bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Progress in the Analytical Capability of X-Rays to Locate Chemical Phenomena in Battery Materials
Authors: Cabana Jordi
Published: December 2024

The evolution of local chemistry determines the performance of electrodes and electrolytes used in batteries because limitations can be tracked to slow kinetics and transport, and irreversibilities in the storage reaction. Tools that provide insight into local chemistry are critical for identifying the underpinnings of electrochemical function. This information must be resolved within architectures, from individual particles to microscale domains, to pinpoint the relationship between local phenomena and their role in macroscopic metrics and degradation. Technical developments in X-ray microscopy and mapping have built a flexible suite of tools that combine the desired spatial resolution and 3D capabilities with a suite of possible contrasts mechanisms, such as diffraction and spectroscopy. In this talk, we will discuss our recent research that demonstrates the diversity of length scales at which important chemical heterogeneity can be induced in battery electrodes. For this purpose, the systems of study will be the leading cathodes for Li-ion batteries. We will highlight the new fundamental insight generated by the tools, but also motivate the need for the extension of the analytical capabilities of the tools into outcomes of high statistical significance. The insight generated by our approaches will be related to their impact on material and architecture properties. Along the way, we will also provide a glimpse into the future by showing how emerging synchrotron techniques can enhance the impact of X-ray microscopy in fundamental battery science. Particularly, we will discuss the prospects of probing time-resolved phenomena using operando measurements to avoid uncertainty due to relaxation under open circuit conditions.
Stress-Induced Modification for Interlayers in Lithium Metal Batteries
Authors: Edgerton Brent , Liu Yangliu , Moon Jaron , Warren Roseanne
Published: December 2024

As solid-state electrolytes (SSE) gain attention in the academic and industrial space, thin film interlayers are increasingly used to enhance wettability and lower interfacial resistance. Gold films, or interlayers, are frequently sputtered on ceramic electrolytes to improve their contact bonding with both anodic and cathodic layers. To-date, adherence between the SSE and current collector without cracks or delamination has been considered sufficient to qualify a “good” interlayer deposition. It is well known in the surface science community, however, that thin films can sustain high levels of residual stress, depending on dose-momentum of the depositing species.

For the first time, this work demonstrates the effects of interlayer residual stress on first and subsequent charge-discharge cycles and formulates a theory identifying the governing physical mechanism. We fabricate Au-Cu electrodes imbued with residual stress (-50 to 160 MPa) and cycle electrodeposited lithium on and off the surface to demonstrate unique morphological, electrochemical, and performance characteristics. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) measurements show that tensile interlayers result in larger, more irregularly shaped lithium structures that have high irreversibility, while compressive interlayers result in small, densely packed lithium structures with minimal solid electrolyte interface (SEI) formation (Figure 1a-d).

We characterize the Au-Cu surface using SEM, nanoindentation, optical spectroscopy (UV-Vis-NIR), and ultraviolet photoelectron spectroscopy (UPS) to relate the physical properties of the interlayer to the electrochemical behavior. The test results show that film stress causes the equilibrium electron energy levels to shift. As the surface becomes more tensile, the contact energy decreases, the color reddens, and the work function increases (Figure 1e-g). This evidences a change in the electronic configuration, leading to distinct thermodynamic behavior in lithium structures. This work demonstrates the high sensitivity of the electrochemical environment to even minor changes in the initial condition of interlayer state and presents a guide for consistent fabrication parameters that maximize the potential interlayer benefits offered by residual stress control.

Figure 1
(Invited) Unified Interphase Design for Electrochemical Stability of Metal Anodes with Liquid-Based and All Solid-State Electrolytes
Authors: Mitlin David
Published: December 2024

Lithium metal battery systems (LMBs) are being sought as an ultimate replacement to lithium ion batteries (LIBs), potentially increasing the cell energy by over fifty percent due to the high capacity and low voltage of the metal anode. Analogous improvement in energy is possible with sodium metal batteries (NMBs) and with potassium metal batteries (KMBs), where existing ion insertion anodes can be replaced by plating/stripping metal. However, in all three cases safety and performance are compromised by an unstable solid electrolyte interphase (SEI) that consumes metal ions and electrolyte, and ultimately leads to dendrites. This presentation provides a series of case studies derived from the group's LMB, NMB and KMB liquid and solid-state research on the microstructural design principles that provide for long-term cycling and fast-charge stability of metal anodes. The approaches may be categorized as the following: a) design of plating/stripping supports and templates with tuned geometry and functionality; b) design of secondary interlayers placed between the metal anode and the separator; and c) design of multifunctional hybrid separators to replace the conventional polymer separators employed with LIBs. It is demonstrated that despite appearing distinct, the efficacy of each in enabling electrochemical stability originates from three fundamental features that are directly interrelated. The wetting behavior of the electrolyte on the anode must be optimized, the wetting/stripping behavior of the metal anode on the current collector must be controlled, and a geometrically and chemically modified SEI must be established. Simultaneously achieving all three leads to stable plating/stripping, while missing even one leads to rapid dendrite growth. Cryogenic FIB cross sections and cryo-TEM are combined to yield new insight regarding film wetting behavior and early dendrite formation in optimized versus baseline specimens, analyzing growth in several representative electrolytes.
The Effect of Surface pH on Rhenium Electrodeposition
Authors: Ahammed Kamal , Huang Qiang
Published: December 2024

Electrodeposition is considered as a cost-effective, controllable, scalable, and facile process for material deposition[1] and has been widely used in the device fabrication[2-4]. Electrodeposition of high quality rhenium films with improved morphology is enabled in the so called water-in-salt (WIS) electrolyte, where a superhigh concentration of salt, such as LiCl, is present to deplete the free water molecules, reduce the proton diffusion, and suppress the hydrogen evolution side reactions[5]. Yet, inclusion of oxygen and chlorine is observed for the films deposited from such electrolytes. While Cl incorporation may result from high concentration of LiCl, the presence of oxygen can relate to oxide formation due to surface pH increase expected during electrodeposition. Therefore, understanding the surface pH during deposition might provide insight on the Re deposition mechanism and a guideline to further develop the chemistry and process for improved film property.

