- AutorIn
- M.Sc. Fabian Teichert Technische Universität Chemnitz
- Titel
- Quantum transport in defective carbon nanotubes at mesoscopic length scales
- Zitierfähige Url:
- https://nbn-resolving.org/urn:nbn:de:bsz:ch1-qucosa2-343266
- Übersetzter Titel (DE)
- Quantentransport in defektbehafteten Kohlenstoffnanoröhrchen auf mesoskopischen Längenskalen
- Datum der Einreichung
- 23.11.2018
- Datum der Verteidigung
- 22.03.2019
- Abstract (DE)
- Diese Dissertation untersucht mittels theoretischer Methoden die elektronischen Transporteigenschaften von defektbehafteten Kohlenstoffnanoröhren (englisch: carbon nanotubes, CNTs). Dabei werden Vakanzen als Defekte fokussiert behandelt. Die Berechnungen werden mittels Quantentransporttheorie und einer zugrunde liegenden dichtefunktionalbasierten Tight-Binding-Methode durchgeführt. Zwei algorithmische Verbesserungen werden hergeleitet, welche die üblichen Methoden für quasi-eindimensionale Systeme für zwei spezifische Fälle beschleunigen: (i) zufällig verteilte Defekte und (ii) lange Einheitszellen. Damit werden das Transmissionsspektrum und der Leitwert als Funktion von CNT-Länge, Durchmesser, chiralem Winkel, Defekttyp, Defektdichte, Defektanteil und Temperatur berechnet. Das Diffusions- und das Lokalisierungstransportregime werden beschrieben, indem die elastische freie Weglänge und die Lokalisierungslänge für metallische und halbleitende CNTs extrahiert werden. Einfache analytische Modelle zur Abschätzung bis hin zur Vorhersage des Leitwertes in Abhängigkeit besagter Parameter werden abgeleitet. Schlussendlich werden die Bildung einer defektinduzierten, langreichweitigen Deformation und deren Einfluss auf den Leitwert studiert.
- Abstract (EN)
- This thesis theoretically investigates the electronic transport properties of defective carbon nanotubes (CNTs). For the defects the focus is set to vacancy types. The calculations are performed using quantum transport theory and an underlying density-functional-based tight-binding method. Two algorithmic improvements are derived, which accelerate the common methods for quasi one-dimensional systems for the specific case of (i) randomly distributed defects and (ii) long unit cells. With this, the transmission spectrum and the conductance is calculated as a function of the CNT length, diameter, chiral angle, defect type, defect density, defect fraction, and temperature. The diffusive and the localized transport regime are described by extracting elastic mean free paths and localization lengths for metallic and semiconducting CNTs. Simple analytic models for estimating or even predicting the conductance dependence on the mentioned parameters are derived. Finally, the formation of defect-induced long-range deformations and its influence on the conductance are studied.
- Andere Ausgabe
- Zeitschriftenartikel
Improved recursive Green’s function formalism for quasi one-dimensional systems with realistic defects
Link: https://www.sciencedirect.com/science/article/pii/S0021999117300347
DOI: 10.1016/j.jcp.2017.01.024 - Zeitschriftenartikel
Strong localization in defective carbon nanotubes: a recursive Green’s function study
DOI: 10.1088/1367-2630/16/12/123026
Link: https://iopscience.iop.org/article/10.1088/1367-2630/16/12/123026 - Zeitschriftenartikel
Electronic transport in metallic carbon nanotubes with mixed defects within the strong localization regime
Link: https://www.sciencedirect.com/science/article/pii/S0927025617302987
DOI: 10.1016/j.commatsci.2017.06.001 - Electronic transport through defective semiconducting carbon nanotubes
Zeitschriftenartikel
Link: https://iopscience.iop.org/article/10.1088/2399-6528/aae4cb
DOI: 10.1088/2399-6528/aae4cb - Influence of defect-induced deformations on electron transport in carbon nanotubes
Zeitschriftenartikel
Link: https://iopscience.iop.org/article/10.1088/2399-6528/aaf08c
DOI: 10.1088/2399-6528/aaf08c - Freie Schlagwörter (DE)
- Kohlenstoffnanoröhre, Defekt, Elektronentransport, starke Lokalisierung, elastische mittlere freie Weglänge, Deformation, dichtefunktionalbasiertes Tight-Binding, rekursiver Greenfunktions-Formalismus, Renormierungs-Dezimierungs-Algorithmus
