Publications by authors named "Jonathan D Emery"

32 Publications

Vaccination in pregnancy: A call to all providers for help.

Cleve Clin J Med 2021 03 1;88(3):157-162. Epub 2021 Mar 1.

Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH.

Vaccination in pregnancy is an important part of maternity care, but maternal immunization rates continue to be below national benchmarks. Influenza and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccinations have been shown to be safe and provide important protections to pregnant women, the fetus, and neonates. Although obstetrician-gynecologists provide the bulk of pregnancy care, general internists and medical specialists have frequent clinical encounters with maternity patients and should assist in immunization education and administration.
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http://dx.doi.org/10.3949/ccjm.88a.20111DOI Listing
March 2021

Thermal Atomic Layer Deposition of Gold: Mechanistic Insights, Nucleation, and Epitaxy.

ACS Appl Mater Interfaces 2021 Feb 9;13(7):9091-9100. Epub 2021 Feb 9.

Material Science Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States.

An microbalance and infrared spectroscopic study of alternating exposures to MeAu(SCNEt) and ozone illuminates the organometallic chemistry that allows for the thermal atomic layer deposition (ALD) of gold. quartz crystal microbalance (QCM) studies resolve the nucleation delay and island growth of Au on a freshly prepared aluminum oxide surface with single cycle resolution, revealing inhibition for 40 cycles prior to slow nucleation and film coalescence that extends over 300 cycles. infrared spectroscopy informed by first-principles computation provides insight into the surface chemistry of the self-limiting half-reactions, which are consistent with an oxidized Au surface mechanism. X-ray diffraction of ALD-grown gold on silicon, silica, sapphire, and mica reveals consistent out-of-plane oriented crystalline film growth as well as epitaxially directed in-plane orientation on closely lattice-matched mica at a relatively low growth temperature of 180 °C. A more complete understanding of ALD gold nucleation, surface chemistry, and epitaxy will inform the next generation of low-temperature, nanoscale, textured depositions that are applicable to high surface area supports.
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http://dx.doi.org/10.1021/acsami.0c17943DOI Listing
February 2021

Microfluidic electrochemical cell for in situ structural characterization of amorphous thin-film catalysts using high-energy X-ray scattering.

J Synchrotron Radiat 2019 Sep 9;26(Pt 5):1600-1611. Epub 2019 Aug 9.

Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave, Lemont, IL 60439, USA.

Porous, high-surface-area electrode architectures are described that allow structural characterization of interfacial amorphous thin films with high spatial resolution under device-relevant functional electrochemical conditions using high-energy X-ray (>50 keV) scattering and pair distribution function (PDF) analysis. Porous electrodes were fabricated from glass-capillary array membranes coated with conformal transparent conductive oxide layers, consisting of either a 40 nm-50 nm crystalline indium tin oxide or a 100 nm-150 nm-thick amorphous indium zinc oxide deposited by atomic layer deposition. These porous electrodes solve the problem of insufficient interaction volumes for catalyst thin films in two-dimensional working electrode designs and provide sufficiently low scattering backgrounds to enable high-resolution signal collection from interfacial thin-film catalysts. For example, PDF measurements were readily obtained with 0.2 Å spatial resolution for amorphous cobalt oxide films with thicknesses down to 60 nm when deposited on a porous electrode with 40 µm-diameter pores. This level of resolution resolves the cobaltate domain size and structure, the presence of defect sites assigned to the domain edges, and the changes in fine structure upon redox state change that are relevant to quantitative structure-function modeling. The results suggest the opportunity to leverage the porous, electrode architectures for PDF analysis of nanometre-scale surface-supported molecular catalysts. In addition, a compact 3D-printed electrochemical cell in a three-electrode configuration is described which is designed to allow for simultaneous X-ray transmission and electrolyte flow through the porous working electrode.
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http://dx.doi.org/10.1107/S1600577519007240DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6730625PMC
September 2019

Resolving the Chemically Discrete Structure of Synthetic Borophene Polymorphs.

Nano Lett 2018 05 23;18(5):2816-2821. Epub 2018 Apr 23.

Center for Nanoscale Materials , Argonne National Laboratory , Argonne , Illinois 60439 , United States.

Atomically thin two-dimensional (2D) materials exhibit superlative properties dictated by their intralayer atomic structure, which is typically derived from a limited number of thermodynamically stable bulk layered crystals (e.g., graphene from graphite). The growth of entirely synthetic 2D crystals, those with no corresponding bulk allotrope, would circumvent this dependence upon bulk thermodynamics and substantially expand the phase space available for structure-property engineering of 2D materials. However, it remains unclear if synthetic 2D materials can exist as structurally and chemically distinct layers anchored by van der Waals (vdW) forces, as opposed to strongly bound adlayers. Here, we show that atomically thin sheets of boron (i.e., borophene) grown on the Ag(111) surface exhibit a vdW-like structure without a corresponding bulk allotrope. Using X-ray standing wave-excited X-ray photoelectron spectroscopy, the positions of boron in multiple chemical states are resolved with sub-angström spatial resolution, revealing that the borophene forms a single planar layer that is 2.4 Å above the unreconstructed Ag surface. Moreover, our results reveal that multiple borophene phases exhibit these characteristics, denoting a unique form of polymorphism consistent with recent predictions. This observation of synthetic borophene as chemically discrete from the growth substrate suggests that it is possible to engineer a much wider variety of 2D materials than those accessible through bulk layered crystal structures.
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http://dx.doi.org/10.1021/acs.nanolett.7b05178DOI Listing
May 2018

Mechanistic understanding of tungsten oxide in-plane nanostructure growth via sequential infiltration synthesis.

