Layer Deposition Research Articles

Research on the Influence of Magnetic Field Assistance on the Quality of an Electro-Spark Deposition Layer

Aimed at solving the problems of single control measures in the electro-spark deposition (ESD) process, difficulty controlling the micro-process using heterogeneous materials (for the electrode and matrix), and the unstable quality and reliability of repairs to the deposition layer, a method of magnetic-field-assistance electro-spark deposition (MFESD) was proposed. An MFESD device was built, and a Ni electrode was used for deposition on the surface of 45 steel under the conditions of deposition voltages of 30 V, 60 V, and 90 V, respectively. This study examined the impact of the magnetic field’s intensity and frequency on the microstructure and mechanical properties of electro-spark deposition layers. The results show that the sputtering and protrusion of the electrode material on the surface of the deposition layer gradually decrease with an increase in the magnetic field’s intensity and frequency, defects such as pores and cracks are obviously improved, and the structure is uninterrupted and compact. The surface roughness of the deposited layer decreases with an increase in the magnetic field’s intensity and frequency, and its surface roughness decreases by 44.3%. The cross-section effect of the deposited layer is improved. The thickness of the deposited layer increases with an increase in the magnetic field’s intensity and frequency; the thickness of the deposited layer increases by 13.39%, and its maximum thickness can reach 54.396 μm. At the same time, the microhardness of the deposited layer increases with an increase in the two aforementioned properties of the magnetic field, and its hardness increases by 5.32%. Using a magnetic field to control ESD can effectively control the microscopic process of deposition and obtain high-quality deposition coatings, which have important significance in the surface remanufacturing of key components of high-end equipment.

Ring-Opening Polymerization of Surface Ligands Enables Versatile Optical Patterning and Form Factor Flexibility in Quantum Dot Assemblies.

The evolution of display technologies is rapidly transitioning from traditional screens to advanced augmented reality (AR)/virtual reality (VR) and wearable devices, where quantum dots (QDs) serve as crucial pure-color emitters. While solution processing efficiently forms QD solids, challenges emerge in subsequent stages, such as layer deposition, etching, and solvent immersion. These issues become especially pronounced when developing diverse form factors, necessitating innovative patterning methods that are both reversible and sustainable. Herein, a novel approach utilizing lipoic acid (LA) as a ligand is presented, featuring a carboxylic acid group for QD surface attachment and a reversible disulfide ring structure. Upon i-line UV exposure, the LA ligand initiates ring-opening polymerization (ROP), crosslinking the QDs and enhances their solvent resistance. This method enables precise full-color QD patterns with feature sizes as small as 3µm and pixel densities exceeding 3788 ppi. Additionally, it supports the fabrication of stretchable QD composites using LA-derived monomers. The reversible ROP process allows for flexibility, self-healing, and QD recovery, promoting sustainability and expanding QD applications for ultra-fine patterning and on-silicon displays.

RETINAL PIGMENT EPITHELIAL DETACHMENTS DEVOID OF RETINAL PIGMENT EPITHELIUM.

To describe two patients with chronic central serous chorioretinopathy showing what appeared to be retinal pigment epithelium detachments lacking imaging findings consistent with retinal pigment epithelium (RPE) over the elevation. The patients underwent comprehensive ophthalmic examination, including multicolor fundus photography, fundus autofluorescence, and spectral-domain optical coherence tomography. A 70-year-old man and a 58-year-old man, diagnosed with chronic central serous chorioretinopathy, showed pigment epithelium detachment-like lesions that were hypoautofluorescent, suggesting an absence of RPE. Spectral-domain optical coherence tomography B scans showed serous, dome-shaped elevations composed of a narrow, mildly hyperreflective band (9-10- µ m thick) that demonstrated hypertransmission of light. The material that constituted the elevation was contiguous with the outer portion of the RPE band at the lesion borders. Based on the multimodal imaging findings, we hypothesize that these pigment epithelial detachments have lost the RPE. A thin layer of material that could represent a residual layer of basal laminar deposit produced by the RPE remains overlying the detachments, possibly accounting for their dome shape and structural stability.

