Thin Film Deposition Techniques Research Articles

Chebyshev spectral Newton iterative analysis on unsteady oblique stagnation flow of Maxwell fluids over an oscillating-rotating disk with Cattaneo–Christov double diffusion

Oblique stagnation flow on a rotating disk is commonly observed in processes such as spinning coating and thin film deposition techniques. The investigation of the unsteady oblique stagnation point flow for Maxwell fluid over an oscillating-rotating disk embedded in a porous medium is meticulously conducted by employing the Darcy–Maxwell framework in conjunction with Cattaneo–Christov double diffusion model. A transformation of similarity is applied to reframe the governing equations into a system of non-dimensional coupled partial differential equations, whose numerical solutions are secured by the Chebyshev Spectral Newton Iterative Scheme. The outcomes underscore that an escalation in the Darcy parameter escalates the resistance within the porous medium, consequently leading to a reduction in velocity. Both the first-order slip and the second-order slip mitigate the fluid's interaction with the disk wall, leading to a retardation in flow velocity. Additionally, the presence of augmented thermal radiation parameters is observed to enhance heat transfer efficiency, resulting in a more homogenized temperature distribution. The two-dimensional and three-dimensional streamlines provide a precise depiction of the flow characteristics at the oblique stagnation point on the oscillating-rotating disk. These findings offer a theoretical foundation that can be instrumental for forthcoming research in analogous fields.

Ultrathin Ge-YF3 antireflective coating with 0.5 % reflectivity on high-index substrate for long-wavelength infrared cameras

Abstract Achieving long-wavelength infrared (LWIR) cameras with high sensitivity and shorter exposure times faces challenges due to series reflections from high-refractive index lenses within compact optical systems. However, designing effective antireflective coatings to maximize light throughput in these systems is complicated by the limited range of transparent materials available for the LWIR. This scarcity narrows the degrees of freedom in design, complicating the optimization process for a system that aims to minimize the number of physical layers and address the inherent large refractive mismatch from high-index lenses. In this study, we use discrete-to-continuous optimization to design a subwavelength-thick antireflective multilayer coating on high-refractive index Si substrate for LWIR cameras, where the coating consists of few (e.g., five) alternating stacks of high- and low-refractive-index thin films (e.g., Ge-YF3, Ge-ZnS, or ZnS-YF3). Discrete optimization efficiently reveals the configuration of physical layers through binary optimization supported by a machine learning model. Continuous optimization identifies the optimal thickness of each coating layer using the conventional gradient method. As a result, considering the responsivity of a LWIR camera, the discrete-to-continuous strategy finds the optimal design of a 2.3-μm-thick antireflective coating on Si substrate consisting of five physical layers based on the Ge-YF3 high-low index pair, showing an average reflectance of 0.54 % within the wavelength range of 8–13 μm. Moreover, conventional thin-film deposition (e.g., electron-beam evaporator) techniques successfully realize the designed structure, and Fourier-transform infrared spectroscopy (FTIR) and thermography confirm the high performance of the antireflective function.

ALD with Enhanced Nucleation on Polymeric Separator for Improved Li-S Batteries

Lithium-sulfur (Li-S) batteries, known for their exceptional energy densities, are at the forefront of the next generation of energy storage systems. However, their practical application is hindered by the polysulfide shuttle effect, which significantly impairs discharge capacity and cycling stability. This research introduces a novel solution to these challenges through the use of atomic layer deposition (ALD) of Al₂O₃ on commercial polypropylene/polyethylene/polypropylene (PP/PE/PP) separators.ALD is a thin-film deposition technique that allows for precise control of layer thickness and composition at the atomic scale. ALD is characterized by its ability to produce extremely uniform and conformal layers, making it an ideal method for applications where surface chemistry plays a critical role, such as in battery separators. The technique is particularly advantageous in applications requiring high precision and control, like in our approach to enhancing Li-S batteries.In our study, the inert separator was treated with UV ozone to enhance the nucleation of ALD precursors, with the goal of reducing polysulfide shuttling. The use of ALD-modified separators in batteries demonstrated a marked increase in specific capacity, reaching approximately 1150 mAh/g, and reduced overpotential, indicative of improved kinetic efficiency. Further, we explored the structural and chemical modifications of the separator, employing X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Our findings indicate that ALD of Al₂O₃ on the separators significantly improved the adsorption of polysulfides, thereby mitigating the shuttle effect.In addition to improved polysulfide interaction, we also examined the impact on polysulfide adsorption on the formation of the solid-electrolyte interphase (SEI). Our results showed that modified batteries exhibited no polysulfide presence on the anode, suggesting a stable and effective SEI. This observation is significant, as it indicates that our approach enhances specific capacity and cycling stability by controlling the formation of a more effective SEI.Overall, our research demonstrates how strategic modifications at the separator level, particularly through the application of ALD and UV ozone, can significantly enhance the overall performance of Li-S batteries. By leveraging the unique advantages of ALD, especially through Al₂O₃ deposition, we provide a viable pathway to enhance the efficiency and stability of Li-S batteries.

