bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical CO2 Reduction to Formic Acid As Feedstock for Biotechnological Processes
Authors: Pangotra Dhananjai , Bohlen Barbara , Vieira Luciana , Fabarius Jonathan , Roth Arne , Sieber Volker , Pietzka Carsten , Wriedt Benjamin , Kost Hans-Joachim , Ziogas Athanassios , Löb Patrick
Published: February 2024

Substituting fossil-based production methods with methods utilizing renewable resources is experiencing growing interest. Incorporating intermittent renewable electricity into such processes is highly desirable, especially for energy storage purposes. In this context, electrocatalytic conversion of renewable raw materials into platform chemicals is an important approach. Biogenic raw materials can be converted into platform chemicals through electrocatalysis, which can then be used in power-to-X-to-Y processes to generate a range of products. One notable example of this approach is the electrochemical conversion of CO2 into formic acid, which has numerous applications in the chemical, textile, agricultural, and pharmaceutical industries [1, 2]. Utilization of CO2-based formate as a microbial substrate is a fascinating research topic that expands the range of possible products. The work presented here focuses on optimizing a compatible interface between efficient electrochemical processs and biotechnology, by identifying key factors, including the choice of catalyst, electrolyte, electrochemical setup, and formate production rate. This study also involves testing of an electrochemical microreactor for the scalable production of formate from CO2. Our results show that formate concentrations of up to 3 mol L-1 can be achieved in a bio-compatible buffer electrolyte using an optimized electrochemical process at high current densities. Additionally, this research successfully demonstrates the biochemical utilization of electrochemically produced CO2-based formate in coupled electro-biochemical processes. The developed process is a sustainable and efficient method for producing value-added products from CO2 and renewable electric energy, contributing to bridging the gap between electrochemical and biological processes.

References

[1] B. Bohlen, D. Wastl, J. Radomski, V. Sieber, L. Vieira, Electrochemical CO2 reduction to formate on indium catalysts prepared by electrodeposition in deep eutectic solvents, Electrochemistry Communications, 110 (2020) 106597.

[2] I. Merino-Garcia, L. Tinat, J. Albo, M. Alvarez-Guerra, A. Irabien, O. Durupthy, V. Vivier, C.M. Sánchez-Sánchez, Continuous electroconversion of CO2 into formate using 2 nm tin oxide nanoparticles, Applied Catalysis B: Environmental, 297 (2021) 120447.
Electrolytic Reduction of UO2 Microspheres Synthesized Via Internal Gelation Method
Authors: Hsu Han-Hung , Breugelmans Tom , Cardinaels Thomas , Geboes Bart
Published: February 2024

Pyroprocessing is the combination of process steps to extract and recycle actinides from fission products in spent nuclear fuels in high-temperature molten salt media. Pyroprocessing has been studied extensively over the past decades. One of the key sub-processes is the electrolytic reduction of uranium oxides. The electrolytic reduction process originated from the FFC Cambridge process, an approach for electrochemically reducing titanium dioxide into titanium metal in molten CaCl2. In the electrolytic reduction of uranium oxides, the uranium oxide feed is applied as the cathode in LiCl-Li2O molten salt electrolyte at 650°C. LiCl appears more promising than conventional CaCl2 owing to the lower melting point (878 K), and higher decomposition voltage (3.46 V at 923 K). Additionally, Li2O is expected to speed up the reduction via an additional chemical reduction pathway with the participation of Li metal, and prevents the direct dissolution of the Pt anode.

This work aims to study the morphology effect of the oxide feed on the reduction kinetics and the incorporation of impurities during the electrolytic reduction process. The electrolytic reduction of UO2 is carried out on sintered UO2 pellets, as well as various UO2 microspheres synthesized via internal gelation. The introduction of uranium oxide microspheres holds several advantages. The spheres provide a higher surface area, which is expected to improve the overall reduction efficiency of uranium oxide during electrolysis. In addition, it is easier to handle the feed during loading and unloading of the cathode basket compared to powder feeds.

The potentiostatic and galvanostatic electrolysis of UO2 is performed, and the comparison between the electrolytic reduction of UO2 pellets and microspheres is investigated. The SEM micrographs in figure 1show the morphology change of a UO2 pellet to uranium metals particles. A significant morphology change between the flat surface of the sintered UO2 feed and the reduced U particles is observed at the surface. Further characterization is performed using XRD and TGA to identify the products of the electrolytic reduction process qualitatively and quantitatively. Results show that galvanostatic electrolysis shows a better reduction efficiency compared to potentiostatic electrolysis, applied both below and above the Li formation onset potential. Overall, there is barely un-reacted UO2 visible in the XRD patterns of the reduced feed after galvanostatic electrolysis. U metal and UO are identified in the XRD patterns depending on electrolysis parameters. The presence of UO can be as an intermediate of UO2 reduction during electrolysis, which is a rare compound to be reported in literature. Overall, the reduction of microspheres does improve the overall reduction efficiency compared to the conventional pellet feeds.

