Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session B45: Semiconductor Surfaces, Films, and Nanostructures |
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Sponsoring Units: DCMP Chair: Elena Cimpoiasu, United States Naval Academy Room: BCEC 211 |
Monday, March 4, 2019 11:15AM - 11:27AM |
B45.00001: Uranium Surface Nitridation and Its Application in Uranium Passivation Kezhao Liu, Qifa Pan, Ruilong Yang, Kangwei Zhu, Xiaofang Wang, Jing Liu, Yin Hu Uranium plays a significant role in the nuclear industry. However, it is chemically active and very easy to be oxidized and corroded in the environment. Therefore, it is very important to study the corrosion and oxidation behavior of uranium metal and to find the appropriate anti-corrosion treatment technology. |
Monday, March 4, 2019 11:27AM - 11:39AM |
B45.00002: The Experimental Research on Oxidation Kinetics of Uranium Surface Treated by Laser Nitriding Yin Hu, Haibo Li, Jianwei Qin, Xiaofang Wang, Yongbin Zhang, Yanzhi Zhang, Kezhao Liu The oxidation kinetics of uranium surface treated by pulsed laser nitriding,which has been proved to be protective during storing at room temperature in the atmosphere, were studied using reflectance spectroscopy and X-ray diffraction (XRD) technique. |
Monday, March 4, 2019 11:39AM - 11:51AM |
B45.00003: Metallic surface states induced perturbation in electron affinity of epitaxial AlN films Monu Mishra, Govind Gupta We report the influence of metallic surface states induced alteration in the electron affinity of epitaxial AlN films. A systematic and in-depth photoemission analysis of epitaxial AlN films grown under different conditions by plasma-assisted molecular beam epitaxy system was performed. The presence of remnant metallic aluminium and native oxide (with different contribution) on the surface (and sub-surface) perturbed the surface chemistry and electronic structure of the grown films. However, no significant change in the morphology of the films was witnessed. It was observed that these metallic states pin the Fermi Level (FL) near valence band edge and lead to the reduction of electron affinity (EA). The metallic states initiate charge transfer from surface to bulk which induces change in the surface and interface dipoles strength. Therefore, the EA of the films varied between 0.6 - 1.0 eV due to the variation in contribution of metallic states and native oxide. However, the surface barrier height (SBH) increased (4.2 - 3.5 eV) adversely due to the availability of donor-like surface states in metallic aluminium rich films. |
Monday, March 4, 2019 11:51AM - 12:03PM |
B45.00004: Plasma Nitriding and Carbon Assisted Plasma Nitriding of Tantalum Ruilong Yang, Kangwei Zhu Plasma nitriding and carbon assisted plasma nitriding of tantalum were carried out. The nitride layer prepared with pure N2 is composed of TaN and Ta2N with hexagonal structure and a nitriding depth of 500 nm. The carbon assisted plasma nitriding process was carried out with the addition of methane into N2 gas (5% and 10% in volume ratio) as carbon source. The carbonitride films were found to be composed of a larger number of micro-crystals nearly 1 um in size, with a uniform and compact surface, as revealed by scanning electron microscopy (SEM). TaC1-xNx with a face-centered-cubic (FCC) and Ta2C1-xNx with hexagonal structure were identified by X-ray diffraction(XRD). The auger electron spectroscopy (AES) depth profiles reveal that the diffusion depth of nitrogen increased from 500 nm in nitride film to 1.5-3 μm in carbonitride films. The high solubility of nitrogen in tantalum carbide might be the main cause that promoted the diffusion of nitrogen during the plasma carbonitriding process. |
Monday, March 4, 2019 12:03PM - 12:15PM |
B45.00005: Atomic layer epitaxy of aluminum nitride: Unraveling the connection between hydrogen plasma and carbon contamination Steven Erwin, John Lyons Atomistic control over the growth of semiconductor thin films, such |
Monday, March 4, 2019 12:15PM - 12:27PM |
