bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave-Induced Crystal Growth of Metal Halide Perovskites to Enhance the Photovoltaic Performance
Authors: Hwang Inchan
Published: December 2024

This poster presents a novel approach for the growth of perovskite crystals utilizing microwave irradiation, offering distince advantages over the conventaional thermal annealing. This approach effectively mitigates both surface and bulk defects, which consequently enhances the performance of perovskite solar cells. First, we demonstrate that microwave irradiation can sucessfully crystallize the nickel oxide (NiOx) thin films at low processing temperatures and substantially reduced processing times, High electrocal conductivity and transmittance are realized comparable to conventionally annealed NiOx films. Morevoer, the microwave-annealed NiOx films exhibit distinct features of chemical compositions with less Ni>3+ attributed to In and Sn cations unexpectedly diffused from the underlying ITO layer. Additionally, we show a new strategy for the perovskite crystal growths that combines microwave irradiation with simultaneous defect passivation with trioctyl-n-phosphine oxide (TOPO). This approach leads to the growth of perovskite crystals with coordinated TOPO ligands within the film, resulting in suppressed non-radiative recombination, reduced defects, and improved morphology compared to conventionally annealed perovskites. The combined effects of enhanced conductivity in MWA-NiOx and defect passivation in perovskite films contribute to the enhanced performance of solar cells, suggesting promising applications for microwave-assisted processing in optoelectronic devices.
(Invited) Towards Outdoor Operation of Perovskite Solar Cells
Authors: Zhu Kai
Published: December 2024

Organic-inorganic hybrid halide perovskites represent a new class of light absorbers that have demonstrated multiple ideal characteristics and a rapid performance progress for solar conversion applications. Perovskite-based photovoltaic (PV) technologies have attracted significant R&D attention in the PV community as a promising next-generation approach for future PV applications. The certified efficiency of single-junction perovskite solar cells (PSCs) has reached greater than 26%. In order to reach the commercialization stage for perovskite PV, significant efforts are still needed to demonstrate the robust operation under real-world condition for multiple decades. To speed up this process, it is important to develop accelerated aging test protocols and understand their correlation to device operation under outdoor conditions. Here, I will first present our recent studies on perovskite surface engineering to improve device stability under indoor operational conditions. Using molecules/structures based on bulky organic cations (e.g., phenethylammonium) to improve the surface or interface properties is promising for improving PSC performance. A few strategies on suppressing defect formation, improving bulk and surface morphology, and reducing transport barriers for better extraction will be highlighted. In the second part of presentation, I will discuss our recent progress toward understanding the correlation between indoor and outdoor PSC degradation behaviours. Understanding device reliability under real-world outdoor conditions where multiple stress factors (e.g., light, heat, humidity) coexist is critical to moving perovskite PV toward commercialization. It is important to understand the link between indoor and outdoor behaviors in order to help identify accelerated indoor testing protocols to quickly guide PSC development.
Contacting of Fabric-Based Current Collectors for Lithium-Ion Batteries
Authors: Ingendoh Benedict
Published: December 2024

Electrical energy storage systems play a decisive role in the success of the global energy transition. On the one hand, they are indispensable stationary storage systems in combination with renewable energies and, on the other, they are a basic prerequisite for the acceptance of electromobility. The driving goals in battery development include increasing the range of electric vehicles and reducing the cost of energy storage systems. This goes hand in hand with increasing the storage density and improving the service life and cycle stability of batteries. At the same time, it is very important to minimize the consumption of scarce or expensive materials and production costs. In line with these objectives, all battery components and production processes need to be further developed.

Currently, copper and aluminum foils are used as current collectors in battery production. A promising approach to improving the quality and efficiency of batteries is the use of fabric-based current collectors. The substitution of metal foils with metallized fabrics leads to a considerable reduction in weight and thus to an increase in gravimetric energy density. The use of metallized fabrics instead of metal foils also enables a significant reduction in metal consumption. This study focuses on a critical process step for the production of fabric-based current collectors, the contacting process. The most relevant results are presented and discussed to derive conclusions for the production process of electrodes with a fabric-based current collector.
Mechanical Interplay in a Silicon-Graphite Composite Electrode Under High Current Density over Long-Term Operation
Authors: Kim Giyong , Kim Sung Yeol
Published: December 2024

Silicon-Graphite (Si-Gr) composite electrodes, composed of heterogeneous active materials, combine the high capacity of silicon with the conductivity and stability of graphite. These anodes, known for their excellent electrochemical performance and cycle stability, are gaining attention as potential replacements for graphite electrodes [1]. However, their long-term cycle stability is not as good as graphite's, and the higher the silicon content, the quicker the degradation occurs. Thus, it is necessary to improve this aspect [2]. The primary reason for the degradation of cycle stability in Si-Gr composite electrodes is the repeated growth of the Solid Electrolyte Interphase (SEI) during the cycling process [3]. Initially, the SEI forms around the active material, and as the cycling progresses, it extends over the entire electrode [4, 5]. During this process, the electrochemical performance of the active materials within the electrode decreases, and occasionally recovers. This fluctuation is influenced by the repeated growth of the SEI. When the residual stress inside the electrode exceeds the yield point, electrode cracking occurs. Unintentionally, these cracks shorten the ion transport pathways, which in turn can restore the electrochemical performance [5]. However, this interpretation is based on the observed capacity reduction and changes in electrode structure ex-situ. Therefore, there are inherent limitations in clearly delineating the step-by-step processes that result in internal structural changes and crack formation within the electrode. Additional analysis is required to further investigate these phenomena.

