bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Understanding Photo-Driven Water Oxidation Mechanisms
Authors: Wang Dunwei
Published: August 2024

Water oxidation is an important reaction that produces electrons and protons, which are important for downstream reactions such as hydrogen production and carbon dioxide reduction. Presently, the slow water oxidation is a key limiting factor for the development of hydrogen production and/or carbon dioxide reduction into practical solar energy storage technologies. An important reason for the slow progress in solve water oxidation problems is the lack of knowledge on the detailed mechanisms by which water is oxidized. As a multi-step process, the reaction involves at least 4 protons and 4 holes (when the desired product is oxygen gas). Intuitively, the coordination of charges and protons plays a critical role, but the details remain unknown. In this talk, we report our recent progress in understanding how water oxidation is influenced by surface hole behaviors. Using an Ir-based catalyst that features atomically defined structures, we were able to systematically vary a number of parameters, including the hole concentration, the density of active sites, as well as the properties of the supporting substrate that determines hole accumulation. It was found that matching the concentrations of surface holes and active site densities is critical. It was also revealed that the support substrate could have a profound influence on the reaction kinetics, even though they do not directly participate in the reactions. This knowledge is expected to propel the development of catalysts for improved water oxidation under photochemical conditions.
(Invited) A Polaron Paradigm for Perovskite Nanocrystal Emitting States
Authors: Kuno Ken
Published: August 2024

Perovskite NCs such as CsPbBr3 have numerous uses. Most involve exploiting their light emission and are motivated by their defect tolerance and large, as-made emission quantum yields. Absent, though, is a fundamental understanding of perovskite NC emitting states, central to these applications. Of particular note are observations of near-universal, size-, temperature-, and composition-dependent absorption/emission Stokes shifts where observed energy differences are between absorbing and emitting states.

Very little is known about the origin of these shifts. Moreover, little is known about the exact identity of the emitting state. This is to be contrasted to more conventional NCs such as CdSe where band edge exciton fine structure quantitatively accounts for both global and resonant Stokes shifts, with emission emerging from a dark exciton. Although similar perovskite NC fine structure might account for their shifts, both theory and experiment predict bright/dark fine structure splittings easily an order of magnitude too small to account for experiment.

We now propose that perovskite NC emitting states are polarons, which result from the lattice accommodation of photogenerated charges. Polaron binding energies and lifetimes are, in turn, suggested to be the origin of observed size-, temperature-, and composition-dependent absorption/emission Stokes shifts and excited state lifetimes. This represents a significant departure from more conventional descriptions of NC band edge states, which exclusively involve exciton fine structure and dark exciton emitting states.
(Invited) Unveiling the Stability Potential of Organic Sulfonium Cations in Perovskite Solar Cells
Authors: Sandhu Sanjay , Lima Farihatun Jannat , Mensah Appiagyei Ewusi , Ahmed Saif , Lee Jae-Joon
Published: August 2024

Although the power conversion efficiency of perovskite solar cells (PSCs) has skyrocketed, its stability remains a major roadblock to its commercialization. The susceptibility of conventional ammonium-based halide perovskites to ambient environment underscores the necessity of developing alternative aprotic materials. The substitution of protic ammoniums cations with their analogous aprotic sulfonium cations can pave the way for moisture-stable PSCs. Recently, efficiency and stability potential of sulfonium cations in PSCs has been investigated extensively through various engineering approaches. We incorporated trimethylsulfonium iodide and trimethylsulfoxonium iodide as an additive and interfacial modifier to improve the PCE and stability of MAPbI3 and FAPbI3, and FAMACsPbI3-xBrx PSCs. The structural, optoelectronic, and PV properties of sulfur-based cations and their corresponding lower dimensional perovskites are explored. This work further addresses the key challenges and strategies for advancing PSCs by incorporating various derivatives (trimethylsulfonium bromide and 2-carboxyethyl dimethyl sulfonium bromide) of organosulfonium cations.
(Invited) Plasmonic-Photoluminescent Inorganic-Organic Hybrid Nanostructures Toward Strong Coupling
Authors: Wu Nianqiang
Published: August 2024

Organic dyes, especially near-infrared ones, have relatively low quantum yield. This talk will introduce our efforts to design and fabricate inorganic-organic hybrid nanostructures to achieve bright photoluminescence. We will design a plasmonic gap mode to achieve strong coupling between plasmon and exciton. In addition, we will demonstrate the plasmonic photoluminescence probes in biosensing applications.
(Invited) Plasmonic Yolk@Shell Nanocrystals for Photocatalytic Hydrogen Production
Authors: Hsu Yung-Jung
Published: August 2024

