Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R31: Nanoribbons: Graphene and Beyond |
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Sponsoring Units: DMP DCMP Room: 294 |
Thursday, March 16, 2017 8:00AM - 8:12AM |
R31.00001: Nonlinear optical response in narrow graphene nanoribbons Farhad Karimi, Irena Knezevic We present an iterative method to calculate the nonlinear optical response of armchair graphene nanoribbons (aGNRs) and zigzag graphene nanoribbons (zGNRs) while including the effects of dissipation. In contrast to methods that calculate the nonlinear response in the ballistic (dissipation-free) regime, here we obtain the nonlinear response of an electronic system to an external electromagnetic field while interacting with a dissipative environment (to second order). We use a self-consistent-field approach within a Markovian master-equation formalism (SCF-MMEF) coupled with full-wave electromagnetic equations, and we solve the master equation iteratively to obtain the higher-order response functions. We employ the SCF-MMEF to calculate the nonlinear conductance and susceptibility, as well as to calculate the dependence of the plasmon dispersion and plasmon propagation length on the intensity of the electromagnetic field in GNRs. The electron scattering mechanisms included in this work are scattering with intrinsic phonons, ionized impurities, surface optical phonons, and line-edge roughness. Unlike in wide GNRs, where ionized-impurity scattering dominates dissipation, in ultra-narrow nanoribbons on polar substrates optical-phonon scattering and ionized-impurity scattering are equally prominent. [Preview Abstract] |
Thursday, March 16, 2017 8:12AM - 8:24AM |
R31.00002: Electronic Structure of Boron-doped Graphene Nanoribbons on Metallic Substrates: Ab Initio Studies and Scanning Probe Measurements Fangzhou Zhao, Ting Cao, Zahra Pedramrazi, Chen Chen, Giang Nguyen, Arash Omrani, Hsin-Zon Tsai, Daniel Rizzo, Trinity Joshi, Christopher Bronner, Won-Woo Choi, Ryan Cloke, Tomas Marangoni, Felix Fischer, Michael Crommie, Steven Louie Graphene nanoribbons (GNRs) have been a very promising candidate for nanoelectronic devices because of their tunable electronic structure with varying width and edge termination. Introducing boron dopants in the backbone of the GNRs further creates new dopant states in the band gap of pristine GNR. In this work, we used density functional theory calculations to investigate the electronic structure of freestanding boron doped GNRs as well as that of GNRs on gold substrate. We find that the boron dopant states change dramatically with doping concentration and interaction with the substrate. The boron atoms bind strongly to the gold substrate, resulting in new features in the GNR's electronic structure. Our calculated results are in good agreement with experimental measurements by scanning tunneling microscopy and spectroscopy. [Preview Abstract] |
Thursday, March 16, 2017 8:24AM - 8:36AM |
R31.00003: Distinct photoresponse in graphene induced by laser irradiation and interfacial gating. Wenhui Wang, Xitao Guo, Haiyan Nan, Zhenhua Ni Graphene-based photodetectors have recently received much attention due to its unique optical and electronic properties. The photoresponse modulation plays a crucial role in the study of photocurrent generation mechanism and optoelectronic applications. Here, the tunable p-p$+$-p junctions of graphene were fabricated through simple laser irradiation process. Distinct photoresponse was observed at the graphene (G)-laser irradiation graphene (LIG) junction. Detailed investigation suggests that the photo-thermoelectric effect, instead of the photovoltaic effect, dominates the photocurrent generation at the G-LIG junction. On the other hand, the localized interface states, existing at the silicon dioxide/lightly doped Si interface, would induce an interfacial gating mechanism, which will enhance the photoresponsivity to 1000 A/W. More important, the photoresponse time of our device has been pushed to 400ns. The current device structure does not need a complicated fabrication process and is fully compatible with silicon technology. This work will open up a route to graphene-based high-performance optoelectronic devices. [Preview Abstract] |
Thursday, March 16, 2017 8:36AM - 8:48AM |
R31.00004: Electronic and Optical properties of Graphene Nanoribbons Elisa Molinari, Andrea Ferretti, Claudia Cardoso, Deborah Prezzi, Alice Ruini Narrow graphene nanoribbons (GNRs) exhibit substantial electronic band gaps, and optical properties expected to be fundamentally different from the ones of their parent material graphene. Unlike graphene the optical response of GNRs may be tuned by the ribbon width and the directly related electronic band gap. We have addressed the optical properties of chevron-like and finite-size armchair nanoribbons by computing the fundamental and optical gap from ab initio methods. Our results are in very good agreement with the experimental values obtained by STS, ARPES, and differential reflectance spectroscopy, indicating that this computational scheme can be quantitatively predictive for electronic and optical spectroscopies of nanostructures. [Preview Abstract] |