Dual-interfacial alloying mechanism in Ti-steel laminated metal composite fabricated by wire-arc directed energy deposition using a Cu-Ni interlayer

Ti-steel laminated metal composites have been widely used in shipbuilding and the chemical industry due to the superior corrosion resistance of Ti and the favorable mechanical properties of stainless steel. In this paper, Ti-steel laminated metal composites without Ti-Fe IMCs have been fabricated by directed energy deposition-arc method using a Cu-Ni transition interlayer. Based on the analysis of microstructure analysis, the cross-sectional microstructure can be divided into 304SS / Cu-Ni interface containing (Fe, Cr) and (Cu) solid solution, Cu-Ni deposition layer containing (Fe, Cr) and (Cu) solid solution, and TA2/Cu-Ni interface containing Ti2FeCu and Ti-Cu IMCs. Besides, the Cu-Ni deposition layer contains a small content of recrystallized grains with {100}<100> texture and a large content of deformed grains with{100}<110> texture due to the impact of arc and droplets during continuous depositions. Furthermore, the peak hardness is decreased to 518 Hv and the mean value of compressive shear strength is enhanced to 195.27MPa, which can be attributed to the elimination of interfacial Ti-Fe IMCs, defect-free microstructure, and residual stress relief. Based on polarization curves and electrochemical impedance spectroscopy, the corrosion resistance reduction of the cross-section is due to the formation of a mass of primary battery systems. Furthermore, based on the thermodynamics calculation of Fe-Cu-Ni, Ti-Fe-Cu, and Ti-Ni-Cu ternary systems, the alloying mechanism is that Ti-based IMCs with lower Gibbs free energy will be formed instead of brittle Ti-Fe IMCs, resulting in the elimination of Ti-Fe IMCs and the formation of less brittle phases at both 304SS / Cu-Ni interface and TA2 / Cu-Ni interface.

Comparison of the Wear and Friction Properties of Titanium Nitride-Based Coatings

This paper describes the wear and friction behavior of titanium nitride (TiN)-based coatings produced via chemical vapor deposition (CVD) in detail. Coatings composed of TiN, titanium carbide (TiC) and aluminum oxide (Al2O3) layers were applied to a tungsten carbide-cobalt composite and steel substrates. The elemental and phase compositions of these coatings, manufactured with varying deposition parameters and layer thicknesses, were determined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The mechanical properties of the coatings were evaluated through Vickers microhardness testing, lubricant-free tribological model tests and scratch testing. For the linearly alternating tribological tests, a static counterpart made of yttria-stabilized zirconium oxide was utilized. The wear, friction and adhesive properties of the coatings were studied, revealing significant differences in tribological behavior based on their hardness, crystal structure and surface roughness. The tribological tests highlighted that coatings with sharp, spherical crystal structures on their surfaces exhibited the greatest resistance to abrasive and frictional stresses. The durability of the surface coatings was found to be primarily dependent on their adhesion and surface roughness.

Electronically Coupled Heterojunctions Based on Graphene and Cu2-xS Nanocrystals: The Effect of the Surface Ligand.

Optoelectronic devices combining single-layer graphene (SLG) and colloidal semiconducting nanocrystal (NC) heterojunctions have recently gained significant attention as efficient hybrid photodetectors. While most research has concentrated on systems using heavy metal-based semiconductor NCs, there is a need for further exploration of environmentally friendly nanomaterials, such as Cu2-xS. Chemical ligands play a crucial role in these hybrid photodetectors, as they enable charge transfer between the NCs and SLG. This study investigates the photoresponse of an SLG/Cu2-xS NCs heterojunction, comparing the effect of two short molecules-tetrabutylammonium iodide (TBAI) and 3,4-dimethylbenzenethiol (DMBT)-as surface ligands on the resulting structures. We have analysed charge transfer at the heterojunctions between SLG and the Cu2-xS NCs before and after modification with TBAI and DMBT using Raman spectroscopy and transconductance measurements under thermal equilibrium. The photoresponse of two hybrid devices based on three layers of Cu2₋xS NCs, deposited in one case on SLG/Cu2-xS/TBAI ("TBAI-only" device) and in the other on SLG/Cu2-xS/DMBT ("DMBT + TBAI" device), with a TBAI treatment applied, for both, after each layer deposition, has been evaluated under 450 nm laser diode illumination. The results indicate that the TBAI-only device exhibited a significant increase in photocurrent (4 μA), with high responsivity (40 mA/W) and fast response times (<1 s), while the DMBT + TBAI device had lower photocurrent (0.2 μA) and responsivity (2.4 μA), despite similar response speeds. The difference is attributed to DMBT's π-π interactions with SLG, which enhances electronic coupling but reduces SLG's mobility and responsivity.