In this study, to understand the internal structural changes of the Si-Gr composite electrode during high-speed, long-term cycling, we monitored the changes in electrode stress states in-situ during 200 cycles at 1C [6]. Additionally, by varying the silicon ratio, we aimed to comprehend the role of each active material over the long term. In Figure 1a, the observed capacity and stress changes in the 6% Si electrode are overlaid values of the two active materials' reactions. To analyze the stress behavior characteristics due to the volumetric behavior of each active material, as shown in Figures 1b and 1c, the capacity and stress were differentiated to distinguish the contributions of each material (dQ/dV, dσ/dV). Additionally, by calculating the differential stress to differential capacity (dσ/dQ), as shown in Figure 1d, we understood the changes in the electrode structure at the reaction point of Silicon (Si1 for Li3.75Si → LixSi). By further analyzing these results and compiling data from different ratios of active materials, we aim to analyze the changes in internal electrode structure and the causes of crack formation in long-term, based on high-speed charging/discharging.

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Optimizing Edge Smoothness in Graphene Nanoribbons for Enhanced Transistor Performance: A Lithography Approach
Authors: Saini Kavish , Sreenivasan Sreeprasad
Published: December 2024

Graphene nanoribbons (GNRs) emerge as quintessential candidates for advanced transistor applications, attributed to their distinctive electronic attributes. Their tunable band gap, coupled with exceptional electron mobility, renders GNRs exceedingly conducive for transistor engineering. Moreover, GNRs' inherent spin-polarized edge states present intriguing prospects for Quantum Information Science (QIS) endeavors, leveraging electron spin for information storage or processing. A pivotal determinant to the performance of GNR-based single electron transistors is the roughness or irregularity of edges. Edge imperfections can introduce scattering events, impeding electron transport and subsequently diminish the device functionality. Attaining optimal edge structure and roughness in GNRs is crucial for mitigating such scattering phenomena, thereby enhancing charge carrier mobility and stability. Here, we employ sophisticated lithography modalities, including electron beam and probe lithography, to meticulously tailor GNR width and edge configurations. We pedantically explore the ramifications of edge roughness on their electronic characteristics and resultant device performance. Through this rigorous analysis, our goal is to elucidate strategies for optimizing edge smoothness in GNRs, thereby unlocking superior electronic performance for transistor and QIS applications, marking a significant stride in the realm of nanoscale semiconductor technology.
(Invited) Photon-Induced Plasmas and Contamination Control in Semiconductor Industry
Authors: Beckers Job
Published: December 2024

One of the crucial steps in the fabrication process of computer chips is photolithography. This process uses Extreme Ultraviolet (EUV) photons with a wavelength as short as 13.5 nm, which are transported from their source, via a multitude of multilayer mirrors and the mask (or reticle) to the wafer, which is to be illuminated. As this high energy radiation is absorbed by almost anything, the inside of such a photolithography scanner is designed to be operated under low pressure hydrogen gas.

Everywhere the beam of EUV photons travels, it photo-ionizes the background gas, turning it into a so-called EUV-induced plasma. The resulting plasma is a peculiar one, as it is governed by high transients in the time and space domain.

The inherent presence of an EUV-induced plasma in high-end lithography scanners may have both positive and negative impact on the process in the machine and on its yield, dependent on local conditions and way of operation. For instance, ions – created in the plasma and accelerated to high energies in the space charge region at plasma-surface interfaces - may impact long term stability and lifetime of delicate and expensive optical parts. Also, the plasma inside the scanner may loft contaminating particles and transport them to locations which are extremely vulnerable to such contaminants. Contrary, the chemistry, induced by the plasma, may assist in cleaning the aforementioned optics parts from hydrocarbon contamination. Nevertheless, in order to optimize the overall photolithography process, in-depth understanding and metrology of such plasmas is desired.

This contribution first elaborates on the physics behind the formation and decay processes of this peculiar type of plasma. A general description of the elementary plasma processes is discussed.

Consecutively, some key diagnostics – and their developments over the last years - will be elaborated on. The first set of key diagnostic includes Electrostatic Quadrupole Plasma analysis (EQP) and Retarding Field Energy Analyzer (FREA) for the measurement of ion fluxes and energies, and ion energy distribution functions. The second key diagnostic evolves around the interaction between the induced plasma and standing microwaves and is called Microwave Cavity Resonance Spectroscopy (MCRS). The MCRS technique is based on exciting a standing wave in a cylindrical resonant cavity of which the resonance frequency is a measure for the density of free electrons present in the plasma.

