@article{petrochenko_scarel_hyde_parsons_skoog_zhang_goering_narayan_2013, title={Prevention of Ultraviolet (UV)-Induced Surface Damage and Cytotoxicity of Polyethersulfone Using Atomic Layer Deposition (ALD) Titanium Dioxide}, volume={65}, ISSN={1047-4838 1543-1851}, url={http://dx.doi.org/10.1007/S11837-013-0565-8}, DOI={10.1007/s11837-013-0565-8}, abstractNote={Nanostructured surfaces are finding use in several medical applications, including tissue scaffolds and wound dressings. These surfaces are frequently manufactured from biocompatible polymers that are susceptible to ultraviolet (UV) damage. Polyethersulfone (PES) is a biocompatible polymer that undergoes oxidation and degradation when exposed to ultraviolet (UV) light. A uniform TiO2 coating can protect PES during exposure to UV sources (e.g., germicidal lamps and sunlight). The goal of this study was to determine whether atomic layer deposition (ALD) can successfully be used to grow TiO2 onto PES, protect it from UV irradiation, and reduce macrophage in vitro cytotoxicity. TiO2 was ALD-coated onto PES at 21 nm thickness. Uncoated PES exposed to UV for 30 min visibly changed color, whereas TiO2-coated PES showed no color change, indicating limited degradation. Macrophages exposed to UV-treated PES for 48 h showed reduced cell viability (via MTT assay) to 18% of control. In contrast, the cell viability for UV-treated TiO2-coated PES was 90% of control. Non-UV treated PES showed no decrease in cell viability. The results indicate that ALD of TiO2 thin films is a useful technique to protect polymers from UV damage and to retain low cytotoxicity to macrophages and other types of cells that are involved in wound healing. TiO2- coated PES membranes also have potential use in direct methanol fuel cells and in wastewater treatment membranes.}, number={4}, journal={JOM}, publisher={Springer Science and Business Media LLC}, author={Petrochenko, Peter E. and Scarel, Giovanna and Hyde, G. Kevin and Parsons, Gregory N. and Skoog, Shelby A. and Zhang, Qin and Goering, Peter L. and Narayan, Roger J.}, year={2013}, month={Feb}, pages={550–556} }
 @article{vasquez_vincent-johnson_hughes_augustine_lee_parsons_scarel_2012, title={Wetting properties induced in nano-composite POSS-MA polymer films by atomic layer deposited oxides}, volume={30}, ISSN={["0734-2101"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000298992800005&KeyUID=WOS:000298992800005}, DOI={10.1116/1.3639134}, abstractNote={Due to their unique properties, nano-composite polyhedral oligomeric silsequioxane (POSS) copolymer films are attractive for various applications. Here we show that their natural hydrophobic character can become hydrophilic when the films are modified by a thin oxide layer, up to 8 nm thick, prepared using atomic layer deposition. A proper choice of the deposition temperature and thickness of the oxide layer are required to achieve this goal. Unlike other polymeric systems, a marked transition to a hydrophilic state is observed with oxide layers deposited at increasing temperatures up to the glass transition temperature (∼110 °C) of the POSS copolymer film. The hydrophilic state is monitored through the water contact angle of the POSS film. Infrared absorbance spectra indicate that, in hydrophilic samples, the integral of peaks corresponding to surface Al–O (hydrophilic) is significantly larger than that of peaks linked to hydrophobic species.}, number={1}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Vasquez, Kyle A. and Vincent-Johnson, Anita J. and Hughes, W. Christopher and Augustine, Brian H. and Lee, Kyoungmi and Parsons, Gregory N. and Scarel, Giovanna}, year={2012}, month={Jan} }
 @article{hyde_stewart_scarel_parsons_shih_shih_lin_su_monteiro-riviere_narayan_et al._2011, title={Atomic layer deposition of titanium dioxide on cellulose acetate for enhanced hemostasis}, volume={6}, ISSN={1860-6768}, url={http://dx.doi.org/10.1002/biot.201000342}, DOI={10.1002/biot.201000342}, abstractNote={Abstract}, number={2}, journal={Biotechnology Journal}, publisher={Wiley}, author={Hyde, G. Kevin and Stewart, S. Michael and Scarel, Giovanna and Parsons, Gregory N. and Shih, Chun-Che and Shih, Chun-Ming and Lin, Shing-Jong and Su, Yea-Yang and Monteiro-Riviere, Nancy A. and Narayan, Roger J. and et al.}, year={2011}, month={Feb}, pages={213–223} }