This work aims to measure the electrolyte pH at the electrode surface during Re electrodeposition and to determine the effects of salt speciation and deposition potential on the hydrogen evolution. How the surface pH impacts the impurity incorporation will also be investigated. A customized rotating ring disk electrode (RRDE) is utilized to perform the measurement. The Iridium Oxide pH sensing layer is fabricated using electrodeposition method on the Au ring and Re deposition is carried out on the Pt disk. The electrolyte pH during deposition is recorded as the open circuit potential (OCP) on the IrOx ring electrode. The interference of the anions or cations in the solution (other than proton or hydroxide) on the OCP reading is studied and calibrated. In-situ pH change under different solute conditions will be investigated to evaluate the efficacy of salts in suppressing hydrogen evolution. Furthermore, a correlation between surface pH and the incorporation of impurities, especially the oxides, will be studied under different solute environments.

References

Zhang, Q., et al., Electrodeposition in ionic liquids. ChemPhysChem, 2016. 17(3): p. 335-351.

Romankiw, L., Compositional Profiles in Electroplated Permalloy and Copper Permalloy: a Methodology Toward Laminated Permalloy for Thin Film Head Applications. Magnetic Materials, Processes, and Devices, 1991: p. 367-379.

Andricacos, P.C., et al., Damascene copper electroplating for chip interconnections. IBM Journal of Research and Development, 1998. 42(5): p. 567-574.

Moffat, T.P. and D. Josell, Superconformal Electrodeposition for 3-Dimensional Interconnects. Israel Journal of Chemistry, 2010. 50(3): p. 312-320.

Huang, Q. and T.W. Lyons, Electrodeposition of rhenium with suppressed hydrogen evolution from water-in-salt electrolyte. Electrochemistry Communications, 2018. 93: p. 53-56.
Fabrication of Patterned TiO2 Nanotube Layers Utilizing 3D Printer Platform and Their Electrochromic Properties
Authors: Kang Kwang-Mo , Nah Yoon-Chae
Published: December 2024

An anodization method can easily fabricate nanostructured oxide layers by controlling electrochemical parameters such as the types of electrolyte solutions, the electrolyte composition, applied voltage/current, temperature and pH. In the anodization process, it is common to form an oxide on the surface of a metal substrate with an area of several to several hundred cm2. However, several approaches have been attempted to form oxide layers on a local area or manufacture a certain oxide layer pattern using the anodization process. For this purpose, partial oxidation can be achieved through the masks and patterned metal substrates can be employed for local anodization. However, these methods are disadvantageous in process-complexity and time-consumption. Therefore, this study realizes complicated patterns composed of anodized TiO2 nanostructures using a 3D printer and apply them to the electrochromic displays. A commercial 3D printer was modified to enable a direct anodization and TiO2 nanotube was anodized on the Ti substrate with the desired pattern designed by a digital code (G-code). High speed anodization was performed at a speed of 1 mm/s. Furthermore, the surface of the patterned TiO2 nanotube was modified by adsorption of the viologen molecules and the electrochromic properties of the viologen-anchored TiO2 (V-TiO2) nanotube layers were investigated.
Multiscale Modeling Approach to Study the Influence of Bilayer Porous Transport Layers on Oxygen Evolution and PEMWE Performance
Authors: Sepe Mitchell , Shah Dhairya , Cho Hyunseok , Shimpalee Sirivatch
Published: December 2024

With the current push for an alternative to traditional fuel-based transportation, hydrogen has the potential to be a viable replacement. Hydrogen has been proposed as a fuel replacement in internal combustion engines, or as fuel in a fuel cell powered automotive vehicle. Before hydrogen can be used in any type of transportation, it must first be produced. Proton Exchange Membrane Water Electrolyzers (PEMWE) produce hydrogen through an oxygen evolution reaction. A key component to PEMWE operation is the porous transport layer (PTL). Specifically, the PTL on the anode side must provide transport pathways for water to access the catalyst layer, while simultaneously removing oxygen.