The last part of this contribution reflects on recent work uncovering how the induced plasma affects the long-term release from surfaces of particles that were immobile before plasma operation. Results from plasma exposure measurements using an off-line hydrogen plasma sources indicate a significant morphology of lead and tin based particles.
Initial Virgin Erase State Engineering for Highly Reliable 2D & 3D NAND Flash Memory
Authors: Yoon JoongHo , Lee Wook Hyoung , Eun Dong Seog , Hong Jun Sik , Yim Yong Sik
Published: December 2024

Over the past 30-40 years, to enhance the integration density of NAND flash, the size of the Cell Transistor(TR) has been reduced in 2-dimensional (2D) structures, and stacking has been employed in 3D structures. The improvement in integration density has led to data loss due to interference between Cell TRs, and to address this, materials, processes, and logic have been improved, but there are limitations. Interference phenomena caused by Cell TR interference are a major factor reducing the reliability of NAND flash. This study confirms the importance of the initial Virgin Cell TR Vth in the reliability of NAND flash. In 2D structures, reducing the size of Cell TR enhances the coupling effect of adjacent Cell TRs, making it appear that they have different electrons originally stored. In 3D structures, the increase in stacked Cell TRs induces a decrease in Cell current, leading to increased interference between adjacent Cell TRs in the vertical direction. Incorrect changes in Cell TR Vth not only result in data loss but also worsen the reliability under Cycle and Retention conditions. The degree of Cell interference confirmed through simulation can be used to assess the extent of data loss in various patterns of Cell TR states. Quantifying data loss through various patterns reveals that erased Cell TRs are weak. However, for Cell TRs with a high initial Virgin Vth, interference between programmed Cell TRs worsens. In a well-designed 3D structure, interference from erased Cell TRs is relatively good, but reliability is equally degraded. The importance of the initial Virgin Cell TR Vth has been confirmed through verification of Cell TR size differences. To reduce interference between Cell TRs, an optimized initial Virgin Cell TR Vth is essential. A low Virgin Cell Vth induces a relatively high Program environment, increasing the interference effect between programmed Cell TRs. A high Virgin Cell Vth causes erased Cell TRs to receive strong interference from adjacent programmed Cell TRs, leading to defects. Therefore, an optimized Virgin Cell TR Vth can minimize degradation even under Cycle and worst-case Retention conditions. The initial erase state of Cell TRs has been identified as the most critical factor in interference phenomena, providing an important benchmark for future NAND flash research. we suggest a design standard for the next generation of 3D NAND flash cell transistors from cell disturb and retention.

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(Invited) Recent Advances in Oxide-TFT Technology for Next-Generation Sustainable Electronics
Authors: Nomura Kenji
Published: December 2024

Metal-oxide semiconductors and the relevant electronic devices, particularly thin-film transistor technology are nowadays acknowledged as promising elements for the development of next-generation ubiquitous sustainable electronics. Due to their superior characteristics, such as high electron mobility even in disordered structures, wide-bandgap nature, and low-temperature processability, these technologies offer high-performance, low-power device operation, and cost-effective fabrication processes. A n-channel oxide-TFT using amorphous In-Ga-Zn-O (a-IGZO) channel has already been successfully commercialized as a pixel TFT back-plane in several state-of-art displays such as high-resolution active-matrix flat panel display (AMFPD), large-sized liquid-crystal display (LCD), and high-resolution organic light-emitting display (OLED). Oxide electronics continues to explore new device applications, extending beyond display technologies to areas such as sensors and back-end-of-line (BEOL) transistors, paving the way for next-generation electronics.

Here I present recent advancements of oxide-TFT technology, mainly based on our research activity. Firstly, we will assess the advancements made in n-channel/p-channel oxide thin-film transistor (TFT) technology and address the outstanding challenges that need to be resolved for the development of next-generation electronics. We will also discuss various types of oxide-TFT-based circuit applications, such as NMOS (n-channel metal-oxide semiconductor), PMOS (p-channel metal-oxide semiconductor), and CMOS (complementary metal-oxide semiconductor).
Investigating the Role of Grain Boundaries in Enhancing Bifunctional Memory Properties of CeO2 Thin Films
Authors: Hung Ching-Heng , Chi Chong-Chi , Lu Ming-Pei , Lu Ming-Yen
Published: December 2024

The rapid expansion of artificial intelligence (AI) has highlighted challenges for traditional von Neumann computing architectures, such as the memory and power limitations posed by complementary metal oxide semiconductor (CMOS) devices. Resistive random-access memory (RRAM) is considered to be an emerging technology for the next generation of non-volatile memory devices due to its simple metal/insulator/metal (MIM) structure, faster write/read speed, and longer retention time. CeO2 with defects is compatible with electrochemical metallization mechanisms make it ideal for use as an active material in memristors.

We conducted the study with CeO2 thin film as the active layer. PVD-CeO2, containing numerous oxygen vacancies, facilitates gradual setting/resetting under low voltage conditions, which enables analog-type switching for applications such as artificial neural synapses. While, after annealing process, grain boundaries within the CeO2 layer serve as migration paths for rapid ion diffusion. When bias is applied to the Ag/CeO2/TiN memristor, electrochemical metallization (ECM) occurs within the CeO2 switching layer, leading to the migration of Ag ions and the formation of stable Ag conductive filaments in the CeO2 layer. Resistive switching allows the realization of typical RRAM devices with stable set/reset switching and an on/off ratio of up to 105. Overall, by varying annealing temperatures and operating voltages, the Ag/CeO2/TiN system can achieve bifunctional functionality.