Figure 1
A Numerical and Experimental Sensitivity Analysis on Electrochemical Neutral Pickling for Stainless Steel Using Secondary Current Distribution
Authors: Bossio Castro Alvaro , Gielen Ruben , Basilico Edoardo , Fransaer Jan , Baelmans Martine
Published: February 2024

Electrochemical neutral pickling (ENP) is an extended process used in the stainless steel industry to remove the oxide surface layer formed during the annealing process. The absence of strong acids such as nitric acid results in a minimum loss of base material, improve operators working conditions, and reduces the pickling environmental impact, while keeping relatively low operation and maintenance costs. However, despite its multiple benefits, ENP may become the bottleneck for integrated annealing and pickling line, especially when processing thin austenitic and duplex steels. Fortunately, there is room for improvement as the total Faradaic efficiency of the process in typical operation is in general low (around 20 – 30 % for austenitic materials) [1]–[3], while estimations of the energy efficiency are as low as to 1 - 2 % [4].

This work provides guidelines to the design and operation of ENP cells to increase the oxide removal rate. We focus on the effect of the geometry and some operational parameters, using secondary current distribution. The simulations are validated against experimental, and a sensitivity analysis of the oxide removal rate with respect to the geometry and some key operational parameters is performed. The electrode-to-strip and the inter-electrode distances were found to have a determining effect on the total cell resistance and on its so-called geometric efficiency (relative current reaching the strip). Moreover, an optimal range for the ratio of these distances is proposed. In addition, the strip thickness and width were found to significantly affect the cell performance, especially for the thinnest gauges.

References

[1] V. I. Dunaevskii, V. T. Stepanenko, M. Y. Shnol’, and L. N. Bespal’ko, “Rate of removal of scale and subscale layer in electrolytic pickling of stainless steels in Na2SO4 solution,” Zaschita Metallov, vol. 21, no. 3, pp. 431–436, 1985.

[2] N. Ipek, B. Holm, R. Pettersson, G. Runnsjö, and M. Karlsson, “Electrolytic pickling of duplex stainless steel,” Materials and Corrosion, vol. 56, no. 8, pp. 521–532, 2005, doi: 10.1002/maco.200403858.

[3] D. Henriet, Surface treatments for stainless steel state of the art - developments and trends, no. 7210. European Comission, 1996.

[4] N. Ipek, N. Lior, F. Bark, A. Eklund, and A. Alemany, “Simple analytical model predicting some features of the electrolytic steel-pickling process,” Russian Journal of Electrochemistry, vol. 38, no. 3, pp. 238–246, 2002, doi: 10.1023/A:1014770404415.

Figure 1
(Digital Presentation) Synthesis and Characterization of Dispersed Zinc Oxide
Authors: Frolova Liliya A , Sergeyeva Olga V
Published: February 2024

Zinc oxide has the subject of numerous studies in recent years. Nearly half of the world's annual production of zinc oxide is used as an activator to speed up vulcanization in the rubber industry. It is also widely used in pharmaceutical and cosmetic industries. It is most widely used in the chemical industry not only as a starting material, but also as a catalyst and chemisorbent. Recently, zinc oxide has been very often studied as an efficient photocatalyst in advanced oxidation processes. The cheapness and availability of zinc oxide makes it possible to use it also as a white pigment. White pigments make up more than 60% of all modern dyes. They are used for the manufacture of paints and varnishes not only white, but also other colors, as well as in the production of plastics, paper, building materials, ceramics, etc.

Obtaining nanodispersed ZnO opens up additional possibilities for controlling its chemical and physical properties. Today, to obtain nanostructured ZnO, chemical deposition, synthesis in colloidal solutions, hydrothermal synthesis, laser vapor deposition, electrochemical deposition, thermal methods, electrochemical deposition, etc. are used. Promising technologies that make it possible to obtain disperse products are physicochemical methods, including those using contact nonequilibrium plasma (CNP).

To form nanodispersed ZnO nanoparticles, we used CNP. This method is economically attractive due to the simplicity of the synthesis process (the temperature varies from room temperature to 50°C, the low cost of equipment and consumables) and the possibility of influencing the structural and morphological characteristics of NPs.

Theoretical (Pourbaix diagrams) and experimental studies (cyclic voltammograms, potentiometry, kinetic dependences, X-ray phase analysis, derivatography, electron microscopy, spectroscopy) were carried out, which made it possible to establish the possibility of obtaining zinc oxide using CNP and investigate its properties.

The results of X-ray diffraction analysis show that under these conditions, a precipitate of ZnO is formed. It was found that with an increase in rarefaction in the plasma-chemical reactor and a decrease in the interelectrode distance, an increase in the degree of conversion of zinc cations into insoluble compounds is observed. To increase the degree of conversion, the effect of organic compounds on the degree of conversion was also investigated. The addition of ethanol in the ratio 50-100 mmol/mol increases the product yield to 99.8% even in dilute solutions. Studies of color characteristics showed that the resulting precipitate has a CRC of 95%, a color purity value of 6%, and a color tone corresponding to a wavelength of 584 nm. The band gap was 3.1 eV.
High Carbon Doping of Amorphous Silicon Nanoparticles in a One-Step Gas-Phase Process for Increased Cycling Stability
Authors: Loewenich Moritz , Orthner Hans , Wiggers Hartmut
Published: February 2024

Silicon as an anode material for Lithium-Ion-Batteries (LIB) is a promising candidate to increase overall specific energy of batteries in comparison to state-of-the-art graphite anodes. Yet the cycling stability of silicon-based electrodes is still an issue, mainly due to problems related to the swelling of silicon during lithiation to up to 300 % of its original volume. While a breakage of silicon particles can be prevented by choosing a nano-material this has the detrimental effect of increasing the surface exposed to the electrolyte, i.e. reducing coulombic efficiency. Other solutions like coatings of silicon particles and complex electrode structures are shown to increase cycling stability, but are typically connected to higher manufacturing cost.