Thursday, March 16, 2017 8:48AM - 9:00AM |
R31.00005: Gate-tunable charge density wave in TiS$_{\mathrm{3}}$ nanoribbons Ce Huang, Enze Zhang, Xiang Yuan, Weiyi Wang, Yanwen Liu, Cheng Zhang, Jiwei Ling, Shanshan Liu, Faxian Xiu Recently, modifications of charge density wave (CDW) in two-dimensional (2D) limit show intriguing optical and electrical properties in quasi-2D materials such as layered transition metal dichalcogenides (TMDCs). However, the CDW in quasi-1D materials like transition metal trichalcogenides (TMTCs) is yet to be explored in low dimension whose mechanism is likely distinct from their quasi-2D counterparts. Here, we report a systematic study on the CDW properties of titanium trisulfide (TiS3). Two phase transition temperatures were observed to decrease from bulk and thin nanoribbon, respectively. It is believed that the nanoribbon structure increases the fluctuation effect across the chain and thus destroys the CDW coherence. Remarkably, by using back gate in 15 nm device, we can tune the second transition temperature largely owing to the altered electron concentration. Laser beams on the sample surface is exploited to manipulate the CDW transition, where the melting of the CDW states shows a strong dependence on the excitation energy. Our results demonstrate TiS3 to be a promising quasi-1D CDW material and open up a new window for the study of collective phases in TMTCs. [Preview Abstract] |
Thursday, March 16, 2017 9:00AM - 9:12AM |
R31.00006: In situ growth and electrical measurement of metal nanowires on DNA wire templates Jorge Barreda, Longqian Hu, Liuqi Yu, Jacob Hudis, Zhibin Wang, Junfei Xia, Jingjiao Guan, Peng Xiong We report on the development of a process for controlled stretching and deposition of DNA wires as templates for in situ growth and electrical measurement of metal nanowires (NWs). The complete process is separated into three main steps: 1) stretching of DNA wires with a one-step dewetting of a DNA solution on a PDMS stamp where the DNA wires are suspended across an array of micropillars along a chosen direction [1]; 2) transfer of the DNA wires to a Si/SiO2/SiNx substrate, via micro-contact printing, over and across a trench lithographically defined to have an opening in the SiNx layer and an undercut in the SiO2 layer; and 3) formation and electronic transport characterization of the metal NWs in ultrahigh vacuum at low temperature. The stretching process provides a high degree of control over the spacing and orientation of the DNA wires, as well as the lengths and widths of the metal NWs. For the metal NW growth, the DNA template is placed in a customized cryogenic system for low temperature quench-condensation deposition resulting in a metal NW. The thickness of the NW is increased incrementally and electrical measurement performed in situ at each thickness. Two-terminal and quasi-four terminal I-V measurements reveal that, with increasing thickness, a transition from strongly nonlinear IV to Ohmic behavior accompanies rapid increase of the NW conductance. [1] Guan, Jingjiao, et al. Soft Matter 3.11 (2007): 1369-1371. [Preview Abstract] |
Thursday, March 16, 2017 9:12AM - 9:24AM |
R31.00007: Silicon nanowire sensor for DNA detection and sequencing: an ab initio simulation Wenchang Lu, Yan Li, Miroslav Hodak, Zhongcan Xiao, Jerry Bernholc Electrical sensors able to detect DNA replication and determine its sequence would enable fast and relatively cheap diagnosis of gene-related vulnerabilities and cancers. At present, it is already possible to electrically monitor DNA replication events using a Klenow fragment of polymerase I attached to a carbon nanotube. Since devices based on Si nanowires would be much easier to produce in quantity, we examine theoretically the sensitivity of a Si nanowire/Klenow fragment for electrical detection of nucleotide addition. A highly parallel real-space multigrid code is used for DFT-based non-equilibrium Green's function calculations involving up to 16,000 atoms, employing highly-accurate variationally-optimized localized orbitals. We find that the “open” and “closed” Klenow fragment configurations, prior and during nucleotide addition, respectively, screen the Si nanowire differently and result in a detectable current difference. The sensitivity is the largest in the subthreshold regime while the absolute current difference is maximized in the turn-on state. The sensitivity decreases with an increase of the nanowire size, as expected, but the current difference between different enzymatic states is nearly independent on the nanowire size up to 800 \AA$^2$ cross section. [Preview Abstract] |
