bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials Properties vs. Device Performance: Batch Testing of MnOx-Loaded Carbon Nanofoam Papers for Low-Energy Faradaic Deionization
Authors: Neale Zachary Garbe , DeBlock Ryan H. , Rolison Debra R. , Sassin Megan B. , Long Jeffrey W.
Published: February 2024

Electrochemical desalination is presently a popular topic in the scientific literature as a response to global challenges with production of potable water. Many of these reports focus on materials/electrode properties for ion capture yet fail to account for other factors that impact practical device performance. For example, gravimetric ion-storage capacity is commonly reported while areal and volumetric capacities may be more important for desalination cell performance. Furthermore, the dynamic fluid mechanics of flow-cell devices require deliberately engineered electrodes in contrast to their static-electrolyte analogs for energy-storage devices (batteries or supercapacitors). To break from the academic status quo, we have designed a computer-controlled batch-process system to investigate desalination performance of practical electrode materials and architectures. This system allows continuous desalination to high degrees of salt removal on a laboratory scale without the need to use large-footprint electrodes. We demonstrate the characteristics of materials-based vs. system-based desalination metrics using NRL-pioneered electrodes — MnOx-decorated carbon nanofoam paper (MnOx@CNFP)1 — relatives of which are effective for faradaic desalination via Na+ capture.2 Scalable and freestanding CNFP electrodes possess three-dimensionally interconnected pore structures with tunable porosities to facilitate ion transport,3 while the interior surfaces of the CNFP (>200 m2 g–1 in mesopores and macropores) are readily functionalized with nanoscale MnOx by self-limiting electroless deposition.1 We investigate the effect of MnOx@CNFP pore structure and electrode thickness on practical desalination performance, and demonstrate the importance of reporting throughput (L/m2/h) and energy consumption (Wh/L) to better validate new electrode materials and architectures in flow-cell desalination devices.

E. Fischer, K. A. Pettigrew, D. R. Rolison, R. M. Stroud, and J. W. Long, Nano Lett., 2007, 7, 281–286.

Hand and R. D. Cusick, Environ. Sci. Technol., 2017, 51, 20, 12027–12034.

C. Lytle, J. M. Wallace, M. B. Sassin, A. J. Barrow, J. W. Long, J. L. Dysart, C. H Renninger, M. P. Saunders, N. L. Brandell, and D. R. Rolison, Energy Environ. Sci., 2011, 4, 1913–1925.
Gold Recovery from Thiosulfate Leaching Solution Using Silicon Powder and Electrochemical Monitoring of Its Process
Authors: Yae Shinji , Iwai Yuna , Takashima Yumi , Osaka Takumi , Matsumoto Ayumu
Published: February 2024

Gold recycling from Waste Electrical and Electronic Equipment (WEEE) has been actively conducted. We previously reported a noble metal recovery process using aqua regia and electroless displacement deposition onto silicon powder [1,2]. Using silicon powder has such advantages as that noble metals and copper are selectively recovered, and sawdust silicon, that is, industrial waste silicon powder is available to use. Recently, ammonium thiosulfate solution has attracted attention as a safe and low-cost solution for gold leaching [3-6]. In this study, we successfully recovered gold from an ammonium thiosulfate solution by using silicon powder [7,8], and tried to monitor the recovering behavior electrochemically. Since the ammonium thiosulfate leaching solution includes copper ions as oxidizing agent, copper is recovered by silicon powder. Thus, the monitoring was conducted in order to determine the suitable timing for efficiently obtaining pure gold during the process. For experimentation, an ammonium thiosulfate solution containing gold(I) sulfite and copper(II) sulfate was prepared (pH = 13). We immersed a gold wire in the solution and measured the rest potential during the recovery process using silicon powder. The potential of gold wire shifted stepwise toward negative direction at each start and end of gold and copper recovery. The results suggest that the efficient recovery of high-purity gold can be achieved by monitoring the potential of gold.

[1] K. Fukuda, S. Yae, N. Fukumuro, S. Sakamoto, and H. Matsuda, ECS Trans., 53(19), 69 (2013). DOI: 10.1149/05319.0069ecst

[2] K. Fukuda, N. Fukumuro, S. Sakamoto, and S. Yae, ECS Trans., 61(10), 1 (2014). DOI: 10.1149/06110.0001ecst

[3] M.G. Aylmore and D.M. Muir, Miner. Eng., 14, 135 (2001). DOI: 10.1016/s0892-6875(00)00172-2

[4] H. Arima, T. Fujita, and W. Yen, Mater. Trans., 43, 485 (2002). DOI: 10.2320/matertrans.43.485

[5] S. Syed, Hydrometallurgy, 115-116, 30 (2012). DOI: 10.1016/j.hydromet.2011.12.012

[6] B. Xu, W. Kong, Q. Li, Y. Yang, T. Jiang, and X. Liu, Metals, 7, 222 (2017). DOI: 10.3390/met7060222

[7] Y. Iwai, Y. Takashima, A. Matsumoto, and S. Yae, Abst. Interfinish2020 20th world congress, P-E2-001 (2021).