By doping silicon nanoparticles already during production in a gas-phase one-step process, this study investigates the influence of high carbon concentrations up to 20 wt.%. This causes the silicon to stay amorphous, even at elevated temperatures. Furthermore it is shown, that the disturbance of the lattice by carbon atoms helps mitigating stress during lithiation, and can form a less reactive surface. By varying precursor concentrations during material synthesis, a range of materials were produced and analyzed physicochemically and electrochemically. For carbon values up to 15 wt.% our results show a strong increase in cycling stability of up to 80 % capacity retention after 500 cycles, and first cycle coulombic efficiencies of 80 – 90 %. Yet the increased stability is going along with a decrease in specific capacities to 1000 – 1500 mAh/g. These values were obtained for a 75 wt.% silicon, 15 % PAA, 10% C65 electrode and 1 mg/cm2, tested against lithium at 0.5 C. By linking further electrochemical results to particle properties the effects of the carbon doping are further unravelled. This material engineering offers another promising pathway to increase overall performance of silicon containing LIBs and is industrially viable, due to its inclusion in a scalable one-step material synthesis process.

Figure 1
(Digital Presentation) Direct Regeneration of NMC622 Cathode Material from Spent EV Li-Ion Batteries Via Hydrothermal Re-Lithiation
Authors: Flores Charles Lois , Cervera Rinlee
Published: February 2024

With the increasing demand for electric vehicles, there is a need to address the issues associated with the increasing number of waste or spent Li-ion batteries. A simpler and less expensive approach to recycle cathode materials from spent batteries, compared to hydrometallurgy and pyrometallurgy, is direct regeneration. In this study, a facile and cost-effective hydrothermal re-lithiation method, followed by post-annealing, was explored to repair the structure, morphology, and composition of spent NMC622. The effects of annealing temperature and purging gas on the physicochemical properties of the regenerated NMC622 were evaluated. The regenerated NMC622, annealed at 800°C under O2, exhibited an XRD profile that closely resembled that of the as-received spent NMC622, with peaks indexed to the planes of the α-NaFe2O4 structure and without any impurities. Additionally, it achieved the highest I(003)/I(104) ratio and the closest c/3a ratio to that of the as-received spent NMC, indicating that the original structure was successfully repaired after regeneration. It also exhibited less agglomeration, with a narrower particle size distribution than the as-received spent NMC622, indicating that the morphology was improved after regeneration. Elemental composition analyses further confirmed that the spent NMC622 was successfully regenerated using the employed method, as the Li content after regeneration increased from 6.99 to 7.20 wt%, a value close to the theoretical (7.16%). In general, this simple and inexpensive direct regeneration strategy provides a new perspective for lithium-ion battery regeneration, which can be extended to other battery systems in the future.
(Invited) Development and Scale-up of Membrane Capacitive Deionization (MCDI) for Desalination and Water Reuse
Authors: Chen Chen-Shiuan , Chen Tsai-Hsuan , Hou Chia-Hung
Published: February 2024

Desalination and water reuse are the key solutions to address global water scarcity. It is important to recognize the water-energy interactions and develop energy-efficient technologies to separate ions from brackish water, seawater and reclaimed wastewater. Most recently, membrane capacitive deionization (MCDI), inspired by energy storage devices (e.g., supercapacitors), is a promising desalination technology with several advantages of energy efficiency (TDS < 4000 ppm), high water recovery, less chemical additive, and environmental friendliness. In MCDI, ions are electrostatically captured within highly porous carbon electrodes through the formation of electrical double layer during the charging step, and then released into the solution by discharging the electrodes. By incorporating ion-exchange membranes (IEMs) in front of each electrode, the desalination performance can be significantly improved, achieving high salt adsorption capacity and charge efficiency. Over the past few years, we have made efforts to scale up the MCDI stacks for commercialization purposes, which are composed of 32 pairs of 400 mm × 200 mm activated carbon electrodes. Note that a stop-flow operation is applied in the discharge process to increase the water recovery (> 75%). A pilot-scale study of an MCDI system was performed to reclaim the secondary effluents from a municipal wastewater treatment plant. In addition, MCDI prototypes offer promising engineering opportunities for water recycling in high-tech industries, including reverse osmosis reject and wet scrubbing. Furthermore, we will discuss the challenges and perspectives for the future of MCDI as a cost-efficient, low-energy approach for desalination and resource recovery.
Electrochemical Dewatering of Cellulosic Nanomaterials
Authors: Vijapur Santosh Hanamant , More Santosh R , Le Huong , Hall Timothy , Taylor E. Jennings , Inman Maria , Snyder Stephen , Nelson Kim , Handler Robert M
Published: February 2024

Cellulose is the most abundant biomass material in nature utilized for the manufacturing of cellulosic nanomaterials that exhibit great potential in a variety of industrial applications. Although cellulosic nanomaterial is cost-effective to produce, it is not economical to ship long distances while containing significant water content (>95 wt.%). Therefore, a need has been identified by manufacturers to develop energy-efficient, dewatering or drying of cellulosic nanomaterials.