Nanoscale 2018 Feb;10(7):3469-3479

Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.

Tungsten oxide (WO) nanostructures with hexagonal in-plane arrangements were fabricated by sequential infiltration synthesis (SIS), using the selective interaction of gas phase precursors with functional groups in one domain of a block copolymer (BCP) self-assembled template. Such structures are highly desirable for various practical applications and as model systems for fundamental studies. The nanostructures were characterized by cross-sectional scanning electron microscopy, grazing-incidence small/wide-angle X-ray scattering (GISAXS/GIWAXS), and X-ray absorption near edge structure (XANES) measurements at each stage during the SIS process and subsequent thermal treatments, to provide a comprehensive picture of their evolution in morphology, crystallography and electronic structure. In particular, we discuss the critical role of SIS AlO seeds toward modifying the chemical affinity and free volume in a polymer for subsequent infiltration of gas phase precursors. The insights into SIS growth obtained from this study are valuable to the design and fabrication of a wide range of targeted nanostructures.
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http://dx.doi.org/10.1039/c7nr07642hDOI Listing
February 2018

Measuring Dipole Inversion in Self-Assembled Nano-Dielectric Molecular Layers.

ACS Appl Mater Interfaces 2018 Feb 12;10(7):6484-6490. Epub 2018 Feb 12.

Materials Research Science and Engineering Center, Northwestern University , Evanston, Illinois 60208, United States.

A self-assembled nanodielectric (SAND) is an ultrathin film, typically with periodic layer pairs of high-k oxide and phosphonic-acid-based π-electron (PAE) molecular layers. IPAE, having a molecular structure similar to that of PAE but with an inverted dipole direction, has recently been developed for use in thin-film transistors. Here we report that replacing PAE with IPAE in SAND-based thin-film transistors induces sizable threshold and turn-on voltage shifts, indicating the flipping of the built-in SAND polarity. The bromide counteranion (Br) associated with the cationic stilbazolium portion of PAE or IPAE is of great importance, because its relative position strongly affects the electric dipole moment of the organic layer. Hence, a set of X-ray synchrotron measurements were designed and performed to directly measure and compare the Br distributions within the PAE and IPAE SANDs. Two trilayer SANDs, consisting of a PAE or IPAE layer sandwiched between an HfO and a ZrO layer, were deposited on the SiO surface of Si substrates or periodic Si/Mo multilayer substrates for X-ray reflectivity and X-ray standing wave measurements, respectively. Along with complementary DFT simulations, the spacings, elemental (Hf, Br, and Zr) distributions, molecular orientations, and Mulliken charge distributions of the PAE and IPAE molecules within each of the SAND trilayers were determined and correlated with the dipole inversion.
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http://dx.doi.org/10.1021/acsami.7b16160DOI Listing
February 2018

Inhibiting Metal Oxide Atomic Layer Deposition: Beyond Zinc Oxide.

ACS Appl Mater Interfaces 2017 Oct 5;9(39):33429-33436. Epub 2017 Apr 5.

Material Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Lemont, Illinois 60439, United States.

Atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au, and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H-plasma pretreatment of the Au substrate prior to the gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles. We study the effect that the ALD precursor purge times, growth temperature, alkanethiol chain length, alkanethiol deposition time, and plasma treatment time have on AlO ALD inhibition. This is the first example of AlO ALD inhibition from a vapor-deposited SAM. The inhibitions of AlO, ZnO, and MnO ALD processes are compared, revealing the versatility of this selective surface treatment. Atomic force microscopy and grazing-incidence X-ray fluorescence further reveal insight into the mechanism by which the well-defined surface chemistry of ALD may eventually be circumvented to allow metal oxide nucleation and growth on SAM-modified surfaces.
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http://dx.doi.org/10.1021/acsami.7b01410DOI Listing
October 2017

Low-Temperature Atomic Layer Deposition of MoS Films.

Angew Chem Int Ed Engl 2017 04 3;56(18):4991-4995. Epub 2017 Apr 3.

Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.

Wet chemical screening reveals the very high reactivity of Mo(NMe ) with H S for the low-temperature synthesis of MoS . This observation motivated an investigation of Mo(NMe ) as a volatile precursor for the atomic layer deposition (ALD) of MoS thin films. Herein we report that Mo(NMe ) enables MoS film growth at record low temperatures-as low as 60 °C. The as-deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift-off patterning for the straightforward fabrication of diverse device structures.
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http://dx.doi.org/10.1002/anie.201611838DOI Listing
April 2017

Low-Temperature Atomic Layer Deposition of CuSbS for Thin-Film Photovoltaics.

ACS Appl Mater Interfaces 2017 Feb 24;9(5):4667-4673. Epub 2017 Jan 24.

Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.