Luminescence and radiocarbon chronology of Bhagatrav: A Sorath Harappan camp site in South Gujarat

Abstract Excavation at the site of Bhagatrav yielded four layers of cultural deposits: the lowermost being the Sorath Harappan, the upper two are medieval, and layer three caps the Sorath Harappan layer. A horn-deity painted dish was found in a stratified context at the lowest level. The medieval deposit includes turquoise glazed and celadon wares, followed by an abundance of Monochrome Glazed Ware, which is otherwise known as Khambhat ware. The date of the Sorath Harappan layer of the site, the time and space of the horn-deity motif in the Harappan world, and the date of Khambhat ware have long been subjects of discussion. With the help of a series of absolute dating (radiocarbon and luminescence), this paper attempts to place the site, horn-deity motif, and the Khambhat ware in the cultural chronology of Gujarat.

Consequences of a major eruption of Shiveluch volcano (Kamchatka, April 11–13, 2023) for forest vegetation (preliminary report)

The strong eruption of Shiveluch volcano in April 2023 led to radical changes in the natural environment of a vast territory. Analysis of changes in the aff ected area using satellite images and during fi eld work in the summers of 2023 and 2024 revealed the features, depth and scale of the impact on forest vegetation. Multimeter layer of high-temperature pyroclastic deposits covered an area of more than 60 sq. km on the southern and southeastern slopes of the volcano. The main buried areas include a vast deposit fi eld measuring 38 sq. km, lying in the altitude range of 400–800 m and a series of pyroclastic fl ow tongues with a total area of 12.5 sq. km, descending to an altitude of 140–350 m, with a maximum length of 22 km from the eruption center. Before the eruption, there were coniferous (Larix cajanderi) and deciduous (Betula ermanii) forests, dwarf alder (Alnus fruticosa) covers, mountain meadows and volcanic badlands (legacy of previous eruptions). Woody vegetation, including valuable coniferous forests, was buried and destroyed over an area of approximately 24 km2. Burial of forests by thick (up to tens of meters) high-temperature strata occurred over an area of more than 20 km2. The pyroclastic surge and the peripheral parts of the pyroclastic fl ows turned forests and dwarf alder forests into dead stands over an area of several square kilometers. The cause of its death was powerful and rapid thermal damage by hot gas-sand vortices. Immediately after the eruption, surface watercourses begin to wash away pyroclastic deposits, transporting them, and burying forest areas with washed-out materials. As a result, the forest dies. Vegetation adjacent to pyroclastic deposit fi elds is aff ected by frequent and intense dust transports that occur in open areas above the tree line. The 2023 eruption was the largest explosive event in Kamchatka and the Kuril Islands in recent decades, and caused large- scale destruction of forests.

Conjugated Polymer-Based Multilayer Thin-Film Triboelectric Nanogenerators via Continuous Layer-By-Layer Coating Process.