Accordingly, Faraday Technology in collaboration with GranBio USA, manufacturers of cellulosic nanomaterials, is addressing this need by developing electrochemical based dewatering system and process to dewater cellulosic nanomaterials while maintaining material properties when dried and re-dispersed. Energy-efficient (70% reduction in energy requirements compared to thermal dewatering), environmentally beneficial (51% reduction in greenhouse gas emissions), economical (31% reduction in cost/ton of dried material), and industrially viable electrochemical based dewatering approach to process up to 2 tons/year of dried nanocellulose at alpha-scale has been demonstrated. The approach is capable of achieving >50 wt.% final solids and 18 wt.% final solids, that could be rehydrated under vortex and confirmed for re-dispersibility. Material properties (structure, particle size) were maintained by the dewatered cellulosic nanomaterials. Specifically, this talk will discuss the results of these advancements.

Acknowledgements: The financial support of DOE Contract No. DE-SC0018787 is acknowledged.
Screening Electrochemical Phosphorous Recovery Conditions in Real and Synthetic Wastewater Streams
Authors: Wolfe Kody D , Heydarian Sana , Ajayi Lawrence O. , Abbas Syed Asad , Trembly Jason , Daramola Damilola
Published: February 2024

The recovery of phosphorus (P) from wastewater via electrochemical precipitation is a promising route to improved nutrient recovery due to its ability to be coupled with current wastewater treatment processes, the viability of both small- and large-scale implementation (allowing for dispersed nutrient recovery systems), and utilization of electrons as an energy source (as opposed to chemically induced precipitation). In this talk, electrochemical P recovery from real and synthetic wastewater will be demonstrated, discussed, and contrasted. This study highlights the viability of electrochemical P recovery by considering waste stream composition, energetics of separation, and analyses of recovered products.

Specifically, both synthetic and real wastewater was tested under similar stirred batch reactor conditions with various mass transfer conditions, electrode types, and applied potentials. The reactor solution chemistry was based upon an analysis of three real waste streams and time series analyses were used to compare the transient stream conditions to conditions used in P recovery studies. Additionally, materials characterization was performed on the product of various recovery conditions and the implications of reactor conditions are discussed.
Selective Surface Feature Electropolishing of Additively Manufactured 316L Using Pulse Electrochemistry
Authors: Mirabal Alex J , Hooks Daniel E , Stull Jamie A
Published: February 2024

Electrochemical finishing of metallic surfaces is a scalable, relatively cost-effective technique that is also versatile. One of the main detractions is that the current distribution is uneven and unspecific, often leading to a lack of shape retention and, if it goes too far, inducing corrosion. Pulsing the electrical input creates an unsteady state during electropolishing, controlling the current distribution across the part. The pulse wave prevention of general non-uniform current distribution across the entire geometry instead produces local non-uniformities in the current distribution at given surface features. Many pulse electropolishing parameters can be varied to target individual surface features, including the electrolyte, pulse height, pulse width (equally and unequally distributed), time of polishing as well as the overall waveform.

Additive manufacturing (AM) can produce unique, complex structures rapidly. The fast local melting of metal AM parts cool quickly due to the small area, causing unique microstructures, pores, and larger surface roughness compared to cast. AM microstructures change mechanical and chemical properties, such as strength and corrosion, compared to traditionally manufactured parts. Variations in build parameters and composition creates a complicated, feature dependent, corrosion response. By polishing the surface, some of the features, namely the corrosion resistance, wear, and aesthetics can be standardized and enhanced.

In this work, we explore the underlying electrochemistry that governs pulse electropolishing. We show that controlling the electrolyte with environmentally benign chemicals ultimately influences the part dimensions that can be polished, the ability to polish, and the propensity to corrode. The pulse height, pulse width (Fig. 1), and total charge passed have an impact on different surface feature removal. We will demonstrate impact of the pulse parameters on the polishing of additively manufactured stainless steel. We go beyond simple planar geometry and apply our understanding to larger scale complex geometry parts, while maintaining near-net shape and minimizing mass loss.