The Impact of ALD Precursor Choice on Nucleation and Growth of Dielectrics on 2D Materials

Recently, atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) have received significant attention due to their unique optical and electrical properties, lending themselves to exciting applications such as microelectronics, sensing, catalysis, photonics, and more. The properties of TMDs can be acutely impacted by their environment due to their atomic thinness. For instance, in a TMD-based transistor with a high-k dielectric surrounding the TMD semiconductor, the dielectric could dope the channel via charge transfer; it can improve charge carrier mobility by screening the impact of charged impurities on scattering; or it can worsen charge carrier mobility by introducing defect states or interfacial roughness. As such, the quality and nature of the dielectric is critical, and ultimately those properties are determined by the means of dielectric deposition. Atomic layer deposition (ALD) is a common thin film deposition technique used for depositing high-k dielectrics for transistor devices. ALD relies on sequential self-limiting reactions between a precursor or co-reactant and a surface in order to deposit a material in a layer-by-layer manner with a high degree of control over thickness, composition, and uniformity. However, the ideal basal planes of 2D materials possess no dangling bonds or reactive functional groups, making their surfaces largely inert to ALD chemistry. Hence, when conventional ALD is performed on TMDs, nucleation and growth proceeds only at defect sites, grain boundaries, and the more reactive edge sites. This sparse nucleation leads to poor quality films of low density, high surface roughness, and pinholes.In this work, we employ physisorption-assisted ALD processes and study the nucleation and quality of the deposited dielectrics. We deposit AlOx on atomically thin monolayer MoS2 (itself on SiO2/Si) using a series of ALD precursors in order to investigate the impact of the ALD precursor on nucleation. Using scanning electron microscopy (SEM), we study film nucleation and continuity as a function of ALD precursor, cycle number, and temperature. After optimizing each process for each precursor in terms of temperature and purge time for maximized nucleation, we fabricate transistor devices in which the deposited AlOx serves as a seed layer for high-k HfO2 deposition to create the gate stack. Au contacts and a Pd top gate were used to complete the devices. Using x-ray photoelectron spectroscopy (XPS) and electrical testing, we investigate the character of the dielectric/MoS2 interface. We observe that the precursor used in the ALD process can lead to a wide range of coverages, with more conventional precursors resulting in sparse coverage, and novel precursors introduced in this study leading to nearly full coverage after just 3 nm of AlOx is deposited. We hypothesize that the improved coverage for the novel precursor is the result of enhanced interactions between the precursor and the 2D material due to its particular chemical structure. The reduced nucleation delay leads to a denser, smoother film with fewer defects at the 2D/3D material interface. The devices fabricated using the novel precursor and improved dielectric show excellent performance such as good on/off ratios (106), small device-to-device variation (ΔV T < 1 V), and low effective oxide thickness (~1 nm). This work provides useful insights into how ALD precursors could be designed to improve the quality of dielectrics on 2D materials, potentially improving the viability of 2D materials for wide ranging applications.