Copper antimony sulfide (CuSbS) has been gaining traction as an earth-abundant absorber for thin-film photovoltaics given its near ideal band gap for solar energy conversion (∼1.5 eV), large absorption coefficient (>10 cm), and elemental abundance. Through careful in situ analysis of the deposition conditions, a low-temperature route to CuSbS thin films via atomic layer deposition has been developed. After a short (15 min) postprocess anneal at 225 °C, the ALD-grown CuSbS films were crystalline with micron-sized grains, exhibited a band gap of 1.6 eV and an absorption coefficient >10 cm, as well as a hole concentration of 10 cm. Finally, the ALD-grown CuSbS films were paired with ALD-grown TiO to form a photovoltaic device. This photovoltaic device architecture represents one of a very limited number of Cd-free CuSbS PV device stacks reported to date, and it is the first to demonstrate an open-circuit voltage on par with CuSbS/CdS heterojunction PV devices. While far from optimized, this work demonstrates the potential for ALD-grown CuSbS thin films in environmentally benign photovoltaics.
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http://dx.doi.org/10.1021/acsami.6b13033DOI Listing
February 2017

Conformal Coating of a Phase Change Material on Ordered Plasmonic Nanorod Arrays for Broadband All-Optical Switching.

ACS Nano 2017 01 19;11(1):693-701. Epub 2016 Dec 19.

Department of Chemistry, Illinois Institute of Technology , 3101 South Dearborn Street, Chicago, Illinois 60616, United States.

Actively tunable optical transmission through artificial metamaterials holds great promise for next-generation nanophotonic devices and metasurfaces. Plasmonic nanostructures and phase change materials have been extensively studied to this end due to their respective strong interactions with light and tunable dielectric constants under external stimuli. Seamlessly integrating plasmonic components with phase change materials, as demonstrated in the present work, can facilitate phase change by plasmonically enabled light confinement and meanwhile make use of the high sensitivity of plasmon resonances to the variation of dielectric constant associated with the phase change. The hybrid platform here is composed of plasmonic indium-tin-oxide nanorod arrays (ITO-NRAs) conformally coated with an ultrathin layer of a prototypical phase change material, vanadium dioxide (VO), which enables all-optical modulation of the infrared as well as the visible spectral ranges. The interplay between the intrinsic plasmonic nonlinearity of ITO-NRAs and the phase transition induced permittivity change of VO gives rise to spectral and temporal responses that cannot be achieved with individual material components alone.
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http://dx.doi.org/10.1021/acsnano.6b07042DOI Listing
January 2017

Liquid Water- and Heat-Resistant Hybrid Perovskite Photovoltaics via an Inverted ALD Oxide Electron Extraction Layer Design.

Nano Lett 2016 12 14;16(12):7786-7790. Epub 2016 Nov 14.

Materials Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.

Despite rapid advances in conversion efficiency (>22%), the environmental stability of perovskite solar cells remains a substantial barrier to commercialization. Here, we show a significant improvement in the stability of inverted perovskite solar cells against liquid water and high operating temperature (100 °C) by integrating an ultrathin amorphous oxide electron extraction layer via atomic layer deposition (ALD). These unencapsulated inverted devices exhibit a stable operation over at least 10 h when subjected to high thermal stress (100 °C) in ambient environments, as well as upon direct contact with a droplet of water without further encapsulation.
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http://dx.doi.org/10.1021/acs.nanolett.6b03989DOI Listing
December 2016

Layer-by-Layer Assembled Films of Perylene Diimide- and Squaraine-Containing Metal-Organic Framework-like Materials: Solar Energy Capture and Directional Energy Transfer.

ACS Appl Mater Interfaces 2016 Sep 16;8(38):24983-8. Epub 2016 Sep 16.

Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.

We demonstrate that thin films of metal-organic framework (MOF)-like materials, containing two perylenediimides (PDICl4, PDIOPh2) and a squaraine dye (S1), can be fabricated by layer-by-layer assembly (LbL). Interestingly, these LbL films absorb across the visible light region (400-750 nm) and facilitate directional energy transfer. Due to the high spectral overlap and oriented transition dipole moments of the donor (PDICl4 and PDIOPh2) and acceptor (S1) components, directional long-range energy transfer from the bluest to reddest absorber was successfully demonstrated in the multicomponent MOF-like films. These findings have significant implications for the development of solar energy conversion devices based on MOFs.
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http://dx.doi.org/10.1021/acsami.6b03307DOI Listing
September 2016

Porphyrins as Templates for Site-Selective Atomic Layer Deposition: Vapor Metalation and in Situ Monitoring of Island Growth.

ACS Appl Mater Interfaces 2016 Aug 28;8(31):19853-9. Epub 2016 Jul 28.

Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.

Examinations of enzymatic catalysts suggest one key to efficient catalytic activity is discrete size metallo clusters. Mimicking enzymatic cluster systems is synthetically challenging because conventional solution methods are prone to aggregation or require capping of the cluster, thereby limiting its catalytic activity. We introduce site-selective atomic layer deposition (ALD) on porphyrins as an alternative approach to grow isolated metal oxide islands that are spatially separated. Surface-bound tetra-acid free base porphyrins (H2TCPP) may be metalated with Mn using conventional ALD precursor exposure to induce homogeneous hydroxide synthetic handles which acts as a nucleation point for subsequent ALD MnO island growth. Analytical fitting of in situ QCM mass uptake reveals island growth to be hemispherical with a convergence radius of 1.74 nm. This growth mode is confirmed with synchrotron grazing-incidence small-angle X-ray scattering (GISAXS) measurements. Finally, we extend this approach to other ALD chemistries to demonstrate the generality of this route to discrete metallo island materials.
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http://dx.doi.org/10.1021/acsami.6b05427DOI Listing
August 2016

A modular reactor design for in situ synchrotron x-ray investigation of atomic layer deposition processes.