Figure 1
Glycerol Electrooxidation in Flow Reactors
Authors: Gaines Rachel Naomi , Sibal Adam , Griebler James John , Gaddam Raghuram , Harris Lauren C , Kleimenhagen Beth Ann , Keshireddy Ashrith , Gewirth Andrew A. , Rodriguez Lopez Joaquin , Rogers Simon A , Stillwell Ashlynn S , Kenis Paul
Published: February 2024

Transitioning away from fossil-fuel-based chemical manufacturing is critical in advancing towards a carbon-neutral society. Chemical manufacturing processes that can be driven by renewable energy and use renewable feeds or waste products from other processes are of particular interest. This talk focuses on utilization of glycerol, a byproduct of biodiesel production and other processes, as a platform chemical for electro-organic synthesis of a number of value-added intermediates.

Oxidation of glycerol can result in ten or more different products. Processes are needed to synthesize specific products of interest selectively. Based on market size and value, the four most promising oxidation products of glycerol are lactic acid, glycolic acid, oxalic acid, and dihydroxyacetone. Electrochemical reduction and oxidation processes can, in principle, be directed to produce different products by tuning reactor and reaction conditions such as catalyst identity, electrolyte/analyte concentration, flow/stir rates, electrolyte composition, etc. While a significant body of work has studied glycerol electrooxidation (GEOR) in electrochemical cells with the goals of unraveling mechanisms and identifying better catalysts (higher rates/selectivities), transitioning some of the most promising GEOR approaches to larger scales has received limited attention.

In our work, we pursue glycerol electrooxidation in flow reactor configurations that could be scaled to industrial levels. Flow electrolysis approaches, in addition to providing a scalable chemical manufacturing platform, enhance mass transfer and kinetics while retaining the ability to tune key operational parameters that determine rates and selectivities. In this talk, we will report on two aspects: (i) Product speciation: what parameters can be used to optimize product selectivity towards key desired products (e.g., lactic acid, glycolic acid), and (ii) Feedstock composition: how to utilize raw glycerol (so-called ‘crude’ glycerol, containing varying amounts of water, NaOH, and methanol), available as a byproduct from a wide variety of plants, as the feedstock. For the former, we employ a systematic design approach that seeks to optimize the interplay between the different parameters that determine current density (conversion rate) and Faradaic efficiency (selectivity). For the latter, we explore which of the other ingredients (methanol, NaOH, water) of crude glycerol needs to be controlled or adjusted for reproducible, desired outcomes of flow glycerol electrolysis.
Lignin Nanoparticles as Charge Storage Centers in Organic Battery Electrodes
Authors: Tran Van Chinh , Morsali Mohammad , Sipponen Mika H. , Engquist Isak
Published: February 2024

Lignin, the second most abundant biopolymer on Earth, has recently emerged as a promising redox-active material for organic batteries. Different types of lignin have been explored but inherent challenges have remained, i.e., the difficulties of processing kraft lignin and the low charge storage capacity retention of lignosulfonate due to its high water-solubility. In this work, we propose the use of an alternative candidate, lignin nanoparticles (LNPs), which are insoluble, but colloidally stable dispersions in aqueous media, which, can be easily processed using different manufacturing techniques. By combining LNPs with a conducting polymer (PEDOT:PSS), we have successfully prepared a composite that has a charge storage capacity of up to 42.5 mAh/g at a current density of 1 A/g, while its capacity retention shows a good improvement (70% after 1000 cycles) in comparison to the similar systems of lignosulfonate-based electrodes. The morphology and chemical structure of LNPs are tunable, therefore, the effects of particle sizes and the preparation methods of LNPs on the electrode performance were also studied. With the obtained results, this work suggests LNPs as promising materials for the preparation of green and low-cost lignin-based energy storage devices.

Keywords: Lignin nanoparticles, Organic batteries, PEDOT:PSS, Electrochemistry.
Development of a Lab-Scale Tribo-Electrochemical Approach for Chemical Mechanical Planarization
Authors: Afekare Dayo Akintan
Published: February 2024

During chemical mechanical planarization (CMP), the electrochemical interactions between slurry additives and the polishing substrate metal films favor the formation of easily removable species that are then detached by mechanical abrasion effects of the CMP pad and nanoparticle abrasives in slurry. Yet, neither the mechanical nor chemical aspects alone dictate the CMP process; rather, it is the intertwined dependencies of tribology and electrochemistry that often control the polish performance. This highlights the importance of the functional synergies, otherwise known as tribo-electrochemistry, which has been largely under-explored in the CMP research community.

This work discusses the development of a novel small-scale tribo-electrochemical approach for metal CMP. It covers the tool design aspects, tribo-electrochemical measurements such as open circuit potentiometry (OCP) and polarization resistance, and relevance to CMP applications. The system is developed based on a small-scale CMP polisher coupled to a 3-electrode cell design circuit that is connected to a potentiostat. The design utilizes a common type of CMP metal film as the working electrode, with the accompanying pad and slurry consumables serving as baseline for method development. All other process conditions, including rotating speed, downforce, polish-hold duration, and pad conditioning process follow typical CMP standards.