In this work, a multiscale modeling approach is used to study the effect of a bilayer PTL, which is a PTL with an added mesoporous layer (MPL), on oxygen evolution and PEMWE performance. A previously developed image processing technique was expanded to generate bilayer PTLs from Xray Tomography scans. This process generates each sample a one combined geometry, which removes the need for interface communication. Due to the improvements in imaging techniques, the ability to mesh complex structures with this technique is possible. Each sample was generated with a 2:1 PTL to MPL ratio, with the total thickness around 400 ums. Porosity and pore size distributions were calculated during the image processing step. First a micro scale model that uses the Finite Volume Method, accompanied with a volume of fluid model, was used to predict permeability and simulate simultaneous two-phase flow of liquid water and oxygen gas. Oxygen evolution, growth, and structure interaction were observed. Results showed that the bilayer structure removes oxygen faster than single layer PTLs. Physical properties calculated using the micro scale model were used to inform a macro scale model of a PEMWE using the Finite Volume Method. The macro scale model predicted performance curves for each bilayer sample. Results showed that the bilayer samples exhibited improved performance as high current densities. Findings from this work show that a bilayer PTL geometry has potential to improve PEMWE performance.
Metallic Glass Nanoparticles Synthesized via Flash Joule Heating for High Performance Catalysis
Authors: Wang Hang , Ma Yuanyuan , Fan Xue , Maclean Stephen A. , Makowski Nathan , Lipton Jason , Meng Juan , Rohr Jason A. , Li Mo , Taylor Andre
Published: December 2024

Metallic glasses (MGs) are a class of amorphous metal materials with remarkable properties. By leveraging an abundance of uncoordinated active sites that can serve as catalytic regions, MGs can have high catalytic activity and long-term stability as compared to their crystalline counterparts. Conventional synthesis methods cannot produce nanosized MGs with precise control over composition, phase, and morphology. This work presents flash Joule heating (FJH) as a novel one-step approach to synthesize fully amorphous MG nanoparticles while enabling unprecedented control over these critical parameters. The rapid heating (up to 2505 K/s) and ultrafast cooling rates (up to 1485 K/s) in FJH surpass the critical rates required for glass formation in metal-phosphide alloys like Pd-P, Pd-Ni-P, and Pd-Cu-P, preventing crystallization. Characterization techniques such as SAED, XRD, and XPS have confirmed the amorphous nature and metallic states of the nanoparticles.

Remarkably, FJH allowed precise tuning of ternary alloy compositions spanning wide ranges from Pd-rich to Ni/Cu-rich regimes, closely matching designed precursor ratios. The technique significantly expanded the glass formation region compared to conventional methods, accessing previously unattainable compositions like binary Pd3P. Moreover, FJH enabled control over particle size from 2.33±0.83 nm to 36.5±10.1 nm with narrow distributions by optimizing precursors, thermal profiles, and alloy chemistries. Incorporation of multiple elements facilitated smaller nanoparticle formation due to enhanced entropy, reduced melting points, and decreased surface tension.

The amorphous MG nanoparticles exhibited outstanding electrocatalytic performance and remarkable stability superiorities over their crystalline counterparts. For the oxygen evolution reaction, Pd-Ni-P MGs displayed ultra-low onset potentials ~300 mV below pure Pd and retained stable activity over 60 hours, contrasting rapid deactivation of crystalline samples of the same composition within 1 hour. PdCoP MGs for methanol oxidation showed high reaction rates and resilience against activity decline during accelerated durability testing, unlike rapidly decaying crystalline variants. This FJH synthesis approach unlocks new opportunities to realize the full potential of MGs by expanding the compositional space of alloy systems with precise control over MG properties, unlocking potential future transformative catalysts.

Figure 1: Schematics for (a) a traditional heating-cooling process and (b) the FJH process. (c) Illustration of temperature vs. time diagram of supercooled liquid alloys and glass transformation.(d) Ternary phase diagrams of the Pd-Ni-P and Pd-Cu-P systems.

Figure 1
Development of in-Situ Method for Synthesis of TiCl2 Electrolyte
Authors: Se Young Lee , Ri Vladislav , Kim Hyun-woo , Kim Wan-gou , Ku Kwang Mo
Published: December 2024

The Kroll process was developed in the 1960s and remains the main commercial process for titanium production. While the production of titanium sponge in large amounts has been established, its drawbacks include high energy consumption, toxicity, high GHG emissions, and the generation of iron-contaminated titanium scrap, which remain unsolved. Therefore, many researchers have attempted to develop alternative methods for titanium production in the past decades, and electrorefining is one of these methods. The titanium electrorefining process is based on the transfer of titanium from an impure electrode (anode) to another electrode (cathode) in the electrolyte environment. The electrolyte plays a huge role in the transport of titanium, as well as in the oxidation and reduction mechanisms on the electrodes. According to past research, it is important to maintain titanium species in the form of divalent titanium (TiCl2). An increase in trivalent titanium in the electrolyte requires more electric energy and results in lowered current efficiency and lower quality of deposits. The preparation of TiCl2 is complicated by its high hygroscopic ability and the high exothermicity of the reaction, which may cause the formation of higher titanium chlorides in gaseous form. Therefore, this study is focused on the development of an in-situ synthesis method for TiCl2 electrolyte. This method is based on the preparation of a CaCl2-NaCl-CuCl solution and the addition of titanium metal powder into the solution at elevated temperatures in an argon atmosphere. As a result of the synthesis, a CaCl2-NaCl-TiCl2 solution is obtained, along with a byproduct of synthesis, copper metal, which sediments in the shape of sponge or flakes at the bottom of the crucible. Thermodynamic equilibrium evaluation revealed that the optimal temperature for TiCl2 synthesis is within the range of 600-700 °C, and the ratio of titanium addition is within the range of 1.0-1.1Ti. Additionally, the influence of temperature and the ratio of titanium addition on synthesis was studied experimentally under the same conditions. TiCl2 electrolytes were prepared and analyzed using hydrogen volumetric analysis to quantify TiCl2 concentration, titration analysis to quantify TiCl3 concentration, and ICP analysis to quantify total Ti concentration in the solution. The sedimented copper byproduct was leached from the electrolyte and analyzed by SEM/EDS to quantify the reaction yield of titanium. Experimental results showed that TiCl2 can be successfully synthesized in molten CaCl2-NaCl and that the temperature of the synthesis process and the ratio of Ti added have a strong impact on the composition of the electrolyte, Ti concentration, copper residual content in the electrolyte, and reaction yield. The optimal temperature was in good agreement with theoretical evaluation and was found to be 650 °C. A stoichiometric ratio or slight excess of Ti (1.0-1.1Ti) is recommended for the highest reaction yield of TiCl2 synthesis at 650 °C.
(Invited) Atomic Layer Deposition of (Semi)Conductive Oxides for Photovoltaics and Mo(o)Re
Authors: Macco Bart
Published: December 2024