Thursday, March 16, 2017 9:24AM - 9:36AM |
R31.00008: Controlled fabrication and selective CVD growth of ZnO Nanowires and Nanoribbons enabled by Direct Write parallel patterning technique Dheyaa Alameri, Robert Schurz, Leonidas E Ocola, Yuzi Liu, Irma Kuljanishvili We present a new approach for controllable synthesis of ZnO nanowires and nanoribbons by employing a `direct write' patterning and subsequent Chemical Vapor Deposition (CVD) methods. In this work we implemented our developed precursor `ink' as catalyst, and demonstrated the growth of high quality ZnO nanostructures prepared in various geometric architectures; nanoflowers, nanoribbons, and more complex shapes. We employ multi-pen AFM cantilevers for parallel writing of the precursor ink to create arrays of patterns (dots, lines) over the large areas on the substrates. We show that the diameter and the length of the grown nanowires can be controlled by the `ink' composition, geometry of the patterns written on the substrate and the growth conditions during the synthesis. Here we show that the individual nanowires can range from (100- 250) nm in diameter , and 1$\mu $m to 3$\mu $m in length. We also demonstrate that various design patterns can be easily created on different substrates such as Si/SiO2 or graphene, and directly on prefabricated devices. Arrays of ZnO nanowires and nanoribbons were characterized by Raman , X-ray photoelectron and Photoluminescence spectroscopies. I/V characteristics of devices will also be discussed. [Preview Abstract] |
Thursday, March 16, 2017 9:36AM - 9:48AM |
R31.00009: Valley Structure and Giant Spin Splitting in Lead Salts Nanowires Ivan Avdeev, Alexander Poddubny, Serguei Goupalov, Mikhail Nestoklon We employ tight-binding method and ${\bf k} \cdot {\bf p}$ theory to analyze valley structure of PbSe nanowires grown along the $[111]$ direction and having unit cells of different point symmetry: $D_{3d}$, $D_3$, and $C_{2h}$. We show that, while all three nanowire symmetries ehxibit large valley splittings of electronic subbands, the $D_3$ wires are of special interest, as they possess a screw axis which results in appreciable spin-dependent splittings of electronic subbands, linear in one-dimensional wave vector. [Preview Abstract] |
Thursday, March 16, 2017 9:48AM - 10:00AM |
R31.00010: Carrier Dynamics and Band Structure of GaAsSb and GaAsSb/InP Nanowires Iraj Shojaei, Samuel Linser, Giriraj Jnawali, Nadeeka Wickramasuriya, Howard Jackson, Leigh Smith, Xiaoming Yuan, Philippe Caroff, Hoe Tan, Chennupati Jagadish We utilize transient Rayleigh scattering (TRS) measurements to investigate the dynamics of photoexcited carriers and the band-structure of zincblende GaAsSb and GaAsSb/InP single semiconductor nanowires. The measurements are performed at 300K and 10K by exciting the samples with 1.5 eV 150 fs pulses and probing with pulses tunable from 0.8 to 1.2 eV. The core-only nanowires exhibit uniformly short lifetimes (~ 3 ps) at both 10 and 300K. In comparison, core-shell nanowires exhibit ~15 times longer lifetime at low temperatures (~670 ps) compared to room temperature measurements (~40 ps). Some core-shell nanowires exhibit a 10K lifetime as long as 1700 ps. The 30\% Sb core-only nanowires reveal weak spectral structure near the band edge energy of 0.88 eV at both temperatures, while the 30\% core-shell nanowires exhibit strong band-edge signals at 0.87 eV at room temperature and at 0.98 eV at 10K. We present a fitting model based on direct band-to-band transition theory to extract the electron-hole-plasma density and temperature as a function of time-delay from TRS measurements from single nanowires. [Preview Abstract] |
Thursday, March 16, 2017 10:00AM - 10:12AM |
R31.00011: Carrier Dynamics and Band Structure in InGaAs and InGaAs/InP Nanowires Samuel Linser, Iraj Shojaei, Giriraj Jnawali, Nadeeka Wickramasuriya, Howard Jackson, Leigh Smith, Amira Ameruddin, Philippe Caroff, Hoe Tan, Chennupati Jagadish We use transient Rayleigh scattering (TRS) measurements to explore the electronic energy structure of wurtzite InGaAs nanowires. We studied single core-only InGaAs nanowires as well as strained core-shell InGaAs-InP heterostructures at 300 K and 10 K, with probe photon energies in the near-infrared from 0.79 to 1.16 eV. We report a factor of four enhancement of the typical lifetime of excited states in the core-shell nanowires (~500 ps) when compared to the core-only nanowires (~125 ps). We observe a clear band-edge-like structure in the core-shell wires at energies of 0.98 eV at 10 K and 0.88 eV at 300 K. In both cases, this structure is at a significantly higher energy than the reported bandgap of bulk zincblende InGaAs of the same nominal composition as our nanowires. We also present a phenomenological fitting model of our TRS spectra which provides insight into the cooling dynamics of the electron-hole plasma within a single photo-excited nanowire. [Preview Abstract] |