The results show tribo-electrochemical responses to the presence of catalyst (C), oxidizer (O), inhibitor (I), and abrasive (A) in the experimental slurries. The data is of significant value in terms of the anodic & cathodic site functions on the CMP metal surface and in the context of material removal. In addition, notable sensitivity to pad texture, downforce, and temperature effects were observed, and removal rate measurements correlated with polarization resistance for varied levels of the O and I additives. In summary, the tribo-electrochemical aspects of CMP have been probed and an innovative analytical approach has been developed and demonstrated.
Low-Temperature Atomic Layer Deposition of High-K SbO
x
for Thin Film Transistors
Authors: Bahrami Amin , Yang Jun , Ding Xingwei , Zhao Panpan , He Shiyang , Lehmann Sebastian , Laitinen Mikko , Julin Jaakko , Kivekäs Mikko , Sajavaara Timo , Nielsch Kornelius
Published: February 2024

SbO
x
thin films are deposited by atomic layer deposition (ALD) using SbCl5 and Sb(NMe2)3 as antimony reactants and H2O and H2O2 as oxidizers at low temperatures. SbCl5 can react with both oxidizers, while no deposition is found to occur using Sb(NMe2)3 and H2O. For the first time, the reaction mechanism and dielectric properties of ALD-SbO
x
thin films are systematically studied, which exhibit a high breakdown field of ≈4 MV cm−1 and high areal capacitance ranging from 150 to 200 nF cm−2, corresponding to a dielectric constant ranging from 10 to 13. The ZnO semiconductor layer is integrated into a SbO
x
dielectric layer, and thin film transistors (TFTs) are successfully fabricated. A TFT with a SbO
x
dielectric layer deposited at 200 °C from Sb(NMe2)3 and H2O2 presents excellent performance, such as a field effect mobility (µ) of 12.4 cm2 V−1 s−1, I
on/I
off ratio of 4 × 108, subthreshold swing of 0.22 V dec−1, and a trapping state (N
trap) of 1.1 × 1012 eV−1 cm−2. The amorphous structure and high areal capacitance of SbO
x
boosts the interface between the semiconductor and dielectric layer of TFT devices and provide a strong electric field for electrons to improve the device mobility.
Morphological and Electrical Characterization of AlGaN/GaN Heterostructures Modified By Atomic Layer Etching
Authors: Miersch Christian , Wege Stephan , Heitmann Johannes , Beyer Franziska Christine
Published: February 2024

Modern microelectronic components for high-power and high-frequency applications based on III-V compound semiconductors offer high break down voltage (GaN: 5 MV/cm and AlN: 15 MV/cm) at low specific on-resistance. However, it requires reliability and reproducibility of the production processes. Going to higher frequencies (5 GHz and beyond) and more integration in consumer electronics, smaller structure sizes are needed. This is going along with increasing demands on the manufacturing processes like dry etching. The main goal is to reach smaller and high controllable etching rates, going down to single atomic layers, low damage, and minimized surface roughness. Atomic layer etching (ALE) represents a key technology in order to achieve such requirements.

An ALE process consists of two independent steps forming a repeatable cycle with a specific etching amount per cycle (EPC). First a surface modification is done by a chemical precursor i.e., adsorbing or oxidizing the surface. The second step is the removal of the modified layer, either physically by low energy non-reactive ion bombardment (Plasma Enhanced ALE [PEALE]) or chemically by a reactive species (Thermal ALE). The two steps are separated by an inert gas purge. This purging grants the removal of the chemistry after the first step, preventing further chemical reaction and transporting the chemical products out of the chamber after the second step.

In this study, a PEALE conducted on different tools is used, for gate and contact recess study in a AlGaN/GaN heterostructure to form high electron mobility transistors (HEMT) with reduced ohmic contact resistance and threshold voltages. The results show a reduction of ohmic contact resistance at reduced forming temperatures and a linear dependence of the threshold voltage on gate recess depth. In order to determine the etching rate and roughness, atomic force microscopy (AFM) measurements were performed.

The PEALE module is either integrated into a cluster tool consisting of atomic layer deposition (ALD) and chemical vapor deposition (CVD) or done in a combined ALD/ALE chamber. This opens the possibility of etching and depositing in-situ, reducing contamination and degradation of the substrate material.

By this means, metal insulator semiconductor (MIS)-HEMTS with a recessed gate are studied. The monitoring of the individual processes is achieved by test structures like transfer length method structures (TLM) and metal oxide semiconductor (MOS), which showed the improved electric performance of these devices and may indicate unwanted interface issues, respectively. Additional, pre- and post-treatments could improve the interfaces further. The results will be presented and discussed in terms of ALE process development and optimization.

This work was financially supported within the ALEStar project by the government of the Free-state of Saxony and the European Regional Development Fund under grant no. SAB 100402929.
Sulfur- and Nitrogen- Containing Molybdenum Films with a Thermally Stable Precursor
Authors: Leoncini Andrea , Barik Chandan Kr , Liu Feng Q , Tang Jiecong , Sudijono John , Saly Mark
Published: February 2024

As devices become more and more complex with each generation, process requirements become more stringent and new materials are necessary. This also translates to the need of new precursors, in particular halide free organometallic precursors with high thermal stability. This combination prevents halide contamination/corrosion of the deposited and neighboring films, and expands the ALD window for processes. However, higher thermal stability should not compromise the reactivity of the precursors in the desired processes.