Plasmonic photocatalysts have garnered significant attention for hydrogen production due to their unique properties and efficiency in harnessing solar energy. This work is designed to develop yolk@shell nanocrystals as a high-efficiency photocatalyst model. The core yolk is composed of Au nanoparticles, and the shell is composed of hollow non-stoichiometric semiconductors. The compositional defects can induce a large number of free carriers, making non-stoichiometric semiconductors behave like noble metals and exhibit surface plasmon resonance (SPR) absorption. For yolk@shell nanocrystals, the core Au particles can move freely, which can effectively stir the surrounding reaction solution to increase the reaction rate. The confined space between the core particle and the shell layer can function as a nanoreactor to promote species diffusion to enhance catalysis kinetics. In addition, the core Au particles and the shell semiconductor can form metal/semiconductor heterojunction so as to exhibit remarkable photocatalytic performance. Several representative works from our lab will be introduced to demonstrate the promising potentials of plasmonic yolk@shell nanocrystals for hydrogen production applications.
Rigid and Flexible Bis-Porphyrinic Tweezers: Efficient Molecular Recognition of Bidentate Bases
Authors: Rein Regis , Solladie Nathalie
Published: August 2024

Increasing efforts are devoted to the synthesis of cofacial bis-porphyrinic tweezers able to complex various bidentate guests through axial coordination of the Zn(II) porphyrins by the two nitrogen atoms. Elaboration of rigid receptors appeared up to now as the ideal way to pre-organize a bis-porphyrinic cavity and increase the stability of the formed host/guest complexes. However, the choice of using rigid spacer to attach the two porphyrins together may cost a lot as far as solubility and stability are concerned. The synthetic pathways necessary to achieve the synthesis of rigid systems are frequently long and tedious. We report here the synthesis and studies of new flexible bis-porphyrinic tweezers bearing uridine as linkers and offering pre-organized cavities able to welcome bidentate guests with extremely high association constants.

As part of our studies concerning complexation of bidentate Lewis bases by bis-porphyrinic tweezers, we have synthesized two new bis-porphyrins bearing a flexible nucleosidic linker. Both uridine and 2’-deoxyuridine spacers were chosen on account of some observations we made a few years ago on the unexpected blocked conformations adopted by a pentaporphyrin consisting of four Zn(II) porphyrins attached to a central free-base porphyrin by four nucleosidic linkers. Since we observed no such blocked conformations in other flexible pentaporphyrins, we thought this might be due to the nucleosidic nature of the linkers. We thus synthesized two dimers, which differ by the attachment positions of the two porphyrins.

The ability of these two tweezers to accomodate guests was investigated through ligand binding studies carried out in dichloromethane with DABCO as bidentate base. The complexation of DABCO by these dimers was monitored by UV-visible spectrophotometric titration in CH2Cl2. The binding constants between these two tweezers and DABCO were calculated from UV-visible spectroscopic data. These association constants are unexpectedly increased by more than one order of magnitude as compared to the association constants of the same bidentate ligand with a reference Zn(II) mono-porphyrin. This enhanced stability of the complexes may be ascribed to a pre-organization of the bis-porphyrinic tweezers forming a cavity, and provides convincing evidence that the bidentate base is inserted into the cavity of the dimers via host/guest interactions.

We demonstrated that similar association constants can be obtained with flexible tweezers bearing uridine as linker and rigid tweezers. However, the stability of these flexible complexes isn’t as convincing as for our rigid tweezers bearing a tris-anthracenic spacer since the addition of an excess of DABCO destroys all the flexible complexes.

Molecular modelling of one of the flexible tweezers and its 1/1 complex with DABCO is represented below, as well as our rigid tweezers bearing a tris-anthracenic spacer.

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research.
Modifying Polymer-Based Hard Carbons for Enhanced Understanding of Sodium Storage Properties
Authors: Ast Marius , Scheiba Frieder
Published: August 2024

Numerous theories on the storage of sodium in hard carbons can be found in the literature. In particular, understanding the contributions of (heteroatom) doping, porosity and graphitic layers is of great importance. Much of the current literature on hard carbons uses different biomaterials as precursors in order to improve the sustainability of the synthesis. However, large differences in the composition of the starting materials and the presence of foreign atoms make a systematic investigation of the storage process extremely difficult.

Therefore, a hard carbon material based on furan resins was used in this work to obtain a well-defined starting material that can be modified systematically. This allows a detailed investigation of the effects caused by those modifications. Modifications can be achieved by directly adding various template materials to the polymerization process. Both doping with heteroatoms by adding template chemicals such as boric acid and the introduction of graphitic layers by adding high-purity graphite during polymerization were investigated.

Addition of boron and phosphorus heteroatoms led to an increase in reversible capacity up to 240 mAh g-1 from 150 mAh g-1 for carbonization temperatures as low as 650°C. Formation of a potential plateau was observed for boron doping, which is usually found at higher carbonization temperature surpassing 1000°C. Utilizing Raman and XRD spectroscopy, crystallite size was found to be decreasing with phosphorus doping, while boron doping led to an increase. This increase could be a possible explanation for the observed capacity plateau.

The addition of high-purity carbon samples, such as KS6L graphite or graphene, allowed for a targeted introduction of single- and multi-layer graphitic domains without alteration of additional properties. Increasing graphite content up to 5 wt-% during polymerization resulted in enhanced electrochemical characteristics, including increased sodium intercalation into the lattice and shift of the sloping proportion to lower potentials. Further increase up to 10 wt-% led to a vanishing of the plateau potential and a lowering of the reversible capacity. The results indicate that the interlayer spacings has now decreased below a threshold, which prohibits the sodium from intercalation between the graphitic layers. Additionally, doping Hard Carbons with graphene revealed a capacity decrease at content ratios as low as 2 wt-%, emphasizing the significance of both the stacking and interlayer spacing of the graphitic lattice, as well as the chemical composition, for efficient sodium storage.