Figure 1
In Situ Synchrotron Based Soft XAS and Resonant Inelastic X-Ray Scattering (RIXS) Characterizations for ε-Cu0.9V2O5 Oscillator
Authors: Li Jialu , Ponis John , Banerjee Sarbajit , Lee Gihyeok , Zhuo Zengqing , Guo Jinghua
Published: December 2024

As traditional semiconductor technology nears its limits in terms of energy efficiency and capacity, the imperative to explore new avenues in semiconductor design grows ever more pressing. One promising direction is neuromorphic computing, which holds the potential to provide real-time learning and embedded intelligence capabilities. Among the materials showing promise in this field, vanadium dioxide (VO2) received extensive research interest due to its unique properties, which undergo a reversible transition from a metallic to a semiconductor state at 340 K. The low-entropy resistive-switching behavior, which involves multiple internal states of vanadium, makes VO2 an ideal candidate for neuromorphic applications, poised to drive advancements in next-generation real-time AI. Studies have explored the effects of composition (doping), electric field, temperature, and pressure on the material properties of VO2, including its electronic device performance. However, despite these investigations, the underlying mechanism governing resistance switching for a neuromorphic response and the associated material properties remain ambiguous.

Synchrotron X-ray absorption spectroscopy (XAS) and resonance inelastic X-ray scattering (RIXS) techniques are powerful tools for investigating the element-specific electronic structure of the materials. The techniques within the soft X-ray regime could provide atomic-level insights into transition metal oxides based on core-level excitations of oxygen K-edge and 3d transition metals L-edges. RIXS reveals electron configuration, especially d-orbital configuration and band gap that majorly contribute to the electric conductivity of neuromorphic transition metal oxides.

Here, temperature/electric field dependent in situ sXAS and RIXS, with a homemade sample holder and devices designed to apply bias (electric field), are employed and demonstrated on the single crystal ε-Cu0.9V2O5 oscillator to provide fundamental insight on metal-insulator transition behaviors. This integrated approach to characterization holds considerable promise in advancing our comprehension of neuromorphic materials and establishing connections between target neuronal behavior and material properties.
(Invited) Sodium Ion Hosts - Similarities and Distinctions from Function in Lithium Based Batteries
Authors: Marschilok Amy C. , Takeuchi Esther S. , Takeuchi Kenneth J.
Published: December 2024

The development of sodium-ion batteries is desirable due to earth abundance and cost considerations. Like lithium, sodium is a monovalent ion. However, the differences in size and standard potential result in interesting distinctions in function for electrochemical energy storage. Case studies involving different negative and positive electrode materials for lithium and sodium ion batteries will be described, including examples of frameworks which can host both ions. The similarities and differences in electrochemical behavior and (dis)charge mechanism of the materials will be highlighted.
Analytical Electrochemistry of Nickel and Platinum Electrolytes
Authors: Troche Kyle , Pillars Jamin R. , Garzon Fernando H.
Published: December 2024

Pt-Ni alloys possess unique catalytic and magnetic properties, and it is highly desirable to synthesize conformal thin films of these materials for integration into magnetic devices and energy conversion systems. Electrodeposition provides large scale and complex form plating without the need for additional equipment such as a vacuum system or furnace used in traditional Pt-Ni synthesis. While nickel and platinum electrodepositions can individually plate effectively, co-deposition provides its own challenges. Large differences in deposition potentials between the two metals and platinum’s reduced overpotential for undesirable hydrogen evolution are necessary challenges that need to be addressed. Investigation into various nickel and platinum bath chemistries over a range of pH’s will help develop a Pt-Ni co-deposition bath that will produce a uniform deposition with desired morphologies.

A rotating disk electrode experiment was conducted on each electrodeposition bath along with a Koutecky-Levich analysis to determine the baths diffusion coefficient and rate constant. Nickel baths include boric acid, acetic acid, citric acid, hydrochloric acid, and phosphoric acid. Platinum baths include hydrochloric acid and acetic acid. Hydrogen suppression techniques were also studied for both nickel and platinum baths to determine the effect on hydrogen generation and metal deposition. Successful suppression of the hydrogen generation reaction would result in greater control of nickel deposition onto platinum as well as thicker platinum films.
Control of Electroplated Copper Layers Microstructure Under Modulated Current: Organic Additives Free Electrolytes
Authors: Dematos Jean , Gigandet Marie-Pierre , Hihn Jean-Yves
Published: December 2024

The use of organic additives is a common thing to improve the properties of copper layer elaborated from a sulfate plating bath. Especially, levelling effects and brightness intensity can be strongly enhanced. But this practice is not without its disadvantages, with high costs, risks of defects in the supply chain, and health and environmental issues [1]. An interesting alternative consists in the current modulation currently named pulsed currents [2] to replace the use of organic molecules to control the roughness of copper deposits. If several works still exist in this field, their application to plating on rough surfaces (Sa around 2 μm) has not been explored yet and the pulse sequence design requires an exhaustive knowledge of each compound effects. In a previous study [3], the mode of operation of industrial organic additives was defined. The modulated current is mainly used to influence the electrocrystallization mechanism, thereby controlling the mechanical and physical properties of the deposited metal [4]. Since the nucleation rate is proportional to the current density, the use of pulsed and reverse currents can reduce porosity and create deposits with finer grain sizes. This allows them to achieve significantly higher densities than their static counterparts [5]. When the current is interrupted at Toff, the active metal ions diffuse into the electrode, where their concentration decreases due to the deposition process. This process promotes the formation of new and smaller grains [6]. Copper layers microstructure and roughness, can, therefore, be greatly modified under the influence of the deposition overpotential. Moreover, the other pulse current parameters, like pulse frequency, have an effect on the surface roughness.