We designed and successfully synthesized a new halide-free Mo precursor. It was characterized by 1H-, and 13C- NMR spectroscopy, and its molecular structure have been confirmed by x-ray crystallography. We studied its thermal stability, volatility, and chemical properties. Thermogravimetric analysis shows good volatility, with T½ of 230 oC and residual mass below 1%.

Isothermal TGA at 130 °C indicates that the chemical is volatile and deliverable to the reaction chamber. Its thermal stress analysis showed that it is stable at 200 oC for more than 1 day, with ~1% residue mass. Pyrolysis experiments showed little decomposition at 475 °C.

We used this precursor to attempt to deposit MoO, MoN and MoS based materials in mild conditions. ALD with NH3 afforded non uniform films with C contamination, and very low gpc. Similar results were obtained with H2O. On the other hand, films deposited with H2S were of uniform thickness with good gpc and selectivity for W over Si. The S content on the Mo-rich films was dependent on the deposition conditions and values as low as 6% could be obtained.

Figure 1
(Invited) Small Molecule Inhibitor-Based Approaches for Area-Selective Deposition from First Principles
Authors: Tonner-Zech Ralf
Published: February 2024

Atomic layer deposition tackles ever new research questions. Area-selective deposition is one of these recent challenges. Several approaches have been developed to achieve selectivity. One of the most promising is using comparatively small molecules to block the non-growth surface while leaving the growth surface uncovered for the ALD process.

This approach requires in-depth knowledge of the surface chemistry of both surfaces involved. In addition, the decomposition pathways of SMI-covered surfaces need to be uncovered to enable stable ALD growth over a maximum number of cycles.

These questions are very challenging for lab-based investigations. We present recent progress in the ab initio description of key questions regarding SMI-based ALD processes. At the example of silanol-based SMIs, surface chemistry for Al2O3 growth on Cu while blocking SiO2 will be discussed and compared to experimental findings.[1] Furthermore, the importance of choosing the appropriate surface model will be highlighted. Especially for the challenging question of SMI-layer decomposition.

[1 J. Yarbrough, F. Pieck, D. Grigjanis, I.-K. Oh, P. Maue, R. Tonner-Zech, S. F. Bent, "Tuning Molecular Inhibitors and Aluminum Precursors for the Area-Selective Atomic Layer Deposition of Al2O3", Chem. Mater. 2022, 34, 4646-4659.

We gratefully acknowledge funding from a Merck KGaA, Darmstadt, Germany 350th Anniversary Research Award. Computations were performed on the CSC Frankfurt, HLR Stuttgart, ZIH Dresden and HPC Regensburg.

Figure 1 General structure (a) of the studied SMIs with different reactive and blocking groups (b). Schematic structures of the calculated condensation reactions of the SMIs with OH groups of the SiO2 surface (c). Color code: Si (blue), O (red), and H (white).

Figure 1
(Invited) Plasma-Enhanced Atomic Layer Etching for Metals and Dielectric Materials
Authors: Chae Heeyeop , Kim Yongjae
Published: February 2024

The critical dimensions of semiconductor devices are continuously shrinking with 3D device structure and are approaching to nanometer scale. The demand for dimension control in angstrom level is drastically increasing also in etching processes. Atomic layer etching (ALE) processes are being actively studied and developed for various semiconductor, dielectric materials as well as metals. In this talk, various plasma-enhanced ALE (PEALE) processes will be discussed for isotropic and anisotropic patterning of metals and dielectric materials such as molibdenum, ruthenium, cobalt, titanium nitride, tantalum nitride, halfnium oxide, zirconium oxides.[1-7] Typical ALE processes consist of surface modification step and removal step. For the surface modification, various fluorination, chlorination and oxidation schemes are applied through fluorocarbon deposition, halogenation, oxidation with radicals generated plasmas. For the removal or etching step, various schemes were applied including ion-bomardment, heating, ligand volatilization, ligand exchange, and halogenation. The surface characteristics and requirements of plasma-enhanced ALE will be also discussed.

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2) Y. Cho, Y. Kim, S. Kim, H. Chae, J. Vac. Sci. Technol. A, 38(2), 022604 (2020)

3) Y. Kim, S. Lee, Y. Cho, S. Kim, H. Chae, J. Vac. Sci. Technol. A, 38(2), 022606 (2020)

4) D. Shim, J. Kim, Y. Kim, H. Chae, J. Vac. Sci. Technol. B., 40(2) 022208 (2022)

5) Y. Lee, Y. Kim, J. Son, H. Chae, J. Vac. Sci. Technol. A., 40(2) 022602 (2022)

6) J. Kim, D. Shim, Y. Kim, H. Chae, J. Vac. Sci. Technol. A., 40(3) 032603 (2022)

7) Y. Kim, S. Chae, H. Ha, H. Lee, S. Lee, H. Chae, Appl. Surf. Sci. 619, 156751 (2023)
Atomic Layer Deposition of Multi-Component Films Using Precursor Co-Dosing
Authors: Poodt Paul
Published: February 2024

A growing number of ALD applications require the deposition of ternary or quarternary compounds. Examples include doped films (e.g. ZnO:Al), mixed oxides to tune dielectric properties (e.g. HfZrO), tunable bandgap materials for solar cells (e.g. ZnOS) or opto-electronic materials (e.g. InGaN), and high mobility oxide semiconductors (e.g. InGaZnO). A common method to deposit multicomponent films in ALD is the supercycle approach [1], where sub-cycles of different binary compounds are combined to deposit films where the resulting net composition is determined by the cycle ratio of the individual sub-cycles. A drawback of the supercycle method is that essentially multilayer stacks are deposited instead of true alloys and the film composition varies out-of-plane, potentially impacting film properties.