In summary the results presented provide an enhanced understanding into the sodium storage properties of Hard Carbons, which help improve the design of synthesis processes for more cost-efficient and high-performance carbon materials.

Figure 1
Architected Carbon Structures for Energy Storage
Authors: Li Yat
Published: August 2024

Carbon materials, owing to their excellent electrical conductivity, tailor-ability, inexpensiveness, and versatility, have been extensively studied as electrode materials for energy storage devices, including batteries and supercapacitors. In this talk, I will discuss how to combine conventional materials/chemical synthesis with 3D printing techniques to develop architected carbon electrode materials for supercapacitors. The capacitance of carbon-based supercapacitor electrodes has remained at a mediocre level between 100 and 200 F/g for decades. Until recently, a new family of carbon materials termed hierarchical porous carbons has pushed the capacitance to new benchmark values beyond 300 F/g and has revitalized the exploration of carbon materials for supercapacitors. We have recently developed some hierarchical porous carbon areogels contain different scales of pores inter-connected together and assembled in hierarchical patterns, through a combination of freeze drying, template, chemical etching and 3D printing. These porous carbons have an open porous structure, providing an extremely large and accessible surface area. They can be used as electric double layer materials that enable ultrafast charging/discharging and retain outstanding capacitive performance even at ultralow temperatures (-70 °C). They can serve as 3D conductive scaffolds/current collectors to support pseudo-capacitive materials with ultrahigh mass loadings. These findings exemplified how to use a deterministic structure to improve the rate capability of supercapacitors and their capacitances at ultrahigh current densities and mass loadings and ultralow temperatures, which are long-standing challenges for SCs.
Artificial Graphene Nanoribbons with Tailored Topological States
Authors: Guisinger Nathan , Darancet Pierre
Published: August 2024

Low-dimensional materials functioning at the nanoscale are a critical component for a variety of current and future technologies. From the optimization of light harvesting solar technologies to novel electronic and magnetic device architectures, key physical phenomena are occurring at the nanometer and atomic length-scales and predominately at interfaces. In this presentation, I will discuss low-dimensional material research occurring in the Quantum and Energy Materials (QEM) group at the Center for Nanoscale Materials. Specifically, the synthesis of artificial graphene nanoribbons by positioning carbon monoxide molecules on a copper surface to confine its surface state electrons into artificial atoms positioned to emulate the low-energy electronic structure of graphene derivatives. We demonstrate that the dimensionality of artificial graphene can be reduced to one dimension with proper “edge” passivation, with the emergence of an effectively-gapped one-dimensional nanoribbon structure. Remarkably, these one-dimensional structures show evidence of topological effects analogous to graphene nanoribbons. Guided by first-principles calculations, we spatially explore robust, zero-dimensional topological states by altering the topological invariants of quasi-one-dimensional artificial graphene nanostructures. The robustness and flexibility of our platform allows us to toggle the topological invariants between trivial and non-trivial on the same nanostructure. Our atomic synthesis gives access to nanoribbon geometries beyond the current reach of synthetic chemistry, and thus provides an ideal platform for the design and study of novel topological and quantum states of matter.

Figure 1
On-Surface Formation and Chemical Transformations of Indigo Coordination Polymers
Authors: Xu Hongxiang , Chakraborty Ritam , Adak Abhishek Kumar , Das Arpan , Yang Biao , Meier Dennis , Riss Alexander , Reichert Joachim , Narasimhan Shobhana , Barth Johannes V. , Papageorgiou Anthoula Chrysa
Published: August 2024

Coordination polymers are attractive candidates for miniaturized electronics. With unconventional electronic and magnetic properties posited, they are interesting for multiple applications including magnetic information storage and spintronics. Natural products are appealing to tailor advanced new materials, bearing inherent advantages in biodegradation. Among them, we distinguished indigo, a common natural dye with a distinctive blue color, used as a pigment since antiquity. Motivated by its optical properties and the reported metal complexes [1], we employed it as a molecular building block for the surface formation of coordination polymers with iron.

We report on the on-surface formation of extended coordination polymers which controllably feature the cis and the transmonomers of the molecular building block. The reaction products of indigo and Fe were characterized atomically by a combination of state-of-the -art experimental and theoretical techniques. By a combination of X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM), it is found that indigo deprotonates and coordinates with Fe atoms on silver surfaces. We identify unambiguously well-defined coordination polymers composed of (1 dehydroindigo : 1 Fe) repeat units with STM, bond-resolving atomic force microscopy and density functional theory (DFT) simulations. On both Ag(100) and on Ag(111), the trans configuration of dehydroindigo results in N,O-chelation in the polymer chains. On the more inert Ag(111) surface, the molecules undergo thermally induced isomerization from the trans to the cisconfiguration and afford N,N- plus O,O-chelation (see figure). This is enabled by the dehydrogenation and is preferential solely in the environment of the coordination chain on Ag(111). DFT calculations also confirm that the coordination polymers of the cis-isomers on Ag(111) and of the trans-isomers on Ag(100) are energetically favored.

