@article{mousa_ovental_brozena_oldham_parsons_2018, title={Modeling and experimental demonstration of high-throughput flow-through spatial atomic layer deposition of Al2O3 coatings on textiles at atmospheric pressure}, volume={36}, ISSN={["1520-8559"]}, DOI={10.1116/1.5022077}, abstractNote={Atomic layer deposition (ALD) shows promise for forming thin films on temperature-sensitive materials, such as polymers, for applications in filtration, sensing, etc. However, traditional batch ALD generally proceeds slowly and requires controlled, low-pressure equipment. One approach to combat this limitation is spatial ALD, which uses moving substrates through zones of reactant exposure. To date, studies of spatial ALD have primarily explored growth on planar and nonporous substrates. Here, the authors demonstrate a proof-of-concept atmospheric pressure flow-through spatial ALD reactor specifically designed for through-porous substrates, such as fiber webs. This paper describes detailed gas flow modeling and experimental analysis of their prototype reactor. Model results identify precursor gas flow rates, channel spacing, and the distance between the substrate and reactor surfaces as key factors to achieve uniform deposition. Using a previously developed surface wetting protocol, the authors experimentally verify operating conditions for uniform ALD alumina on polypropylene as a model fiber substrate. Under good ALD conditions, the spatial ALD reactor can complete ∼60 cycles/min over a large substrate area, which is 60 times faster than batch ALD. The authors quantify growth saturation conditions and find that under reduced gas flow rates or slow fiber translation speeds, a transition from ALD to chemical vapor deposition-like growth can be induced. Additionally, the authors demonstrate that fiber mat properties such as mat density and air permeability play important roles in the penetration depth of the precursors and, therefore, the conditions needed to achieve ALD. Overall, this work demonstrates a proof-of-concept reactor for high throughput ALD on porous substrates, and identifies important design challenges and considerations for future high-throughput ALD.Atomic layer deposition (ALD) shows promise for forming thin films on temperature-sensitive materials, such as polymers, for applications in filtration, sensing, etc. However, traditional batch ALD generally proceeds slowly and requires controlled, low-pressure equipment. One approach to combat this limitation is spatial ALD, which uses moving substrates through zones of reactant exposure. To date, studies of spatial ALD have primarily explored growth on planar and nonporous substrates. Here, the authors demonstrate a proof-of-concept atmospheric pressure flow-through spatial ALD reactor specifically designed for through-porous substrates, such as fiber webs. This paper describes detailed gas flow modeling and experimental analysis of their prototype reactor. Model results identify precursor gas flow rates, channel spacing, and the distance between the substrate and reactor surfaces as key factors to achieve uniform deposition. Using a previously developed surface wetting protocol, the authors experimenta...}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Mousa, Moataz Bellah M. and Ovental, Jennifer S. and Brozena, Alexandra H. and Oldham, Christopher J. and Parsons, Gregory N.}, year={2018}, month={May} }
 @article{daubert_hill_gotsch_gremaud_ovental_williams_oldham_parsons_2017, title={Corrosion Protection of Copper Using Al2O3, TiO2, ZnO, HfO2, and ZrO2 Atomic Layer Deposition}, volume={9}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.6b13571}, abstractNote={Atomic layer deposition (ALD) is a viable means to add corrosion protection to copper metal. Ultrathin films of Al2O3, TiO2, ZnO, HfO2, and ZrO2 were deposited on copper metal using ALD, and their corrosion protection properties were measured using electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Analysis of ∼50 nm thick films of each metal oxide demonstrated low electrochemical porosity and provided enhanced corrosion protection from aqueous NaCl solution. The surface pretreatment and roughness was found to affect the extent of the corrosion protection. Films of Al2O3 or HfO2 provided the highest level of initial corrosion protection, but films of HfO2 exhibited the best coating quality after extended exposure. This is the first reported instance of using ultrathin films of HfO2 or ZrO2 produced with ALD for corrosion protection, and both are promising materials for corrosion protection.}, number={4}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Daubert, James S. and Hill, Grant T. and Gotsch, Hannah N. and Gremaud, Antoine P. and Ovental, Jennifer S. and Williams, Philip S. and Oldham, Christopher J. and Parsons, Gregory N.}, year={2017}, month={Feb}, pages={4192–4201} }
 @article{daubert_wang_ovental_barton_rajagopalan_augustyn_parsons_2017, title={Intrinsic limitations of atomic layer deposition for pseudocapacitive metal oxides in porous electrochemical capacitor electrodes}, volume={5}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C7TA02719B}, DOI={10.1039/c7ta02719b}, abstractNote={By comparing the pseudocapacitive performance of ALD V2O5 in micro-, meso-, and macro-porous carbon electrodes, we describe the fundamental limits to ALD in very fine pores for pseudocapacitive charge storage. Comparing experimental trends with an ALD coating model, we find that the thermal V2O5 ALD process using vanadium triisopropoxide (VTIP) and water is unable to deposit in pores where the pore diameter is below a critical diameter of 13 A. By adding the ALD V2O5 layer onto activated carbon electrodes, we find that the energy storage capacity could be increased by 144% for carbon with micropores and macropores, whereas for carbon black powder containing only macropores (i.e. a low surface area resulting in a relatively small starting capacity) the ALD coating increased the capacity more than 40-fold. To understand the ALD coating limits, the pores of the carbon electrodes were modeled as a series of connected tubes, and the volume of V2O5 deposited determined experimentally was compared to the calculated deposition limit. Pores below this critical diameter were sealed and decreased the accessible volume for V2O5 deposition by more than half, decreasing the maximum capacity. The effect of the pore sealing by the ALD process on the capacitive response of the activated carbon based electrodes was also studied. This work highlights the intrinsic capabilities and limitations of coating microporous materials using ALD.}, number={25}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Daubert, James S. and Wang, Ruocun and Ovental, Jennifer S. and Barton, Heather F. and Rajagopalan, Ramakrishnan and Augustyn, Veronica and Parsons, Gregory N.}, year={2017}, month={Jul}, pages={13086–13097} }