An alternative method is to use precursor co-dosing, where two or more precursors are simultaneously dosed and co-adsorb during a half-reaction. The resulting film composition is then determined by the ratio of the partial pressures of the individual precursors during the precursor dose. As each ALD cycle deposits a true alloy, it results in excellent out-of-plane compositional uniformity. The co-dosing method has first been reported in the late 1980’s to deposit ternary and quarternary III-V compounds [2] and has been used since for a wide range of materials. In the last decade it has become the method of choice for depositing multicomponent materials with Spatial ALD.

A proper understanding of the relation between film composition and precursor partial pressure during co-dosing is essential for accurate control of the film composition. This is not straightforward, as the surface chemistry of co-dosing can be quite complex, involving competitive adsorption, heterogeneity of reactive sites, exchange reactions and more. We will discuss how the surface chemistry of precursor co-dosing determines the film composition. In analogy to the IUPAC classification of adsorption isotherms for single adsorbents [3], we will introduce a similar classification of adsorption isotherms for multiple absorbing precursors which we will use to review and explain results reported in literature. Finally, we will discuss some interesting new opportunities for co-dosing, such as the deposition of gradient composition films and the use of co-dosing for area-selective deposition.

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(Invited) Dual Coatings, Triple the Benefit; Atomic Armor for Better Battery Performance
Authors: Hughes Barbara K , Herbert-Walters Meghan , Martinez Madison , Turner Nicholas , DuMont Jaime W , Trevey James
Published: February 2024

ALD is a platform technology that has been widely demonstrated throughout the literature to impart significant processing and performance gains on lithium-ion battery technologies. Forge Nano has elevated this predominantly research-scale technique to production-scale heights, making ALD a viable and affordable technology to meet a variety of materials enhancement needs. From state-of-the-art lithium-ion batteries to solid-state cells, from electric vehicles to personal electronics; ALD enhancements have shown promise to bring longer lifetimes, safer cell performance, and reliability to cutting-edge rechargeable battery technologies. In this work we explore the performance enhancements imparted on cells with ALD modifications to multiple cell components and the mechanisms of resulting protections.
Forming Artificial Solid-Electrolyte-Interfaces between Lithium Metal Anodes and Halide and Sulfide Solid Electrolytes in All-Solid-State-Batteries Via Spatial-Atomic-Layer-Deposition
Authors: Kudu Ulas , Chaykina Diana , Huijssen Nico , Kronemeijer Auke , Ameen Mahmoud
Published: February 2024

Increasing need in energy density and safety of current lithium-ion batteries has resulted in a search for next generation battery technologies1,2. All-solid-state-batteries (ASSBs) could answer these needs owing to the use electrode materials with higher capacities and potential difference, and by replacing flammable liquid electrolytes with solid electrolytes3,4. ASSBs using inorganic sulfide and halide solid electrolytes in particular have drawn a lot of attention as the electrolytes have very high RT ionic conductivities (>10-3 S.cm-1)5–7. Nevertheless, they suffer from issues related to electro-chemical and chemo-mechanical stabilities at electrode – electrolyte interfaces7,8. One promising approach to mitigate this issue is depositing an artificial solid-electrolyte-interface (SEI) layer via atomic-layer-deposition (ALD)9–11. In this work, we deposited a variety of artificial layers with different thicknesses and chemistries on the lithium metal anode using spatial ALD. We characterized the bonding within the thin film layer using X-ray photoelectron spectroscopy, and evaluated the stabilizing effect of the artificial SEI layer using electrochemical impedance spectroscopy and galvanostatic lithium plating and stripping methods. We compared the growth of lithium dendrites within the solid electrolyte pellets post-mortem analysis via scanning electron microscopy.

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Beyond the Disturb Limit of Conventional 2D NAND: Superior Coupling Characteristics from Structural Benefit of 3D NAND
Authors: Yoon Joung Ho , Lee Ji Hwon , Hong Jun Sik , Yim Yong Sik
Published: February 2024

Cell disturb is an essential limiting factor in scaling NAND flash devices, which results in interference failures and reduced cell reliabilities. In this study, we compared the Planar(2D) versus Vertical(3D) NAND flash structure and characteristics and found that cell transistor disturb makes the integration limit of 2D NAND flash structure become the improvement in 3D NAND flash structure innovatively. The 3D structure and charge trap flash (CTF) cause the result of innovative not only cell disturb but also excellent data retention. Furthermore, we suggest a design standard for the next generation of 3D NAND flash cell transistors from cell disturb and retention.

Figure 1