Rev Sci Instrum 2015 Nov;86(11):113901

Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.

Synchrotron characterization techniques provide some of the most powerful tools for the study of film structure and chemistry. The brilliance and tunability of the Advanced Photon Source allow access to scattering and spectroscopic techniques unavailable with in-house laboratory setups and provide the opportunity to probe various atomic layer deposition (ALD) processes in situ starting at the very first deposition cycle. Here, we present the design and implementation of a portable ALD instrument which possesses a modular reactor scheme that enables simple experimental switchover between various beamlines and characterization techniques. As first examples, we present in situ results for (1) X-ray surface scattering and reflectivity measurements of epitaxial ZnO ALD on sapphire, (2) grazing-incidence small angle scattering of MnO nucleation on silicon, and (3) grazing-incidence X-ray absorption spectroscopy of nucleation-regime Er2O3 ALD on amorphous ALD alumina and single crystalline sapphire.
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http://dx.doi.org/10.1063/1.4934807DOI Listing
November 2015

Keeping primary care "in the loop": General practitioners want better communication with specialists and hospitals when caring for people diagnosed with cancer.

Asia Pac J Clin Oncol 2015 Jun 6;11(2):152-9. Epub 2015 Jan 6.

WA Cancer and Palliative Care Network, WA Department of Health, East Perth, Western Australia, Australia; School of Surgery, The University of Western Australia, Crawley, Western Australia, Australia.

Aim: To investigate general practitioners' (GP) perceptions about communication when providing cancer care.

Methods: A self-report survey, which included an open response section, was mailed to a random sample of 1969 eligible Australian GPs. Content analysis of open response comments pertaining to communication was undertaken in order to ascertain GPs' views about communication issues in the provision of cancer care.

Results: Of the 648 GPs who completed the survey, 68 (10%) included open response comments about interprofessional communication. Participants who commented on communication were a median age of 50 years and worked 33 h/week; 28% were male and 59% practiced in the metropolitan area. Comments pertaining to communication were coded using five non-mutually exclusive categories: being kept in the loop; continuity of care; relationships with specialists; positive communication experiences; and strategies for improving communication.GPs repeatedly noted the importance of receiving detailed and timely communication from specialists and hospitals, particularly in relation to patients' treatment regimes and follow-up care. Several GPs remarked that they were left out of "the information loop" and that patients were "lost" or "dumped" after referral.

Conclusion: While many GPs are currently involved in some aspects of cancer management, detailed and timely communication between specialists and GPs is imperative to support shared care and ensure optimal patient outcomes. This research highlights the need for established channels of communication between specialist and primary care medicine to support greater involvement by GPs in cancer care.
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http://dx.doi.org/10.1111/ajco.12327DOI Listing
June 2015

New Insights into Sequential Infiltration Synthesis.

ECS Trans 2015 ;69(7):147-157

CanmetMATERIALS, Hamilton, Ontario L8P 0A5, Canada.

Sequential infiltration synthesis (SIS) is a process derived from ALD in which a polymer is infused with inorganic material using sequential, self-limiting exposures to gaseous precursors. SIS can be used in lithography to harden polymer resists rendering them more robust towards subsequent etching, and this permits deeper and higher-resolution patterning of substrates such as silicon. Herein we describe recent investigations of a model system: AlO SIS using trimethyl aluminum (TMA) and HO within the diblock copolymer, poly(styrene-block-methyl methacrylate) (PS-b-PMMA). Combining in-situ Fourier transform infrared absorption spectroscopy, quartz-crystal microbalance, and synchrotron grazing incidence small angle X-ray scattering with high resolution scanning transmission electron microscope tomography, we elucidate important details of the SIS process: 1) TMA adsorption in PMMA occurs through a weakly-bound intermediate; 2) the SIS kinetics are diffusion-limited, with desorption 10× slower than adsorption; 3) dynamic structural changes occur during the individual precursor exposures. These findings have important implications for applications such as SIS lithography.
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http://dx.doi.org/10.1149/06907.0147ecstDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5424714PMC
January 2015

Atomic layer deposition of metastable β-Fe₂O₃ via isomorphic epitaxy for photoassisted water oxidation.

ACS Appl Mater Interfaces 2014 Dec 9;6(24):21894-900. Epub 2014 Dec 9.

Materials Science Division and ‡X-ray Science Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.

We report the growth and photoelectrochemical (PEC) characterization of the uncommon bibyite phase of iron(III) oxide (β-Fe2O3) epitaxially stabilized via atomic layer deposition on an conductive, transparent, and isomorphic template (Sn-doped In2O3). As a photoanode, unoptimized β-Fe2O3 ultrathin films perform similarly to their ubiquitous α-phase (hematite) counterpart, but reveal a more ideal bandgap (1.8 eV), a ∼0.1 V improved photocurrent onset potential, and longer wavelength (>600 nm) spectral response. Stable operation under basic water oxidation justifies further exploration of this atypical phase and motivates the investigation of other unexplored metastable phases as new PEC materials.
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http://dx.doi.org/10.1021/am507065yDOI Listing
December 2014

Oxygen-free atomic layer deposition of indium sulfide.

