through technical modifications of the PAT-Cell-Force, the dilation of the cell-stack Δd has been derived from the amplitude of the force signal ΔF, reproducibly and in very good agreement to the expected values. This has been achieved for applied forces of up to F0 ~ 100 N, corresponding to Pressures of approximately P0 ~ 400 kPa. Tests for higher pressures are currently pending.

Figure 1
(Invited) Multiscale Modeling and Machine Learning Investigation of Battery Interphase Dynamics
Authors: Cheng Tao 
Published: August 2024

In recent years, the solid electrolyte interphase (SEI) has emerged as a critical component in the development of efficient and durable electrochemical storage systems. Understanding the dynamics and properties of SEI is paramount for the enhancement of battery performance and longevity. This study presents a novel multi-scale simulation approach, incorporating Hybrid Ab Initio Reactive Molecular Dynamics (HAIR), to elucidate the intricate mechanisms governing SEI formation and evolution. Our methodology involves simulation under operando conditions, closely mimicking real-world scenarios, to provide insights into the molecular interactions and structural changes within the SEI layer. By leveraging HAIR, we bridge the gap between quantum mechanical precision and the expansive temporal-spatial scales of molecular dynamics, facilitating a more comprehensive understanding of SEI behavior [1,2]. Furthermore, we integrate machine learning (ML) techniques to refine our predictive models. These ML algorithms are trained on a rich dataset derived from HAIR simulations, enabling the prediction of key electrochemical properties, including chemical composition and electronic structure. The application of machine learning significantly enhances our ability to forecast SEI evolution under various operational conditions. A critical aspect of our research is the prediction of X-ray photoelectron spectroscopy (XPS) and Coulombic Efficiency (CE) outcomes [3]. By simulating these properties, we provide valuable predictions that align closely with experimental data, thereby validating our simulation framework.
In summary, our study offers a groundbreaking perspective on SEI analysis, merging the fidelity of HAIR with the predictive power of machine learning. This approach not only deepens our fundamental understanding of SEI properties but also paves the way for the development of more efficient and durable electrochemical storage systems. Our findings hold significant implications for the future of battery technology and underscore the importance of advanced simulation techniques in electrochemical research.

Reference

1. Liu Y; Yu PP; Sun QT; Wu Y; Xie M; Yang H; Cheng T*; Goddard WA; ACS Energy Lett.
2021, 6, 2320.
2. Liu Y; Sun QT; Yue BT; Zhang YY; Cheng T*; J. Mater. Chem. A
2023, 11, 14640.
3. Sun QT; Xiang Y; Liu Y; Xu L; Leng TL; Ye YF; Fortunelli A*; Goddard WA*; Cheng T*; J. Phys. Chem. Lett. 2022, 13, 8047.

Figure 1
Accurate Ionic Conductivity Calculations of Battery Electrolytes at High Salt Concentration Using Molecular Dynamics Simulations
Authors: Bhati Manav , Agarwal Garvit , Banik Suvo , Browning Andrea R , Halls Mathew D 
Published: August 2024

The ionic conductivity of an electrolyte formulation is a crucial property influencing battery performance. The dependence of ionic conductivity on multiple parameters, such as salt and solvent type, concentration, and temperature complicates the design of next-generation electrolytes. Efficient design of superior electrolytes requires methods capable of accurately and rapidly predicting ionic conductivity. Such methods would enable high-throughput screening of electrolyte chemistries to establish structure-property relationships.
The simple Nernst-Einstein approximation is widely used in the literature to estimate ionic conductivity of electrolytes using the measured self-diffusivity. However, the failure of this approximation for concentrated solutions due to stronger intermolecular interactions requires incorporating a rigorous concentrated solution theory, such as Maxwell-Stefan (MS) diffusivity. Here, we present a molecular dynamics (MD) simulation workflow for calculating the ionic conductivity of liquid electrolytes utilizing the ion-correlated MS diffusion approach. We explore the sensitivity of calculated ionic conductivity to various simulation parameters and various methods in the literature to guide a standardized simulation protocol. Through rigorous benchmarking across a diverse range of electrolyte systems, we validate the model's accuracy by directly comparing the calculated ionic conductivities against experiments and existing literature. This work is a significant step toward a more unified and comprehensive evaluation procedure for ionic conductivity, accelerating the development of advanced electrolytes for improved battery performance.