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Spatial atomic layer deposition (SALD) is a powerful thin-film deposition technique to control surfaces and interfaces at the nanoscale. To further develop SALD technology, there is need to deepen our understanding of the effects that process parameters have on the deposited film uniformity. In this study, a 3D computational model that incorporates laminar-flow fluid mechanics and transport of diluted species is developed to provide insight into the velocity streamlines and partial-pressure distributions within the process region of a close-proximity atmospheric-pressure spatial atomic layer deposition (AP-SALD) system. The outputs of this transport model are used as the inputs to a surface reaction model that simulates the self-limiting chemical reactions. These coupled models allow for prediction of the film thickness profiles as they evolve in time, based on a relative depositor/substrate motion path. Experimental validation and model parameterization are performed using a mechatronic AP-SALD system, which enable the direct comparison of the simulated and experimentally measured geometry of deposited TiO2 films. Characteristic features in the film geometry are identified, and the model is used to reveal their physical and chemical origins. The influence of custom motion paths on the film geometry is also experimentally and computationally investigated. In the future, this digital twin will allow for the capability to rapidly simulate and predict SALD behavior, enabling a quantitative evaluation of the manufacturing trade-offs between film quality, throughput, cost, and sustainability for close-proximity AP-SALD systems. 

Synthesis of bimetallic electrocatalysts for CO₂ reduction using atomic layer deposition results in changes in chemical state and product selectivity. 

Spatial atomic layer deposition (SALD) is a thin film deposition technique that could provide precise atomic-scale control at a large enough scale for many applications, such as clean energy technologies, catalytic conversion, batteries, and anti-fouling coatings. The spatially separated precursor zones are sequentially exposed to the substrate surface to deposit a film with precise control. If the precursor zones were to intermix during a deposition process, the precise control over film thickness would be lost. Therefore, it is essential to control the location of the precursors within the process region during a manufacturing process. This is typically achieved by controlling the gas flow rates and/or pressures, however it is challenging to actively monitor the location of the precursors during a deposition process as the process region has a small characteristic length and the vapor/gas precursors are difficult to observe/monitor. Therefore, there is a need to validate the precursor location and consequential process quality during a deposition. This can be of particular importance for substrate surfaces that are highly irregular or for manufacturing conditions where external factors such as temperature and ambient air speeds could change dynamically. In this study, a reduced order COMSOL Multiphysics® model is introduced that can predict the location of precursors in the process region. The model itself is discussed; the mesh size is selected considering accuracy and computation time; the model outputs are shown; and an initial experimental validation of the model is demonstrated. 

Abstract Halide perovskite solar cells (PSCs) are a state-of-the-art photovoltaic technology that exhibit high efficiencies and can be manufactured using roll-to-roll systems. However, PSCs are currently fabricated using sequential layer-by-layer deposition, which constrains the selection of suitable functional layers in the solar cell and limits the processing conditions and techniques that can be used. Lamination via diffusion bonding is a scalable parallel-processing technique that has the capability to overcome some of the challenges of sequential deposition by widening the thermal processing window and reducing the chemical compatibility requirements for PSC manufacturing. However, there remains a lack of detailed understanding of the process-structure-property relationships needed to accelerate the development of high-volume lamination-based manufacturing processes. In this work, we introduce a method to study the process-structure-property relationships of laminated perovskite semiconductors by using a custom photoluminescence (PL) spectroscopy system to quantify spatial heterogeneity in laminated halide perovskite (HP) materials. PL is an important figure-of-merit used to quantify the optoelectronic properties of semiconductor materials used in PV manufacturing. The spatial variation in PL of a laminated HP film is compared to that of an unlaminated HP film. The PL system uses servomotors and an Arduino microcontroller to automate a PL mapping procedure. The PL equipment is tunable to achieve a minimum possible spot size of ∼50 μm, enabling high-resolution measurements. The system is used to measure the PL of 19 separate locations on both a laminated and unlaminated HP material. The results of this study reveal that lamination at optimal conditions will improve the average PL peak intensity of the HP by 55%, indicating that lamination has the potential to improve the optoelectronic characteristics of PSCs. However, lamination also increases the standard deviation of PL peak intensity. Therefore, although lamination improves the PL of HPs, it also induces unwanted spatial heterogeneity. This warrants future studies on the governing physical mechanisms that determine quality control metrics in lamination-based PSC manufacturing. 

Marine biofouling is a complex and dynamic process that significantly increases the carbon emissions from the maritime industry by increasing drag losses. However, there are no existing non‐toxic marine paints that can achieve both effective fouling reduction and efficient fouling release. Inspired by antifouling strategies in nature, herein, a superoleophobic zwitterionic nanowire coating with a nanostructured hydration layer is introduced, which exhibits simultaneous fouling reduction and release performance. The zwitterionic nanowires demonstrate >25% improvement in fouling reduction compared to state‐of‐the‐art antifouling nanostructures, and four times higher fouling‐release compared to conventional zwitterionic coatings. Fouling release is successfully achieved under a wall shear force that is four orders of magnitude lower than regular water jet cleaning. The mechanism of this simultaneous fouling reduction and release behavior is explored, and it is found that a combination of 1) a mechanical biocidal effect from the nanowire geometry, and 2) low interfacial adhesion resulting from the nanostructured hydration layer, are the major contributing factors. These findings provide insights into the design of nanostructured coatings with simultaneous fouling reduction and release. The newly established synthesis procedure for the zwitterionic nanowires opens new pathways for implementation as antifouling coatings in the maritime industry and biomedical devices.