Drop–Dry Deposition of SnO2 Using Na2SnO3 and Fabrication of SnO2/NiO Transparent Solar Cells

In this work, SnO2 thin films are deposited by drop–dry deposition (DDD), which is a simple, low-cost chemical technique for thin film deposition. The deposition solution contains Na2SnO3 as the Sn source, and is highly stable without spontaneous reactions in the solution. The solution is dropped on a substrate heated to 60°C on a heater plate. According to Auger electron spectroscopy, the deposit will be stoichiometric SnO2. The film is n-type and transparent in the visible range. The pn heterostructure is fabricated by depositing SnO2 on p-type NiO. The NiO film is also fabricated by DDD. Ni(OH)2 is deposited using a solution containing Ni(NO3)2 and NaOH, and then is converted to NiO by annealing at 400°C. The SnO2/NiO structure is transparent in the visible range and shows clear rectification properties and photovoltaic effects. Thus, a transparent solar cell is successfully fabricated by DDD.

Spin coating on a budget: A 3D-Printed all-mechanical alternative for cost-effective thin-film deposition

Spin coating stands out as the most employed thin-film deposition technique across a variety of scientific fields. Particularly in the past two decades, spin coaters have become increasingly popular due to the emergence of solution-processed semiconductors such as quantum dots and perovskites. However, acquiring commercial spin coaters from reputable suppliers remains a significant financial burden for many laboratories, particularly for smaller research or educational facilities. Prompted by the simple mechanical principles of the device, in this work, we present a 3D-printed analogue that can be printed and assembled in under 10 h and costs less than 5 euros per device. The operating principle is fully mechanical since the rotating motion is induced by gas flow. It does not require any additional components such as DC motors, motor drivers, circuitry or software and thus it can be fully operational off the grid. Additionally, the gas flow generates a purging effect that was found to be rather advantageous for film formation. To prove the effectiveness of this device, we have employed it to fabricate planar thin-film antimony sulfide (Sb2S3) solar cells. The optoelectronic characteristics of solar cells revealed noteworthy improvements, particularly in terms of repeatability, when compared to those fabricated with a commercial spin coater.

Enhancing plasma discharge dynamics through analysis of secondary electron emission: A numerical modeling approach for improved thin film deposition

This research examines the impact of the coefficient of secondary electron emission (SEE) on various discharge features of plasma to improve the performance of deposited thin films. Unlike previous studies, we employed two-dimensional numerical modeling (2D) of an ICP reactor at a radiofrequency of 13.56 MHz and a low pressure of 1 Torr, using a finite element approach. This detailed investigation into parameters such as ionization rate, electric field, electron temperature, and electron density provides new insights into plasma interactions. Our findings reveal a significant correlation between the SEE coefficient and key plasma attributes. Notably, increased secondary electrons lead to a substantial rise in electron density and a reduction in sheath thickness, indicating an impactful change in the spatial distribution of plasma particles. Additionally, electron temperature increases exclusively in sheath regions, a novel observation not reported in earlier studies. Furthermore, higher SEE coefficients correlate with increased ionization rates within each sheath, suggesting a crucial role in maintaining discharge processes. This comprehensive analysis uncovers complex interdependencies within the plasma discharge system, offering valuable advancements for thin film deposition techniques.

A mechanistic approach to determine the relationship between film structure, electronic properties, and photocatalytic activity of ALD ZnO thin films on glass gibers

Atomic layer deposition (ALD), a high-conformality thin-film deposition technique, offers the opportunity to immobilize photocatalytic materials on high surface area substrates. Textile substrates are inexpensive, easily accessible materials with a fibrous nature, making them high surface area scaffolds for photocatalytic applications. This study applied ZnO thin-film coatings to fabric structures with different numbers of ALD cycles. The effect of coating thickness on the surface and electronic properties of the films and their photocatalytic properties were investigated. SEM, XRD, PL, and UV–Vis were used to examine the surface morphology, crystal structure, defects, and optical properties of the ZnO thin films. As the film thickness increased, the crystal sizes and the number of defects in the structure increased. Contact angle and Hall Effect measurements revealed that these structural defects are present on the surface of the films. Optimum wettability, mobility, and photocatalytic efficiency values were observed in the 15-nm coated samples, resulting in the highest photocatalytic activity and a turning point.