 @article{johnston-peck_scarel_wang_parsons_tracy_2011, title={Sinter-free phase conversion and scanning transmission electron microscopy of FePt nanoparticle monolayers}, volume={3}, ISSN={["2040-3372"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000295618200024&KeyUID=WOS:000295618200024}, DOI={10.1039/c1nr10567a}, abstractNote={Thermally robust monolayers of 4-6 nm diameter FePt nanoparticles (NPs) were fabricated by combining chemical synthesis and atomic layer deposition. Spin-cast monolayers of FePt NPs were coated with thin, 11 nm-thick layers of amorphous Al(2)O(3), followed by annealing to convert the FePt NPs from an alloy (A1) into intermetallic FePt (L1(0)) and FePt(3) (L1(2)) phases. The Al(2)O(3) layer serves as a barrier that prevents sintering between NPs during annealing at temperatures up to 730 °C. Electron and X-ray diffraction in conjunction with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) show that as-synthesized A1 FePt NPs convert into L1(0) and L1(2) phase NPs through annealing. HAADF-STEM measurements of individual NPs reveal imperfect ordering and show that the NP composition determines which intermetallic phase is obtained. Mixed-phase NPs with L1(0) cores and FePt(3) L1(2) shells were also observed, as well as a smaller number of unconverted A1 NPs. These results highlight the need for improved control over the compositional uniformity of FePt NPs for their use in bit-patterned magnetic recording.}, number={10}, journal={NANOSCALE}, author={Johnston-Peck, Aaron C. and Scarel, Giovanna and Wang, Junwei and Parsons, Gregory N. and Tracy, Joseph B.}, year={2011}, pages={4142–4149} }
 @article{hyde_scarel_spagnola_peng_lee_gong_roberts_roth_hanson_devine_et al._2010, title={Atomic Layer Deposition and Abrupt Wetting Transitions on Nonwoven Polypropylene and Woven Cotton Fabrics}, volume={26}, ISSN={["0743-7463"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000274342200056&KeyUID=WOS:000274342200056}, DOI={10.1021/la902830d}, abstractNote={Atomic layer deposition (ALD) of aluminum oxide on nonwoven polypropylene and woven cotton fabric materials can be used to transform and control fiber surface wetting properties. Infrared analysis shows that ALD can produce a uniform coating throughout the nonwoven polypropylene fiber matrix, and the amount of coating can be controlled by the number of ALD cycles. Upon coating by ALD aluminum oxide, nonwetting hydrophobic polypropylene fibers transition to either a metastable hydrophobic or a fully wetting hydrophilic state, consistent with well-known Cassie-Baxter and Wenzel models of surface wetting of roughened surfaces. The observed nonwetting/wetting transition depends on ALD process variables such as the number of ALD coating cycles and deposition temperature. Cotton fabrics coated with ALD aluminum oxide at moderate temperatures were also observed to transition from a natural wetting state to a metastable hydrophobic state and back to wetting depending on the number of ALD cycles. The transitions on cotton appear to be less sensitive to deposition temperature. The results provide insight into the effect of ALD film growth mechanisms on hydrophobic and hydrophilic polymers and fibrous structures. The ability to adjust and control surface energy, surface reactivity, and wettability of polymer and natural fiber systems using atomic layer deposition may enable a wide range of new applications for functional fiber-based systems.}, number={4}, journal={LANGMUIR}, author={Hyde, G. Kevin and Scarel, Giovanna and Spagnola, Joseph C. and Peng, Qing and Lee, Kyoungmi and Gong, Bo and Roberts, Kim G. and Roth, Kelly M. and Hanson, Christopher A. and Devine, Christina K. and et al.}, year={2010}, month={Feb}, pages={2550–2558} }