[8] Y. Takashima, A. Matsumoto, Y. Iwai, S. Arita, and S. Yae, J. Surf. Finish. Jpn., 73, 98 (2022). DOI: 10.4139/sfj.73.98
Electrochemical Reduction of Ytterbium in Non-Aqueous Solvents - Towards Production of Pure Medical Lutetium-177
Authors: Aerts Robin , Geboes Bart , Van Hecke Karen , Binnemans Koen , Cardinaels Thomas
Published: February 2024

In recent years targeted radionuclide therapy has become a topic of great interest as a growing number of cancers can potentially be treated with radionuclides like lutetium-177 and samarium-153. To facilitate this growth and meet the demand, preparation and purification of lutetium-177 is increasing in importance. In the most common production route, enriched ytterbium-176 targets are irradiated and the produced lutetium-177 is separated from the ytterbium target material. This challenging separation is commonly performed using ion exchange resins, a method limited in scalability as the chemical similarity between ytterbium and lutetium results in poor separation at higher concentrations.

An alternative method to aid the separation of lutetium from ytterbium is the electrochemical reduction of ytterbium as a change in oxidation states changes chemical properties significantly. Ytterbium has an accessible divalent state, whereas lutetium has not. However, the very negative value of the Yb(III)/Yb(II) standard reduction potential (E0= -1.04 V vs. SHE) does pose some challenges as it becomes a necessity to work in non-aqueous solvents with a very low water content. Similar research has already been performed in our group, looking into the separation of samarium-153 from europium-154, reducing europium in nitrate media, followed by a separation over TEVA resin. In this study, we investigated the reduction of ytterbium in ethylene glycol, dimethyl sulfoxide, tetrahydrofuran and N,N-dimethyl formamide by cyclic voltammetry, linear sweep voltammetry and electronic impedance spectroscopy. The influence of multiple variables such as moisture content on the reduction kinetics and stability of Yb(II) was determined and a Koutecky-Levich analysis was performed. Our results demonstrate that the reduction of ytterbium in non-aqueous solvents is feasible but attempts to perform bulk electrolysis were not successful yet. Ethylene glycol, dimethyl sulfoxide and N,N-dimethyl formamide demonstrate favorable conditions and in each solvents clear reduction and oxidation peaks were observed. It was found that the solvents do affect the peak separation, reduction potential and sensitivity to passivation.

Figure 1
Electrochemical Direct Air Capture of Carbon Dioxide by a Redox-Mediated Salt Splitting Process
Authors: George Thomas Young , Mangold Lucie , Wang Cliffton , Schrag Daniel P. , Aziz Michael J.
Published: February 2024

Direct air capture of carbon dioxide is an important emerging direction for electrochemical separation technology. Carbon dioxide removal has a critical role to play in the coming century as a complement to deep decarbonization efforts, because removal may offset emissions we cannot avoid, such as agriculture for food security. Direct air capture might even be used to decrease the atmospheric carbon dioxide level if the value at which it stabilizes is deemed too high. Electrochemical methods allow us to power a carbon removal device directly by carbon-free electricity. Here, we present a salt splitting process, based on bipolar membrane electrodialysis, which begins with a neutral electrolyte (e.g. KCl), and creates a strong base (e.g., KOH) and a strong acid (e.g., HCl). The base may then be used to absorb carbon dioxide from ambient air; the acid is then used to extract the carbon dioxide by recombining with the base, reversing the salt splitting process. The process is driven by iron(II/III) hexacyanide redox on carbon cloth electrodes, which is kinetically facile and contributes relatively little to the cell voltage.

Energy required for redox-mediated salt splitting depends on contributions from water dissociation in the bipolar membrane, ohmic resistances in ion exchange membranes and electrolyte layers, and electrode reactions. We show that the largest contribution to the energy required comes from the bipolar membrane, motivating further research on bipolar membrane development. We also discuss the role of ion exchange membranes in this system: these membranes must provide high ion conductivity while providing selectivity against leakage of acid and base products. Several commercial membranes were screened for conductivity and water content, and their electrodialysis performance is compared. Finally, we use technoeconomic modeling to assess how electrodialysis operating conditions and electrolyte composition affect energy, land, and water demands of a continuously operating direct air capture process, with redox-mediated salt splitting as the centerpiece.

Figure 1
(Invited) Industrial Relevance of Pulsed Electrochemical Methods
Authors: Hansal Wolfgang , Hansal Selma , Weiß Susanna
Published: February 2024

Industrial demands are the driving force on any optimization and development process for electrochemical plating processes and coatings. The classical demands focused on the mechanical properties such as wear resistance and hardness as well as the stability against corrosion.

The galvanic coatings were tailored for meeting these requirements, defining the electrochemical systems that are currently standard in galvanic protection of industrial parts.

With the introduction of new applications and production methods over the last 10 to 15 years additional functionality has been seeked by the industry, including chemical stability, bio-compatibility, microstructured surfaces, lubrication effects, magnetic properties and the ability of shock absorbance. Coating had to be adjusted, leading to the industrial realisation of dispersion and compound coatings, alloy deposition on a wider scale and Pulse (reverse) plating. While these, from an industrial perspective, relatively new plating processes already required some major rethinking of the traditional galvanic industry, the industrial requirements got even more demanding over the last few years. Especially with the origin of new industrial production methods, the homogenous treatment and coating of e.g. complex bionical structures became relevant.

In order to follow the changing demands, the transfer from the classical thermodynamically controlled direct current or constant potential based surface treatment towards a kinetically controlled pulsed surface finishing has to be executed.

While pulse plating is the most popular representation of these categories of finishing processes, pulsed electrochemical processes comprise a much larger variety of methods. Among these, pulse anodization, pulsed plasma electrolytic oxidation (PEO), pulsed electropolishing, electrochemical machining (ECM) and the recently introduced Hirtisation process are industrially used.