Continuous wave laser-assisted evaporation of halide perovskite thin films from a single stoichiometric source

We report continuous wave laser-assisted evaporation (CLE), a thin film deposition technique that yields phase-pure and stoichiometric thin films of halide perovskites (HaPs) from stoichiometric HaP targets. We use methylammonium lead bromide (MAPbBr3) to demonstrate the ability to grow with CLE well-oriented and smooth thin films on various substrates. Further, we show the broader applicability of CLE by preparing films of several other 3D HaP compounds, viz., methylammonium lead iodide, formamidinium lead bromide, and a 2D one, butylammonium lead iodide. CLE is a single-source, solvent-free, room-temperature process that needs only roughing pump vacuum; it allows the deposition of hybrid organic-inorganic compound films without needing post-thermal treatment or an additional organic precursor source to yield the intended product. The resulting films are polycrystalline and highly oriented. All these features, and the fact that one stoichiometric source serves as the target, make for an attractive, potentially scalable dry deposition approach.

Conformal High-Aspect-Ratio Solid Electrolyte Thin Films for Li-Ion Batteries by Atomic Layer Deposition.

Lithium phosphorus oxynitride (LiPON) is a state-of-the-art solid electrolyte material for thin-film microbatteries. These applications require conformal thin films on challenging 3D surface structures, and among the advanced thin-film deposition techniques, atomic layer deposition (ALD) is believed to stand out in terms of producing appreciably conformal thin films. Here we quantify the conformality (i.e., the evenness of deposition) of thin ALD-grown LiPON films using lateral high-aspect-ratio test structures. Two different lithium precursors, lithium tert-butoxide (LiOtBu) and lithium bis(trimethylsilyl)amide (Li-HMDS), were investigated in combination with diethyl phosphoramidate as the source of oxygen, phosphorus, and nitrogen. The results indicate that the film growth proceeded significantly deeper into the 3D cavities for the films grown from LiOtBu, while the Li-HMDS-based films grew more evenly initially, right after the cavity entrances. These observations can be explained by differences in the precursor diffusion and reactivity. The results open possibilities for the use of LiPON as a solid electrolyte in batteries with high-surface-area electrodes. This could enable faster charging and discharging as well as the use of thin-film technology in fabricating thin-film electrodes of meaningful charge capacity.

Enhancing perovskite solar cell performance: Investigating the impact of post-annealing on the optoelectrical and structural properties of RF-sputtered NiO films via SCAPS-1D device modeling

In recent years, perovskite solar cells have garnered significant interest in the field of solar cell research and development, primarily due to their notable efficiency. However, their limited lifespan and material defects, particularly in the interface layer and during deposition or fabrication processes, pose challenges to their widespread adoption. Innovative approaches to material processing and design are essential to addressing these issues. This paper introduces a novel method for the deposition of nickel oxide (NiO) thin films aimed at enhancing the performance of perovskite solar cells. Our study involved depositing NiO films on glass substrates using an optimised RF magnetron sputtering process at room temperature. These films were then annealed at temperatures ranging from 100 to 400 °C in an open-air setting. X-ray diffraction analysis showed that pure NiO thin films were formed. These films had a cubic crystalline structure and were mostly oriented along the (200) plane. Crucially, annealing at 100 °C significantly improved the crystallinity of the NiO films, reducing the average crystallite size from 21.05 to 6.10 nm, as evidenced by field emission scanning electron microscopy. For solar cells, this kind of microstructural refinement is very important because it changes the optical band gap, which ranged from 3.81 to 3.86 eV depending on the annealing temperature, and it also has a big effect on the films' electrical properties. The outstanding electrical characteristics of the NiO film annealed at 100 °C are particularly remarkable. We used these improved NiO films in perovskite solar cells that had a structure of FTO/NiO/MAPbI3/PCBM/Ag and ran SCAPS-1D simulations to see how well they worked. The simulation results are promising, indicating an enhancement in cell efficiency with the potential to surpass 22 %. This advancement highlights the critical role of advanced thin film deposition techniques in advancing photovoltaic technology and marks a substantial step towards unlocking the full potential of perovskite solar cells.

Novel fabrication of mixed wettability micromodels for pore-scale studies of fluid-rock interactions.