Our results demonstrate post-synthetic linker isomerization in interfacial metal-organic nanosystems. Both types of coordination polymers are predicted to be spin-crossover systems and the isomerization is anticipated to have a significant impact on their magnetic properties.

References

1. W. Beck, K. Sünkel, Z. Anorg. Allg. Chem.
2020, 646, 248-255.

Figure 1
From BN-Doped Molecular Carbon Scaffolds to BNC Sheets
Authors: Auwarter Wilhelm
Published: August 2024

In carbon nanoscience, the on-surface synthesis strategy emerged as a promising route to achieve structural control at the atomic scale. This approach might be applied to fabricate well-defined two-dimensional BN-substituted carbon nanomaterials with tunable electronic properties [1]. In this talk, I will review our activities on the self-assembly of BN-doped molecular precursors, including borazine [2] and BN-doped carbon scaffold [3], on noble metal supports. Temperature-induced dehalogenation and dehydrogenation reactions are applied to introduce intramolecular ring-closing and intermolecular coupling, e.g., yielding random BNC sheets, probed by low-temperature scanning tunneling microscopy and X-ray photoelectron spectroscopy. The potential transfer and characterization of such two-dimensional BNC materials in devices will be discussed.

[1] Sánchez-Sánchez et al., ACS Nano 9, 9228 (2015)

[2] Weiss et al., Adv. Mat. Interfaces, accepted, doi: 10.1002/admi.202300774

[3] Schwarz et al., Chem. Eur. J. 24, 9565 (2018)
Galvanic Corrosion Behavior of Zn and Al Couples in NaCl Solution
Authors: Jang Junho , Ooi Azusa , Tada Eiji
Published: August 2024

Multi-materialization is being promoted in automotive structural materials, and fuel economy is being improved by replacing steel with aluminum and other lightweight metallic materials. Automotive steel is often galvanized for corrosion protection, and galvanic corrosion of aluminum and zinc in an atmospheric environment is a very important issue in evaluating automotive durability. Zinc is usually considered to be an anode when combined with aluminum, but its galvanic corrosion behavior can be complicated by environmental conditions because the corrosion potentials of the two are relatively close. Therefore, the objective of this study is to investigate the galvanic corrosion behavior of the couples consisting of zinc and aluminum under corrosive environmental conditions.

The galvanic couple used in this study was fabricated from AA1050 Al and zinc plates. The width and length of both plates are 10 mm and 15 mm, respectively. After connecting lead wires to each plate, both plates were embedded in epoxy resin. To fabricate coplanar galvanic couples in this study, both plates were placed separately along the surface from a gap size of 500 um. The surfaces of the galvanic pairs were polished with SiC paper to JIS 2000 grit and cleaned with EtOH. The test solutions used in this study were aqueous NaCl solutions of various concentrations from 0.01 to 2 M, prepared with Milli-Q water and reagent grade chemicals. Galvanic currents and corrosion potentials were measured to investigate the galvanic corrosion behavior of the couples after 72 hours of galvanic corrosion experiments in the test solutions.

The results of the galvanic corrosion test showed that the immersion potentials of the galvanic couples were lower at higher NaCl concentrations. The galvanic current decreased with immersion time, finally reaching about 1 uA in all NaCl solutions. The results of the electrochemical impedance measurements for galvanic couples in various NaCl concentrations showed that the impedance gradually increased with immersion time. It was also found that the impedance can be expressed as an electrical equivalent circuit consisting of two time constants, and that the impedance increases at intermediate frequencies between 0.1 and 1 Hz, which is thought to correspond to the dissolution reaction of Zn. This was the same trend as the behavior of the galvanic current. These results suggest that prolonged immersion reduces the galvanic current and the dissolution rate of zinc due to the passivation of the A1050 surface and the suppression of cathodic reactions.
(Dielectric Science and Technology Division Poster Award, 1st Place) The Influence of Pad Micro-Features on Chemical Mechanical Polishing (CMP) Performance: Insights from Computational Fluid Dynamics (CFD)
Authors: Sadri Mofakham Atefeh , Cho Hanchul , Kim Hyongjae , Ahmadi Goodarz , Seo Jihoon
Published: August 2024

With semiconductor chip dimensions shrinking below 7 nanometers, Chemical Mechanical Planarization (CMP) becomes more critical [1], [2]. To meet the increasing demand for precision and uniformity in the fabrication of wafers and chips, enhancements in CMP consumables and operating conditions are necessary. To address these requirements, novel pad designs have been developed, particularly those that do not require conditioning [3]. It is known that the CMP polishing rate depends on pressure, pad wafer relative velocity, and the distribution of pad asperities [4]. As conventional pads provide small and random contact areas, the external pressure applied by the head determines the material removal rate (MRR) [5] Advanced pads with micro-features provide more contact areas and help deliver consistent pressure and slurry distribution during Chemical Mechanical Polishing (CMP) [6], [7]. This study uses computational fluid dynamics (CFD) to simulate the flow between pad and wafer surfaces to determine how pad surface micro-features affect the CMP process. The abrasive residence time, total fluid pressure, and slurry flow velocity are evaluated for four distinct pad micro-feature geometries: square, square-circle, circle, and ellipse. Increasing the number of edges in the pad micro-feature patterns increases pressure drop, leading to more interaction between pad and slurry and enhancement of MRR. The findings of this study confirm the effectiveness of micro-featured pads in optimizing CMP processes and provide valuable insights into the influence of microfeature geometries on critical parameters for improving the semiconductor fabrication process.