[1]: https://www.anses.fr/en/content/carcinogenic-mutagenic-and-reprotoxic-substances-cmrs

[2]: P. Leisner, M. Fredenberg and I. Belov, Pulse and pulse reverse plating of copper from acid sulphate solutions, Transactions of the Institute of Metal Finishing, Vol 88 N° 5, 2010.

[3]: J. Dematos, M-P. Gigandet and J-Y. Hihn, Organic Additive Free Copper Plating, Oral Communication, ISE, 74th Annual Meeting, Lyon, France, sept. 2023.

[4]: Green, T. A., Su, X. & Roy, S. Pulse electrodeposition of copper in the presence of a corrosion reaction. J. Electrochem. Soc. 168, 062515 (2021).

[5]: Kim, M. J. et al. Pulse electrodeposition for improving electrical properties of Cu thin film. J. Electrochem. Soc. 157, D564 (2010).

[6]: J.C. Puippe and F. Leaman, Theory and Practice of Pulse Plating, American Electroplaters and Surface Finishers Society, 1986.

Figure 1
Power Modules Assembling By Thermocompression of Copper Layer Obtained by Dynamic Hydrogen Bubble: Elaboration Sequences and Electrical Efficiency
Authors: Janod Goulven , Schoenleber Jonathan , Chachay Lucas , Gigandet Marie-Pierre , Avramovic Vanessa , Hihn Jean-Yves , Avenas Yvan , Daudin Remi , Missiaen Jean-Michel , Bouvard Didier , Khazaka Rabih
Published: December 2024

Supported by aircraft future developments with the increase in engines electrification, there is a need of extremely high-power converters in the power electric chain, interfacing the electrical network and the electric motors. The COPPERPACK project (COPPER based PACKaging for direct cooled power module ANR-19-CE05-0011) aims to module assembling by thermocompression. This requests the elaboration of thin nanoporous copper films to be placed between chips and metallized ceramic substrates and the faster and simpler way resides in electroforming deposition made by Dynamic Hydrogen Bubble Template (DHBT) [1]. This process works in unusual potentials and current densities where the competition between hydrogen discharge (commonly avoided) and copper reduction is very high. In this case, this method achieves thick deposits in very short time (few seconds) with high currents allowing a very fast growth of copper around hydrogen bubbles which can be driven by several parameters [2].

In the 4 years duration of the project, several elaboration conditions have been tested i.e. various current densities, pulse current sequences, and increase of the current to compensated the increase of the surface induced by the high level of porosity. Functional properties of films were investigated during thermal compression of chips on a copper substrate such as electrical conductivity, mechanical resistance to shear constraints, behavior after ageing etc. The film properties were paralleled with their structures, morphologies, pores, ligaments sizes as well as behavior during deformation.

Surprisingly, the most efficient films were found to be those with the lowest copper densities. Various situations close to the conditions of use are then tested for chips sticking to copper substrate: electroforming to compensate differences in height followed by DHBT, film deposits on clips used to connect two separate tracks (with very small surfaces), full systems composed by assembling of copper foams and complex copper shapes, designed for cooling fluid circulation. All these systems were extensively described and copper layers obtained by DHBT allow to build compact and efficient systems.

[1] Abdel-Karim, R.; El-Raghy, S. Chap 4 in Advanced materials and their applications - micro to nano scale. One Central Press, United Kingdom, pp 69–91, 2017

[2] Shin, H.-C.; Liu, M. Chem. Mater. 2004, 16, 25, 5460–5464 doi.org/10.1021/cm048887b

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Electrochemical Synthesis of Tellurium Nanostructure on Non-Conductive Substrateby Redox Reaction of Tellurium Ions
Authors: Seo Jinmyeong , Park Subeen , Hwang Inseong , Yoon Sanghwa , Yoo Bongyoung
Published: December 2024

In recent years, the utilization of low-dimensional nanodevices has emerged as a promising avenue for advancing Moore’s Law. With remarkable electrical characteristics, controllable bandgap, and favorable environmental stability, tellurium nanostructures have attracted considerable interest for their potential applications in next-generation electronics and optoelectronic devices. Consequently, investigations into manipulating the dimensions, morphology, and configuration have been conducted to improve the electrical characteristics of tellurium nanostructures. Electrochemical deposition is suitable for synthesizing tellurium nanostructure, enabling control over the nanostructure through manipulation of deposition parameters such as applied potential, temperature, agitation speed, and the incorporation of additives. Despite this advantage, electrodeposition encounters a challenge in detaching the electrodeposits from the conductive substrate for accurate characterization and advanced device fabrication. To address this issue, redox reaction of tellurium ions can be utilized for deposition on insulators, even those unable to conduct electrons required for ion reduction. By controlling the generation of tellurium ionic states (Te4+, Te0, and Te2-) and triggering the redox reaction involving these ions, tellurium nanostructures can be synthesized on insulators using the following reaction: 2H2Te(aq) + HTeO2+
(aq) → 3Te(s) + 2H2O + H+