(Semi)conductive oxides are a peculiar class of materials that combine optical transparency and (tunable) electrical conductivity, and are typically composed of combinations of In, Zn, Sn or Ga. These materials play a profound role in solar cells, but are also more and mo(o)re considered in memory, logic, photonics and sensing. When they are highly (degenerately) doped, these materials can act as transparent conductive window layers (e.g. in solar cells), and are often referred to as Transparent Conductive Oxides (TCOs). Conversely, for lowly-doped (non-degenerate) semiconductive oxides, the Fermi level is susceptible to external influences. The electrical conductivity can then be modulated, for example by gating in a transistor or gas exposure in a sensor. Often amorphous alloys such as InGaZnO are used, and the more common term is hence amorphous oxide semiconductors (AOS).

Especially since the early 2000s, many ALD processes for doped and compound (semi)conductive metal oxides have been developed. The interest in ALD for preparing these oxides can most likely be attributed to the distinct merits of ALD, such as low-temperature processing, excellent uniformity and conformality, and accurate control over the doping level and composition. Moreover, as device dimensions shrink the need for high-quality ultrathin materials becomes ever more important. These merits of ALD stem directly from the self-limiting nature of the surface chemistry that drives the ALD growth. On the other hand, the strong role that surface chemistry has in the growth mechanism brings in many intricacies, and detailed understanding of these aspects has been vital for the development of high-quality doped and compound oxides by ALD. Examples of growth effects that can occur during ALD of compound oxides include growth delays, clustering of dopants and interruption of grain growth by doping. Such effects often need to be accounted for or mitigated, while on the other hand there are also clear cases where such growth effects can be leveraged to achieve enhanced or new functionality.

Recently, we have reviewed these aspects, focusing on how such underlying ALD mechanisms relate to the resulting performance of the (semi)conductive oxide.[1] In this contribution, we apply these learnings to the application side, specifically looking at silicon and perovskite (tandem) solar cells and back end of line-compatible transistors for nanoelectronics. While these application areas are seemingly distinct, many learnings and parallels can be drawn from an ALD point of view. Topics that will be covered include (1) isotropic doping vs. nanolaminates, (2) advanced ALD (super)cycles, (3) soft deposition, (4) crystallinity control, (5) ultrathin films and more. We will highlight these aspects through case studies, drawing from our own recent work as well as examples from the field.

[1] B. Macco, W.M.M. Kessels, Atomic layer deposition of conductive and semiconductive oxides, Appl. Phys. Rev. 9 (2022) 041313.

Figure 1
(Invited) Silanes As Precursors and Inhibitors for Area-Selective Deposition
Authors: Brick Chad , Ogata Tomoyuki
Published: December 2024

Silanes play a unique dual role in the field of area-selective deposition (ASD), serving as both precursors for common semiconductor-device films such as silicon dioxide, silicon oxycarbide (low-k) and silicon nitride, or as inhibitors of deposition processes via selective surface passivation. In this presentation we will review the evolution of silane precursors from simple thermal chemical vapor deposition (CVD) and epitaxial precursors such as tetraethoxysilane and silane, to the increasingly complex molecules used for plasma-enhanced CVD, atomic layer deposition, and ASD. Contemporary reported strategies for the use of silicon-containing molecules as ASD precursors and inhibitors will be assessed, and the inherent challenges of using similar chemistry for two contrasting purposes will be discussed. Specific topics that will be covered include the use of silanes to inhibit growth on both oxide and non-oxide surfaces, an inherently selective thermal process for growing mixed oxide films on dielectric layers, an inherently selective plasma-enhanced process for depositing silicon dioxide on dielectric layers, and an inherently selective plasma-enhanced process for growing silicon dioxide on metals.
Plasma Atomic Layer Etching of Dielectric Materials with Low Global Warming Fluoro-Ether Isomers
Authors: Chae Heeyeop , Hong Daeun
Published: December 2024

