@article{gong_peng_na_parsons_2011, title={Highly active photocatalytic ZnO nanocrystalline rods supported on polymer fiber mats: Synthesis using atomic layer deposition and hydrothermal crystal growth}, volume={407}, ISSN={["0926-860X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000297234400025&KeyUID=WOS:000297234400025}, DOI={10.1016/j.apcata.2011.08.041}, abstractNote={Photocatalytically active zinc oxide nanocrystalline rods are grown on high surface area polybutylene terephthalate (PBT) polymer fiber mats using low temperature solution based methods, where the oxide crystal nucleation is facilitated using conformal thin films formed by low temperature vapor phase atomic layer deposition (ALD). Scanning electron microscopy (SEM) confirms that highly oriented single crystal ZnO nanorod crystals are directed normal to the starting fiber substrate surface, and the extent of nanocrystal growth within the fiber mat bulk is affected by the overall thickness of the ZnO nucleation layer. The high surface area of the nanocrystal-coated fibers is confirmed by nitrogen adsorption/desorption analysis. An organic dye in aqueous solution in contact with the coated fiber degraded rapidly upon ultraviolet light exposure, allowing quantitative analysis of the photocatalytic properties of fibers with and without nanorod crystals present. The dye degrades nearly twice as fast in contact with the ZnO nanorod crystals compared with samples with only an ALD ZnO layer. Additionally, the catalyst on the polymer fiber mat could be reused without need for a particle recovery step. This combination of ALD and hydrothermal processes could produce high surface area finishes on complex polymer substrates for reusable photocatalytic and other surface-reaction applications.}, number={1-2}, journal={APPLIED CATALYSIS A-GENERAL}, author={Gong, Bo and Peng, Qing and Na, Jeong-Seok and Parsons, Gregory N.}, year={2011}, month={Nov}, pages={211–216} }
 @article{scarel_na_parsons_2010, title={Angular behavior of the Berreman effect investigated in uniform Al2O3 layers formed by atomic layer deposition}, volume={22}, ISSN={["1361-648X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000276097500013&KeyUID=WOS:000276097500013}, DOI={10.1088/0953-8984/22/15/155401}, abstractNote={Experimental transmission absorbance infrared spectra of γ-Al2O3 showing evidence of the angular dependence of the peaks of surface modes appearing next to the longitudinal optical phonon frequency ωLO (the Berreman effect) are collected from heat-treated thin oxide films deposited with thickness uniformity on Si(100) using atomic layer deposition. The peak area of the most intense surface longitudinal optical mode is plotted versus the infrared beam incidence angle θ0. The experimental points closely follow the sin4(θ0) function in a broad thickness range. The best match occurs at a critical thickness, where a linear relationship exists between the surface longitudinal optical mode intensity and film thickness. Simulations suggest that below the critical thickness the sin4(θ0) behavior can be explained by refraction phenomena at the air/thin film and thin film/substrate interfaces. Above the critical thickness, the experimentally obtained result is derived from field boundary conditions at the air/thin film interface. The sin4(θ0) functional trend breaks down far above the critical thickness. This picture indicates that infrared radiation has a limited penetration depth into the oxide film, similarly to electromagnetic waves in conductors. Consequently, surface longitudinal optical modes are viewed as bulk phonons excited down to the penetration depth of the infrared beam. Comparison with simulated data suggests that the infrared radiation absorptance of surface longitudinal optical modes tends to approach the sin2(θ0) trend. Reflection phenomena are considered to be the origin of the deviation from the sin4(θ0) trend related to refraction.}, number={15}, journal={JOURNAL OF PHYSICS-CONDENSED MATTER}, author={Scarel, Giovanna and Na, Jeong-Seok and Parsons, Gregory N.}, year={2010}, month={Apr} }
 @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{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{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{na_ayres_chandra_gorman_parsons_2008, title={Nanoencapsulation and Stabilization of Single-Molecule/Particle Electronic Nanoassemblies Using Low-Temperature Atomic Layer Deposition}, volume={112}, ISSN={["1932-7447"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000261835000061&KeyUID=WOS:000261835000061}, DOI={10.1021/jp8066298}, abstractNote={This work addresses a significant challenge in engineered molecular systems regarding both understanding and controlling the stability of molecule/nanoparticle nanostructures under ambient exposure. Results deal specifically with molecular electronic junctions, where electronic contacts and transport are known to be sensitive to sample history and ambient exposure. We demonstrate that low-temperature atomic layer deposition can gently encapsulate and stabilize molecular electronic junctions, making it feasible to handle and transport junctions in air for many days with minimal change in electronic conduction. These findings indicate the potential for long-term stability of advanced synthetic nanoparticle/molecule nanoconstructs. For this study, conductivity through nanoparticle/molecule/nanoparticle junctions is analyzed and found to be consistent with nonresonant charge tunneling through a single or a small number of oligomeric phenylene ethynylene molecules in the electrical junction. The conductivity w...}, number={51}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Na, Jeong-Seok and Ayres, Jennifer A. and Chandra, Kusum L. and Gorman, Christopher B. and Parsons, Gregory N.}, year={2008}, month={Dec}, pages={20510–20517} }
 @article{na_ayres_chandra_chu_gorman_parsons_2007, title={Conduction mechanisms and stability of single molecule nanoparticle/molecule/nanoparticle junctions}, volume={18}, number={3}, journal={Nanotechnology}, author={Na, J. S. and Ayres, J. and Chandra, K. L. and Chu, C. and Gorman, C. B. and Parsons, G. N.}, year={2007} }
 @article{chu_na_parsons_2007, title={Conductivity in alkylamine/gold and alkanethiol/gold molecular junctions measured in molecule/nanoparticle/molecule bridges and conducting probe structures}, volume={129}, ISSN={["1520-5126"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000244330800030&KeyUID=WOS:000244330800030}, DOI={10.1021/ja064968s}, abstractNote={Charge transport through alkane monolayers on gold is measured as a function of molecule length in a controlled ambient using a metal/molecule/nanoparticle bridge structure and compared for both thiol and amine molecular end groups. The current through molecules with an amine/gold junction is observed to be more than a factor of 10 larger than that measured in similar molecules with thiol/gold linkages. Conducting probe atomic force microscopy is also used to characterize the same monolayer systems, and the results are quantitatively consistent with those found in the nanoparticle bridge geometry. Scaling of the current with contact area is used to estimate that approximately 100 molecules are probed in the nanoparticle bridge geometry. For both molecular end groups, the room-temperature conductivity at low bias as a function of molecule length shows a reasonable fit to models of coherent nonresonant charge tunneling. The different conductivity is ascribed to differences in charge transfer and wave function mixing at the metal/molecule contact, including possible effects of amine group oxidation and molecular conformation. For the amine/Au contact, the nitrogen lone pair interaction with the gold results in a hybrid wave function directed along the molecule bond axis, whereas the thiol/Au contact leads to a more localized wave function.}, number={8}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Chu, Changwoong and Na, Jeong-Seok and Parsons, Gregory N.}, year={2007}, month={Feb}, pages={2287–2296} }
 @article{na_ayres_chandra_gorman_parsons_2007, title={Real-time conductivity analysis through single-molecule electrical junctions}, volume={18}, number={42}, journal={Nanotechnology}, author={Na, J. S. and Ayres, J. and Chandra, K. L. and Gorman, C. B. and Parsons, G. N.}, year={2007} }