In this research, we synthesize tellurium nanostructure on the insulators, overcoming the limitation of electrodeposition, which only can deposit on conducting materials. Linear sweep voltammetry is conducted to study the electrochemical behavior of tellurium ions. Based on this analysis, the redox reaction of tellurium is induced on an insulator between Au microelectrodes, which are used for further analyses and application. The nanostructures of tellurium are controlled by manipulating the parameters of electrodeposition. The investigation into the structure and crystallinity of tellurium nanostructures is carried out, alongside the characterization of their electrical properties for electronics applications. This discovery addresses the primary challenge associated with electrodeposition by effectively depositing of metal chalcogenides and other chalcogen elements onto an insulator, thereby broadening its potential applications in advanced electronics fields.
Suppression Effect of Sn on Irregular Shape Deposition of Zn for Negative Electrode of Large-Scale Energy Storage Devices
Authors: Kunimoto Masahiro , Ono Fumimasa , Komiya Ayumu , Harasawa Sayaka , Homma Takayuki
Published: December 2024

Zn is one of the promising negative electrode materials for next-generation large-scale energy storage device. This is ascribed to its several advantages: (1) it shows high energy density, (2) aqueous solvent is to be used, which can prevent hazardous accident, or (3) it is abundant material. In order to put the electrode into practice, it is necessary to develop innovative electrolyte that contains effective additives to prevent shape-changes of the electrode. The undesirable phenomena taking place on the electrode surface should degrade the performance of the electrode, such as cyclabilities and current efficiencies. In particular, a filament-like deposition of Zn, what we call a “mossy” structure, is a serious problem. It takes place under relatively low overpotential environment, which is different mode from a dendritic growth under high overpotential range.

The mossy structure has been a big interest and our past study explained the mechanism underlying the structure in terms of diffusivity of deposited Zn atom on the electrode surface.1 We also try to find effective additives to prevent the mossy structure: heavy metals, such as Pb2 or Sn3, are now one of the candidates. For more precise controls of the shape-change of the electrode, such effective additives are to be analyzed in detail, so that we understand the key to controlling deposition behavior of Zn. This study performed both theoretical calculation with DFT, and electrochemical measurements to identify working mechanism of Sn that mitigates mossy formation on Zn in strongly alkaline solution.

Polarization curves indicated that Sn should work as a suppressor for mossy in the form of [Sn(OH)6]2- ion. It is due to high concentration of OH- in KOH. The results also showed that the complex form is so stable that Sn is not likely to be reduced and deposited on Zn electrode surface. DFT calculation with ESM-RISM, based on the experimental results, evaluated the additive effect of the [Sn(OH)6]2-, by comparing an energy diagram of [Zn(OH)4]2- reduction with the Sn complex to that of without it. It turned out that [Sn(OH)6]2- facilitated reduction of [Zn(OH)4]2-, by interacting with its intermediate. According to a statistic model we formerly proposed, the interaction should effectively suppress the mossy growth of Zn. The theoretical results were in good agreement with electrochemical impedance spectroscopy measurements.

Acknowledgements

This work was supported by JSPS KAKENHI Grant Number JP21H01642.

References

1. Yusuke Onabuta, Masahiro Kunimoto, Songyi Wang, Yasuhiro Fukunaka, Hiromi Nakai, Takayuki Homma, J. Phys. Chem. C, 126, 5224 (2022).

2. Yusuke Onabuta, Masahiro Kunimoto, Fumimasa Ono, Yasuhiro Fukunaka, Hiromi Nakai, Giovanni Zangari, Takayuki Homm, Electrochem. Commun., 138, 107291 (2022).

3. T. Otani, Y. Fukunaka, T. Homma, Electrochim. Acta, 242, 364 (2017).
Deep Metal-Assisted Chemical Etching Using a Porous Monolithic AgAu Layer to Develop Neutral-Colored Transparent Silicon Photovoltaics
Authors: Shin HyeonOh , Kwon Tae_Hyuk
Published: December 2024

Neutral-colored transparent crystalline silicon photovoltaics (c-Si TPV) was reported as remarkable building-integrated photovoltaics (BIPV) due to its high efficiency with excellent transmittance. Deep reactive ion etching (DRIE) is required to fabricate this photovoltaics where the microhole-shaped light transmission windows were placed on bare crystalline silicon (c-Si, ca. 200 μm thickness) to transmit all visible wavelengths, which causes both high fabrication cost and the plasma damage on Si surface. A prominent replaceable method is metal-assisted chemical etching (MACE) which occurs through the redox reaction at the Si/metal catalyst/etchant solution interfaces because it features simplicity, versatility, and cost-effectiveness. However, the metal catalysts that grow via electroless deposition are deposited as particle-form, which act individually during MACE and induce the uneven MACE, thus yielding a lot of defects on the resultant Si.

