Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session X17: Thin Film and Surface Applications |
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Sponsoring Units: DCMP Chair: Alexandra Curtin, NIST Boulder Room: LACC 306A |
Friday, March 9, 2018 8:00AM - 8:12AM |
X17.00001: Abstract Withdrawn
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Friday, March 9, 2018 8:12AM - 8:24AM |
X17.00002: Optical properties of a Portable Colloidal Array Meneka Banik, Rabibrata Mukherjee Colloidal crystals with hexagonal closed packed (HCP) ordering can be obtained on a planar surface by simple spin coating technique, in presence of trace amount of surfactant. By spin coating on a topographically patterned substrate we can also obtain ordered colloidal structures with non-HCP ordering. It is however not possible to obtain a non-HCP ordering on a flat substrate without any chemical or topographic patterning. We have developed a method by which we can overcome this problem, by fabricating the array on a patterned UVO degradable polymer layer and subsequently transfering the array on to another substrate. The flexible nature of the master makes it possible to transfer the array on to non-planar substrates. Our proposed method allows the colloidal structures to be transported across substrates irrespective of their surface energy, wettability or morphology. The transmittance data of the transferred non-HCP colloidal arrays on glass show wide-spectrum anti-reflectivity, yielding about 99.5% transmission over the entire spectral region between 450 and 1700 nm. Reflectance of glass is also reduced to 3.3% over the entire spectral region. |
Friday, March 9, 2018 8:24AM - 8:36AM |
X17.00003: Nano-engineering of cesiated chromium surfaces for tailoring electron absorption above work function Andre Luis Fernandes Cauduro, Jared Schwede, Andreas Schmid Precise work function measurements are important for a variety of physical applications, including control of charge injection/extraction to/from surface adsorbates1 and thermionics2. It is particularly interesting to understand the role of the substrate on the electron reflectivity as function of energy as well as on the work function drop when the substrate is exposed to surface adsorbates like alkali metals (e.g. Cs). In this study, we use low-energy electron microscopy in mirror electron microscopy mode to measure the electron energy dependence of electron reflectivity. By comparing with computed band diagrams, we show how these spectra characterize the surface electronic states of cesiated surfaces. Absorbed current measurements, as function of the electron landing energy, of chromium films oriented on (110) and on (100) planes are compared with their nano-crystalline counterpart. Interestingly, we show that increasing the degree of disorder of the Cr films reduces electron reflectivity independently of the electron energy above the vacuum level. |
Friday, March 9, 2018 8:36AM - 8:48AM |
X17.00004: Resistive Switching Mechanisms in Silica Nanoparticle Composites Mon-shu Ho, Yu-Li Chen, Pei-Fang Chung, Wen-Jay Lee In this work, we investigate the resistive switching properties of three ReRAM models based on heterojunction structures of Pt/SiOx nanoparticles(NP)/Si, Cu/SiOx NP/Si, and Si/SiOx NP/Si, in which dielectric layers of the silica nanoparticles present dislocations at bicrystal interfaces. Our analysis of the electrical, thermal, and structural aspects of resistive switching revealed that switching behavior depends on the material properties and electrical characteristics of the switching layers, as well as the metal electrodes and the interfacial structure of grains within the dielectric materials. We also determined that the application of an external electric field at grain boundaries is crucial to resistive switching behavior. Molecular dynamics simulations revealed the mechanism underlying resistance switching. Our results indicate that this behavior is influenced by variations in the atomic structure and electronic properties, at the atomic length scale and picosecond time scale. Our findings provide useful reference for the future development and optimization of materials used in this technology. |
Friday, March 9, 2018 8:48AM - 9:00AM |
X17.00005: Superhydrophobic nanocomposite coating with functionalized SiO2 nanoparticles embedded in a hybrid matrix of ZnO RAJAT SRIVASTAVA, Abhijit Mishra There has been an exponential growth in the development of superhydrophobic coatings over the last few decades. Superhydrophobic surfaces developed worldwide consist of complex structures with adequate surface roughness depicting contact angles (>1500) at the glass-water interface. Such surfaces are fragile having poor abrasion resistance. In this work, superhydrophobic surfaces were prepared by coating a layer of functionalized SiO2 nanoparticles embedded in a hybrid inorganic matrix of ZnO nanocrystallites on a glass surface. Specific silanes were used as functionalizing agents instead of fluorine thereby making the coating environment-friendly. The nanocomposite coating consists of a complex solution of (zinc acetate dihydrate) mixed with SiO2 nanoparticle dispersion. Hydrophilic sites attached with ZnO nanocrystallites helped the coating in adhering to the hydroxyl groups present on the glass surface which improved its abrasion resistance. Functionalized SiO2 nanoparticles formed a composite network with the ZnO nanocrystallites on the glass surface which roughened the surface to give the desired superhydrophobicity. This route allowed development of a superhydrophobic surface exhibiting contact angles (>1500) along with increased resistance to mechanical abrasion. |