The presenation will give an overview of possibilities for electrochemical engineering of surfaces for high-end technical applications by pulsed electrochemical techniques.
Pulse and Pulse/Reverse Techniques for Electrodeposition of Rhenium and Refractory Metals
Authors: Hooks Daniel E , McBride Michael , Brown Nathan , Clark Courtney L , Dervishi Enkeleda
Published: February 2024

Refractory metals possess unique properties including high melting points, high hardness at room temperature, chemical resistance, and high density. Electrodeposition of refractory metals is of interest as a scalable approach to apply uniform coatings to enable a wide range of applications in aerospace, nuclear, catalysis, biomedical fields. This talk will focus on pulse electrochemical variables to enable methods to electrodeposit high quality metallic rhenium (Re).

Re has traditionally been difficult to deposit from aqueous solutions due to the over potential for hydrogen evolution and complex electrochemical reactions. Electrodeposition of rhenium usually occurs from the perrhenate ion (ReO4-) with an oxidation state of +7. The exact mechanism to reduce the perrhenate ion from +7 to metallic rhenium is still unknown. It is unlikely that the 7 electrons transfer in a single step, so reduction likely occurs through intermediate oxide species including ReO2, ReO3 and Re2O5. Combined with the hydrogen evolution reaction, Re coatings are generally deposited at low faradaic efficiency, are brittle, and limited in thickness (sub-micron). In our previous work, water-in-salt electrolytes and complexing additives have enabled resolution of some of the issues associated with this complexity and a range of deposit qualities, though cracking issues remain and coating quality issues still needed optimization.

Herein, we present on the effects of pulsed electrochemical approaches to eliminate cracking in the film by balancing nucleation and growth and the competing hydrogen evolution reaction. A custom high-throughput cell was developed to rapidly screen parameters and explore time-dependent evolution of the electrodeposition processes.
Surface Finishing or Shaping By Pulse/Pulse-Reverse Electrolysis
Authors: Hall Timothy , Radhakrishnan Rajeswaran , Le Houng , Moran Andrew , Garich Holly , Liu Danny , Snyder Stephen , Inman Maria , Taylor Earl Jennings
Published: February 2024

Faraday Technology Inc. is a research, development and electrochemical engineering firm developing electrochemical innovations based has pulse/pulse reverse electrolytic principles. [1,2] With that founding basis Faraday has been able to bridge the gap between academic understanding and small-scale demonstrations to commercialization of practical components for over 32 years of operation.

This presentation will discuss a broad range of surface finishing studies including a wide range of metals, additively manufactured parts, electrochemical machining, and highly complex structures. We will highlight some of the key factors that determine the usefulness and successfulness of using pulse/pulse reverse principles to enable simple water-based HF free electrolytes to finish or shape a wide range of metal surfaces. For instances, we will discuss electropolishing of Nb superconducting cavities, additively manufactured grade 5 Ti impellers, and electrochemical machining to create complex impossible to machine shapes. Each process utilizes pulse/pulse reverse operations to overcome key challenges with boundary layer control, oxidation/reduction of the surface, and the uniformity of the finish.

References:

J. Taylor “Adventures in Pulse/Pulse Reverse Electrolytic Processes: Explorations and Applications in Surface Finishing” J. Applied Surface Finishing,
3(4), 178-189 (2008).

J. Taylor, et al., (2019; Chapter 7) “Breaking the Chemical Paradigm in Electrochemical Engineering: Case Studies and Lessons Learned from Plating to Polishing” R.C. Alkire (Volume 18). Electrochemical Engineering: The Path from Discovery to Product.Wiley-VCH.
Hydrogen Production Via Mediated Electrolysis of Biomass from Distillery Whisky Waste Streams
Authors: Price Robert , MacDonald Lewis , Li Jun , Brightman Edward
Published: February 2024

Fuel-flexible hydrogen generation methods, such as electrochemical conversion of waste biomass, offer a route to sustainable production of hydrogen (in addition to steam or water electrolysis using renewable electricity [1]) whilst valorising feedstocks that are often overlooked. [2] In this research, the authors explore the potential of a novel, two-stage electrolysis process to convert biomass-containing solid and liquid distillery waste products into hydrogen, using a phosphomolybdic acid (H3[PMo12O40] or PMA) catalyst, at lower operating voltages (<0.95 V) than proton exchange membrane (PEM) water electrolysers (1.5 – 1.6 V). [3]

Firstly, an overview of the processes, energy usage and waste stream generation at the Isle of Raasay Distillery (Hebrides, Scotland) will be provided, before results from the characterization of whisky waste products are introduced. This provides a detailed compositional analysis of both solid (draff/spent barley) and liquid (pot ale and spent lees) wastes, as well as residual alcohol analysis of the liquid wastes, and their potential for conversion to hydrogen.

Subsequently, the concept of thermal digestion of each waste-type, using the Keggin-type polyoxometalate PMA catalyst to abstract protons and electrons from biomass, will be outlined. Finally, details of electrolysis of the PMA-biomass solutions using a PEM flow cell will be provided, including electrochemical data (AC impedance spectroscopy, linear sweep voltammetry and potentiostatic operation) in order to determine the optimal operating conditions for the process, in addition to the respective yield of hydrogen from each biomass source. Prospects for upscaling the process will also be discussed.

References

Götz, M., Lefebvre, J., Mörs, F., McDaniel Koch, A., Graf, F., Bajohr, S. Reimert, R. and Kolb, T., Renew. Energ., 85, 1371 – 1390 (2016).