 @article{na_scarel_parsons_2010, title={In Situ Analysis of Dopant Incorporation, Activation, and Film Growth during Thin Film ZnO and ZnO:Al Atomic Layer Deposition}, volume={114}, ISSN={["1932-7447"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000273268600054&KeyUID=WOS:000273268600054}, DOI={10.1021/jp908332q}, abstractNote={In situ characterization of low temperature atomic layer deposition (ALD) of ZnO and aluminum-doped ZnO (ZnO:Al) establishes a relationship between species adsorption, mass uptake, and surface electrical conductance during deposition and dopant atom incorporation. Conductance measured in situ during ZnO ALD oscillates with species surface adsorption, consistent with surface potential modulation and charge transfer during surface reaction. Dopant introduction using trimethylaluminum impedes both surface potential modulation and film growth, and a reaction scheme involving surface proton exchange complexes is presented to understand the observed results. Electronically active doping is achieved only after Al species transition four to five monolayers into the film bulk, consistent with a nonuniform dopant atom distribution in the direction of film growth. Results have important implications in understanding relations between dopant incorporation, activation, and film growth mechanisms in atomic layer deposi...}, number={1}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Na, Jeong-Seok and Scarel, Giovanna and Parsons, Gregory N.}, year={2010}, month={Jan}, pages={383–388} }
 @article{scarel_na_gong_parsons_2010, title={Phonon Response in the Infrared Region to Thickness of Oxide Films Formed by Atomic Layer Deposition}, volume={64}, ISSN={["1943-3530"]}, DOI={10.1366/000370210790571954}, abstractNote={ Experimental transmission infrared spectra of γ-Al2O3 and ZnO films are collected from heat-treated thin oxide films deposited with uniform thickness on Si(100) using atomic layer deposition. We show that the Berreman thickness, i.e. the upper limit for a linear relationship between oxide film thickness and phonon absorbance in the infrared region in transmission configuration, is a concept that applies to both transverse and longitudinal optical phonons. We find that for aluminum oxide films the Berreman thickness is 125 nm, and we estimate that it is around approximately 435 nm for zinc oxide films. Combining experiment and simulation, we also show that the Berreman thickness is the maximum distance allowed between interfaces for Snell's law and Fresnel's formulas to determine the optical properties in the infrared region and in transmission configuration for a layer system including an oxide film. Below the Berreman thickness, a Taylor series expansion of the absorbance coefficient determines the linear relationship between phonon absorbance and oxide film thickness t, so that as t → 0 absorption Ap ∝ 4πωph t, where ωph indicates optical phonon frequency. Above the Berreman thickness, field boundary conditions at the air/oxide film interface effectively contribute with a single interface in explaining optical phonon absorbance. Preliminary infrared spectra in reflection configuration for γ-Al2O3/Si(100) are discussed, and the obtained data support the conclusions reported for the transmission configuration. }, number={1}, journal={APPLIED SPECTROSCOPY}, author={Scarel, Giovanna and Na, Jeong-Seok and Gong, Bo and Parsons, Gregory N.}, year={2010}, month={Jan}, pages={120–126} }
 @article{na_peng_scarel_parsons_2009, title={Role of Gas Doping Sequence in Surface Reactions and Dopant Incorporation during Atomic Layer Deposition of Al-Doped ZnO}, volume={21}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000272084500009&KeyUID=WOS:000272084500009}, DOI={10.1021/cm901404p}, abstractNote={Aluminum incorporation into ZnO films during atomic layer deposition (ALD) is investigated using in situ quartz crystal microbalance and electrical conductance analysis. Chemical interactions between Zn and Al species during ZnO:Al ALD depend on the order of metal precursor exposure. Exposing the growing ZnO surface to trimethyl aluminum (TMA) impedes the subsequent ∼4 monolayers of ZnO growth. However, the extent of interaction can be reduced by performing the TMA exposure immediately following a diethyl zinc step, without an intermediate water exposure step, consistent with increased surface mixing of Zn and Al species. Infrared spectroscopy analysis of heavily aluminum doped ZnO shows features consistent with the presence of amorphous ZnAl2O4 bonding units. For more lightly doped films, mass spectroscopic depth profiling confirms nonuniform aluminum distribution, even after annealing at 500 °C. Film conductance measured during growth shows complex trends that are highly repeatable over multiple doping ...