This study introduces a flexible and scalable charge-trapping intermediate layer of conjugated polymeric film comprising [PANI/PEDOT:PSS]n between the [PVA/PDDA]n triboelectric layer and graphene-based [PVA/GNP-PSS]n electrode using the layer-by-layer (LbL) assembly method. By varying the deposition layers, the optimal coating layout was identified as 2 and 8 bilayers of intermediate and triboelectric layers, respectively. The triboelectric nanogenerator (TENG) fabricated with this optimal configuration achieved peak output voltage and current of 180 V and 9 μA, respectively, at 3 Hz and 5 N against PDMS. This represents a 63.6% increase in output voltage and a 20% increase in output current compared to the TENG without the intermediate charge-trapping layer, owing to the surface charge density reaching 61.5 μC/m2. Furthermore, an ultrathin, free-standing PANI-PEDOT:PSS film was encapsulated in a free-standing PVA-PDDA film, which resulted in a significant TENG output performance of 315 V. Inspired by these TENG results, we investigated the flame-retardant properties of the LbL [PANI/PEDOT:PSS]n coating on polyurethane foam (PUF) and demonstrated, through the open flame test, that the presence of the flame-retardant coating prevented flame flashover, melting, and dripping of the burning PUF. The coated PUF exhibited a lower heat release capacity of 402 J/g·K compared to neat PUF, and the thermal degradation of coated PUF resulted in the formation of 10.95 wt % residue in the TGA test. In addition, the TENG fabricated using the coated foam achieved a significant output performance. Therefore, this study contributes to future flame-retardant energy harvesting materials via sustainable LbL assembly.

Parameters of graphite shock compression at the initial stages of Popigai astrobleme formation

A numerical modeling of the process of a high-speed impact of a massive asteroid with the Earth’s surface was carried out to study the hypothesis of the meteoritic origin of the impact diamond deposit located in the Popigai River basin. A normal collision of a chondritic asteroid with a layered structure of the Earth’s soil at a speed of 25 km/s is simulated in 2D axisymmetric formulation. The natural carbon deposit layer is located in the near-surface zone of the loaded area. The calculations were carried out using a multidimensional parallel implementation of the finite-size particle-in-cell method. Models of the equations of state of chondrite, quartz and carbon are used to describe the properties of the meteorite and soil material. Thermodynamic parameters of impact compression of soil materials at the initial stages of loading and crater formation processes are obtained.

Silver CVD and ALD Precursors: Synthesis, Properties, and Application in Deposition Processes.

This review summarized the developments in the field of volatile silver complexes, which can serve as precursors in gas-transport reactions for the production of thin films and metal nanoparticles via chemical vapor deposition (CVD) and atomic layer deposition (ALD). Silver-based films and nanoparticles are widely used in various high-tech fields, including medicine. For effective use in CVD and ALD processes, the properties of silver precursors must be balanced in terms of volatility, thermal stability, and reactivity. In this review, we focus on the synthesis and comprehensive analysis of structural and thermal characteristics for the most promising classes of volatile silver complexes, as well as organometallic compounds. Following the specifics of silver chemistry, some features of the use of precursors and their selection, as well as several key directions to improving the efficiency of silver material deposition processes, are also discussed.

Investigation of thermal and fluid dynamics behaviors of melt pool during laser direct metal deposition on inclined substrates

The laser direct metal deposition (DMD) technique offers an efficient solution for repairing and manufacturing structures with variable curvatures, such as impeller blades. However, how the non-vertical laser irradiation on curved surfaces impacts the thermal and fluid dynamics of the melt pool still remains unclear. In the current research, a high-fidelity multi-physics numerical model is developed to explore the mechanisms of melt pool development and the effects of inclined angle and laser spot diameter on morphological evolution of deposition layers during DMD under non-vertical irradiation on inclined substrates. Results indicate that as the inclination angle increases, deposited track fluctuations become evident, with a critical angle from 40° to 42.5° identified for hump formation. A smaller laser spot diameter increases the likelihood of humps and irregularities, while a larger spot diameter expands the deposition layer and enhances melt pool wettability. This study is expected to provide significant theoretical guidance for selecting and applying process parameters for the fabrication of curved structures by DMD.

Clinical and Genetic Characteristics of Patients with Peripheral Retinal Flecks in Koreans.