Liu, W., Cui, Y., Du, X., Zhang, Z., Chao, Z. and Deng, Y., Energy Environ. Sci., 9, 467 – 472 (2016).

Oh, H., Choi, Y., Shin, C., Nguyen, T. V. T., Han, Y., Kim, H., Kim, Y. H., Lee, J-W., Jang, J-W. and Ryu, J., ACS Catal.
10, 2060 – 2068 (2020).
Electro-Oxidative Valorization of Biomass-Derived Furanics
Authors: Holewinski Adam
Published: February 2024

Electrocatalysis poses many potential advantages for distributed scale biomass valorization. Furanic biomass derivatives such as furfural and 5-hydroxymethylfurfural (HMF) can provide access to a number of value-added chemicals by partial oxidation, including furoic acid, maleic acid, and 2,5-furandicarboxylic acid (FDCA). Here, we have utilized differential reactor studies with online electrochemical mass spectrometry (OLEMS), as well as in-situ attenuated total reflectance surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS), to probe these reaction pathways on various metal electrodes. Experimental insights are combined with computational results to piece together plausible mechanisms. We find tradeoffs between decarbonylation activity and self-assembly of furoate intermediates on late transition metals to be critical selectivity-determining and rate-determining process. We also characterize oxidative dehydrogenation paths for furanic aldehydes, which co-produce (anodic) hydrogen gas. Strategies for improved catalyst design will be discussed.
NAD-Regenerating Biocathode Applied to Electroenzymatic Conversion of Lignin
Authors: Mishyn Vladyslav , Hickey David , Abdellaoui Sofiene
Published: February 2024

Non-renewable and limited fossil resources (i.e. petroleum, coal, and natural gas) have been used over the last years for the production of energy, commodity chemicals, and polymer materials. Nonetheless, the extraction and consumption of these resources leads to deleterious and irreversible environmental impacts. As a sustainable alternative, lignin, one of the major components of lignocellulosic biomass, represents the most promising renewable raw material to produce aromatic-based chemicals and high value-added products. However, the use of lignin as a source of valuable molecules similar to the petroleum-derived chemicals is hindered due to its recalcitrance and structural heterogeneity. Biological approaches have been studied to develop selective and ecofriendly pathways for lignin valorization. It has been reported that some microorganisms can cleave selectively β-ether bonds representing more than a half of lignin bonding pattern.[1] The etherolytic pathway of the soil probacterium Sphingobium paucimobilis, which involves NAD-dependent dehydrogenases and β-etherases, has been well characterized for this purpose.[2] Here we focus on the design of a bioanode combining NAD-regenerating properties and the immobilization of lignin degrading enzymatic cascade to cleave such bonds. We explored the possibility of combing in situ electrochemical regeneration of NAD+ cofactor with a surface immobilized biocatalysts on a single interface. First, we have demonstrated that the electrodes based on multiwalled carbon nanotubes modified with toluidine blue are capable to regenerate NAD+ cofactor at low potential from its reduced form. This process is essential for dehydrogenases activities. Secondly, we used cross-linked hydrogel of pyrene-modified linear poly(ethyleneimine) to entrap the enzymes on the electrode surface.[3] The obtained bioanode modified with NAD-regenerating catalyst and the multi-enzymatic cascade of Lig enzymes was tested in the presence of guaiacylglycerol-β-guaiacylether (GGE), a lignin dimer substrate with β-ether bond, to produce γ-hydroxypropiovanillone (HPV). We believe that such electrochemical systems employing the enzymatic cascade acting like a metabolic funnel with the simultaneous regeneration of the cofactor would permit to refine the heterogeneous mixture of aromatics from lignin depolymerization products into a uniform distribution of value-added compounds.

[1] Renewable Sustainable Energy Rev., 2022, 157, 112025.

[2] Catal. Sci. Technol., 2016,6, 2195-2205.

[3] Chem. Sci., 2018,9, 5172-5177.

Figure 1
Electromediated Oxidation of Hydrolysed Bacterial Cellulose
Authors: Yousefi Neptun , Wilson Benjamin , Kontturi Eero
Published: February 2024

The state-of-the-art method to isolate cellulose nanofibres employs a 2,2,6,6-Tetramethylpiperidinyloxyl (TEMPO)/NaBr/NaClO system, where the primary alcohols on the surface of cellulose microfibrils are oxidised. However, the large consumption of hypochlorite in this system makes it problematic for industrial implementation. Previously, electrochemical oxidation with a TEMPO catalyst has been reported for the preparation of cellulose nanofibres. Here, we present a study on the electromediated oxidation of bacterial cellulose (BC), the purest form of cellulose. BC has been used in a hydrolysed form, enabling the electromediated preparation of cellulose nanocrystals (CNCs), which is generally deemed even more costly than the preparation of cellulose nanofibres.

In this work, the electromediated oxidation and cyclic voltammetry were performed in an electrochemical cell, which featured three electrodes: A Hg|Hg2SO4|K2SO4 reference electrode, a titanium net counter electrode, and a carbon foam working electrode, offering a high surface area. A static potential of 0.5 V was applied during the chronoamperometry and explored oxidation times were 3, 5, 9, 12 and 24 h.