ACS Appl Mater Interfaces 2014 Aug 25;6(15):12137-45. Epub 2014 Jul 25.

Materials Science Division and ‡Chemical Sciences and Engineering Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.

Atomic layer deposition (ALD) of indium sulfide (In2S3) films was achieved using a newly synthesized indium precursor and hydrogen sulfide. We obtain dense and adherent thin films free from halide and oxygen impurities. Self-limiting half-reactions are demonstrated at temperatures up to 225 °C, where oriented crystalline thin films are obtained without further annealing. Low-temperature growth of 0.89 Å/cycle is observed at 150 °C, while higher growth temperatures gradually reduce the per-cycle growth rate. Rutherford backscattering spectroscopy (RBS) together with depth-profiling Auger electron spectroscopy (AES) reveal a S/In ratio of 1.5 with no detectable carbon, nitrogen, halogen, or oxygen impurities. The resistivity of thin films prior to air exposure decreases with increasing deposition temperature, reaching <1 Ω·cm for films deposited at 225 °C. Hall measurements reveal n-type conductivity due to free electron concentrations up to 10(18) cm(-3) and mobilities of order 1 cm(2)/(V·s). The digital synthesis of In2S3 via ALD at temperatures up to 225 °C may allow high quality thin films to be leveraged in optoelectronic devices including photovoltaic absorbers, buffer layers, and intermediate band materials.
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http://dx.doi.org/10.1021/am501331wDOI Listing
August 2014

Real-time observation of atomic layer deposition inhibition: metal oxide growth on self-assembled alkanethiols.

ACS Appl Mater Interfaces 2014 Aug 21;6(15):11891-8. Epub 2014 Jul 21.

Department of Chemistry, Northwestern University , 2145 Sheridan Road Evanston, Illinois 60208, United States.

Through in situ quartz crystal microbalance (QCM) monitoring, we resolve the growth of a self-assembled monolayer (SAM) and subsequent metal oxide deposition with high resolution. We introduce the fitting of mass deposited during each atomic layer deposition (ALD) cycle to an analytical island-growth model that enables quantification of growth inhibition, nucleation density, and the uninhibited ALD growth rate. A long-chain alkanethiol was self-assembled as a monolayer on gold-coated quartz crystals in order to investigate its effectiveness as a barrier to ALD. Compared to solution-loading, vapor-loading is observed to produce a SAM with equal or greater inhibition ability in minutes vs days. The metal oxide growth temperature and the choice of precursor also significantly affect the nucleation density, which ranges from 0.001 to 1 sites/nm(2). Finally, we observe a minimum 100 cycle inhibition of an oxide ALD process, ZnO, under moderately optimized conditions.
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http://dx.doi.org/10.1021/am503008jDOI Listing
August 2014

Self-assembled organic monolayers on epitaxial graphene with enhanced structural and thermal stability.

Chem Commun (Camb) 2014 Aug;50(64):8852-5

Dept. of Materials Science & Engineering, Northwestern Univ., Evanston, IL 60208, USA.

Scanning tunnelling microscopy and X-ray reflectivity are used to characterize adlayers of perylenetetracarboxylic diimide (PTCDI) deposited on epitaxial graphene (EG) on SiC(0001). PTCDI adopts a herringbone structural phase on EG/SiC that can accommodate sub-5 nm voids with molecularly defined boundaries and isolated molecular vacancies at room temperature. The PTCDI monolayer remains intact up to substrate temperatures of ~260 °C, thus demonstrating enhanced thermal stability compared to previously studied perylene derivatives on EG/SiC.
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http://dx.doi.org/10.1039/c4cc02761bDOI Listing
August 2014

Chemically resolved interface structure of epitaxial graphene on SiC(0001).

Phys Rev Lett 2013 Nov 19;111(21):215501. Epub 2013 Nov 19.

Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.

Atomic-layer 2D crystals have unique properties that can be significantly modified through interaction with an underlying support. For epitaxial graphene on SiC(0001), the interface strongly influences the electronic properties of the overlaying graphene. We demonstrate a novel combination of x-ray scattering and spectroscopy for studying the complexities of such a buried interface structure. This approach employs x-ray standing wave-excited photoelectron spectroscopy in conjunction with x-ray reflectivity to produce a highly resolved chemically sensitive atomic profile for the terminal substrate bilayers, interface, and graphene layers along the SiC[0001] direction.
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http://dx.doi.org/10.1103/PhysRevLett.111.215501DOI Listing
November 2013

Systematic investigation of organic photovoltaic cell charge injection/performance modulation by dipolar organosilane interfacial layers.

ACS Appl Mater Interfaces 2013 Sep 6;5(18):9224-40. Epub 2013 Sep 6.

Department of Chemistry and the Argonne-Northwestern Solar Energy Research Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.