Wettability plays a crucial role in multiphase fluid flow in porous media, impacting various geological applications such as hydrocarbon extraction, aquifer remediation, and carbon dioxide sequestration. Microfluidic methods have attracted interest for their capacity to explore and visualize essential multiphase flow dynamics at the pore level, mimicking actual rock pore structures. However, creating micromodels with representative mixed wettability is currently a challenge. Existing technology is limited to producing micromodels with a singular wettability, either water-wet or oil-wet, leaving a gap in representing mixed-wet scenarios. In this study, we introduce a novel method to fabricate microfluidic devices with controlled spatial distribution of wettability at the micro-scale, mimicking actual configurations of mixed-wet rocks arising from varied mineralogy and pore structures. The proposed method combines the soft lithography process with thin film deposition techniques. The micromodels were designed to mimic the pore network of actual reservoir rocks, and a silicon substrate served as the foundation for the photolithography process optimization and wettability alteration methodology. Perfluorodecyltrichlorosilane coating was applied using molecular vapor deposition technology for surface wettability modification. The coated parts of the microdevice substrate altered the localized wetting state of the silicon towards hydrophobic, while the wettability remained unchanged in the non-coated areas. We utilized surface measurements, including contact angle, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy, to assess the wettability, composition, thickness, shape, roughness, and overall quality of the coating. Our fabrication process successfully produced a microfluidics device with tailored mixed-wet attributes at the micro-scale, which is, to our best knowledge, the first achievement in the field. This method enables the replication of mixed-wet characteristics commonly seen in various applications, such as carbonates and shales within underground rocks, providing a more accurate examination of fundamental multiphase fluid dynamics and rock interactions at the pore level.

Assessing the Potential of Non-pyrophoric Zn(DMP)2 for the Fast Deposition of ZnO Functional Coatings by Spatial Atomic Layer Deposition

Spatial atomic layer deposition (SALD) is a promising thin-film deposition technique that enables fast, large-scale deposition and nanoscale thickness control by utilizing spatially separated precursor vapors and a substrate-specimen relative...

Development of in-Situ Methods for Solution ALD

We have proposed and demonstrated a novel thin film deposition technique by transferring the principles of atomic layer deposition (ALD), known with gaseous precursors, towards precursors dissolved in a liquid.1,2 'Solution ALD'(sALD) shares the fundamental properties of standard ‘gas ALD’ (gALD), specially the self-limiting growth and the ability to coat conformally deep pores. It has been already shown that it is possible to transfer standard reactions from gALD to sALD such as oxides and sulfides deposition. However, sALD also offers novel opportunities such as overcoming the need for volatile and thermally robust precursors, offering the possibility to grow materials that cannot be obtained by gALD and using mild conditions which allow the growth on sensitive substrates. Recently we extended the understanding of the nucleation of selected materials grown by sALD such as CuSCN, TiO2 and SnSx. The study of the nucleation process relies on, first the identification of the absorbed chemical species at the surface by in-situ infra-red spectroscopy, second the ability to determine the type of interaction of the precursor with the surface by ex-situ solid state nuclear magnetic resonance (NMR) and third the evolution of nuclei formation with in-situ x-ray reflectometry (XRR) and atomic force microscopy. We developed the necessary instrumentation to obtain measurement compatible in liquid environment for each in-situ method. Form IR we can identify the phase preferential phase that is obtained as well as the defects formation for extremely thin films and NMR shows the chemical bonding of precursors at an early stage. Additionally, the AFM and XRR investigations are needed to follow the evolution of the nuclei size and their distribution of a surface as well as the nuclei density of each half cycle.The extension of the knowledge on the reaction mechanism in sALD process appears to be crucial to design next reactions and to understand later on the properties of the layers obtained with sALD. Wu, D. Döhler, M. Barr, E Oks,M. Wolf, L. Santinacci and J. Bachmann, Nano Lett. 2015, 15, 6379 Fichtner, Y. Wu, J. Hitzenberger, T. Drewello and J. Bachmann, ECS J. Solid State Sci. Technol. 2017,6, N171

Inherently Selective Atomic Layer Deposition for Optical and Sensor Applications: Microreactor Direct Atomic Layer Processing (μDALP™)