[1] J. Seo, Journal of Materials Research, 36, 235–257, Jan, 2021.

[2] B. Suryadevara, Advances in Chemical Mechanical Planarization (CMP). Woodhead Publishing, 2021.

[3] S. Lee and E. Hwang, “Smart pad fabrication for CMP,” LMA Res Rep, vol. 10, pp. 100–104, 2002.

[4] G. Ahmadi and X. Xia, J Electrochem Soc, 148, G99, 2001.

[5] X. Xia and G. Ahmadi, Particulate Science and Technology, 20, 187–196, 2002.

[6] S. Lee, G. Kim, M. Mcgahay, H. Kim, and H. Cho, “Pad Designs-To navigate the fundamentals of CMP.”

[7] M. Mcgahay, G. Kim, S. Lee, H. Cho, and H. Kim, “Critical Feature Size of Polishing Pad and Its Performance.”
Developing CMP for Future of Memory
Authors: Jindal Anurag , Mishra Maneesh , Carswell Andrew
Published: August 2024

Micron is an industry leader in innovative memory and storage solutions, transforming how the world uses information to enrich life for all. Every day, innovations driven by our team fuel the data economy, enabling advances in 5G applications and artificial intelligence applications. At the core of these innovations are development of the process and equipment technologies faster yet at lower manufacturing costs. Over the past four decades, since its inception, Chemical Mechanical Planarization (CMP) has evolved from lab to fab in most significant ways. In this presentation, we focus on four aspects of CMP, namely, technology, applications, consumables, and cost to enable the memory roadmap for today and tomorrow. Wafer-to-wafer bonding, a revolutionary technology for memory roadmap, will also be discussed to lay out challenges ahead for CMP.
Bridging Technology and Environment: Sustainable Approaches in Semiconductor Chemical Mechanical Planarization (CMP)
Authors: Seo JIhoon
Published: August 2024

As semiconductor technologies continue to advance in areas such as autonomous driving, artificial intelligence, 5G communications, the Internet of Things, and large-scale data processing, the demand for a reliable semiconductor industry is on the rise.(1) This growing demand necessitates the use of advanced device architectures, which heavily rely on two crucial processes: Chemical Mechanical Planarization (CMP) and post-CMP cleaning.(2)

This talk will focus on the development of CMP slurries and post-CMP cleaning solutions, emphasizing their vital roles in these processes. We will delve into the comprehensive development of CMP slurries and post-CMP cleaning solutions, highlighting how synthesis methods can significantly affect the surface chemistry of ceria abrasives and impact the removal rates of SiO2 surfaces during STI CMP.(3, 4)

Our research also demonstrates how our cleaning solutions can effectively remove even the most 10 nm-sized ceria particles from SiO2 surfaces,(5) thereby enhancing process efficiency. Furthermore, we will discuss the use of aliphatic amino acids as environmentally friendly corrosion inhibitors in CMP slurries, offering a sustainable alternative to the traditionally used benzotriazole (BTA) and addressing key environmental challenges.(6) In the context of the rapidly expanding semiconductor industry, it becomes critical to address global sustainability concerns and environmental health and safety (EHS) objectives. Our research proposes a comprehensive methodology for evaluating the sustainability of CMP consumables in semiconductor manufacturing, with a primary focus on CMP slurries due to their significant market share and shorter usage lifetimes. This research serves as a foundation for future CMP sustainability analyses, encouraging self-correction strategies within the CMP community to reduce environmental impact. We will also introduce a robust framework for the Life Cycle Assessment (LCA) of CMP consumables, marking a crucial step toward achieving these sustainability goals. In summary, this talk will explore the intricate details of CMP and post-CMP processes, their pivotal roles in the advancement of semiconductor manufacturing, and the imperative task of aligning these processes with environmental and sustainability objectives.