With the goal of investigating and enhancing anode performance in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells, the glass/tin-doped indium oxide (ITO) anodes are modified with a series of robust silane-tethered bis(fluoroaryl)amines to form self-assembled interfacial layers (IFLs). The modified ITO anodes are characterized by contact angle measurements, X-ray reflectivity, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, atomic force microscopy, and cyclic voltammetry. These techniques reveal the presence of hydrophobic amorphous monolayers of 6.68 to 9.76 Å thickness, and modified anode work functions ranging from 4.66 to 5.27 eV. Two series of glass/ITO/IFL/active layer/LiF/Al BHJ OPVs are fabricated with the active layer = poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) or poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]thi-eno[3,4-b]thiophenediyl]]:phenyl-C71-butyric acid methyl ester (PTB7:PC71BM). OPV analysis under AM 1.5G conditions reveals significant performance enhancement versus unmodified glass/ITO anodes. Strong positive correlations between the electrochemically derived heterogeneous electron transport rate constants (ks) and the device open circuit voltage (Voc), short circuit current (Jsc), hence OPV power conversion efficiency (PCE), are observed for these modified anodes. Furthermore, the strong functional dependence of the device response on ks increases as greater densities of charge carriers are generated in the BHJ OPV active layer, and is attributable to enhanced anode carrier extraction in the case of high-ks IFLs.
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http://dx.doi.org/10.1021/am4030609DOI Listing
September 2013

Ambient-processable high capacitance hafnia-organic self-assembled nanodielectrics.

J Am Chem Soc 2013 Jun 11;135(24):8926-39. Epub 2013 Jun 11.

Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.

Ambient and solution-processable, low-leakage, high capacitance gate dielectrics are of great interest for advances in low-cost, flexible, thin-film transistor circuitry. Here we report a new hafnium oxide-organic self-assembled nanodielectric (Hf-SAND) material consisting of regular, alternating π-electron layers of 4-[[4-[bis(2-hydroxyethyl)amino]phenyl]diazenyl]-1-[4-(diethoxyphosphoryl) benzyl]pyridinium bromide) (PAE) and HfO2 nanolayers. These Hf-SAND multilayers are grown from solution in ambient with processing temperatures ≤150 °C and are characterized by AFM, XPS, X-ray reflectivity (2.3 nm repeat spacing), X-ray fluorescence, cross-sectional TEM, and capacitance measurements. The latter yield the largest capacitance to date (1.1 μF/cm(2)) for a solid-state solution-processed hybrid inorganic-organic gate dielectric, with effective oxide thickness values as low as 3.1 nm and have gate leakage <10(-7) A/cm(2) at ±2 MV/cm using photolithographically patterned contacts (0.04 mm(2)). The sizable Hf-SAND capacitances are attributed to relatively large PAE coverages on the HfO2 layers, confirmed by X-ray reflectivity and X-ray fluorescence. Random network semiconductor-enriched single-walled carbon nanotube transistors were used to test Hf-SAND utility in electronics and afforded record on-state transconductances (5.5 mS) at large on:off current ratios (I(ON):I(OFF)) of ~10(5) with steep 150 mV/dec subthreshold swings and intrinsic field-effect mobilities up to 137 cm(2)/(V s). Large-area devices (>0.2 mm(2)) on Hf-SAND (6.5 nm thick) achieve mA on currents at ultralow gate voltages (<1 V) with low gate leakage (<2 nA), highlighting the defect-free and conformal nature of this nanodielectric. High-temperature annealing in ambient (400 °C) has limited impact on Hf-SAND leakage densities (<10(-6) A/cm(2) at ±2 V) and enhances Hf-SAND multilayer capacitance densities to nearly 1 μF/cm(2), demonstrating excellent compatibility with device postprocessing methodologies. These results represent a significant advance in hybrid organic-inorganic dielectric materials and suggest synthetic routes to even higher capacitance materials useful for unconventional electronics.
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http://dx.doi.org/10.1021/ja4019429DOI Listing
June 2013

Templating sub-10 nm atomic layer deposited oxide nanostructures on graphene via one-dimensional organic self-assembled monolayers.

Nano Lett 2013 11;13(12):5763-70. Epub 2013 Mar 11.

Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208, United States.

Molecular-scale control over the integration of disparate materials on graphene is a critical step in the development of graphene-based electronics and sensors. Here, we report that self-assembled monolayers of 10,12-pentacosadiynoic acid (PCDA) on epitaxial graphene can be used to template the reaction and directed growth of atomic layer deposited (ALD) oxide nanostructures with sub-10 nm lateral resolution. PCDA spontaneously assembles into well-ordered domains consisting of one-dimensional molecular chains that coat the entire graphene surface in a manner consistent with the symmetry of the underlying graphene lattice. Subsequently, zinc oxide and alumina ALD precursors are shown to preferentially react with the functional moieties of PCDA, resulting in templated oxide nanostructures. The retention of the original one-dimensional molecular ordering following ALD is dependent on the chemical reaction pathway and the stability of the monolayer, which can be enhanced via ultraviolet-induced molecular cross-linking.
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http://dx.doi.org/10.1021/nl4000932DOI Listing
September 2014

Fundamental performance limits of carbon nanotube thin-film transistors achieved using hybrid molecular dielectrics.