In this work, the comparative study of the plasmas of C5F10O and C4H3F7O isomers with low global warming potential (GWP) was conducted in plasma atomic layer etching (ALE) processes of dielectric materials. Plasma atomic layer etching processes for silicon oxide and silicon nitride were developed with perfluoropropyl vinyl ether (PPVE) and perfluoroisopropyl vinyl ether (PIPVE) as C5F10O isomers, and heptafluoropropyl methyl ether (HFE-347mcc3) and heptafluoroisopropyl methyl ether (HFE-347mmy) as C4H3F7O isomers. In the surface fluorination step, the dielectric surfaces were fluorinated with C5F10O and C4H3F7O isomer plasmas and the fluorinated layer was removed by ion bombardment with Ar plasma. The F1s/C1s ratio of the fluorocarbon layer in PPVE plasma analyzed by X-ray photoelectron spectroscopy (XPS) was higher when it is compared to those in PIPVE, HFE-347mcc3, and HFE-347mmy plasmas. In the removal step, ALE window was identified in 50.0 ~ 57.5 V for C5F10O isomers and 50 ~ 60 V for C4H3F7O isomers and the etch per cycle (EPC) of SiO2 was determined to be 5.4, 3.3, 2.1, and 1.8 Å/cycle for PPVE, PIPVE, HFE-347mcc3, and HFE-347mmy, respectively in the ALE window region. The EPC of SiO2 was the highest in the PPVE with a high F1s/C1s ratio of 1.57, and the lowest in the HFE-347mmy with a low F1s/C1s ratio of 1.05. The global warming effect of the exhaust gases was evaluated by carbon dioxide equivalent values determined from the concentration of the exhaust gases. The carbon dioxide equivalent was reduced up to 90%, compared to that of C4F8 plasma. The carbon dioxide equivalent of C4H3F7O isomer plasmas was the lower than that of C5F10O isomer plasmas due to the generation of HF and CO, having much lower GWPs as major reaction products.
(Invited) Surface Analysis of GaN by Cyclic Etching Process for ALE of III-V Materials
Authors: Sekine Makoto
Published: December 2024

In the fabrication of next-generation power electronic devices based on the III-V materials i.e. gallium nitride (GaN), AlGaN, etc., atomic layer etching (ALE) with the cyclic process of ion irradiation and Cl adsorption steps has been attracted for the reduction of plasma induced damages and the precise definition of etch depth. For controlling the GaN ALE, we investigated the surface layer of GaN at each Ar ion and Cl radical reaction step using a beam experiments with in situ X-ray photoelectron spectroscopy (XPS).[1,2]

Samples were GaN films on a sapphire substrate by Hydride Vapor Phase Epitaxy (HVPE) method. Native oxide on GaN surface was removed by wet cleaning (5% HF) and Ar ion sputtering before the beam experiments. The wet cleaned surface was exposed to Cl radicals generated in Cl2 gas plasma. Then, Ar ions were irradiated with the accelerating voltage of 100 V or 200 V.

The one cycle consisted of these Cl radical exposure and Ar ion irradiation. To stabilize the GaN surface, five cyclic processes were carried out. The GaN surface at each step was analyzed by angle-resolved XPS with the take-off-angles (TOA) of 20, 30, 40, 60, and 90 degrees with respect to the wafer surface. The depth profiles were analyzed by the maximum entropy method.

In the GaN cycle process by Cl adsorption and Ar ion irradiation, the reaction in the Cl adsorption step is saturated at the order of 1019 cm−2. The reaction in the Ar ion irradiation step was saturated by Ar ion irradiation of the order of 1016 cm−2, and the formation of Ga dangling bonds occurred with the etching of Ga chloride and the desorption of N atoms. Increasing the Ar ion energy increased the amount of Ga dangling bonds formation and the subsequent increase of Cl adsorbed amount by the radical irradiation. At the same time, higher the Ar ion energy, higher the required doses of Cl and Ar ions to saturate the reaction in each step.

The Cl adsorption behavior was depended on the depth profile of the Ga dangling bonds and varied with Ar ion energy. At 47.6 eV, which is below the energy of GaN ALE window, the Ga chloride could not be desorbed, but ions in this energy break Ga-N bonds and desorb N atoms. At 86.8 eV, which is the energy band of the ALE window of GaN, Ga chloride and N atoms can be desorbed, and it was confirmed that the Cl adsorption behavior depends on the ion energy. From these results, it is considered that the Cl adsorption depth and etching depth continue to change even in the energy band of the ALE window.

Consequently, to achieve a higher Synergy and precise etching of GaN, tuninng of ion energy beside the ALE window should be necessary.

Acknowledgement

The author thanks Drs. Masaki Hasegawa, Takayoshi Tsutsumi, Kenji Ishikawa, Masaru Hori, Hiroki Kondo, Shouhei Nakamura, Atsushi Tanide, Souichi Nadahara, Osamu Oda, Jia He for their discussions and providing the data.

[1] T. Takeuchi et al., J. Phys. D: Appl. Phys. 46, 102001 (2013).

[2] Y. Zhang et al., J. Vac. Sci. Technol. A 35, 060606 (2017).
Size and Structure Selective Indium Sulfide Cluster Formation Via Vapor Phase Sequential Infiltration Synthesis
Authors: Kim Kihoon , Havenridge Shana , Zaluzec Nestor , Kang Donghyeon , Jayaweera Nuwanthaka , Elam Jeffrey W. , Liu Cong , Mulfort Karen L. , Martinson Alex B. F.
Published: December 2024