In parallel to additive manufacturing leading the revolution in traditional manufacturing, the same principles can revolutionize traditional thin film deposition techniques. Where lithography and vapor phase deposition techniques struggle, for example, with rapid iterations for prototyping or incompatibility with the used chemistry, additive manufacturing can shine. Indeed, several approaches are in development for 3D nanopriting1,2,3.Atomic Layer Deposition, and in more general Atomic Layer Processing, offers a unique opportunity for localized 3D processing/printing due to its two-step process. While simple in theory, due to well-developed examples of Spatial Atomic Layer Deposition (SALD), in practice miniturization of SALD requires substantial effort into the creation of suitable micro-nozzles. Uniquely, ATLANT 3D has developed proprietary Spatial ALD micronozzles, naming the process microreactor Direct Atomic Layer Processing - µDALPTM.The µDALPTM process undergoes the same cyclic ALD process but, thanks to the in-house microreactor development, is only done in a localized area. The microreactor or micronozzle confines the flows of gases used for ALD within a µm-scale area on the substrate, wherein the reactive species adsorb on the surface to deposit one monolayer of the desired material. Similarly, to spatial ALD, the creation of this monolayer then hinges on the movement of the substrate.4 Since the µDALPTM process is based on physical separation, it is theoretically compatible with any ALD process. As such, the material capabilities can match traditional ALD and exceed other special or patterning thin film techniques, such as lithography, which can be costly and time-consuming, especially for rapid prototyping required for innovation.Films deposited with ATLANT 3D technology have been shown to produce high-quality, crystalline, atomically precise thin films.1 It has been used to fabricate temperature (Fig.1) and capacitive sensors with sensitivities that meet or exceed those of devices made using conventional vapor phase deposition techniques.5 Low-cost rapid prototyping facilitated by ATLANT 3D technology of such devices enables design innovation and optimization not possible with other thin film deposition techniques.ATLANT 3D platform provides flexibility in deposition geometry (Fig.2) that enables a range of optical applications that require high-precision fabrication techniques. Optically transparent films can be used as localized thin protective layers for device encapsulation, as well as for atomic corrections of defects. Alternating deposition materials enable multilayer mirror fabrication of custom dimensions. Smooth thickness gradients can be used to manufacture ultrathin optical lenses. Overlapping depositions with discrete steps enable the manufacturing of binary lenses and phase masks. Growth rate enhancement in rastered direct processing mode using ATLANT 3D technology can produce periodic grating structures.1 Conformal coatings on complex surfaces can act as functionalization layers or seed layers for further material deposition through e.g. electrochemical processes.[1] Kundrata I. et al., ALD/ALE 2022 [Int. Conf.], 2022 [2] de la Huerta C. A. M. et al., arXiv, 2020, 0523. [3] Winkler, R. et al., J. Appl. Phys., 2019, 125, 210901[4] Paul Poodt., JVSTA., 2012, 30, 010802[5] Kundrata, I. et al., Small Methods., 2022, 6 (5), 2101546 Figure 1

Accelerating the Development of New Silicon-Based Anode Materials

In this work we have demonstrated the feasibility of using thin film systems as a steppingstone to accelerate the development of commercially relevant silicon-based anode materials for Li-ion batteries. Understanding new materials in conventional particle-based electrode systems is often complex. Lithium and electrolyte interact not only with the active material particles, but also with the different supporting components of the electrode, leaving it difficult to directly assess the electrochemical contribution of the active material. This is further complicated by the electrochemical behavior of such electrodes also being strongly dependent on processing conditions, like casting and drying procedures. Additionally, it is often also a challenge to synthesize such materials in particle form with the required chemical composition and monodispersity in the first place. Therefore, it would be highly beneficial to study and screen new anode materials without having to assume and assess these different factors. That is of particular importance during the optimization stage of the chemical composition for the active material, for which a significant number of samples is typically needed. Thus, evaluating the material in a thin film system is a simple and reproducible method of determining a material’s potential as a future anode material.Such thin films of active materials can reliably be made with a large range of thicknesses, compositions, element combinations and coatings, using multiple flexible and reproducible thin film deposition techniques available. In the present work, we have investigated silicon-based materials made by PECVD and sputtering: pure silicon and sub-stoichiometric versions of silicon nitride, silicon carbide, and silicon phosphide (SiNx, SiCx, SiPx). For evaluation of the applicability of the thin film model system, in several cases we have also compared the results to particles of the same material with similar chemical composition synthesized via a free space CVD process [1].Preliminary evaluation shows good agreement between results for thin film systems compared to what is known for particles of the same material. SiNx particles show good agreement with thin film results where a high nitrogen content decreases the capacity, while increasing the stability due to the formation of a stabilizing matrix around the active silicon [2]. Differences in the differential capacity analysis of similar materials in particle and thin film forms demonstrates the greater complexity in interpreting the data from the more intricate particle-based systems. SiCx is known to react in a similar fashion as SiNx where its coulombic efficiency and capacity decreases with increasing carbon-content, while its stability has been seen to increase due to a similar stabilizing matrix [3]. Reference s : [1] H. F. Andersen et al., ECS Trans., vol. 62, no. 1, pp. 97–105, 2014.[2] A. Ulvestad et al., ACS Nano, vol. 15, no. 10, pp. 16777–16787, 2021.[3] X. D. Huang et al., RSC Adv., vol. 8, no. 10, pp. 5189–5196, 2018.