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

S. Babu, Advances in Chemical Mechanical Planarization (CMP), Woodhead Publishing (2021).

J. Seo, Journal of Materials Research, 36, 235 (2021).

J. Seo, J. W. Lee, J. Moon, W. Sigmund and U. Paik, ACS applied materials & interfaces, 6, 7388 (2014).

J. Seo, J. H. Kim, M. Lee, J. Moon, D. K. Yi and U. Paik, Journal of colloid and interface science, 483, 177 (2016).

J. Seo, A. Gowda and S. Babu, ECS Journal of Solid State Science and Technology, 7, P243 (2018).

H. T. T. Tran, J. Gichovi, E. J. Podlaha and J. Seo, in Electrochemical Society Meeting Abstracts 243, p. 1809 (2023).
Decoding CMP Challenges: A Metrospection Insight
Authors: Ramakrishnan Suresh
Published: August 2024

We live in a digitally connected world with Global data to exceed 180 ZB by 2025 per some estimates1. Memory is the fiber connecting our world. New applications drive continued demand growth for memory and storage applications. Micron is a leader in the memory and storage industry, helping the world use information to enrich lives. As memory devices scale and new memory technologies arise, the requirements for Chemical Mechanical Planarization (CMP) processes are becoming tighter and more stringent node over node. Furthermore, memory scaling continues to become more dependent upon CMP, with not only a steady increase in the number of CMP steps but that of unique CMP steps as well node over node. In this presentation we focus on CMP challenges from a METROSPECTION (Metrology & Inspection) lens. We explore the critical role of inspection and metrology techniques in optimizing CMP for semiconductor memory fabrication. The ability and need for the integration of cutting-edge inspection techniques and metrology strategies emerges as a pivotal element in enhancing CMP cycles of learning and hence the reliability, yield, and overall quality of semiconductor memory devices.

1 - Statista
(Invited) Polarization Stability Improvement for Hf0.5Zr0.5O2-Based Ferroelectric Capacitor
Authors: Liang Yan-Kui , Peng Li-Chi , Chiu Ching-Hua , Hsiao Yuan-Yu , Lin Chun-Hsiung
Published: August 2024

The instability in polarization during the endurance test of Hf0.5Zr0.5O2 (HZO) ferroelectrics thin films including the wake-up and the fatigue are still major challenges for the development of HZO-based ferroelectric memories. In this work, we will review the proposed mechanisms of the instabilities in polarization including wake-up and fatigue of the HZO-based metal-ferroelectric-metal (MFM) capacitors. Then, the material processing techniques to address the issues of instabilities are provided. The in-situ deposition of electrode and ferroelectric layers by atomic layer deposition (ALD) attracted considerable attention as a promising solution. Owing to the improved interface quality, both the endurance characteristics and remanent polarization were enhanced. We have also developed a HfO2/ZrO2 superlattice structure to further enhance the ferroelectric endurance of the MFM capacitors. The superlattice MFM capacitors show wake-up free characteristics with excellent endurance. The device performances and endurance characteristics of ferroelectric thin film transistor will also be presented.
Dielectric Materials As Optical Emitters for Thermophotovoltaics
Authors: Leite Marina , Kopper Declan
Published: August 2024

Thermophotovoltaics (TPV) are a promising route for converting heat generated as a byproduct into usable electricity through a clean energy paradigm. A primary challenge in the field is that the material options used to date for the optical emitters substantially constrain the power conversion efficiency of this process. Thus, we screened the optical response (i.e. permittivity) of >2,800 material combinations with melting point >2,000 oC, comprising refractory silicides, borides, carbides, nitrides, oxides, and metals [1]. Overall, the mismatch in permittivity allowed for emission control, key for the development of high performing TPV. We found a handful of emitters for TPV with theoretical efficiency >60% at 1800 oC, for GaSb solar cells. To complement our analysis, we also identified optimal material combinations for InGaAsSb, InGaAs, Ge, GaSb, and Si photovoltaic devices. The final down selection of materials is also based on their thermal expansion and thermochemical stability, which are frequently overlooked. The discussion of the best material options will be accompanied by the optical characterization of selected materials up to 1500 oC, using in situ reflection and transmission measurements [2]. Finally, we will discuss the specific case of SiC/AlN emitters for the abovementioned photovoltaic options [3].

References:

[1] M. R. S. Dias et al, Joule 7, 2209 (2023)

[2] T. Gong et al. ACS Appl. Optical Materials 1, 1615 (2023)

[3] M. Duncan, et al. In preparation (2024)
(Invited) Next-Generation Photonic Source Based on Lateral GaAs/AlgaAs Heterostructure Devices
Authors: Sfigakis Francois , Wasilewski Zbig , Reimer Michael , Baugh Jonathan D
Published: August 2024

Quantum communications and remote sensing protocols rely on preparing individual quanta of light, or photons, as carriers of quantum information. While it is easy to generate many-photon classical states of light (e.g., a light bulb or a laser), it is challenging to generate single quanta or pairs of entangled quanta on-demand. Yet, only in this latter regime can the fundamentally quantum nature of light be exploited to achieve performance exceeding classical bounds.

We are developing a single-photon source based on combining a one-parameter single electron pump (Figure 1a,b) – an electrically controlled, on-demand, high-fidelity emitter of single electrons [1] – with a lateral p-n junction [2] (Figure 1c,d) in which injected single electrons recombine with holes to produce single photons. These devices are realized in undoped GaAs/AlGaAs heterostructures and designed to be ambipolar. Such a quantum light source could lead to a paradigm shift in metrology, providing a quantum redefinition of two of the seven SI base units, the ampere and the candela. It is also possible in principle to realize scalable source arrays on a single chip. I will discuss progress towards realizing and characterizing these sources, including work on optimizing collection efficiency and Purcell enhancement using a lateral distributed Bragg reflector in a concentric ring geometry. Beyond fundamental studies, the proposed photon source will find practical use in quantum communications protocols (QKD), where it can offer fast data transmission rates, and quantum sensing with LiDAR, where it could outperform laser-based systems in the few-photon regime for low-power, stealth applications.