Energetically favorable formation of atomically precise clusters, known as magic-size clusters from solution phase synthesis are studied extensively enlightening their unique properties and consecutive nucleation and growth mechanism to bulk structures. However, those from vapor phase synthesis are comparatively underdeveloped, especially for the metal chalcogenide materials. Here we report that vapor phase sequential infiltration synthesis enables the formation of indium sulfide magic-size clusters. Based on the experimental and computational study, we found that the reaction between trimethylindium and hydrogen sulfide in the presence of polymethylmethacrylate led to the formation of In6S6(CH3)6. While semiconductor cluster growth might be expected after multiple cycles of In and S precursors, the same magic size clusters form in multiple polymer films and the ultraviolet-visible absorption spectra of clusters are largely independent of the SIS cycles number. We observed that the only variation in the reaction temperature altered the reaction pathway, changing the extinction spectral feature and air stability of the resulting clusters.
Molecular Layer Deposition of Novel Lithicones and Promising Applications
Authors: Meng Xiangbo , Velasquez Kevin , Shao Aiying , Watanabe Fumiya
Published: December 2024

Molecular layer deposition (MLD) represents an emerging technique for growing polymeric films in a controllable mode.1 Compared to its sister counterpart, atomic layer deposition (ALD) for growing inorganic materials,2 MLD still has not been well explored and has unlimited opportunities to provide new solutions for many challenges facing us. While our society is experiencing a transition from gas-powered vehicles to electric vehicles, we urgently need robust rechargeable batteries to empower this transition. In this respect, lithium metal batteries (LMBs) are particularly attractive, featuring their high energy density of ≥ 350 Wh/kg. However, their lithium metal (Li) anodes suffer from two serious issues: (1) continuous formation of solid electrolyte interphase (SEI) with the consumption of liquid electrolytes and cyclable Li and (2) Li dendritic growth posing high safety risks. Striving for addressing these issues, recently we developed a series of novel polymeric lithicone coatings using MLD, including LiGL (GL = glycerol) 3, LiTEA (TEA = triethanolamine) 4, and LiHQ (HQ = hydroquinone). These polymeric lithicones demonstrated remarkable effects on tackling the issues of Li anodes, enabled extremely long cyclability of Li||Li symmetric cells, dramatically improved sustainable capacities of LMBs. In our studies, we studied the growth behaviors of these lithicones using in situ quartz crystal microbalance, analyzed their compositions using X-ray photoelectron spectroscopy, and observed their morphologies with scanning electron microscopy. Furthermore, we investigated their applications in Li||Li symmetric cells and Li||NMC full cells (NMC = LiNixMnyCozO2). Our studies demonstrated that lithicones are a promising class of polymeric materials having great potential to provide new solutions for high-energy LMBs.

References:

Meng, X., An overview of molecular layer deposition for organic and organic-inorganic hybrid materials: Mechanisms, growth characteristics, and promising applications. J. Mater. Chem. A
2017,
5 (35), 18326-18378.

Meng, X.; Yang, X. Q.; Sun, X. L., Emerging applications of atomic layer deposition for lithium-ion battery studies. Adv. Mater.
2012,
24 (27), 3589-3615.

Meng, X.; Lau, K. C.; Zhou, H.; Ghosh, S. K.; Benamara, M.; Zou, M., Molecular Layer Deposition of Crosslinked Polymeric Lithicone for Superior Lithium Metal Anodes. Energy Material Advances
2021,
2021, 9786201.

Wang, X.; Cai, J.; Velasquez Carballo, K.; Watanabe, F.; Meng, X., Tackling issues of lithium metal anodes with a novel polymeric lithicone coating. Chem. Eng. J.
2023,
475, 146156.
Molecular Dynamics Simulation of Bubble Formation in Confined Water in Si/SiO2 Nanochannels
Authors: Taghavi Nasrabadi Amir , Nishikido Shuuichi , Simms Ihsan , Nakamori Mitsunori
Published: December 2024

Megasonic-based techniques are employed in the etching and cleaning processes in the semiconductor industry since they are gentler than other cleaning techniques and less apt to cause damage. In these processes, sound waves, at a frequency of 1 MHz or higher, are sent into etching or cleaning fluid, which could result in the formation of bubbles inside the fluid, revealing features and producing patterns. The formation and collapse of bubbles in nano-scale features is of interest in the semiconductor industry due to the potential effects on etching performance and surface roughness. Our understanding is still limited, however, because of the dimensions involved. Typically, the bubble size is too small, and the duration of bubble formation/collapse is too short, to allow easy study of the characteristics of bubble formation or collapse through experimental methods. Molecular dynamics (MD) simulation is a powerful tool to simulate such a phenomenon, which can facilitate understanding of bubble behavior in a confined space, and in the vicinity of the surface.

In this work we use MD simulations to simulate bubble formation in confined water in silicone (Si) and silicon dioxide (SiO2) nanochannels. Our focus of study is to identify the mechanism type for bubble formation in these nanofeatures, and determine how the surface characteristics, including the wettability, influence bubble formation. Figures 1a and 1b show the simulation results of bubble formation in confined water in the Si and SiO2 nanochannels, respectively. Our results show that the bubble forms on the hydrophobic Si surface, indicating a heterogeneous bubble formation, while for the hydrophilic SiO2 surface, the bubble tends to form away from the surface and in the bulk of the liquid, indicating a homogeneous bubble formation. In a hybrid situation where both the hydrophobic Si and hydrophilic SiO2 surfaces are present (Figure 1c), heterogenous bubble formation is dominant and the bubble forms on the Si surface. Our work provides insights into the mechanism of bubble formation in the confined water in nanofeatures and how surface wettability affects it.
(Invited) Applications of Complimentary FETs Using Low Temperature Deposited Phase Composite Semiconductor Channel Materials
Authors: Lee Byoung Hun
Published: December 2024