Using a TEMPO catalyst, the electromediated oxidation was applied to hydrolysed and non-hydrolysed BC fibres in a pH 10 buffer. The C6 primary hydroxyls of BC were successfully converted to sodium carboxylate groups. By the application of the TEMPO electro-mediated oxidation to hydrolysed BC for 9 h, high carboxylate and aldehyde concentrations of 1.4 and 0.3 mmol/g, respectively, were formed in the oxidized fibre. The carboxylate and aldehyde content was determined by a conductometric titration method. Surface morphologies after oxidation were investigated, showing alteration of the microfibril morphology for BC and the production of cellulose nanocrystals for hydrolysed BC. Hence, we present an effective and environmentally friendly route, which is particularly suitable for the preparation of cellulose nanocrystals.
Atomic Layer Deposition for Quantum Dots Displays’ Devices Stabilization
Authors: Wen Di , Cao Kun , Gu Eryan , Jiang Xuewei , Wen Yanwei , Chen Rong
Published: February 2024

As display plays an increasingly important role in people's life, from mobile phones, automobile displays to AR, VR and 3D naked eye screens. There are increasing demands for pursuing higher resolution, refresh frequency, wider color gamut, etc. Therefore, photoluminescence materials with excellent photoelectric performance have attracted broad attention, but there are still some problems in their application, and achieving higher performance with stability is still urgent to be solved. Atomic layer deposition (ALD) has been developed as an attractive method to modify and stabilize photoluminescence materials. For photoluminescence PL performance, the stabilization of crystal structure can be achieved by solution treatment, and the luminescence performance can be improved. ALD was performed to enhance the stability of CsPbBr3 quantum dots in light, water and heat, which originated from the surface defects passivation. The combined method of organic hydrophobic surface modification and ALD infiltration is used to construct a dual-shelled to prevent the crystal deformation and ligand desorption of luminescent materials, and is also applicable to phosphor materials. For electroluminescence EL performance, ALD modification methods were developed for the light-emitting layer modifying, gas phase ALD and colloidal ALD were developed to decreasing the transport barrier between the quantum dots, improve the carrier mobility of the device, and lift the EQE and stability of the device. In addition, ultrathin film grow through ALD could effectively balance the carrier and improve the recombination efficiency as well as important functional layers. ALD of dual Electron transport layers(ETLs) and dual hole injection layers(HILs) is developed to enhance luminance performance of the PQLEDs but also achieve a long lifetime under constant voltage. Our works provide a versatile method for preparing ultra stable photoluminescence materials through ALD and significantly improve their potential in LED illumination and displays.
(Invited) Advanced Atomic Layer Deposition Cycle Schemes for Large-Area Synthesis of 2D Transition Metal Dichalcogenides
Authors: Bol Ageeth Anke
Published: February 2024

2D materials have been the focus of intense research in the last decade due to their unique physical properties. This presentation will highlight our recent progress on the large-area synthesis of two-dimensional transition metal chalcogenides for nanoelectronics using advanced atomic layer deposition cycle schemes. First, how we can use advanced cycle schemes to deposit wafer-scale polycrystalline MoS2 thin films at very low temperatures down to 100 °C. We have identified the critical role of hydrogen during the plasma step in controlling the composition and properties of molybdenum sulfide films. By increasing the H2/H2S ratio or adding an extra hydrogen plasma step to our ALD process, we are able to deposit pure polycrystalline MoS2 films at temperatures as low as 100 °C. To the best of our knowledge, this represents the lowest temperature for crystalline MoS2 films prepared by any chemical gas-phase method.[1]

ALD-grown 2D films tend to exhibit a high density of out-of-plane 3D structures in addition to 2D horizontal layers. While the out-of-plane 3D structures are ideal for catalysis applications, the presence of such 3D structures can hinder charge transport, which hampers device applications. In this presentation I will show how we used mechanistic insight obtained by HRTEM to tune the shape and density of the 3D structures during plasma-enhanced ALD using advanced atomic layer deposition schems. The obtained morphology control was further confirmed by electrical measurements.[2]

Earlier [3] we have shown that ALD is an excellent technique to make MoxW1-xS2 alloys with precise control over the alloy composition. Here, I will focus on how (plasma-enhanced) atomic layer deposition can aid in synthesizing doped 2DTMCs with precise control over the doping concentration by using elaborate ALD dosing schemes.

[1] M. Mattinen et al., Chem. Mater. (2022), 34, 5104

[2] S. Balasubramanyam, et al. ACS Appl. Mater. Interfaces (2020), 12, 3873

[3] J. J. P. M. Schulpen et al.
2D Mater. (2022), 9, 025016
Atomic Layer Etching of Al2O3 Using F Radical and Al Precursors: Surface Reaction and Reaction Mechanism Study
Authors: Kim Yewon , Cho Gyejun , Kim Okhyeon , Choi Ye Rim , Khumaini Khabib , Kim Hye-Lee , Kwon Jun Hyuck , Kim Minsu , Cho Byungchul , Park Sangjoon , Lee Won-Jun
Published: February 2024

In order to overcome the miniaturization of semiconductor devices, devices with a three-dimensional (3D) structure, such as FinFET and 3D vertical NAND devices, were introduced. The manufacturing of 3D devices requires both anisotropic etching in the vertical direction and isotropic etching in the horizontal direction. Therefore, a new technology with atomic-level precision is required for isotropic etching, which is dependent on wet etching. It is the thermal atomic layer etching (ALE) process that meets these requirements. Since the first report in 2016, the thermal ALE processes by alternating exposures to HF vapor and a metal precursor have been reported for various thin films. However, HF has issues with safety and corrosion. Recently, ALE processes using F radicals produced by inductively coupled plasma (ICP) of SF6 or NF3 have been reported [1,2]. However, the study on the reaction mechanism of F radicals is lacking. In this study, the surface reaction was studied for the modification and removal steps by NF3 remote plasma and Al precursors. We used quartz crystal microbalance (QCM) to measure the mass change during the ALE process and X-ray photoelectron spectroscopy (XPS) to analyze the composition of the modified layer. The mechanism of ALE using F radical was different from that using HF, due to the absence of H atoms. Density functional theory (DFT) simulation shows that amorphous carbon or fluorocarbon layer can be formed during the ALE by F radicals. Al precursor with fewer organic ligands was beneficial to suppress the formation of a carbon-containing surface layer.

