Beyond zone folding: effect of curvature and NT bundles Márk Géza István MTA Research Institute for Technical Physics and Materials Science Budapest

Slides:

Advertisements

Similar presentations

Mechanisms of Terahertz Radiation Generation in Graphene Structures Institute for Nuclear Problems, Belarus State University, Belarus The XII-th International.

Advertisements

Electronic Structure Carbon nanotubes possess large π -electronic systems similar to planar graphene 1 Reduced dimensionality around the circumference.

PHYS466 Project Kyoungmin Min, Namjung Kim and Ravi Bhadauria.

Mikhail Rybin Euler School March-April 2004 Saint Petersburg State University, Ioffe Physico-Technical Institute Photonic Band Gap Structures.

Forms of Carbon. Diamond Covalent crystals: C, Si, Ge, SiC Strong sp 3  bonds form tetrahedral structure Face Centered Cubic lattice (fcc) –8 C atoms.

An ab-initio Study of the Growth and the Field Emission of CNTs : Nitrogen Effect Hyo-Shin Ahn §, Tae-Young Kim §, Seungwu Han †, Doh-Yeon Kim § and Kwang-Ryeol.

Electronic states of finite length carbon nanotubes Yuki Tatsumi, Wataru Izumida Tohoku University, Department of Physics Outline  Background “SWNT quantum.

© 2013 Eric Pop, UIUCECE 340: Semiconductor Electronics ECE 340 Lecture 3 Crystals and Lattices Online reference:

Graphene: why πα? Louis Kang & Jihoon Kim

1 1.Introduction 2.Electronic properties of few-layer graphites with AB stacking 3.Electronic properties of few-layer graphites with AA and ABC stackings.

If you re-use any material in this presentation, please credit: Michael S. Fuhrer, University of Maryland.

Screening of Water Dipoles inside Finite-Length Carbon Nanotubes Yan Li, Deyu Lu,Slava Rotkin Klaus Schulten and Umberto Ravaioli Beckman Institute, UIUC.

Interpretation of the Raman spectra of graphene and carbon nanotubes: the effects of Kohn anomalies and non-adiabatic effects S. Piscanec Cambridge University.

CNT – Characteristics and Applications

University of Notre Dame Carbon Nanotubes Introduction Applications Growth Techniques Growth MechanismPresented by: Shishir Rai.

6. Carbon nanostructures: fullerenes and carbon nanotubes 1.

Nanotube as a gas Sensor

PY4007 – Quantum wires nanoparticle V1V1 V2V2 0 V C,R 1 C,R 2 C,R 3 A small conductive nanoparticle is connected via 3 tunnelling junctions to voltage.

1 A Multi-scale Electro-Thermo-Mechanical Analysis of Single Walled Carbon Nanotubes PhD defense Tarek Ragab Electronic Packaging Laboratory CSEE department,

Institute of Optics, University of Rochester1 Carbon Nanotubes: theory and applications Yijing Fu 1, Qing Yu 2 1 Institute of Optics, University of Rochester.

Chemical Bonding of Carbon Nanotubes

Symmetry of Single-walled Carbon Nanotubes. Outline Part I (November 29) Symmetry operations Line groups Part II (December 6) Irreducible representations.

Quantum Dots: Confinement and Applications

Gaxela N, Manaetja K.P, Mulaudzi S, Senosi R Supervisor: Dr V.L.Katkof.

Carbon nanotubes John, Sarah, Doug.

Nanotubes In The Name Of Allah excitons in single – walled carbon nanotubes nasim moradi graduate student of atomic and molEcular physics.

Base Pairing in DNA. Red = O Grey = C White = H Purple = K Ionic Radii Li + = 0.68 Å Na + = 0.97 Å K + = 1.33 Å Rb + = 1.47 Å Cavity Size (O-O Dist.)

Computational Solid State Physics 計算物性学特論第４回 4. Electronic structure of crystals.

Electron diffraction on carbon nanotubes Marko Viršek adviser: doc. dr. Maja Remškar.

Chapter 10: Covalent Bond Theories

Electronic structure (properties) single atom  multiple atoms  solid atomic orbitals  molecular orbitals  band For core-level they are still atomic-like,

Electrons in Solids Carbon as Example

Piezoelectric Nanotubes (!) Electrons on Carbon NT’s Heteropolar Nanotubes Pyroelectricity Piezoelectricity Photogalvanics Tubes as Optical Materials ….with.

Network for Computational Nanotechnology (NCN) Purdue, Norfolk State, Northwestern, MIT, Molecular Foundry, UC Berkeley, Univ. of Illinois, UTEP NEMO5.

Start. Calculations for the electronic transport in molecular nanostructures Gotthard Seifert Institut für Physikalische Chemie und Elektrochemie Technische.

Background about Carbon Nanotubes CAR Seminar 5 November 2010 Meg Noah.

Johnson Space Center May 18, Single-walled Carbon Nanotube (SWCNT) Carbon Nanostructures C 60 (Buckminsterfullerene)

Delocalization of Electrons Section Introduction Delocalization allows the pi electrons to spread over more than two nuclei This spreading out of.

PROPERTIES OF CARBON NANOTUBES

1 Electronic structure calculations of potassium intercalated single-walled carbon nanotubes Sven Stafström and Anders Hansson Department of Physics, IFM.