B45.00006: The Effect of Embedded Ag versus Au Nanoparticles on the Photovoltaic Conversion Efficiency in CdTe/CdS Thin Films Olivia Rodgers, Yunis Yilmaz, Selam Woldegerima, Mehmet Alper Sahiner The addition of metal nanoparticles to photovoltaic cells creates the possibility of improving cell efficiency and reducing production costs. Impressive improvements in photovoltaic conversion efficiencies were found in CdTe/CdS/ITO (indium tin oxide) based solar cells with the addition of embedded Ag nanoparticles. Ag nanoparticles were deposited between the CdS and CdTe layers through pulse laser deposition method. Structural and electrical characterizing was achieved using x-ray diffraction ellipsometry, scanning electron microscopy, energy dispersive x-ray diffraction, atomic force microscopy and Keithley source meter photovoltaic measurement set. Previous research revealed that the photovoltaic conversion efficiency exhibits sensitive dependence on the size and the particle density of the embedded Ag nanoparticles. This work focuses on identifying at what amount of Ag deposition time will yield maximum efficiency. A similar study was conducted using Au nanoparticles deposited with the same parameters. An assessment of the differences between Ag and Au nanoparticles size and density was done. More importantly, a comparison on the photovoltaic conversion efficiency in thin films with Au versus Ag nanoparticles will be discussed. |
Monday, March 4, 2019 12:27PM - 12:39PM |
B45.00007: Non-classical effects of extrinsic doping on Au quantum wires Zamin Mamiyev, Christoph Tegenkamp, Herbert Pfnür Self-assembled atomic wires on vicinal Si(hhk) surfaces are very versatile quasi-1D objects to study their interaction with the embedding environment [1,2]. Here we employ plasmon spectroscopy to study the response of Au-induced quantum wires to extrinsic doping by hydrogen adsorption. Si(553) and Si(557) surfaces are used as templates, which form double and single atomic strands per terrace upon evaporation of 0.48ML and 0.19ML of Au, respectively. |
Monday, March 4, 2019 12:39PM - 12:51PM |
B45.00008: Kinetics of a Solid-Solid Charge Transfer Reaction Ying Pan, Dimos Poulikakos, Nate J. Cira, Ye Tao We present an analysis of the kinetics of charge transfer at a solid-solid interface. The study was enabled by measuring the conductance of ultra-thin, fully suspended single-crystalline silicon nanowires across 7 orders of magnitude with a detection sensitivity of order single event over a 10^3 μm^2 reaction area. We find that a classic, first-order process is unable to capture the reaction progress and propose a new kinetic model based on a continuum of reactant geometries inherently present at typical solid-solid interfaces. The new model captures the kinetic manifestation of heterogeneity in a single, global rate constant. Quantitative agreement with data and an analysis of the parameters suggest that this model may be generally applicable to charge transfer at solid-solid interfaces. |
Monday, March 4, 2019 12:51PM - 1:03PM |
B45.00009: Growth of CuMnAs by molecular beam epitaxy: Control over structure and properties Filip Krizek, Zdenek Kaspar, Martin Brajer, Jan Zubáč, Aliaksei Vetushka, João Godinho, Dominik Kriegner, Zbyněk Šobán, Richard Champion, Peter Wadley, Kamil Olejník, Tomas Jungwirth, Vít Novák Antiferromagnetic materials have recently attracted significant attention in connection with the discovery of a way to electrically manipulate their magnetic ordering [1]. Especially magnetic reorientation of tetragonal CuMnAs layers by electrical current has potential for future industrial applications of antiferromagnetic memories [2]. We will present a detailed strategy for growth of CuMnAs by molecular beam epitaxy, while focusing on crystallinity of the grown thin films. These typically contain different densities of specific structural defects, which likely influence their electrical and magnetic properties. This, together with ageing in ambient conditions and siginificant surface roughness complicates practical implementations of CuMnAs thin films. We will show how careful tuning of the growth conditions improves the structural properties of the material and how growth parameters are reflected in conductivity, Hall coefficient and effectivity of Néel vector manipulation. |
Monday, March 4, 2019 1:03PM - 1:15PM |
B45.00010: Preparation of epitaxial ScF3 thin films – a negative thermal expansion material Amani Jayakody, Zhiwei Zhang, Zhihai Zhu, Hope R Whitelock, Joseph I Budnick, Jason Hancock, Barrett Otis Wells Scandium trifluoride (ScF3) is known for a pronounced negative thermal expansion over a wide range of temperature, from 10 K to 1100 K. The structure of ScF3 can be described as an ABX3 perovskite with an empty A-site. Growing films of ScF3 allows for tuning the lattice constant, the thermal expansion, and the construction of devices based upon differential thermal expansion. We have investigated the growth of ScF3 films on oxide and fluoride substrates using pulsed laser deposition (PLD). There are several unique features to this material that pose challenges for PLD growth: poor adhesion of ScF3 pressed powder targets, a narrow stability range, and complex interfaces between fluorides and oxides. Nonetheless, we have found growth routes for producing films with very good epitaxy and narrow mosaic. This report describes the growth and initial characterization of high quality ScF3 films. |
