Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session L51: Quantum dots and other nanostructuresFocus
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Sponsoring Units: DMP Chair: Dmitri Talapin, University of Chicago Room: LACC 511C |
Wednesday, March 7, 2018 11:15AM - 11:51AM |
L51.00001: Assembling colloidal quantum dots for materials properties and device performance Invited Speaker: Ted Sargent I will review advances in the materials physics and materials chemistry of solids built from colloidal quantum dots. I will discuss ways in which this progress has enabled progress in the performance of photodetectors, solar cells, light-emitting diodes, and lasers. |
Wednesday, March 7, 2018 11:51AM - 12:03PM |
L51.00002: Plasmonic Effects on Photobrightening in Cadmium-Selenide Quantum Dots David French, Madison Whitby, Stephen Bauman, Desalegn Tadesse Debu, Ahmad Darweesh, Joseph Herzog When quantum dots are exposed to certain wavelengths of light, they photoluminesce. The intensity of this photoluminescence can increase over time, a phenomenon known as photobrightening. The maximum value of the photoluminescence, as well as the rate of photobrightening, are related to the intensity of the excitation light. Metallic nanostructures can enhance this photoluminescence via plasmonic effects. Here, cadmium-selenide quantum dots have been combined with various gold nanostructures, including nanospheres, nanorods, and other structures, to study the enhancement of the rate of photobrightening. Dark-field spectroscopy has been used to determine the wavelengths with which the nanostructures will most readily interact, and photoluminescence has been utilized to find the actual rate of photobrightening. This research shows the relationship between structure and photobrightening rate for various structure shapes, sizes, and concentrations of quantum dots. |
Wednesday, March 7, 2018 12:03PM - 12:15PM |
L51.00003: Abstract Withdrawn
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Wednesday, March 7, 2018 12:15PM - 12:27PM |
L51.00004: Synthesis of nano-Ag with different morphologies by extraction of garlic (allium sativum) and onion (allium cebae); sol-gel via acrylamide and microwaves; and in solution of acetone, distilled water and ammonium hydroxide. Daphne Meixueiro, Elizabeth Chavira, Magali Ugalde, Rubi Vázquez, Yoxkín Estévez-Martínez, Martha Teresita Ochoa, Francisco Espinosa, Adriana Tejeda, Karla Eriseth Morales Reyes, Omar Novelo, Josué Romero-Ibarra, Carlos Quintanar, Saúl Hernández, Abelardo Ramírez Silver nano-crystals have exceptional optical, electrical, thermal and antibacterial properties. The purpose of studying three different methods of nano-Ag synthesis is to compare their morphologies. The first one uses two different solvents, nitrate and water, in garlic (allium sativum) and onion (allium cebae). The second one was sol-gel method, using polyacrylamide with microwaves. Finally, the third one studied the synthesis based on three different solutions of acetone, distilled water and ammonium hydroxide; via stirrer and an ultrasound obtained the nano-crystals solutions. |
Wednesday, March 7, 2018 12:27PM - 12:39PM |
L51.00005: Band Structure Engineering in C-doped Boron-Nitride Atomic-Layer Materials via Interlayer Interaction and Electron Correlation Susumu Saito, Taishi Haga, Yoshitaka Fujimoto We study the electronic properties of C-doped hexagonal boron-nitride (h-BN) atomic-layer materials in the framework of the density functional theory for utilizing them as next-generation nanoelectronics device mateirals. It has been shown that the strain effect as well as the curvature effect can modify the electronc band structure of h-BN atomic-layer materials. In the present work we first study the effect of the interlayer interaction in C-doped systems. It is found that, in the case of multiwall BN nanotubes, the ionization energy of the donor state can strongly depend on the radius and the chirality of the system. We next study the effect of multiple C-doping at B and N sites. Interestingly, the electronic structure of the system is found to depend strongly on the relative geometries of C dopants due to the interimpurity interaction and the electron correlation. In the case of C-doped BN nanotubes, these multiple-doping effects, combined with the curvature effect, can give rise to even the metallic electronic structure. |