To describe the clinical and genetic features of Korean patients with peripheral retinal flecks unrelated to aging. A retrospective analysis was conducted on the clinical characteristics of patients with symmetric peripheral retinal flecks. Age-related deposits such as reticular pseudodrusen were excluded, as well as secondary deposits related to intraocular inflammation, tumor, and drug toxicity. Multimodal imaging, electrophysiological examinations, and genetic testing were analyzed. A total of 10 patients (two men and eight women) with bilateral peripheral flecks were enrolled in this study. A mean age at diagnosis was 30.5 ± 19.6 years (range, 4-59 years). Within the 10 patients, six were genetically confirmed with monogenic retinal disorders. Biallelic pathogenic variants in RDH5 were found in five patients, and one patient was diagnosed with retinopathy related to Alport syndrome due to a pathogenic variant in COL4A5. Although not genetically confirmed, one case associated with nanophthalmos and another case showing chorioretinal mottling in a carrier of ocular albinism have been identified. In one patient, genetic testing also revealed unknown causes. The mean logarithm of the minimum angle of resolution initial visual acuity was 0.12 ± 0.18 and 0.07 ± 0.18 in right and left eyes, respectively. Night blindness was reported by four patients (40%), with three showing decreased or delayed rod response in electroretinogram, particularly those with RDH5 mutations. Differences in the deposit layers and the patterns of flecks were observed on multimodal imaging. In the study population, we observed various causes and clinical differences in the retinal fleck patterns among Koreans, including RDH5-related fundus albipunctatus and Alport syndrome. Despite reports of night blindness symptoms in some cases, all patients demonstrated satisfactory corrected visual acuity.

An experimental study on laser cleaning of the soot deposition layer on a white marble surface

A coordinated application of the image binarization, area extrapolation, and laser-induced breakdown spectroscopy (LIBS) detection for monitoring and controlling the laser cleaning soot deposition layer process on a white marble surface was reported. The laser cleaning process used a fiber pulsed laser beam with a fixed wavelength of 1064 nm, a pulse repetition frequency of 100 kHz, and a focal spot diameter of 95 μm. Image binarization was conducted to determine 150 ns as the appropriate fixed pulse width for laser cleaning of the soot deposition layers from four discrete values of 50 ns, 100 ns, 150 ns, and 200 ns. The optimal laser energy density of 2.82 J·cm-2 was obtained through area extrapolation, while the optimal spot overlap rate of 20 % was determined to maximize the effective laser cleaning speed. The optimal number of cleanings for a soot deposition layer with a thickness of 77μm was determined to be 5 using LIBS detection and to monitor the laser cleaning process in real time for each small area of the soot deposition layer. Image binarization was used to evaluate the overall cleaning quality of large marble surfaces. By dynamically adjusting the optimal number of cleanings, the cleaning efficiency of the soot deposition layers on half of the surface area of a 20 cm diameter white marble artifact exceeded 95 %. The results indicate that the synergistic use of various online monitoring methods can optimize multiple laser parameters, enabling precise removal of the soot deposition layer on the white marble surfaces caused by anthropic factors, without damaging its surface.

Potentiostatic electrolysis of fluoride melts with zirconium oxide additives

Currently, the demand for zirconium-based alloys and materials is growing significantly due to their high thermal and corrosion resistance combined with mechanical strength. Existing technologies for producing zirconium and its alloys are complicated by the high temperature of the process, or labor intensity and multi-stage nature, which significantly increases the cost of the target material up to the loss of profitability of the process. Electrochemical synthesis of zirconium and its alloys in fluoride-based melts, using zirconium oxides as the main metal-containing consumable component, seems more profitable. In this work, a series of electrolysis tests were carried out to deposit Al-Zr alloy at a potential of 1.6 V on graphite and molybdenum cathodes. According to the previously obtained results, in the presence of ZrO2 in the KF-AlF3-Al2O3 melt, a plateau and a discharge peak of electroactive ions appear on the cathode branch of the voltammograms at potentials of -1.4 and -1.7 V, ZrI and ZrII, respectively. Similar responses appear on tungsten at potentials of -1.3 and -1.6 V, respectively, and in the potential region of -1.9 V there is a clear peak (Al) of electroreduction of aluminum ions. As a result of electrolysis, it was found that the graphite anode was consumed, and a fairly well-bonded deposit was formed on the cathode. Part of the cathode deposit was mechanically separated from the cathode for analysis of its chemical and phase composition. Based on the results of X-ray phase analysis, it was found that the cathode deposit mainly consists of Al3Zr and aluminum compounds with molybdenum impurities, with the composition Al12Mo, which is consistent with known ideas about the formation of intermetallic compounds during the interaction of aluminum with other metals. Electrolysis of the melt on the graphite cathode was carried out under similar conditions. Based on a microphotograph of the cathode cross section, it was found that during electrolysis, a layer of deposit containing both zirconium and aluminum was formed at the electrode-electrolyte phase boundary.