Acknowledgments This research was supported by the MOTIE (Ministry of Trade, Industry & Energy (project number 20012588) and KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device.

References [1] N. Chittock et al., Appl. Phys. Lett. (2020) [2] J. Kim et al., J. Vac. Sci. Technol. A (2022)
Platinum Catalysts via Fluidized Bed Atomic Layer Deposition for PEM Fuel Cells
Authors: Pescher Fiona , von Holst Miriam , Salihi Arbëri , Heizmann Philipp , Stiegeler Julian , Vierrath Severin
Published: February 2024

One of the major challenges for viable and durable proton exchange membrane fuel cells (PEMFC) in heavy duty applications is the development of stable and high-performing catalysts. The highest mass activities and stabilities can be achieved with platinum nanoparticles supported on a porous carbon support. However, these systems still suffer from degradation processes during cell operation, such as carbon corrosion and Ostwald ripening. [1] Atomic layer deposition (ALD) is an attractive alternative to the conventional wet chemical deposition of the platinum catalyst onto the carbon, promising to counteract these problems. [2,3]

ALD is a surface coating method, which employs self-limiting half-reactions between gaseous precursor molecules and a solid substrate surface. Usually, two half-reactions separated by purging or vacuuming steps represent one ALD cycle. By performing a defined number of cyclic repetitions, thin films or nanoparticles can be grown on the substrate surface with atomic-layer precision. [4]

Typically, ALD is used to coat flat surfaces. To achieve homogeneous coatings on powders, so-called fluidized bed ALD reactors fluidize the nanoparticle-powders in a gas flow, which also contains the gaseous precursor materials. This method ensures a high utilization of the precursor molecules while providing a good mixing of the sample. Thin films and nanoparticles can be deposited in a homogeneous manner onto the powder surface and into its pores. [4]

Carbon corrosion of PEMFCs can be suppressed by applying conformal ALD coatings onto the support structure. Additionally, a porous overcoating can fixate the nanoparticles against detachment and dissolution while still leaving access to the reactive sites. [5] Applying ALD to deposit fuel cell catalysts with monodisperse and highly dispersed platinum nanoparticles can counteract Ostwald ripening. [2,6]

In this study we show platinum particles deposited via ALD, which are highly dispersed and show a monodisperse size distribution. We further show TiO2-overcoatings to protect the carbon.

Literature:

[1] J. C. Meier, Beilstein J. Nanotechnol., 2014, 5, 55-67. [2] W-J. Lee, Adv. Mater. Interfaces, 2019, 6 1901210. [3] B. J. O’Neill, ACS Catal., 2015, 5, 1804. [4] W. W. McNeary, Appl. Catal. B, 2019, 254, 587-593. [5] Q. Liu, Chem. Soc. Rev., 2022, 51, 188-236. [6] Z. Xu et al., Appl. Catal. B, 2012, 111-112, 264.
Oxygen Evolution Reaction Performance Changes with Varying Crystallinity and Thickness of Atomic Layer Deposited RuO2 Film
Authors: Lee Jaehwan , Chung Seung-min , Kim Hyungjun
Published: February 2024

As the world's population grows and the energy consumption has increased, the use of fossil fuels is gradually increasing. The carbon dioxide emitted from burning fossil fuels is a major cause of greenhouse effect. Therefore, hydrogen is widely recommended as an energy source to alternate fossil fuels due to its high energy per mass, no production of pollutant. Among several ways to obtain hydrogen, electrolysis of water is considered the most promising method. However, the slow-rate determining step of the oxygen evolution reaction (OER) compared to hydrogen evolution reaction (HER) is a main reason for interrupting wide use of electrolysis of water in the industry. So, there have been various research for enhancing the effectiveness of water electrolysis.

The development of OER electrocatalysts is needed for promote the efficiency of OER process, noble metals-based materials has been researched due to its superior activity. Among noble metals, RuO2 has been researched as promising catalyst for oxygen evolution, and the efficiency of the catalyst varies on the preparation technique (e.g., sputtering, hydrothermal methods and sol-gel). Therefore, there have been diverse studies to enhance the RuO2 electrocatalytic effectiveness of oxygen evolution via crystallinity control, increase of electrochemically active surface area by adjusting synthesizing method of RuO2 film.

Atomic Layer Deposition (ALD) has strengths of large-area uniformity, excellent conformality, and being able to control the thickness of the film at the atomic scale. ALD is suitable technique to deposit catalysts materials conformably on 3D nano-structured complex materials, so the catalytic activity in the OER can be improved by increasing the surface-to-volume ratio. Therefore, ALD is assumed as a suitable synthesizing method for electrocatalyst. Besides, ALD allows low mass loading of catalyst material which is most needed factor in the industrial area. However, there have no enough research of ALD RuO2 for OER analyzing condition (crystallinity, thickness) for obtaining enhanced OER performance.