Wednesday, March 7, 2018 12:39PM - 12:51PM |
L51.00006: Electronic Structure of Type-II InAs/GaSb Superlattices: a DFT+GW Study Zahra Taghipour, Ezad Shojaee, Sanjay Krishna Type-II InAs/GaSb strained layer superlattices (T2SLs) are promising candidates for mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) applications. Since the bandgap and the band topologies have direct implications on the functionality of electronic devices based on superlattices, it is essential to study the electronic properties of these complex structures. For this purpose, we have investigated the performance of the many-body perturbative method in the GW approximation, to our knowledge for the first time, to study the electronic structure of T2SLs. The structures considered in this study are (4,7), (6,7), (8,8), (10,8), and (10,10) superlattices, denoted by (monolayers of InAs, monolayers of GaSb). Our results predict bandgaps in good agreement with experimental data. The band structure and the electronic density of states, as well as the effective masses along in-plane and growth directions were calculated. Finally, the Bethe-Salpeter equation was used to investigate the absorption spectra of the selected structures. |
Wednesday, March 7, 2018 12:51PM - 1:03PM |
L51.00007: First Principles Calculations of the Stability of CdSe Nanoparticle Superlattices Sergio Mazzotti, Federico Giberti, Giulia Galli The periodic superlattice structure and the collective physical behavior of semiconductor nanoparticle (NP) solids are largely governed by the ground-state dipole moment1and polarizability of the NPs forming the lattice. We used plane wave Density Functional Theory (DFT) and the Qbox code2 to compute dipole moment and polarizability of CdSe clusters of different sizes3 and study the effect of NP interaction on these fundamental properties. We then used our results to derive an analytical model of the dipole moment and polarizability as a function of cluster distance. We employed our model to investigate the energy and stability of clusters in different superlattice structures. |
Wednesday, March 7, 2018 1:03PM - 1:15PM |
L51.00008: Understanding quantum transport in a Ge-Si semiconductor core-shell nanowire transistor Meghnath Jaishi, Ranjit Pati Semiconductor core-shell nanowires are one-dimensional radial heterostructures composed of different semiconductor material in the core and shell. Energy band offsets between the core and shell part provides a unique opportunity to modulate carrier transport in these nanowires making them ideal candidates for designing field effect transistors (FETs). Experimental measurements have shown high-performance behavior in a Ge-Si semiconductor core-shell nanowire FET (Xiang et al., Nature, 2006, v. 441, 489); the scaled transconductance and on current values in these transistors are reported to be three to four times higher than that of state-of-the-art MOSFETs. Key to understanding the high-performance behavior of this transistor requires a first principles approach that does not make any assumptions on the charge, electronic structure and potential profile of the device. Herein, using a quantum transport approach, we have unraveled the most probable tunneling pathway for electrons in a Ge–Si core-shell nanowire FET with orbital level spatial resolution (Jaishi et al., Nanoscale, 2017, v. 9, 13425) that explains the observed transistor characteristics. |
Wednesday, March 7, 2018 1:15PM - 1:27PM |
L51.00009: Band structure of borophene Lok Lew Yan Voon, Morten Willatzen, Mathias Jensen Borophene is one of the latest elemental two-dimensional material realized experimentally [Mannix et al., Science 350, 1515 (2015); Feng et al., PRL 118, 096401 (2017)]. The band structure of the 8-Pmmn structure has been studied using ab initio techniques, revealing the presence of Dirac cones and ionicity in the bonds [Lopez-Bezanilla and Littlewood, PRB 93, 241405 (R) (2016)]. We present a k.p theory of the band structure in order to reveal electronic properties determined by symmetry, including in the presence of external perturbations such as strain and electric and magnetic fields. Comparison to phosphorene [ L. C. Lew Yan Voon, A. Lopez-Bezanilla, J. Wang, Y. Zhang and M. Willatzen, New J. Phys. 17, 025004 (2015)], another orthorhombic two-dimensional material, is given. |