}, number={23}, journal={CHEMISTRY OF MATERIALS}, author={Na, Jeong-Seok and Peng, Qing and Scarel, Giovanna and Parsons, Gregory N.}, year={2009}, month={Dec}, pages={5585–5593} }
 @article{na_gong_scarel_parsons_2009, title={Surface Polarity Shielding and Hierarchical ZnO Nano-Architectures Produced Using Sequential Hydrothermal Crystal Synthesis and Thin Film Atomic Layer Deposition}, volume={3}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000271106100043&KeyUID=WOS:000271106100043}, DOI={10.1021/nn900702e}, abstractNote={Three-dimensional nanoscale constructs are finding applications in many emerging fields, including energy generation and storage, advanced water and air purification, and filtration strategies, as well as photocatalytic and biochemical separation systems. Progress in these important technologies will benefit from improved understanding of fundamental principles underlying nanostructure integration and bottom-up growth processes. While previous work has identified hydrothermal synthesis conditions to produce nanoscale ZnO rods, sheets, and plates, strategies to systematically integrate these elements into more complex nano-architectures are not previously described. This article illustrates that amorphous nanoscale coatings formed by atomic layer deposition (ALD) are a viable means to modulate and screen the surface polarity of ZnO crystal faces and thereby regulate the growth morphology during successive hydrothermal nanocrystal synthesis. Using this new strategy, this work demonstrates direct integration and sequential assembly of nanocrystalline rods and sheets to produce complex three-dimensional geometric forms, where structure evolution is achieved by modifying the surface growth condition, keeping the hydrothermal growth chemistry unchanged. Therefore, rational planning of seed layer and feature spacing geometries may allow researchers to engineer, at the nanoscale, complex three-dimensional crystalline and semicrystalline constructs for a wide range of future applications.}, number={10}, journal={ACS NANO}, author={Na, Jeong-Seok and Gong, Bo and Scarel, Giovanna and Parsons, Gregory N.}, year={2009}, month={Oct}, pages={3191–3199} }
 @article{scarel_hyde_hojo_parsons_2008, title={Berreman effect in infrared absorption spectroscopy of ionic oxide coatings formed by atomic layer deposition on three-dimensional structures}, volume={104}, ISSN={["1089-7550"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000260941700110&KeyUID=WOS:000260941700110}, DOI={10.1063/1.3013439}, abstractNote={We show through modeling and experimentation that the Berreman effect, physically manifested and investigated on planar surfaces for more than four decades, can be readily realized and studied in three-dimensional nonplanar structures. The Berreman effect is also used as a nonlocal probe to evaluate topography and homogeneity of insulating ionic oxide layers in nonplanar geometries. During infrared transmission studies the macroscopic angular dependence of the longitudinal optical mode absorbance deviates from that observed in the planar case, and the angular dependence is shown to be physically linked to geometry and homogeneity of the ionic oxide layer. Spectroscopic modeling confirms the observations on the angular dependence of longitudinal optical mode absorbance on various nonplanar systems. A linear combination of [sin(θ)]4 with appropriate coefficients is found to describe the trend of longitudinal optical mode absorbance in nonplanar structures.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Scarel, Giovanna and Hyde, G. Kevin and Hojo, Daisuke and Parsons, Gregory N.}, year={2008}, month={Nov} }