Deposition, deformation, and flexure in a transpressional trough, Queen Charlotte fault, offshore Haida Gwaii (British Columbia, Canada)

Transpressional deformation along the Pacific–North American plate boundary off British Columbia (Canada) generates interactions between tectonic and depositional processes; first-order deformation is creation of a bathymetric trough by flexure of the Pacific plate. Interpretation of a suite of single-channel seismic reflection data in the central and southern trough shows second-order internal structure and depositional systems within the trough. Much of these sediments originated from Quaternary slope fans, although the age of the underlying oceanic crust is 8–13 Ma. These turbidite deposits overlie hemipelagic deposits. Two distinct layers of turbidite deposits in the trough can be explained by sediment deposition systems rather than tectonic events. We infer that the most recent flat-lying deposits, which have been previously interpreted in the northern trough as indicating a lack of compressive deformation, consist, in fact, of along-axis flows based on the general geomorphology of the margin. Second-order deformation consists of small-offset extensional and compressive structures common within 15 km of the foot of the continental slope. A few normal faults are observed tens of kilometers further out on the flexural bulge. Recent faults that cut the seafloor are observed offshore from the rupture plane of the 2012 M7.8 earthquake and match an area of extensional aftershocks. These faults may not be from bending of the entire bulge, which is 30–40 km wide, but from the plate being pulled into the underthrust zone. Maximum depression of the Pacific plate is also offshore from the region of recent rupture, indicating that this rupture is representative of long-term geologic processes.

Additive Manufacturing of Tungsten Carbide (WC)-Based Cemented Carbides and Niobium Carbide (NbC)-Based Cermets with High Binder Content via Laser Powder Bed Fusion

The additive manufacturing technique performed via laser powder bed fusion has matured as a technology for manufacturing cemented carbide parts. The parts are built by additive consolidation of thin layers of a WC and Co mixture using a laser, depending on the power and scanning speed, making it possible to create small, complex parts with different geometries. NbC-based cermets, as the main phase, can replace WC-based cemented carbides for some applications. Issues related to the high costs and dependence on imports have made WC and Co powders emerge as critical raw materials. Furthermore, avoiding manufacturing workers’ health problems and occupational diseases is a positive advantage of replacing WC with NbC and alternative binder phases. This work used WC and NbC as the main carbides and three binders: 100% Ni, 100% Co, and 50Ni/50Co wt.%. For the flowability and spreadability of the powders of WC- and NbC-based alloy mixtures in the powder bed with high cohesiveness, it was necessary to build a vibrating container with a pneumatic turbine ranging from 460 to 520 Hz. Concurrently, compaction was promoted by a compacting system. The thin deposition layers of the mixtures were applied uniformly and were well distributed in the powder bed to minimize the defects and cracks during the direct sintering of the samples. The parameters of the L-PBF process varied, with laser scanning speeds from 25 to 125 mm.s─1 and laser power from 50 to 125 W. Microstructural aspects and the properties obtained are presented and discussed, seeking to establish the relationships between the L-PBF process variables and compare them with the liquid phase sintering technique.

Investigation of three-dimensional forces during additive friction stir deposition — How could force signals reveal the deposition quality?

Additive friction stir deposition (AFSD) is a solid-phase forming technology based on microzone forging, which is essentially a force-driven additive manufacturing process. This work focuses on the effects of the AFSD parameters on the force signals and forming quality, which is highly important for optimizing the process parameters and controlling the forming quality. By analyzing the force features in the time‒frequency domain, the evolution mechanism of three-dimensional forces during AFSD was explored. A 3D scanner, scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) were used to clarify the surface morphology and microstructures of the deposition layers. It was found that deposition defects were accompanied by a lack of plasticization or nonuniform deformation between the advancing side (AS) and the retreating side (RS). Moreover, the relationships among the process parameters, three-dimensional forces and deposition quality were investigated. It is proved that force signal can effectively reflect the deposition quality. A comprehensive prediction model based on three-dimensional force features was developed, achieving an accurate prediction of deposition quality. Furthermore, this work demonstrated the feasibility of AFSD quality control on the basis of force signals. The currently employed control strategies can be further extended to address the AFSD of large components in the future.