Friday, March 9, 2018 9:00AM - 9:12AM |
X17.00006: Measuring the Unoccupied Band Structure with ~10nm Lateral Resolution Johannes Jobst, Jaap Kautz, Jesse Balgley, Eugene Krasovskii, Cory Dean, Rudolf Tromp, Sense Jan Van der Molen The properties of any material are fundamentally determined by its electronic band structure. But, while the occupied bands below the Fermi level can be routinely measured, it is remarkably difficult to characterize the empty part of the band structure experimentally. We introduce angle-resolved reflected-electron spectroscopy (ARRES), a technique to measure these bands [J. Jobst et al. Nature Commun. 6, 8926 (2015)]. It relies on the dependence of the reflectivity of low-energy electrons on their incidence angle on the sample and their kinetic energy and has a spatial resolution 10nm. We use ARRES to study the unoccupied band structure of van der Waals crystals – custom-built stacks of two-dimensional materials, such as graphene, boron nitride, or transitionmetal dichalcogenides. We show that ARRES can shed light on the interaction between electronic states of individual layers [J, Jobst, et al. Nature Commun. 7, 13621 (2016)], an important step towards tailoring the properties of Van der Waals crystals in a LEGO-like fashion. |
Friday, March 9, 2018 9:12AM - 9:24AM |
X17.00007: A Molecular Dynamics Study on the Orientation Dependence of Nano-Scale Scratching of Sapphire Woo Kyun Kim
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Friday, March 9, 2018 9:24AM - 9:36AM |
X17.00008: Tailoring the Properties of Al-doped LiCoO2 Surfaces Liang Hong, Linhua Hu, Juan Garcia, Hakim Iddir, Serdar Ogut, Jordi Cabana, Robert Klie Undesired reactions at electrode/electrolyte interfaces impose challenges in the durability of Li-ion battery. Core−shell heterostructures at the nanocrystal level offer opportunities for improving the functionality of the electrode by precise control of the interfacial structures and electronic properties. This ability is demonstrated with the compositional and structural tailoring of passivating layers based on Al3+, grown conformally onto LiCoO2 nanoplates, using thermal treatments. They result in the heterostructures from core−shell LiCoO2/Al2O3 to LiCo1-xAlxO2 gradient structures composed by an Al-rich outer layer on a Co-rich core. Scanning transmission electron microscopy and X-ray adsorption spectroscopy are performed to characterize the Al-doped LiCoO2 surface structures. First-principles density functional theory calculations are further performed to investigate the Co 3d spin states and O 2p states at different LiCo1-xAlxO2 surfaces. The presence of the surface Co high spin states, combined with the structural epitaxy and the Al/Co ratio at the surfaces, is found to be critical to obtain the best electrode properties and electrode/electrolyte interface stabilization. |
Friday, March 9, 2018 9:36AM - 9:48AM |
X17.00009: Amorphous CaAlOx Thin Film as Transparent Conducting Oxide So Hee SIM, Kyeong Tae Kang, Sang A Lee, Sangyun Lee, Jong-Seong Bae, Seulki Roh, Hiroki Taniguchi, Tuson Park, Jungseek Hwang, Woo Seok Choi Transparent conducting oxides (TCO) has been an important constituent in modern opto-electronic devices. To satisfy competing demands, approaches of increasing carrier concentration in a wide-bandgap semiconductor through heavy doping, in case of tin-doped indium oxide, have been employed. Based on the various degrees of freedom in fabrication, e.g. chemical composition, crystallography and epitaxial strain, diverse methods for engineering of transparent window and conductance of TCO have been reported. The modulation of orbital state involved in the chemical state of thin film can give rise to high conductivity nature even in amorphous material which could be in good use as flexible electronics. |
Friday, March 9, 2018 9:48AM - 10:00AM |
X17.00010: Experimental Investigations Toward Improving Thermal Noise in Amorphous Coatings for Advanced LIGO Gabriele Vajente Coating thermal noise is one of the fundamental limits to the sensitivity of the current and future gravitational wave detectors in their most sensitive region between 40 and 100 Hz. Presently, silica and titania doped tantala are used as the low and high refractive index material respectively in the multilayer, amorphous dielectric coatings used in Advanced LIGO. Our goal is to reduce coating thermal noise, opening the road to a similar improvement in the gravitational wave detector sensitivities at all frequencies. In this talk we present the status of current experimental efforts aimed at reducing the thermal noise of amorphous coatings, in the framework of the stable glass hypothesis. In particular, we discuss the effect of deposition at elevated substrate temperature on the mechanical properties of pure tantala thin films. |
Friday, March 9, 2018 10:00AM - 10:12AM |