Monday, March 4, 2019 1:15PM - 1:27PM |
B45.00011: Atom-Scale Dynamics in Surface-Catalyzed Nitrogen Incorporation in Epitaxial Growth of Gallium Nitride Kieu My Bui, Mauro Boero, Kenji Shiraishi, Atsushi Oshiyama GaN is a principal material in optoelectronics and now emerging as a key material in power electronics [1]. One of the challenges to the device fabrication is the formation of higher quality thin films of GaN, that is not yet achieved to date. We here report density-functional total-energy electronic-structure calculations [2] and Car-Parrinello Molecular Dynamics simulations [3] that clarify atom-scale mechanisms of N incorporation in GaN bonding network during Metal Organic Vapor Phase Epitaxy (MOVPE). The results obtained for the first time in this work include (i) that Ga atoms on the growing surface are extremely mobile at the growth temperature, forming a liquid-like phase, and (ii) that ammonia NH3 and its related species NHx intervene into the weak Ga-Ga bond on the growing surface spontaneously or with surprisingly small energy barriers. This finding leads to a conclusion that the epitaxial growth is a reaction enhanced by the existence of weak surface Ga-Ga bonds. Computations have been performed with our own real-space code highly tuned and scalable on for massively parallel HPC architectures. |
Monday, March 4, 2019 1:27PM - 1:39PM |
B45.00012: A SCAN+rVV10 study of Thiophene adsorption on Ir, Rh, and Ag (100) Abdelkader Kara, Walter Malone Using density functional theory we study the adsorption of thiophene on Ir, Rh, and Ag(100) surfaces. Specifically, we employ the meta-GGA SCAN+rVV10 functional. To assess the performance of SCAN+rVV10 we compared our SCAN+rVV10 results to results calculated using the popular van der Waals (vdW) inclusive GGA functional, optB88-vdW. To find the equilibrium adsorption geometry, we explore a variety of adsorption sites with the plane of the molecule both parallel and perpendicular to the surface. Along with the equilbirum adsorption geometry we present various geometric and electronic properties of the adsorbate/substrate systems such as adsorption energy, adsorption height, buckling of the first layer of the substrate, charge transfer to the molecule, change in the width and center of the surface’s d-band, and change in the surface’s work funcntion. We find over all surfaces both functionals predict thiophene to adsorb parallel to the surface. Besides the consensus on a flat adsorption site, generally we find SCAN+rVV10 and optB88-vdW to agree very well concerning thiophene adsorption over Ag(100) and moderately well concerning thiophene adsorption over Rh(100) and Ir(100). |
Monday, March 4, 2019 1:39PM - 1:51PM |
B45.00013: A Density Functional Theory Study of the Adsorption of Thiophene on Transition Metal Surfaces Walter Malone, Abdelkader Kara, William Kaden Using density functional theory we study the adsorption of thiophene (C4H4S) over a wide variety of transition metal surfaces including V, Cr, Ta, W, Mo, Nb, Co, and Al(100). To account for long range dispersion we utilize the van der Waals (vdW) inclusive optB88-vdW functional. We explore several adsorption sites with the plane of the molecule either parallel or perpendicular to the surface. We find that on all of the surfaces thiophene prefers to bond in a flat configuration. Along with the equilibrium adsorption sites, we present a variety of other properties of the substrate/adsorbate system including adsorption energy, adsorption height, C-S bond lengths, and charge transfer to the molecule. Using the previously mentioned geometric and electronic data we find the thiophene/substrate interaction increases moving from right to left on the periodic table. Focusing specifically on charge transfer to the thiophene molecule, we find a strong correlation between the charge transfer to thiophene’s S atom and the thiophene/substrate interaction, which we build into a descriptor for the surfaces’ reactivity. |
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