Thursday, March 16, 2017 10:12AM - 10:24AM |
R31.00012: Characterization of $\beta $-Ga$_{\mathrm{2}}$O$_{\mathrm{3}}$ nanowires and their application in CO gas sensors Monshu Ho, Tzu-Feng Weng Monoclinic gallium oxide ($\beta $-Ga2O3) is an important semiconductor material with a wide band gap of Eg ¡ã 4.9 eV at room temperature (RT) and high chemical and thermal stability. This makes $\beta $-Ga2O3 an ideal material for gas sensors, phosphors, transparent conductors, and transparent electronic devices. This paper reports on the fabrication of high-density single crystalline $\beta $-Ga2O3 nanowires on silicon (100) and sapphire (0001) substrates using a vapor-liquid-solid growth method. The morphology of as-grown $\beta $-Ga2O3 nanowires was investigated using field emission scanning electron microscopy (FESEM). The diameter of the 1D nanostructures ranged from tens to a few hundreds of nanometers. X-ray diffraction (XRD) and field emission transmission electron microscopy (FETEM) confirmed the single crystalline monoclinic structure of the $\beta $-Ga2O3 nanowires. Multiple-networked CO gas sensors fabricated using the proposed $\beta $-Ga2O3 nanowires achieved remarkably sensitivity of 2158 ppm CO gas at room temperature. We also compared the CO gas sensing properties of multiple- networked bare $\beta $-Ga2O3 nanowires with those of Au-functionalized $\beta $-Ga2O3 nanowires at room temperature. [Preview Abstract] |
Thursday, March 16, 2017 10:24AM - 10:36AM |
R31.00013: Periodically Diameter-Modulated Semiconductor Nanowires for Enhanced Optical Absorption Minjee Ko, Seong-Ho Baek, Bokyung Song, Jang-Won Kang, Chang-Hee Cho Semiconductor nanowires could enable efficient light trapping, thereby giving rise to enhanced optical absorption at specific resonance wavelengths depending on their size. In this study, we introduce a novel approach to enhancing optical absorption by modulating the diameters of nanowires, in which the diameter changes periodically in a sinusoidal manner along the axis of the wire. We found that the absorption of diameter-modulated silicon nanowire exhibits stronger and multiple resonance peaks compared to simple cylindrical nanowire, leading to the enhanced absorption over a broad spectral range. To understand the resonance modes that are responsible for the enhanced absorption, we analyzed leaky guided modes in the diameter-modulated nanowire through finite-difference time-domain (FDTD) simulations and analytical calculations. Our finding is that the stronger and multiple resonances originate from substantial transverse components of the Poynting vector, giving rise to enhanced coupling with higher-order mode resonances by means of the periodically modulated diameter. Our results suggest that unique capability of semiconductor nanowires with periodically modulated diameters offers enhanced broadband absorption beyond that of simple nanowire geometries. [Preview Abstract] |
(Author Not Attending)
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R31.00014: Nonradiative Auger recombination in coaxial GaAs/AlGaAs nanowire lasers Roman Vaxenburg, Alexander Efros Owing to their unique geometry, semiconductor nanowire lasers are rapidly emerging nanoscale coherent light sources.[1] Currently, one of the major goals in the device performance of nanowire lasers is the reduction of their threshold power. In nanoscale systems, the dissipative Auger recombination is an important nonradiative recombination channel which competes with gain development, thereby complicating the search for threshold reduction solutions. Here, we investigate theoretically the Auger recombination in coaxial GaAs/AlGaAs quantum well nanowire structures using the 8-band effective mass model. Specifically, we focus on the dependence of the Auger rate on quantum well radius and thickness. The calculations show that increasing delocalization of the carrier wavefunctions with increasing quantum well thickness reduces the rate of the Auger processes. The efficiencies of two Auger recombination channels, which lead to excitation of either electrons or holes, are compared. The results are compared with available experimental data. A possible strategy to reduce the rate of Auger recombination without changing the quantum well width is proposed. [1] T. Stettner, P. Zimmermann, B. Loitsch, M. D\"{o}blinger, A. Regler, B. Mayer, J. Winnerl, S. Matich, H. Riedl, M. Kaniber, G. Abstreiter, G. Koblm\"{u}ller, and J. J. Finley, Appl. Phys. Lett. 108, 011108 (2016). [Preview Abstract] |
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