Hybrid Orbitals. Why Covalent Bonds Exist Atoms share electrons when their orbitals overlap When orbitals overlap, electrons are simultaneously attracted.

Chapter 1: Structure and Bonding mcmurry. Coverage: 1. Electron Configurations. 2. Lewis Structures 3. Covalent and Ionic bonds 4. Atomic and Molecular.

S. E. Thompson EEL What is a Carbon Nanotube? Start with Carbon Graphite C 60 Single Wall Carbon Nanotubes Multi Wall Carbon Nanotubes.

Bandstructures: Real materials. Due my interests & knowledge, we’ll mostly focus on bands in semiconductors. But, much of what we say will be equally valid.

Carbon Nanotubes Riichiro Saito

An introduction to the theory of Carbon nanotubes A. De Martino Institut für Theoretische Physik Heinrich-Heine Universität Düsseldorf, Germany.

Band Structure Of Graphene Sheets and Carbon Nanotubes

The many forms of carbon Carbon is not only the basis of life, it also provides an enormous variety of structures for nanotechnology. This versatility.

Team work Majed AbdELSalam Nashaat,

Electronic structure of carbon nanotubes 林永昌.

Hybridization Combination of atomic orbitals to form hybrid orbitals OR Hybridization is also way to explain molecular shapes that can't be explained easily.

Metallic Bonding. Metallic Bonds are a special type of bonding that occurs only in metals A metallic bond occurs in metals. A metal consists of positive.

Carbon Allotropes Fullerenes Carbon nanotubes Graphene Diamond.

Many-Body Effects in the Optics of Single-Wall Nanotubes

Carbon nanotubes John, Sarah, Doug.

CARBON NANO TUBES AND THEIR APPLICATIONS

Many-Body Effects in the Optics of Single-Wall Nanotubes

of single-wall nanotube DNA hybrids

Spin-orbit interaction in a dual gated InAs/GaSb quantum well

Invisible excitons in hexagonal Boron Nitride Claudio Attaccalite

CHAPTER 11 Semiconductor Theory and Devices

Band structure: Semiconductor

CHAPTER 11 Semiconductor Theory and Devices

Observed by Photoemission

First principles calculation on field emission of boron/nitrogen doped carbon nanotube I’m going to talk about the first principles calculation on field.

Nanotube Fluorescence Spectroscopy

Energy Band 7 In free electron model, electrons occupy positive energy levels from E=0 to higher values of energy. They are valence electron so called.

Orbital Bonding Theory

DEPARTMENT OF CHEMISTRY

Presentation transcript:

Beyond zone folding: effect of curvature and NT bundles Márk Géza István MTA Research Institute for Technical Physics and Materials Science Budapest

Outline j Introduction -- zone folding jEffect of curvature -- jellium model results jEffect of curvature -- small energy: secondary gap jEffect of curvature -- hybridization of Pi and Sigma states: shift of the bands jBundles -- low energy: secondary gap jBundles -- visible energy range: shift of the bands

Graphene layer lattice

Graphene 2D band structure Tigh binding first neighbor Ab-initio

Rolling vector C h = na 1 +ma 2 C h = 3a 1 +2a 2

Different rollings armchair zigzag general

Nanotube bandstructure IF (n-m)/3 THEN metallic ELSE semiconductor

Metallic tube 1D band structure

NT density of states and tunneling spectroscopy STS J. W. Wildöer et al., Nature 391 (1998) 59

1. effect of rolling: inequivalent neighbors Rolling a d<a Along the circumference: bond length and angle change Along the NT axis: no change

2. effect of rolling: Pi - Sigma mixing Graphene: pure sp 2 bonds Nanotube: mixed sp 2 and sp 3 bonds

Effect of curvature in simple jellium NT model Zone foldingCylindrical geometry

Jellium solutions Zone folding: superposition of plane waves Cylindrical geometry: superposition of Bessel functions

Effect of NT radius L.Tapasztó et. al., AIP Conf. Proc., 685, 439, (2003) E(r;m) functionsE(m;r) functions

First neighbor tight binding -- inequivalent neighbors Use different  1 and  2 interaction energy for the two types of neighbors! zigzagarmchair Only armchair tubes remain true metallic because shift in k z is parallel to allowed line Zigzag: finite gap opens!

Curvature induced gap at E F armchair points Calculated secondary gap in quasi-metallic nanotubes STS measurement 1/d 2 gap energy

Sigma - Pi hybridization (5,0) NT m=0 eigenfunction at the Gamma point Most of the wave function concentrated outside the NT Strong component with equal sign on both sides

Curvature effect on armchair tube Zone folding is good for armchair tubes level anticrossing

Curvature effect: zigzag tube Pi* bands shifted down Sigma* bands shifted up

Effect of curvature Valence bands not affected by curvature Two-fold degeneracy of Sigma* is lifted in NT Armchair Sigma* does not change Pi* band moves down Sigma* band moves up

Nanotube bundles (or ropes) HRTEM image of NT ropeHexagonal packing of (10,10) tubes

Effect of proximity: pseudogap Hexagonal packing of (10,10) tubes Calculated DOS

Effect of bundles Band shifts Van-Hove singularities: - peak splitting and - decreased intensity