In this report, RuO2 film was prepared based on ALD on Carbon Fiber Paper (CFP) at different deposition temperature and it showed different crystallinity, one was amorphous, the other one was crystalline. The crystalline one showed better OER performance due to its enlarged active sites of OER. We analyzed their growth characteristics and material properties by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), XRD spectrometer (XRD). And dependence of film thickness of ALD RuO2 films was also studied. Electrocatalytic properties of ALD RuO2 on CFP was measured in three-electrode. It showed low overpotential and Tafel slope, which shows electrocatalytic performances.

Figure 1
Mechanism of Infiltration between Alumina and Polyurea for Stretchable Patterned Thin Film
Authors: Lee Jae Seok , Song Seung Hak , Choi Byoung-Ho
Published: February 2024

Conventional display panels could be replaced by OLED displays, which are a leading and popular technology in display industry. While OLEDs are quite stretchable, they are vulnerable to oxygen and moisture, and currently, there is no proper barrier film that can protect them from these elements while also maintaining high stretchability. In this study, a horizontally patterned organic/inorganic layer that can increase the stretchability of the film while also providing the necessary protection is proposed. The final structure of the thin film will consist of two layers: a stripe-patterned organic/inorganic layer created using area-selective ALD/MLD processes, followed by an organic layer.

To achieve the research objectives, the degree of infiltration of the inorganic layer into the organic layer is crucial. In this study, the mechanism behind the generation of the interface layer between alumina and polyurea is investigated. Trimethylaluminum (TMA) and H2O were used as precursors for fabricating alumina by ALD, while 1,4-phenylene diisocyanate (PPDI) and ethylene diamine (ED) were used for fabricating polyurea by MLD. The porous structure of the polymer allows ALD precursors to spread into it. During TMA pulsing on the polymer layer, the degree of infiltration is affected by the type of chemical bond in the polymer. Previous research has shown that TMA precursors are more likely to infiltrate polymers with C=O bonds into the polymer layer. Therefore, polyurea, which contains a carbonyl functional group (-C(=O)-), is suitable for this research. While the conditions for polyurea MLD are fixed, five chamber temperature conditions for depositing alumina were selected: 30℃, 50℃, 70℃, 90℃, and 110℃. Alumina was deposited by ALD on 30nm of polyurea which was deposited on a Si wafer.

From X-ray reflectivity (XRR) data, it was observed that three main types of thin films were formed. As the temperature increased, the density and thickness of the alumina layer forming the thin film changed. To verify the change in the alumina thin film, FTIR and XPS were used to compare the peaks representing the bonds of Aluminum and Oxygen.
Atomic Layer Deposition and Characterization of Bi1Se1 Thin Films
Authors: Bahrami Amin , He Shiyang , Zhang Xiang , Cichocka Magdalena Ola , Yang Jun , Charvot Jaroslav , Bures Filip , Schulz Stephan , Nielsch Kornelius , Heckel Alla
Published: February 2024

Van der Waals (vdWs) heterostructured materials have attracted considerable interest due to their intriguing physical properties. Here, we report on the deposition of BiSe by atomic layer deposition (ALD) using Bi(NMe2)3 and Se(SnMe3)2 as volatile and reactive Bi and Se precursors, respectively. The growth rate varies from 1.5 to 2.0 Å/cycle in the deposition temperature range of 90–120 °C. Higher deposition temperatures lead to increased grain sizes and enhanced crystallinity of resulting films. Further microstructure characterization reveals the formation of crystalline domains with varying orientations and nanotwinned boundaries. The presence of Bi-Bi zigzag bilayers and the formation of the BiSe phase were confirmed by the existence of the Bi-Bi binding energy peak in the XPS spectra and Raman spectra. Furthermore, the electrical conductivity of BiSe ranged from 1420 to 1520 S/cm due to the ultrahigh carrier concentration (2–3.5 × 1021 cm−3), which is the highest among undoped bismuth selenide-based materials.
(Invited) Atomistic Insights into Continuous and Area-Selective ALD Processes: First-Principles Simulations of the Underpinning Surface Chemistry
Authors: Karasulu Bora
Published: February 2024

Atomic layer deposition (ALD) is a highly advanced thin film deposition technology that has found widespread use in nanoelectronics, photovoltaics, fuel cell and recently all-solid-state battery applications. It is widely regarded as the state-of-the-art technique for producing thin films due to its exceptional conformality on high-aspect ratio structures, atomic level thickness control, and tuneable film composition. In recent years, area-selective atomic layer deposition (AS-ALD) has emerged as a promising technology for high-fidelity nano-patterning, and significant progress has been made in understanding and developing highly selective processes for various material systems. Along these lines, we have recently shown that high-throughput, low defectivity, highly selective SiO2 deposition can be achieved on various substrates by combining atmospheric-pressure spatial ALD with integrated area-deactivation using small molecule inhibitors and plasma-enhanced spatial etching [1].

ALD is a surface-controlled technique that relies on the self-limiting reactions of the precursors and co-reactants with the deposition surface in alternating cycles. The initial step in ALD nucleation on the target substrate is a key factor in the deposited film quality, and efficient precursor binding on the surface is critical. Molecular dynamics (MD) simulations and minimum-energy reaction pathway analysis based on ab initio Density Functional Theory (DFT) calculations provide invaluable insights into the surface chemistry, enabling customisation of ALD processes to boost uniformity, conformality, and area-selectivity of the resulting films.