Wednesday, March 7, 2018 1:27PM - 1:39PM |
L51.00010: Modification of The Chemisorption Properties of Epitaxial Delafossite CuFeO2 thin films by substituting Fe for Ga in the Crystal Structure Alejandro Cabrera, Susana Rojas, Toyanath Joshi, Qiang Wang, Mikel Holcomb, David Lederman Films of CuFe0.75Ga0.25O2 were grown over sapphire substrates in high vacuum using a pulsed laser deposition technique. The films were made alternating deposition of CuFeO2 and CuGaO2 in a ratio 3/1 and the films are terminated in CuFeO2. Surface of the films were inspected with X-ray and UV photoelectron spectroscopy. Adsorption of CO2 and H2O was studied by a thermal program desorption technique (TPD). |
Wednesday, March 7, 2018 1:39PM - 1:51PM |
L51.00011: Robust Resistive Memory Devices Using Solution-Processable Metal-Coordinated Azo-aromatics Sreetosh Goswami, Thirumalai Venkatesan Non-volatile memories will play a decisive role in the next generation of digital technology. Flash memories are currently the key player in the field, yet they fail to meet the commercial demands of scalability and endurance. Resistive memory devices, and in particular memories based on low-cost, solution-processable and chemically tunable organic materials, are promising alternatives explored by the industry. However, to date, they have been lacking the performance and mechanistic understanding required for commercial translation. Here we report a resistive memory device based on a spin-coated active layer of a transition-metal complex, which shows high reproducibility (~350 devices), fast switching (<30 ns), excellent endurance (~1012 cycles), stability (>106 s) and scalability (down to ~ 60 nm2). In-situ Raman and UV-Vis spectroscopy alongside spectroelectrochemistry and quantum chemical calculations demonstrate that the redox state of the ligands determines the switching states of the device whereas the counterions control the hysteresis. This insight may accelerate the technological deployment of organic resistive memories [1]. |
Wednesday, March 7, 2018 1:51PM - 2:03PM |
L51.00012: Blue Emission from CsPbBr3 Quantum Dots for Light-Emitting Diodes Preston Vargas, Gopi Adhikan, August Bont, Hongyang Zhu, Peifen Zhu Lighting technology has is on the verge of bringing true white-emission LEDs into commercial use, but there are a few factors preventing widespread adoption of quantum dot LED technology over YAG phosphors, not the least of which is production cost. Lead-halide perovskite QDs are a leading choice for QDLED manufacture because they have become efficient in recent years. In previous synthesis processes for CsPbX3 quantum dots, the main focus has been on product efficiency, and not so much on production efficiency. This practice has so far produced unnecessarily complex synthesis processes which can be greatly simplified via removing unneeded chemicals and considering alternate sources for others. In this presentation I will go over a new method to produce CsPbBr3 quantum dots. This method is so simple that it requires no equipment other than a heat source and a centrifuge to produce quantum dots that can have emissions in the blue range. This process is also completely scalable in manufacture, making this synthesis method a contender for processes that would be used in industrial manufacture. |
Wednesday, March 7, 2018 2:03PM - 2:15PM |
L51.00013: Imaging Dopant-Based Quantum Devices in Si Piotr Rozanski, Martyna Patera, Wiktor Lachmanski, Garnett Bryant, Michal Zielinski Atom-based devices can be fabricated in Si using scanned-probe lithography to place P dopants with near atomic precision. Such devices have received tremendous attention as potential atomic-scale solid-state qubits. Theoretical procedures and rules have been developed to use scanning tunneling microscopy (STM) to image and locate individual dopants with atomic precision a few nanometers from a Si surface. Real devices will have qubits formed from multiple, nearby dopants and atomic-scale wires made from high densities of dopants. Determining the geometry of such multiple-dopant qubits and assessing the quality of atomic-scale wires will be an essential step in device fabrication. |
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