Coherent Workflows for Sustainable Electrocatalytic Hydrogenation Reactions with Pentlandite Catalysts

The hydrogenation of organic substances is a central process type in various industries[1]. The usage of gaseous hydrogen, which is primarily sourced from fossil fuels, entails the release of CO2 during its production. In addition, the usage of gaseous hydrogen also carries a safety risk, which should be reduced as much as possible. An alternative approach is direct electrochemical hydrogenation with water or other protic liquids, where the required hydrogen is produced in situ and directly utilized. If this is driven by renewable energy, it represents a sustainable synthesis method that does not require stoichiometric reduction agents or high-temperature conditions[2].Transition metal chalcogenides, particularly pentlandites (FexCoyNizSaSeb, x+y+z=9, a+b=8), exhibit high conductivity and serve as efficient and affordable electrocatalysts for this purpose. The utilization of hierarchical functional layers in the final electrode greatly enhances their efficiency[3, 4]. A comprehensive approach to analyzing the vast and complex electrode production parameter space, encompassing process parameters and material variables for ink formulation and layer deposition, is critical for understanding the intricate mechanisms within the manufacturing process chain and to maximize the electrochemical conversion efficiency. For this purpose, a time-saving and cost-effective coherent workflow was developed which enables a systematic analysis of several parameters, maximizing the knowledge gained from each experiment while minimizing the total amount of experiments. The workflow can be seen in Figure 1. In step 1, the materials and substrates to be investigated are first selected. Then, in step 2, catalyst inks are formulated, examined, and optimized concerning their sedimentation stability and compatibility with different binders and organic additives. Subsequently, in step 3, substrates are coated with the optimized catalyst inks and coating parameters such as catalyst mass loading are varied at the same time. In the fourth and final step, the resulting electrodes are tested electrochemically and with the help of imaging methods to shed light on process-structure-property relationships. The described procedure enables successive optimization and establishment of efficient membrane-electrode-assemblies for electroorganic reactions, offering new avenues for efficient, green, and sustainable synthesis pathways. These methods are also readily adaptable for scalable industrial applications.[1] Lauren S. Jackson, Fadwa Al-Taher, Chapter 23 - Processing Issues: Acrylamide, Furan and Trans Fatty Acids, Ensuring Global Food Safety, Academic Press (2010)[2] Ya Zhang, Weibin Qiu, Yongjun Ma, Yonglan Luo, Ziqi Tian, Guanwei Cui, Fengyu Xie, Liang Chen, Tingshuai Li, and Xuping Sun, High-Performance Electrohydrogenation of N2 to NH3 Catalyzed by Multishelled Hollow Cr2O3 Microspheres under Ambient Conditions, ACS Catalysis (2018)[3] David Tetzlaff, Kevinjeorjios Pellumbi, Daniel M. Baier, Lucas Hoof, Harikumar Shastry Barkur, Mathias Smialkowski, Hatem M. A. Amin, Sven Grätz, Daniel Siegmund, Lars Borchardt and Ulf-Peter Apfel, Sustainable and rapid preparation of nanosized of Fe/Ni-pentlandite particles by mechanochemistry, Chemical Science (2020)[4] Daniel Siegmund, Sebastian Metz, Volker Peinecke, Terence E. Warner, Carsten Cremers, Anna Grevé, Tom Smolinka, Doris Segets and Ulf-Peter Apfel, Crossing the Valley of Death: From Fundamental to Applied Research in Electrolysis, JACS Au (2021)[5] Mena-Alexander Kräenbring, Leon Wickert, Meinert Hansen, Sebastian Sanden, Kevinjeorjios Pellumbi, Jonas Wolf, Daniel Siegmund, Fatih Özcan, Ulf-Peter Apfel, and Doris Segets. Navigating through Complexity: Optimizing Cathodes for Organic Electrohydrogenation through Coherent Workflows, ChemCatChem (2023) Figure 1