Here, we report deep MACE using a porous monolithic AgAu layer on c-Si for fabricating c-Si TPV. To prevent the uneven etching of c-Si by Ag particles, the porous monolithic Ag layer is developed by introducing acetonitrile (AN) to enhance the interaction between the c-Si surface and Ag precursor. This results in cooperative motion during MACE, as confirmed by microscopic observation, surface area measurement, and computational simulations. The durability of this Ag catalyst can be further improved by passivation with Au via galvanic replacement (i.e., the porous monolithic AgAu layer), thereby preventing indiscriminate defect generation. Thus, the fabricated c-Si TPV using MACE and a porous monolithic AgAu layer exhibits high performance of 13.0% with 20% neutral-colored transparency, representing results superior to those obtained with samples fabricated by DRIE (11.5%).

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Sustainable Semi-Continuous Rare Earth Alloy Production in Chloride Based Molten Salts
Authors: Holcombe Benjamin P , Sinclair Nicholas Scott , Baker Alex , Kim Eunjeong , Mccall Scott , Akolkar Rohan
Published: December 2024

Rare earth elements have numerous uses ranging from green energy to defense applications. Nd metal production uses a neodymium/lithium fluoride molten salt with a consumable carbon anode where dissolved neodymium oxide and carbon are converted to neodymium metal and CO2. In addition to producing CO2, the process releases PFCs, making it environmentally unsustainable. We have shown that neodymium chloride can be electrolyzed to produce Nd metal at the cathode and chlorine gas at the anode. The chlorine can be recycled in the conversion of the neodymium oxide (from ore) to neodymium chloride. In our process, the anode is non-consumable which allows for continuous processing without producing deleterious greenhouse gases. Chloride rare earth electrowinning historically suffered from low Coulombic efficiency obtained in lab-scale efforts (10-50%). The electrolytic reduction of neodymium chloride is a two-step reaction where a stable intermediate (Nd2+) is formed,1-2 The intermediate species can diffuse away from the cathode resulting in efficiency losses. Further, anodic overpotentials for the chlorine evolution reaction are significant due to the somewhat sluggish kinetics and poor wetting characteristics of the salt on traditional graphite anodes. Solid metal electrowinning in molten salts tends to produce rough deposits which trap significant salt impurities necessitating downstream purification. However, producing liquid metal allows for easy density separation from the salt, leading to a purer as-deposited product as well as faster metal deposition kinetics (i0 ~ 1 A/cm2) which reduces the effects of Nd2+ out diffusion, and chlorine evolution kinetics (i0 ~ 0.2 A/cm2) because of the higher temperature. In this talk, we report our work on improvements to Coulombic efficiency (~85%), and a stable anode that catalyzes chlorine evolution. The combination of improved Coulombic efficiency and reduced anode overpotentials results in low specific energy consumption (~3 kWh/kg) and thus lower operating costs. We will also report on efforts to produce liquid metal in the form of an NdFe alloy at ~800 °C which can be collected semi-continuously at rates of >1 A/cm2.

References
:

R. Akolkar, J. Electrochem. Soc., 169, 043501 (2022).

D. Shen and R. Akolkar, J. Electrochem. Soc., 164, H5292–H5298 (2017).

Holcombe et al., ACS Sustainable Chem. Eng. 2024, 12, 10, 4186–4193, (2024).

Holcombe et al., Holcombe et al 2024 Electrochem. Soc. Interface 33 49, (2024).

Rohan Akolkar. System and Process for Sustainable Electrowinning of Metals. US Patent 20230279572. Sept. 2023

Portions of this work were performed by LLNL under Contract DE-AC52-07NA27344.
Implementation of Electrolytic Phosphating for Steel Wire Drawing as an Alternative to Conversion Coatings
Authors: Lissandrello Federico , Corti Nicola , Mazzeo Gabriele , Magagnin Luca
Published: December 2024

Wire drawing is a cold deformation process in which a steel wire is pulled through several dies of decreasing size, in order to reduce its diameter. To ensure smooth operations and to maximize the lifetime of the expensive dies, lubrication of the wire is mandatory prior to the drawing step. More importantly, the lubricating layer is required to remain adherent to the steel surface for multiple deformation steps, while also maintaining its performance throughout the entire process. For this application, zinc phosphate conversion coatings are widely utilized in combination with an aqueous lubricant based on stearate salts. In fact, phosphate coatings can easily deform under the compressive load of the drawing step, while their porous nature maximizes the amount of lubricant that can be applied to the wire surface. [1]

Despite the good performance offered by conversion phosphating, there is an active interest in replacing this technology as it generates a significant amount of waste byproduct, the so called “phosphate sludge”. At the same time, finding an alternative conversion formulation that ensures the same performance is not a trivial task, especially when price is also factored in. In this context, electrolytic phosphating could offer an elegant, yet effective solution: the process allows the formation of coatings with the same chemical composition and morphology as conversion phosphating but prevents the formation of the sludge byproduct. With the application of an external voltage, it is in fact possible to trigger the local increase in pH responsible for phosphate formation without having to rely on the dissolution of the substrate. [2]

In this talk we will present the implementation of electrolytic phosphating in what is arguably its most relevant industrial application. In particular, by designing the phosphating tank around the symmetry of the steel wire, it is possible to ensure uniform distribution of the current density on the substrate, effectively avoiding the main drawback of the electrolytic process. Furthermore, the higher deposition rate obtained with the electrolytic setup allows the implementation of a continuous operation process, with a higher throughput than traditional batch conversion phosphating. The presentation will showcase results coming from laboratory-scale experiments as well as data resulting from real case-studies at the industrial level.