Phase composite material is an ultrathin film structure having both crystalline islands and amorphous matrix which exhibit unique carrier conduction properties. Due to the coupling of conduction states between quantum dot like crystalline islands, an isolated conduction band is formed near the mobility edge of the conduction band of amorphous states. Effective mobility of carrier conduction via the mobility edge states are in between the values of single crystal and polycrystalline film. The primary benefit of phase composite material is the process compatibility with silicon process, especially at the back end of line process where the process temperature is limited below 400°C. Since this material state can be easily formed using high pressure atomic layer deposition process at low temperature below 200°C, various semiconductor channel materials can be deposited on arbitrary shaped substrate. Using the process flexibility of this process, nMOS and pMOS can be easily fabricated in planar form or in vertically integrated form. In this talk, various applications of devices fabricate using phase composite semiconductor channel materials will be discussed.
(Invited) Physics Informed Data Driven Manufacturing for Li-ion Batteries
Authors: Anapolsky Abraham , Aung Kumu , Bhargava Arjun , Chang Benjamin , Chen Flora , Forker Thomas , Gordon Matthew , Shibusawa Takumi , Tieskoetter Brian
Published: December 2024

The road to carbon neutrality requires a massive scale up of battery manufacturing on a rapid timescale. Li ion batteries are complex systems with many materials and interfaces, and the challenge of controlling microcale material properties of millions of units per year demands a physics and a data driven approach to manufacturing. Conversely, the Toyota Production System (TPS) for manufacturing is a deeply human-led process, thus, we have a need to integrate a variety of models with human expertise and experience. We will present our manufacturing optimization experience and approach with safety and cost as target metrics. Economics incorporates both cost of production (including yield and throughput) as well as future performance (reliability). We will present several case studies of the complexities of implementing ML for complex manufacturing problems, with emphasis on the role of inspection and safety. Finally, we will place advanced manufacturing in the context of the entire battery life cycle from materials to use, and draw on these case studies to present a vision of both data- and human-driven process improvements for battery manufacturing. Key area will focus on defect detection, root cause analysis using production data, and rapid adoption of new chemistries and cell infrastructure.
(Invited) Ultra-thin Oxide TFTs and Related Instabilities
Authors: Kim Junghwan , Song Minju , Kim Soohyun , Shin Hyoseon , Yeom Jiho
Published: December 2024

Keywords: Amorphous oxide semiconductors, Ultra-thin oxide TFTs, NBTS, PBTS

Recently, amorphous oxide semiconductors have attracted much attention for BEOL-compatible electronics such as next-generation memory applications (e.g. 2T0C). For practical use of oxide TFTs in BEOL-compatible electronics, ultra-thin channel thickness is essential. However, we have recently discovered that the well-known reliability issues such as negative bias temperature stress (NBTS) and positive bias temperature stress (PBTS) become more serious in ultra-thin oxide TFTs. In this respect, we investigated on how channel thickness relates with the instabilities in this study. As seen in Fig.1, PBTS instability becomes worse with the decrease in channel thickness. It is discovered that back-channel trap states are critical to PBTS instabilities, and such a back-channel effect appears more seriously when the channel thickness decreases. More details including experimental evidence and TCAD simulation results will be discussed at the conference.

Figure 1. Comparison of positive bias temperature stress (PBTS) test results of IGZO TFTs with different channel thickness (7, 15, 20, 30, 40, 60 nm).

References:

Shiah, Yu-Shien, Kihyung Sim, Yuhao Shi, Katsumi Abe, Shigenori Ueda, Masato Sasase, Junghwan Kim, and Hideo Hosono. "Mobility–stability trade-off in oxide thin-film transistors." Nature Electronics 4, no. 11 (2021): 800-807.

Figure 1
The Influence of Nickel Doping on the Metal-Oxide in Solution-Processed Transistors Based on Indium Zinc Oxide
Authors: Shin Jung Min , Kim Hwan Drew , KIM Kyung-MIN
Published: December 2024

Solution-processing of nickel zinc oxide (IZO) thin-film transistors (TFTs) is gaining traction as a cornerstone of future display technology, promising cost-effective production. However, achieving stability in the off-current state of IZO without using Ga, a less eco-friendly dopant, remains a challenge. This study proposes a solution-based doping method for IZO semiconductors employing a Ni carrier suppressor and examines the impact of Ni on transistor operation. By leveraging the similar size of Ni2+ to Zn2+, an optimal Ni concentration selectively substitutes Zn sites, leading to a reduction in hydroxide groups bonded to Zn and enhancing the bonding strength of Ni with O. Conversely, excessive Ni addition impedes the formation of a smooth thin film. Ni-doped IZO TFT devices with optimized Ni concentrations exhibit superior performance, characterized by significantly lower off-state currents while maintaining high on-state currents compared to conventional IZO TFTs. This approach expands the repertoire of solution-processed metal oxide semiconductors, offering a sustainable alternative for carrier suppression and facilitating the cost-effective and straightforward fabrication of TFTs.
(Invited) Interface Band Engineering for High-Performance 2D Semiconductor Electronics
Authors: Lee Chul-Ho
Published: December 2024