ACS Nano 2012 Aug 18;6(8):7480-8. Epub 2012 Jul 18.

Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.

In the past decade, semiconducting carbon nanotube thin films have been recognized as contending materials for wide-ranging applications in electronics, energy, and sensing. In particular, improvements in large-area flexible electronics have been achieved through independent advances in postgrowth processing to resolve metallic versus semiconducting carbon nanotube heterogeneity, in improved gate dielectrics, and in self-assembly processes. Moreover, controlled tuning of specific device components has afforded fundamental probes of the trade-offs between materials properties and device performance metrics. Nevertheless, carbon nanotube transistor performance suitable for real-world applications awaits understanding-based progress in the integration of independently pioneered device components. We achieve this here by integrating high-purity semiconducting carbon nanotube films with a custom-designed hybrid inorganic-organic gate dielectric. This synergistic combination of materials circumvents conventional design trade-offs, resulting in concurrent advances in several transistor performance metrics such as transconductance (6.5 μS/μm), intrinsic field-effect mobility (147 cm(2)/(V s)), subthreshold swing (150 mV/decade), and on/off ratio (5 × 10(5)), while also achieving hysteresis-free operation in ambient conditions.
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http://dx.doi.org/10.1021/nn302768hDOI Listing
August 2012

In-situ probe of gate dielectric-semiconductor interfacial order in organic transistors: origin and control of large performance sensitivities.

J Am Chem Soc 2012 Jul 5;134(28):11726-33. Epub 2012 Jul 5.

Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208-3113, USA.

Organic thin film transistor (OTFT) performance is highly materials interface-dependent, and dramatic performance enhancements can be achieved by properly modifying the semiconductor/gate dielectric interface. However, the origin of these effects is not well understood, as this is a classic "buried interface" problem that has traditionally been difficult to address. Here we address the question of how n-octadecylsilane (OTS)-derived self-assembled monolayers (SAMs) on Si/SiO(2) gate dielectrics affect the OTFT performance of the archetypical small-molecule p-type semiconductors P-BTDT (phenylbenzo[d,d]thieno[3,2-b;4,5-b]dithiophene) and pentacene using combined in situ sum frequency generation spectroscopy, atomic force microscopy, and grazing incidence and reflectance X-ray scattering. The molecular order and orientation of the OTFT components at the dielectric/semiconductor interface is probed as a function of SAM growth mode in order to understand how this impacts the overlying semiconductor growth mode, packing, crystallinity, and carrier mobility, and hence, transistor performance. This understanding, using a new, humidity-specific growth procedure, leads to a reproducible, scalable process for highly ordered OTS SAMs, which in turn nucleates highly ordered p-type semiconductor film growth, and optimizes OTFT performance. Surprisingly, the combined data reveal that while SAM molecular order dramatically impacts semiconductor crystalline domain size and carrier mobility, it does not significantly influence the local orientation of the overlying organic semiconductor molecules.
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http://dx.doi.org/10.1021/ja3036493DOI Listing
July 2012

Mental illness related disparities in diabetes prevalence, quality of care and outcomes: a population-based longitudinal study.

BMC Med 2011 Nov 1;9:118. Epub 2011 Nov 1.

School of Population Health, The University of Western Australia, Crawley, Australia.

Background: Health care disparity is a public health challenge. We compared the prevalence of diabetes, quality of care and outcomes between mental health clients (MHCs) and non-MHCs.

Methods: This was a population-based longitudinal study of 139,208 MHCs and 294,180 matched non-MHCs in Western Australia (WA) from 1990 to 2006, using linked data of mental health registry, electoral roll registrations, hospital admissions, emergency department attendances, deaths, and Medicare and pharmaceutical benefits claims. Diabetes was identified from hospital diagnoses, prescriptions and diabetes-specific primary care claims (17,045 MHCs, 26,626 non-MHCs). Both univariate and multivariate analyses adjusted for socio-demographic factors and case mix were performed to compare the outcome measures among MHCs, category of mental disorders and non-MHCs.

Results: The prevalence of diabetes was significantly higher in MHCs than in non-MHCs (crude age-sex-standardised point-prevalence of diabetes on 30 June 2006 in those aged ≥20 years, 9.3% vs 6.1%, respectively, P < 0.001; adjusted odds ratio (OR) 1.40, 95% CI 1.36 to 1.43). Receipt of recommended pathology tests (HbA1c, microalbuminuria, blood lipids) was suboptimal in both groups, but was lower in MHCs (for all tests combined; adjusted OR 0.81, 95% CI 0.78 to 0.85, at one year; and adjusted rate ratio (RR) 0.86, 95% CI 0.84 to 0.88, during the study period). MHCs also had increased risks of hospitalisation for diabetes complications (adjusted RR 1.20, 95% CI 1.17 to 1.24), diabetes-related mortality (1.43, 1.35 to 1.52) and all-cause mortality (1.47, 1.42 to 1.53). The disparities were most marked for alcohol/drug disorders, schizophrenia, affective disorders, other psychoses and personality disorders.

Conclusions: MHCs warrant special attention for primary and secondary prevention of diabetes, especially at the primary care level.
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http://dx.doi.org/10.1186/1741-7015-9-118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3215928PMC
November 2011

The impact of mental illness on potentially preventable hospitalisations: a population-based cohort study.