[1] B. Buonacorsi et al, “Non-adiabatic single-electron pumps in a dopant-free GaAs/AlGaAs 2DEG”, Appl. Phys. Lett.
119, 114001 (2021).

[2] L. Tian et al, “Stable electroluminescence in ambipolar dopant-free lateral p-n junctions”, Appl. Phys. Lett.
123, 061102 (2023).

Figure 1
(Invited) Shape Engineering of Nanostructured III-V Semiconductor Lasers
Authors: Tan Hoe
Published: August 2024

Group III-V semiconductors have revolutionised electronics and optoelectronics due to their superior physical and optoelectronic properties including high carrier mobility, direct bandgap and band structure engineering capability. Reducing the device size to nanoscale brings many unique properties, such as large surface-area-to-volume ratio, high aspect ratio, carriers and photons confinement effect. These nanostructures have already been demonstrated for potential applications in light emitters, photodetectors, solar cells and for photoelectrochemical water splitting. However, to date most efforts on the growth of these nanostructures have been limited to nanowires.

In this talk, we demonstrate selective area growth of III-V nanostructures, showing the possibility of obtaining other functional nanostructures, beyond the limitation of rod-like geometry. We demonstrate that by changing the pattern design on the mask and growth conditions, we are able to grow and control the shapes to form nanostructures such as membranes, flowers, rings, spirals, stars, ellipses etc. These shape-engineered nanostructures open up possibilities of new applications based on devices with novel geometries.

In particular, we will show the results of our InP micro-ring lasers which have excellent cavity due to the atomically flat facets. Micro-disk and micro-ring lasers are light emitting devices that operate in the whispering gallery mode. They are important components for integrated photonics applications as light from can these devices can be efficiently coupled to on-chip waveguides. By coupling the micro-ring laser to a nanowire antenna, we further demonstrate that we can tune the emission directionality to the device.
(Invited) Forecasting Hybrid Perovskites’ Dynamic Response through Machine Learning
Authors: Leite Marina
Published: August 2024

Machine learning (ML) can significantly accelerate the discovery of materials for clean energy. Hybrid perovskites (an emerging class of materials for photovoltaics and light-emitting diodes) encompass an enormous chemical composition space, resulting in a hyperparameter space that is nearly impossible to be interrogated via traditional trial-and-error methods. Thus, there has been a pressing need within the materials research community to identify ML models that can be implemented to inform the physical and chemical behavior of the perovskites. Here, we apply distinct ML models (mostly based on recurrent neural networks) to classify and forecast physical properties encompassing electrical conductivity, photoluminescence response, the power conversion efficiency of photovoltaic devices, etc. Specifically, we use automated, in situ optical measurements to predict the optical response of a series of perovskites for 50+ hours, upon materials’ exposure to moisture. We quantitatively compare linear regression, echo state network, and seasonal auto-regressive integrated moving average with eXogenous regressor algorithms and achieve accuracy of >90% for the latter. Demonstrating the ability of this model to capture non-linear features. Our high-throughput measurements and ML-assisted data analysis exemplifies the potential of ML to diagnose and forecast hybrid perovskites’ response with a variety of chemical compositions.
(Invited) Modeling Cyclic Voltammetry during Solid Electrolyte Interphase Formation
Authors: Steinruck Hans-Georg
Published: August 2024

The solid electrolyte interphase (SEI) is an electronically insulating film on anode surfaces in Li-ion batteries (LIBs), formed by the reaction of Li-ions with reduced electrolyte species [1]. The SEI leads to a reduction of the electrochemical current in heterogeneous electrochemical redox reactions at the electrode-electrolyte interface, thereby passivating the electrode surface [2]. Accordingly, the growth of the SEI is, in principle, self-limited. However, under realistic conditions, these phenomena are much more complex and not well understood.

Towards a better understanding of SEI formation and passivation, we have developed a baseline quantitative model within Butler–Volmer electrode kinetics that describes the cyclic voltammetry (CV) of a flat macroelectrode during SEI formation [3]. We assumed that the SEI, which builds up electrochemically during CV, forms a homogeneous, single-phase, electronically insulating thin film due to the corresponding current. The model is based on a dynamically evolving electron tunneling barrier with increasing film thickness. Our framework allows both the qualitative, intuitive interpretation of the characteristic features of CV measurements and the quantitative extraction of physicochemical parameters through model fitting.

In this contribution, we will introduce the basic concepts and equations of our baseline model, illustrate several examples, discuss its limitations, and provide a brief outlook for improvements and for more complex scenarios. Finally, comparisons are presented to exemplary CVs from the literature relevant to LIB science and to self-inhibition phenomena.