Two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDs) have emerged as promising materials for implementing beyond-CMOS electronics due to excellent gate coupling and immunity to short-channel effects at the ultimate scaling. In addition, owing to a van der Waals layered structure, they hold great potential for non-conventional electronics capable of heterogeneous integration and deformation. To achieve high-performance 2D field-effect transistors (FETs), it is highly required to control the electronic states and energy band profiles at various heterointerfaces among the semiconductor channel, the gate dielectric, and metal electrodes. In this talk, I will present two types of proof-of-concepts 2D FETs enabled by interface band engineering: 1) modulation-doped FETs (MODFETs) and 2) metal-semiconductor FETs (MESFETs). In a MODFET, we demonstrated remote modulation doping in the type-II band-modulated channel, enabling us to achieve high mobility by suppressing dopant-induced charge impurity scattering. The 2D MESFETs were also demonstrated using the Fermi-level pinning-free metal Schottky gate, whose device characteristics approach the Boltzmann switching limit.
(Invited) Atomically Thin Electronic Channels with Programmed Molecular and Ionic Interactions
Authors: Kim Cheol-Joo
Published: December 2024

The electronic properties of two-dimensional materials are highly susceptible to the types of nearby chemical substances, including molecules and ions. Furthermore, when electrons transport through materials with widths narrowed down to the nanoscale, their motions can be significantly modulated by interactions with chemicals similar in size to the channel width. Here, I present two such material platforms, including graphene nanoribbon grids and grain boundaries of monolayer MoS2. The atomic structures of ultra-narrow electronic channels are designed during growth by chemical vapor deposition to host programmed interactions with targeted chemicals. I show examples of how these platforms can be used to electrically identify the isomer states of nearby molecules and the types of ions.
(Invited) Understanding the Impact of Defects and Disorder in Materials for Advanced Energy Devices
Authors: Ghuman Kulbir
Published: December 2024

The critical challenges related to climate change and energy security could be solved if we can find the champion materials to build sustainable and environment-friendly devices. With this aim in mind, my research leverages leading-edge computational techniques and a multidisciplinary approach to understand and optimize the behavior of complex materials used in batteries, fuel cells and photonic devices. The functionality of the materials used for energy devices is critically determined by the physical properties of small active regions such as dopants, dislocations, interfaces, and grain boundaries. The capability to manipulate and utilize the inevitable disorder in materials - whether due to the finite-dimensional defects (such as vacancies, dopants, grain boundaries) or due to the complete atomic randomness (as in amorphous materials) - can bring innovation in designing energy materials. With the increase in computational material science capabilities, it is now possible to understand the complexity present in materials due to various defects resulting in pathways required for optimizing their efficiencies. In this presentation, I will provide a critical overview of recent computational advancements focused on designing realistic materials with diverse defect landscapes, spotlighting materials like Yttria Stabilized Zirconia (YSZ), Li-La-Ti-O (LLTO), and transition metal nitrides employed in solid oxide fuel cells (SOFCs), lithium-ion batteries, and photonic devices.
(Invited) Emerging Two-Dimensional Materials for Device Applications
Authors: Lou Jun
Published: December 2024

Two-dimensional (2D) materials, such as Graphene, h-BN and MoS2, are promising candidates in a number of advanced device applications, owing to their exceptional electrical, optical and mechanical properties. Scalable growth of high quality 2D materials is crucial for their adoption in technological applications the same way the arrival of high-quality silicon single crystals was to the semiconductor industry. While CVD growth of wafer-scale monolayer graphene and TMDs has been demonstrated, considerable challenges still remain. In this talk, we first report a CVD method to grow fluorine rich 2D polymer (2DP-F) on varies substrates for low-k dielectrics in 2D TMDs based devices. Using precursors with low vaporize temperature, a uniform and ultra-flat 2DP-F film with controlled thickness can be deposited on silicon oxide wafer, glass, sapphire and mica substrates. Dielectric properties and relevant mechanical properties were carefully characterized. These 2DP-F films were then used as the substrate for transition metal dichalcogenides (TMDs) based devices, and significant improvements in device performances were found, possibly owing to the ultra-smooth and dangling bond free surface of 2DP-F that can significantly reduce the interfacial scattering of carriers.

Next, we show that atomically thin Cs3Bi2I9, an all-inorganic lead-free perovskite derivative with strong optical activity can be successfully synthesized by vapor growth method. Reducing the dimensionality of such perovskites could utilize the materials’ advantages for solid-state information devices like valleytronics. By breaking the inversion symmetry, 2D Cs3Bi2I9 flakes with odd-layer number exhibited persistent, optically addressable valley polarization. This study potentially opens generalizable CVD method for growing a broad range of 2D perovskites towards cost-effective and energy-efficient integrated device applications. Finally, we report a two-step vapor phase growth process for the creation of high-quality vdW heterostructures based on perovskites and TMDCs, such as 2D Cs3Bi2I9/MoSe2, with a large lattice mismatch. Supported by experimental and theoretical investigations, we discover that the Cs3Bi2I9/MoSe2 vdW heterostructure possesses hybrid band alignments consisting of type-I and type-II heterojunctions because of the existence of defect energy levels in Cs3Bi2I9. More importantly, we demonstrate that the type-II heterojunction in the Cs3Bi2I9/MoSe2 vdW heterostructure not only shows a higher interlayer exciton density, but also exhibits a longer interlayer exciton lifetime than traditional 2D TMDCs based type-II heterostructures. Such vdW heterostructures provide promising platforms for exploring novel physics and cutting-edge optoelectronics and valleytronics applications.