Controlled Surface Polarity and Crystallinity of Gallium Nitride on Si (111) Using Atomic Layer Deposition for Selective Wet-Etch and STEM Analysis

Gallium nitride (GaN) has gained interest as photoelectronic materials and a buffer layer for other III-V deposition with applications in power electronics operated at high voltage and high temperature. The crystallinity and polarity of III-V semiconductors have a key role for the passivation layers on microLED, the formation of 2D electron gasses in high electron mobility transistors, and for templating growth of piezoelectric materials. The atomic layer annealing (ALA) was reported to improve the crystallinity of the III-V compounds (aluminum nitride) at low temperatures as compared to the conventional thermal ALD. In ALA, a pulse of ion bombardment is added to each ALD cycle to ensure polycrystalline film formation at low temperature. Polycrystalline GaN has been deposited by ALA at low temperatures even on amorphous substrates, but the polarity was not reported. The selective wet-etch process has several advantages for the III-V semiconductor device integration since the conventional plasma ion etching process is expensive, complicated, and leads to the surface damage by reactive plasma ion. The GaN surface polarity (N-polar or metal-polar) on sapphire was selectively etched by aqueous KOH solution. However, electrochemical etching study on the polarity of GaN ALD films has not yet been studied as types of ALD process. Figure 1a and 1b show the process parameter switching diagram for the GaN thermal ALD and GaN ALA processes, respectively. The chemical compositions of ALA and ALD GaN on Si were estimated by in-situ AES as shown in Figure 1c. Lower O content (below 3.3 at. %) and higher N/Ga atomic ratio were observed in the ALA GaN on Si (111) as compared to the thermal ALD GaN film (4.6 at. %). Figure 1d shows that the intensity of GaN (002) XRD pattern in thermal ALD GaN on Si was greatly improved in the GaN stacks (GaN thermal ALD/ALA/Si) with an ALA GaN buffer layer. The electrochemical behavior of the GaN ALD films was studied to elucidate the impact of surface polarity on selective KOH wet-etch. The linear sweep voltammograms of GaN thermal ALD and GaN ALA films in 1 M KOH solution were shown in Figure 1e. The applied potential was swept from zero (vs. Normal Hydrogen Electrode) to positive 3.7 V. The peak of current density at ~1.7 V was observed in the voltammogram of the GaN ALA film (N-polar), suggesting the occurrence of etching reaction by the dissolution and formation via the equations in Figure 1f. On the other hand, the absence of current density peak in the GaN thermal ALD film (Ga-polar) could suggest the unfavorable etching reaction as compared to the GaN ALA film. Figure 2a and 2b shows the HAADF-STEM images of ALD GaN on Si demonstrate highly ordered 3 nm x 5 nm ALD GaN layers with bright and dark regions. The circles of bright regions and the center of dark regions represent Ga atoms and tunnel points (empty element), respectively. The GaN polarity could be determined by drawing triangles connecting adjacent three tunnel points without the interruption of Ga. Using this method, upward triangles were obtained in the HAADF-STEM image (Figure 2a), suggesting the formation of N-polar GaN layers during the ALA GaN process on Si. Conversely, downward triangles from the STEM image of thermal ALD GaN /ALA GaN /Si (Figure 2b) suggested Ga-polar GaN during GaN thermal ALD process. The inset figures show the top-view SEM image of selectively wet-etched (30 min, 20 wt.% KOH (aq)) GaN films. The etched surface on the ALA GaN layers (inset of Figure 2a) indicated N-polar GaN surface. The inset SEM image in Figure 2b shows a nearly unchanged GaN surface in thermal ALD GaN /ALA GaN / Si is consistent with the Ga-polar GaN surface. These observations are in good agreement with the HAADF-STEM images.The data is consistent with being able to control the polarity of GaN by switching between thermal ALD and ALA. The ion bombardment in ALA promotes N-polar GaN while thermal ALD promotes metal polar GaN. This allows the facile formation of both electron and hole gas layers between ALA and ALD GaN. Figure 1