In this talk, I will discuss how first-principles simulations can be used synergistically with experimental findings to achieve high-efficiency plasma-enhanced atomic-layer cleaning (ALC) of impurities from various ALD films and substrates, design proper chemical surface modifications that enable continuous and conformal ALD nucleation even on chemically-inert surfaces (like graphene), and unveil the particular surface chemistry governing high-fidelity area-selectivity with an atomic-level precision in ultrathin coatings [1-9]. By combining the insights gained from first-principles simulations with experimental techniques, we can push the frontiers of device manufacturing to new heights, opening up exciting possibilities for further technological advances in nanoelectronics, photovoltaics, fuel cell and energy storage applications.

[1] Advanced Materials,

Just Accepted, (DOI: 10.1002/adma.202301204); [2]Nanoscale,

2021, 13, 10092-10099; [3] Chem. Mater.
2019, 31 (4), 1250-1257.; [4] Adv. Mater. Interfaces
2018, 5 (13), 1800268.; [5] Chem. Mater.
2017, 29 (3), 921–925.; [6] ACS Nano
2017, 11 (9), 9303–9311.; [7] Sol. Energy Mater. Sol. Cells
2017, 163, 43–50.; [8] Chem. Mater.
2017, 29 (5), 2090–2100.; [9] Nanoscale
2016, 8 (47), 19829–19845.

Figure 1
Surface Reaction Kinetics for Inherent Selective Atomic Layer Deposition of Tantalum Oxide
Authors: Cao Kun , Qi Zilian , Gu Eryan , Wen Yanwei , Chen Rong
Published: February 2024

The chemical principal and mechanisms that enable selective atomic layer depositions are gaining rapid growing interests, which have unlocked attractive avenues for the development of novel nanostructures by depositing atoms at desired surface locations. It has found versatile applications in emerging fields beyond semiconductor industry. Yet with the continuing downscaling, it is important to expand approaches for selective ALD with atomic scale precision on nanoscale features. The self-driven selective growth is needed, modifying specific surface down to atoms, to enable unprecedented capability of tuning the structure-property relationship for emerging applications. In this talk, the inherently selective atomic layer deposition processes will be discussed. Previously, we have demonstrated facet-selective ALD processes, which based on intrinsic differences of precursors chemisorption on terraces or step edges of nanoparticles. To expand the inherently ASD, the acidity and alkaline, surface electronegativity, lattice strains could be exploited to achieve this inhibitor-free selective deposition process. Tantalum oxide was studied on a series of oxide substrates. Although the oxides have -OH groups on the surface and proposed to have similar nucleation sites, there are long nucleation delays on basic oxides. The H-transfer reaction is a key factor to influence the reaction barrier. It is hard to nucleate on basic substrates because the H-transfer reaction is blocked. Another demonstration is the redox-coupled inherently selective ALD for self-alignment of tantalum oxide on SiO2/Cu nanopatterns. By adding an in-situ ethanol reduction pulse before each traditional binary ALD cycle, and the ‘reduction-adsorption-oxidation’ ALD process increases the selectivity. Self-aligned manufacturing on nanoscale Cu/SiO2 patterns without excessive mushroom growth at the edge and undesired nucleation defects on the Cu region. The process can be reliably repeated to yield more than 5 nm-thick Ta2O5 on the SiO2 region, while no undesired deposition occurs on Cu patterns. In addition, an anisotropic growth model with the dynamical competition of expansion and dissociation of the nucleus is proposed to nucleation delay are quantitively predicted and the model provides a practical method to evaluate the selectivity of ALD theoretically. It provides a new strategy for inherently selective ALD, which will expand the selective toolbox of nanofabrication for next-generation nanoelectronic applications.
(Invited) Area Selective Deposition Using Homometallic Precursor Inhibitors
Authors: Lee Han-Bo-Ram
Published: February 2024

Area-selective atomic layer deposition (AS-ALD) is envisioned to play a key role in next-generation nanofabrication for Si devices. In this presentation, various types of precursor inhibitors studied in our group will be summarized and another opportunity of our AS-ALD will be discussed. The chemical and physical interactions of inhibitors with precursors were successfully explained through theoretical calculations by density functional theory (DFT) and Monte Carlo simulation. Another concept of selective deposition by using a homometallic precursor inhibitor was proposed for seam-less deposition inside 3D structures. The results could provide insights for the next generation nanofabrication in the semiconductor technology using ALD.
(Invited) FALP (Fast Atomic Layer Processing) a Chamber for Combined PEALD and ALE Processes
Authors: Wege Stephan , Soni Aditya Kumar , Ricken Elias , Singh Chaudhary Vardhman
Published: February 2024

Atomic Layer Etching and (PE) Atomic Layer deposition are processes that are needed for the advanced nm silicon processing technologies.

Also, for high power application with GaAs, GaN this type of application getting more and more important. Even for optical applications extremely high quality and thick films are of interest.

Our new Tool FALP combines low temperature (20°C-120°) PEALD and ALE InSitu with high thruput and good electrical quality.

The Tool can handle even heavy optical 17” substrates (20mm thick 8kg heavy) and is able to deal with 8”,6”,4” small wafer sizes. For 300mm we will have a version for 300mm with ESC. This ESC is developed by Plasway-Technologies.

We will present first proven PEALD results on 17” for optical applications.

On our Pre-Development (joint work with Fraunhofer IKTS) we will present the results of ALE etching for Si, Ga, GaN, SiO2, AL2O3 and TiO2 with different chemistries.

We will also present first electrical results to prove the dielectric quality of the films (SiO2 and Al2O3) .

We will show also first InSitu integrated ALE and PEALD processed wafers.