(Digital Only Presentation) Effects of Ink Solvent on the Screen-Printing Fabrication and Morphology of LSM-YSZ Thin Films Deposited on YSZ Substrate for Solid Oxide Electrochemical Cells

Screen-printing is a cheap and easy thin film deposition technique utilized in energy devices fabrication, specifically, in solid oxide electrochemical cells (SOCs). This technique offers simple set-up, film quality control and mass production. In this study, LSM-YSZ, a promising component material for SOCs application was deposited on YSZ electrolyte via screen-printing. Specifically, the study aimed to investigate the effect of the solvent used in screen-printing on the quality of the deposited film. LSM-YSZ precursor powders synthesized via glycine-nitrate combustion process (GNP) were screen-printed on YSZ substrate using different solvents, ethanol and alpha-terpineol. The structure, morphology, and conductivity values of the GNP LSM-YSZ thin films using two solvents were compared. Results showed that both solvents produced a uniform distribution of rhombohedral LSM and cubic YSZ thin films with porous morphologies but alpha-terpineol solvent exhibited more agglomerated particles. Despite having this morphology, alpha-terpineol is still preferred than ethanol due to its reproducibility and scalability as it is less volatile than the other one. Moreover, there was no significant difference between the measured total conductivities of the half-cells using two solvents with the values of 4.63e-3 S/cm and 2.07e-3 S/cm at 700°C, and activation energies of 0.374 eV and 0.483 eV from 500°C - 700°C, for ethanol and alpha-terpineol, respectively.

Molecular Layer Deposition of Metal Phosphonates: A New Class of Hybrid Coating Layers