References

[1] P. Verma, P. Maire, P. Novák, Electrochim. Acta 2010, 55, 6332

[2] F. T. Krauss, I. Pantenburg, B. Roling, Adv. Mater. Interfaces 2022, 2101891

[3] H.-G. Steinrück, J. Chem. Phys. 2021, 154, 174703

[4] I. Bhugun, J.-M. Savéant, J. Electroanal. Chem. 1995, 395, 127
A Novel Approach to Continuum FE Multiphysics Simulation of Batteries via Heterogeneous Homogenization
Authors: Carlson Timothy , Salazar Tio Rafael , Hahn Youngwon , Oancea Victor , Balasubramanian Ganapathi Raman , Crouse Bernd
Published: August 2024

Advancements in modern technology necessitate batteries that can be safely charged and discharged at high rates with minimal aging. A promising strategy to achieve these ends is through optimization of porous microstructures of existing electrode materials to promote better electrical and ionic transport without compromising energy density, as has been shown experimentally by introducing laser ablation channels to the electrodes. The present work proposes a microstructure up-scaling methodology that efficiently accounts for material heterogeneity by assigning a porosity field to a continuum scale finite element mesh, effectively homogenizing materials while maintaining the heterogeneous porosity distribution inherent to the original microstructure. Constitutive relationships relating solid electric conductivity and pore tortuosity to local porosity are directly computed from fully resolved anode, cathode, and separator microstructure 3D models and assigned in the continuum as material properties of a finite element mesh. This allows for utilization of the computationally efficient, homogenized Newman model while maintaining dependency on the heterogeneous local porosity. Then, coupled electrochemical-thermal-mechanical-pore pressure finite element simulations are performed on the battery cell model with this heterogeneous porosity field, and associated local variations on transport properties are prescribed as material properties by the precomputed constitutive relationships. Performance metrics and lithium plating potential are compared to the results of simulations of the fully homogenized cell with the same constitutive relationships and to the base case of a fully homogenous cell with typical modelling assumptions applied to porosity dependent constitutive relationships. These comparisons are made both as a means of validating the methodology and to demonstrate the vast differences that arise when simplifying assumptions are used instead of the constitutive relationships of the actual material microstructure. Finally, the methodology is used in its intended optimization application to compare the performance of a typical battery microstructure to a similar porous microstructure with micro holes added via laser ablation. The results indicate that differences in the microstructure of materials with identical average porosities and similar constitutive relationships can have significant differences in both cell performance and aging that would typically be impossible to detect using fully homogeneous continuum modeling.

Figure 1
Structural Characterization of Mixed Metal Cathodes via in Operando X-Ray Diffraction
Authors: Henderson Nathan , Jones Brian
Published: August 2024

Complex metal oxides used in lithium-based energy storage technologies undergo distinct crystallographic changes based on chemical composition, specific voltage and current states, degree of lithiation, and more. Crystallographic studies via X-ray diffraction (XRD) are a critical part of understanding structure-property relationships and engineering devices to meet specific performance requirements. For the raw electrode materials, XRD provides information about exact crystal structure (e.g. symmetry, unit cell parameters, atomic site mixing) as well as the presence of impurity phases that might arise from a poor sintering process or non-stoichiometric starting reagents. For formed devices such as button- or pouch-cells, XRD can be used in operando to measure changes in phase composition, phase quantification, and crystal lattice expansion/contraction as a function of charge state. This can provide useful information such as the level of reversibility of a device or the onset of impurity phases during aging and long cycling.

In this presentation, we will review diffraction data for case studies based on NMC electrodes and highlight key insights into reversible structural changes during device cycling. The figure attached to this abstract shows diffraction data as a function of charge state during a single charge/discharge cycle. The observed peaks show modifications to the crystalline lattice (expansion in one direction, contraction in another orthogonal direction).

Figure 1
Mechanisms of Ni Dissolution from Ni-Rich Cathode in Li-Ion Batteries
Authors: Zheng Yu , Zheng Yu B.
Published: August 2024

Nickel-rich cathodes are the most promising candidates for realizing high-energy-density Li-ion batteries because of the high theoretical capacity. However, their structural instability detrimentally affects the battery performance during cell cycling, which restricts its large-scale commercial application. One impediment to their commercialization is the dissolution of transition metal ions, which can diffuse to the anode, corrupt the solid electrolyte interphase (SEI) films protecting the anode, and accelerate battery capacity fading. Here, we use ab initio molecular dynamics (AIMD) simulations to investigate the mechanism of Ni dissolution from the LiNiO2 cathode surfaces. Our calculations identified that the proton-transfer reactions between electrolytes and cathode surfaces cause the reduction of surface Ni atoms from Ni3+ to Ni2+, which weakened the Ni-O bonding. As the LiNiO2 cathode surface gets delithiated, more surface protonation reactions were observed, and the reduced Ni atoms were found to be dissolved from the cathode surfaces in the form of NiOOH, which is the fundamental origin of phase transition of LiNiO2 cathode from a layered to electrochemically inactive spinel-like structure, accompanied by H2O elimination and O2 evolution. Besides, we also studied the impact of various factors on Ni dissolution rates such as the presence of fluorine attachment and the coordination of Ni atoms and electrolyte species. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces for Ni-rich cathode.