BMC Psychiatry 2011 Oct 10;11:163. Epub 2011 Oct 10.

School of Population Health, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.

Background: Emerging evidence indicates an association between mental illness and poor quality of physical health care. To test this, we compared mental health clients (MHCs) with non-MHCs on potentially preventable hospitalisations (PPHs) as an indicator of the quality of primary care received.

Methods: Population-based retrospective cohort study of 139,208 MHCs and 294,180 matched non-MHCs in Western Australia from 1990 to 2006, using linked data from electoral roll registrations, mental health registry (MHR) records, hospital inpatient discharges and deaths. We used the electoral roll data as the sampling frame for both cohorts to enhance internal validity of the study, and the MHR to separate MHCs from non-MHCs. Rates of PPHs (overall and by PPH category and medical condition) were compared between MHCs, category of mental disorders and non-MHCs. Multivariate negative binomial regression analyses adjusted for socio-demographic factors, case mix and the year at the start of follow up due to dynamic nature of study cohorts.

Results: PPHs accounted for more than 10% of all hospital admissions in MHCs, with diabetes and its complications, adverse drug events (ADEs), chronic obstructive pulmonary disease (COPD), convulsions and epilepsy, and congestive heart failure being the most common causes. Compared with non-MHCs, MHCs with any mental disorders were more likely to experience a PPH than non-MHCs (overall adjusted rate ratio (ARR) 2.06, 95% confidence interval (CI) 2.03-2.09). ARRs of PPHs were highest for convulsions and epilepsy, nutritional deficiencies, COPD and ADEs. The ARR of a PPH was highest in MHCs with alcohol/drug disorders, affective psychoses, other psychoses and schizophrenia.

Conclusions: MHCs have a significantly higher rate of PPHs than non-MHCs. Improving primary and secondary prevention is warranted in MHCs, especially at the primary care level, despite there may be different thresholds for admission in people with established physical disease that is influenced by whether or not they have comorbid mental illness.
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http://dx.doi.org/10.1186/1471-244X-11-163DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3201897PMC
October 2011

Solution-deposited organic-inorganic hybrid multilayer gate dielectrics. Design, synthesis, microstructures, and electrical properties with thin-film transistors.

J Am Chem Soc 2011 Jul 10;133(26):10239-50. Epub 2011 Jun 10.

Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.

We report here on the rational synthesis, processing, and dielectric properties of novel layer-by-layer organic/inorganic hybrid multilayer dielectric films enabled by polarizable π-electron phosphonic acid building blocks and ultrathin ZrO(2) layers. These new zirconia-based self-assembled nanodielectric (Zr-SAND) films (5-12 nm thick) are readily fabricated via solution processes under ambient atmosphere. Attractive Zr-SAND properties include amenability to accurate control of film thickness, large-area uniformity, well-defined nanostructure, exceptionally large electrical capacitance (up to 750 nF/cm(2)), excellent insulating properties (leakage current densities as low as 10(-7) A/cm(2)), and excellent thermal stability. Thin-film transistors (TFTs) fabricated with pentacene and PDIF-CN(2) as representative organic semiconductors and zinc-tin-oxide (Zn-Sn-O) as a representative inorganic semiconductor function well at low voltages (<±4.0 V). Furthermore, the TFT performance parameters of representative organic semiconductors deposited on Zr-SAND films, functionalized on the surface with various alkylphosphonic acid self-assembled monolayers, are investigated and shown to correlate closely with the alkylphosphonic acid chain dimensions.
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http://dx.doi.org/10.1021/ja202755xDOI Listing
July 2011

Seeding atomic layer deposition of high-k dielectrics on epitaxial graphene with organic self-assembled monolayers.

ACS Nano 2011 Jun 12;5(6):5223-32. Epub 2011 May 12.

Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.

The development of high-performance graphene-based nanoelectronics requires the integration of ultrathin and pinhole-free high-k dielectric films with graphene at the wafer scale. Here, we demonstrate that self-assembled monolayers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) act as effective organic seeding layers for atomic layer deposition (ALD) of HfO(2) and Al(2)O(3) on epitaxial graphene on SiC(0001). The PTCDA is deposited via sublimation in ultrahigh vacuum and shown to be highly ordered with low defect density by molecular-resolution scanning tunneling microscopy. Whereas identical ALD conditions lead to incomplete and rough dielectric deposition on bare graphene, the chemical functionality provided by the PTCDA seeding layer yields highly uniform and conformal films. The morphology and chemistry of the dielectric films are characterized by atomic force microscopy, ellipsometry, cross-sectional scanning electron microscopy, and X-ray photoelectron spectroscopy, while high-resolution X-ray reflectivity measurements indicate that the underlying graphene remains intact following ALD. Using the PTCDA seeding layer, metal-oxide-graphene capacitors fabricated with a 3 nm Al(2)O(3) and 10 nm HfO(2) dielectric stack show high capacitance values of ∼700 nF/cm(2) and low leakage currents of ∼5 × 10(-9) A/cm(2) at 1 V applied bias. These results demonstrate the viability of sublimated organic self-assembled monolayers as seeding layers for high-k dielectric films in graphene-based nanoelectronics.
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http://dx.doi.org/10.1021/nn201414dDOI Listing
June 2011