X17.00011: Strain-Induced Raman Shifts Due to Ice Adhesion Samuel Pasco, Joseph Murphy, Teresa Reilly, John Ackerman, Vladimir Alvarado, William Rice When ice is formed on a material, it creates a strain proportional to the adhesive strength between the ice and substrate. In order to quantify this adhesion, we use Raman spectroscopy to measure the vibrational modes of various materials with and without ice. Carbon nanotubes, gold nanoparticles, and Raman-tagged gold nanoparticles were used to isolate effects at the interface where the largest strain occurs. The temperature of the substrate at the interface was measured using the intensity ratio of the Stokes and anti-Stokes shifts, allowing us to account for the temperature dependence of the vibrational modes. Preliminary data on silicon and aluminum suggests that ice causes the Raman modes to shift to higher energies. This optical data, calibrated with mechanical measurements, provides a non-destructive technique to measure adhesive strength. |
Friday, March 9, 2018 10:12AM - 10:24AM |
X17.00012: Electronic Structure Dependent Electrocatalytic Activity in Perovskite Ruthenate Epitaxial Thin Films Sang A Lee, Jegon Lee, Seokjae Oh, Suyoun Lee, Jong-Seong Bae, Won Chegal, Mangesh Diware, Sungkyun Park, Taekjib Choi, Woo Seok Choi Defect engineering in transition metal oxides provides facile ways to control the crystal and electronic structures which leads to a modification of physical and chemical properties of interest. In particular, perovskite Ruthenates are interesting model systems where both A- and B-site ionic concentration can be modified through the epitaxial film growth control, to further tailor the electronic, magnetic, and structural properties via strong coupling among different degrees of freedom [1]. In this presentation, we show that a strong correlation exists even between the physical and chemical properties of the epitaxial ARuO3 (A = Sr and Ca) thin films. Particularly, the electrocatalytic activity was found to be strongly dependent on the changes in the electronic structure of the epitaxial ARuO3 thin films induced by elemental vacancy via pulsed laser epitaxy. The strong hybridization between the Ru 4d and O 2p states critically influence the oxygen evolution reaction, providing an activity descriptor for the electrochemical activity [2]. We believe that our results help to understand the fundamental correlation between the electronic structure and the catalytic reaction. |
Friday, March 9, 2018 10:24AM - 10:36AM |
X17.00013: The Effect of Embedded Ag Nanoparticle on the Photovoltaic Conversion Efficiency in CdTe/CdS Thin Films Olivia Rodgers, Anthony Viscovich, Yunis Yilmaz, Mehmet Sahiner The addition of Ag nanoparticles to photovoltaic cells may improve cell efficiency while reducing production costs. The addition of embedded Ag nanoparticles in CdTe/CdS/ITO (indium tin oxide) base solar cells have been investigated in this study. Ag nanoparticles were deposited between the CdS and CdTe layers through pulse laser deposition method onto ITO coated glass. This research investigates how the inclusion of Ag nanoparticles will affect light scattering at the interfaces and whether the different size and density of Ag nanoparticles will have a positive effect on the overall photovoltaic conversion efficiency of the thin films solar cells. In order to structurally and electrically characterize the silver nanoparticles added efficiency to the cells x-ray diffraction ellipsometry, scanning electron microscopy, energy dispersive x-ray diffraction, atomic force microscopy and Labview assisted Keithley source meter photovoltaic measurement set were used. The photovoltaic conversion efficiency exhibits a sensitive dependence on the size and the particle density of the embedded Ag nanoparticles. At what amount of Ag will there be the greatest electrical efficiency and at what amount of Ag the electrical efficiency will begin to plateau will also be discussed. |
Friday, March 9, 2018 10:36AM - 10:48AM |
X17.00014: Optimized pore geometry on silicon substrate surface for long time phospholipid cell membrane stability Marcelo Cisternas, Nicolas Moraga, Rodrigo Catalan, Maria Retamal, Diego Diaz, Tomas Corrales, Tomas Perez-Acle, Marco Soto-Arriaza, Patrick Huber, Birger Seifert, Ulrich Volkmann The study of artificial membranes composed by phospholipid bilayer on solid substrates has become a relevant way to gain insights into the physical behavior of cell membranes. In this work, using very high resolution ellipsometry (VHRE), was studied the behavior of lipid bilayers of DPPC deposited from their gas phase on porous silicon (pSi) substrates with different pore sizes. The film thickness was controlled during deposition, in situ, with VHRE. In a first step, it was necessary to optimize the pore depth that permits to obtain a reproducible ellipsometric signal for the bare, clean substrate. In the next step, we studied the lipid bilayers formation over different pore diameters to achieve membranes, which are stable during an extended period of time (several days) after hydration. Using VHRE and Stray Light Intensity (SLI) measurements, we observed for some characteristic substrate geometries changes in thickness and roughness of the lipid bilayers, related to phase transitions as a function of temperature, according to the literature. |
Friday, March 9, 2018 10:48AM - 11:00AM |
X17.00015: Oxide heterostructure with 105 % electroresistance at room temperature Joseph Scola, Bruno Bérini Many strongly correlated electron systems host a metal-insulator transition (MIT). The possibility to trigger it with moderate external stimuli has drawn a lot of attention on these materials. Several ways have been put forward to trigger the MIT (electrical pulses, 2D confinement, heating, ionic electromigration) but the application of the phenomenon in devices is limited by the fact the transition temperature is often imposed by the system. |
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