References

[1] A. Dubois, L. Lazzarotto, L. Dubar, J. Oudin, A multi-step lubricant evaluation strategy for wire drawing–extrusion–cold heading sequence, Wear 249 (2001) 951–961. https://doi.org/10.1016/S0043-1648(01)00830-4.

[2] F. Lissandrello, N. Lecis, L. Magagnin, Investigating the effect of current density in ultra-fast electrolytic zinc phosphate deposition, Electrochim Acta 478 (2024) 143840. https://doi.org/10.1016/J.ELECTACTA.2024.143840.
Understanding the Role of the Black Anodic Film in Copper Electrodeposition in Sulfuric Acid Medium: Organic Additives Free Electrolytes
Authors: Dematos Jean , Gigandet Marie-Pierre , Hihn Jean-Yves
Published: December 2024

In the process of copper electroplating from a sulfuric acid bath it is well known that the copper anodes must contain a small quantity of phosphorous (CuP) (0.04 to 0.06 %). In the other hand, the electrolyte must contain a small amount of chloride ions (50 to 100 mg/L). The result is the formation on an anodic black film. The latter is essential in the proper functioning of the copper electroplating process. The presence of this black film prevents the formation of anodic sludge which compromises the quality of the copper deposits. The anodic behavior of copper is of great interest not only from the theoretical point of view but also as an important practical problem. The anodic sludge is formed by one of the following mechanisms [1], [2], Eq. (1) which is the disproportionation reaction of the cuprous ions, mechanism 1:

2 Cu+ ↔ Cu2+ + Cu (1)

Eq. (1) is responsible for the formation of anodic sludges. The mechanism 2 is the preferential dissolution along the intergrain boundaries and the consequent detachment of complete crystal grains from the crystalline structure. The addition of phosphorus as an alloying element during the manufacture of the anodes and the presence of chloride ions in the plating bath result in the formation of the anodic black film which eliminates the possibility of copper anode grains detachment and the alteration of the anodic dissolution mechanism. Copper anode dissolution proceeds under a two steps mechanism described by Eq. (2) and (3):

Cu ↔ Cu+ + e- (2)

Cu+ -> Cu2+ + e- (3)

Both of these reactions take place in the anodic film. In order to move from a bath with additives to a bath without additives, it is essential to answer the following questions: What is the effect of organic additives on the anodic side? What is the optimal concentration range for chloride ions? What is the influence of the grain size of Copper-Phosphorus anodes?

The present work deals with a extended characterization of the black anodic film and relevant insights about its formation mechanisms.

[1] : ST. RASHKOV and L. VUCHKOV, The Kinetics and Mechanism of The Anodic Dissolution of Phosphorus-Containing Copper in Bright Copper Plating Electrolytes, Surface Technology, 14 (1981) 309 – 321.

[2] : G. S. Frankel, A. G. Schrott, H. S. lsaacs, J. Horkans, and P. C. Andricacos, Behavior of CuP and OFHC Cu Anodes under EIectrodeposition Conditions, United States. Department of Energy, Brookhaven National Lab., Upton, NY (United States), 1992.

Figure 1
Understanding Electrochemical Measurements of Lithium Diffusion in Porous LiNiO2 Cathodes
Authors: Vettori Kilian , Henss Anja , Janek Jürgen
Published: December 2024

The chemical diffusion coefficient of lithium in cathode active materials is one of the key parameters determining battery performance. Fast diffusion allows fast charging and access to higher capacities before the potential limits of typical cycling routines are reached. Understanding the measurement of this crucial parameter through simple, non-invasive, in-situ electrochemical methods facilitates the investigation and optimization of cathode active materials for lithium-ion batteries. In this presentation, these electrochemical procedures are applied to LiNiO2 cathodes as a model system of the Ni-rich cathode active materials in liquid electrolyte cells.

These measurement routines have a history of almost 5 decades and have been adapted and modified since then. Recently they have received renewed interest for the reasons mentioned above. The presented electrochemical methods, including variations of galvanostatic and potentiostatic intermittent titration techniques (GITT and PITT), electrochemical impedance spectroscopy (EIS) and newer adaptations such as the Atlung method for intercalant diffusion (AMID) and Intermittent current interruption (ICI), are compared and reviewed with respect to underlying physical concepts of solid state diffusion and their application in typical porous cathodes for liquid electrolyte lithium ion batteries. Figure 1 gives a schematic view of lithium concentration in a cathode particle during delithiation and its relation to the electrode potential and the diffusion process.

The aim of this presentation is to enable more researchers to include diffusion measurements into their experiments and to facilitate the choice of method by comparing different techniques. By revisiting the fundamentals of solid state diffusion, it allows a deeper understanding of the chemical lithium diffusion coefficient and its measurement.

Figure 1