Atomic layer deposition (ALD) is a vapor phase thin film deposition technique where materials can be grown atom-by-atom in a layer-by-layer manner. Over the course of just few years, it has become to be one of the most sophisticated methods of producing high quality thin films with control at the sub-nanometer scale. Molecular layer deposition (MLD) is a variant of ALD where molecular fragments are intentionally built into the growing films.MLD is one of the techniques which allows to grow organic-inorganic hybrid materials with thickness control at sub-nanometer level.1 Nowadays, organic-inorganic hybrid materials have been found to attract a lot of attention because of their distinctive properties obtained by combining chemical and physical properties of organic and inorganic segments. Numerous hybrid materials have been synthesized by MLD over the time; however, commercial application of those materials are still a challenge due to their hydrolytic instability in most cases. Perhaps, the most widely used hybrid materials in our daily life is polysiloxanes, or commonly called as silicones, a silicon-based hybrid material . The hydrolytic stability of Si-C and Si-O-Si bonds is the main reason of their practical usage as hybrid materials. Similarly, organophosphorus compounds are an important class of materials because they offer several alternatives to silicon-based linking in the field of hybrid materials. Most of the hybrid films produced by MLD technique contain C, O, N, and S elements in the organic part. Hybrid materials containing P-atoms are yet to be explored by MLD.Among others, metal phosphonates, in particular, an important class of organophosphorus compound, show promising application covering from ion-exchange, proton conductors, catalysts, sensors, membranes, fire retardants etc.2,3 Examples of metal-organic compounds based on phosphonic acid derivatives can be found in literature stemming several decades back. Phosphonates are widely considered as an effective metal chelating ligand. Their dianionic tetrahedral form (RPO3 -2) enables different modes of coordination with metal which is not possible with the extensively used contemporary carboxylate (RCO2 -2) ligands. P-O-M and P-C linkages are quite stable, and therefore organophosphorous compounds with phosphonate ligands have been used to produce thermally and chemically stable hybrid materials by several other techniques.4 Here, we report the synthesis of novel aluminum phosphonate hybrid layers obtained with MLD method. Trimethyl aluminum (TMA) has been used as the metal source and two different novel phosphonate ester precursors with two different organic groups have been used to grow the aluminum phosphonate layers. The growth characteristics of the layers have been studied by in situ ellipsometry, whereas the as-grown films have been characterized with different ex situ techniques like FTIR, XPS, XRD, SEM and AFM. As-deposited metal phosphonate layers show superior thermal (>500 0C in air) and complete water stability. We believe, this kind of metal phosphonate layers may open up new opportunities in the field of organic-inorganic hybrid coatings for various applications. Meng, X. J. Mater. Chem. A 5, 18326–18378 (2017).Goura, J. & Chandrasekhar, V. Chem. Rev. 115, 6854–6965 (2015).Zhu, Y.-P., Yuan, Z.-Y. & Alshareef, H. N. ACS Materials Lett. 2, 582–594 (2020).Vioux, A., Le Bideau, J., Mutin, P. H. & Leclercq, D. New Aspects in Phosphorus Chemistry IV 145–174 (Springer Berlin Heidelberg, 2004).

Machine learning-based exploration of molecular design descriptors for area-selective atomic layer deposition (AS-ALD) precursors.

Area-selective atomic layer deposition (AS-ALD) is a thin film deposition technique developed using conventional ALD by considering the surface chemical nature of the substrate. Selecting appropriate precursors is a critical step in developing an efficient AS-ALD process with high deposition selectivity. However, the current efficiency of research on viable AS-ALD precursors is limited because of the absence of theoretical design rules for precursor chemical structures. In this study, our objective is to propose molecular design principle for precursors for AS-ALD, particularly focusing on achieving high deposition selectivity of oxides on diverse substrates. Current preliminary results suggest that ML-based prediction model may provide a fundamental molecular-level understanding of the reactivity of metal oxide precursors, that can be useful for efficient selection of suitable precursors for AS-ALD. We employ density functional theory (DFT) calculations and machine learning (ML) techniques to analyze the relationship between the structure and the surface reactivity of the precursor. Considering DFT calculation data (M06L/def2-tzvp, Gaussian 09 and Orca 4.0) and information on precursor structures, artificial neural networks (ANN, neuralnet, R) are applied to identify critical descriptors of the AS-ALD process. Furthermore, we utilize this ANN model to predict precursor reactivity according to surface terminations.

Effects of sputtering pressure and annealing temperature on the characteristics of indium selenide thin films

Indium selenide is a significant two-dimensional lamellar semiconductor with excellent physical properties whose enormous potential utilization in optoelectronic devices has been practically hindered by the lack of suitable thin film deposition techniques. Herein, γ-In2Se3 thin films were successfully fabricated from an InSe-target via magnetron sputtering combined with subsequent annealing process. The effects of sputtering pressure and annealing temperature on the characteristics of as-deposited thin films were investigated. The x-ray diffraction (XRD) patterns reveal that the pristine thin films are amorphous in nature, whereas transform into polycrystalline and are identified as γ-In2Se3 phase after annealing treatment. The growth mechanism of as-deposited layers combines a two-dimensional lateral growth and a three-dimensional island growth. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) images indicate that all the samples show uniform and compact structures with no evident holes and crevices. The UV–vis-NIR spectrophotometer was employed to measure the optical transmittance and band gap of the synthesized thin films. The results show an obvious decrease in the band gap from 2.56 eV to 1.88 eV with annealing temperature increased from 400 °C to 600 °C, respectively. In addition, the difficult reasons for preparing monophase InSe thin films by magnetron sputtering method were discussed. These intriguing findings in this study may shed light on the growth of indium selenide thin films with well-crystallized and high quality.