- Freie Schlagwörter (EN)
- carbon nanotube, defect, electron transport, strong localization, elastic mean free path, deformation, density-functional-based tight binding, recursive Green’s function formalism, renormalization-decimation algorithm
- Klassifikation (DDC)
- 530
- Normschlagwörter (GND)
- Kohlenstoff-Nanoröhre, Defekt, Elektronentransport, Starke Lokalisation, Mittlere freie Weglänge, Deformation, Starke Kopplung, Dichtefunktionalformalismus, Green-Funktion
- GutachterIn
- Prof. Dr. Michael Schreiber
- Prof. Dr. Thomas Frauenheim
- BetreuerIn Hochschule / Universität
- Prof. Dr. Michael Schreiber
- BetreuerIn - externe Einrichtung
- Dr. Jörg Schuster
- Den akademischen Grad verleihende / prüfende Institution
- Technische Universität Chemnitz, Chemntiz
- Version / Begutachtungsstatus
- publizierte Version / Verlagsversion
- URN Qucosa
- urn:nbn:de:bsz:ch1-qucosa2-343266
- Veröffentlichungsdatum Qucosa
- 17.07.2019
- Dokumenttyp
- Dissertation
- Sprache des Dokumentes
- Englisch
- Inhaltsverzeichnis
1 Introduction 2 Fundamentals 2.1 Carbon nanotubes 2.1.1 Structure 2.1.2 Properties 2.1.3 Defects 2.1.4 Synthesis 2.1.5 Characterization 2.1.6 Applications 2.2 Electron structure theory 2.2.1 Introduction 2.2.2 Density functional theory 2.2.3 Density-functional-based tight binding 2.2.3.1 First-order expansion 2.2.3.2 Creation of the parameter set 2.2.3.3 Second-order expansion 2.2.3.4 Usage 2.3 Electron transport 2.3.1 Equilibrium Green’s-function-based quantum transport theory 2.3.2 Transport regimes 2.3.3 Classical derivation: drift-diffusion equation with a sink 2.3.4 Quantum derivation: Dorokhov-Mello-Pereyra-Kumar theory A Improved recursive Green’s function formalism for quasi one-dimensional systems with realistic defects (J. Comput. Phys. 334 (2017), 607–619) A.1 Introduction A.2 Quantum transport theory A.3 Recursive Green’s function formalisms A.3.1 Forward iteration scheme A.3.2 Recursive decimation scheme A.3.3 Renormalization decimation algorithm A.4 Improved RGF+RDA A.5 Performance test A.5.1 Random test matrix A.5.2 Transport through carbon nanotubes A.6 Summary and conclusions B Strong localization in defective carbon nanotubes: a recursive Green’s function study (New J. Phys. 16 (2014), 123026) B.1 Introduction B.2 Theoretical framework B.2.1 Transport formalism B.2.2 Recursive Green’s function formalism B.2.3 Electronic structure B.2.4 Strong localization B.3 Modeling details of the defective system B.4 Results and discussion B.4.1 Single defects B.4.2 Randomly distributed defects B.4.3 Localization exponent B.4.4 Diameter dependence and temperature dependence of the localization exponent B.5 Summary and conclusions Supplementary material C Electronic transport in metallic carbon nanotubes with mixed defects within the strong localization regime (Comput. Mater. Sci. 138 (2017), 49–57) C.1 Introduction C.2 Theoretical framework C.3 Modeling details C.4 Results and discussion C.4.1 Conductance C.4.2 Localization exponent C.4.3 Influence of temperature C.4.4 Conductance estimation C.5 Summary and conclusions D An improved Green’s function algorithm applied to quantum transport in carbon nanotubes (arXiv: 1806.02039) D.1 Introduction D.2 Electronic transport D.3 Decimation technique and renormalization-decimation algorithm D.4 Renormalization-decimation algorithm for electrodes with long unit cells D.4.1 Surface Green’s functions D.4.2 Bulk Green’s functions and electrode density of states D.5 Complexity measure and performance test D.6 Exemplary results D.7 Summary and conclusions E Electronic transport through defective semiconducting carbon nanotubes (J. Phys. Commun. 2 (2018), 105012) E.1 Introduction E.2 Theoretical framework E.3 Modeling details E.4 Results and discussion E.4.1 Transmission and transport regimes E.4.2 Energy dependent localization exponent and elastic mean free path E.4.3 Conductance, effective localization exponent and effective elastic mean free path E.5 Summary and conclusions Supplementary material F Influence of defect-induced deformations on electron transport in carbon nanotubes (J. Phys. Commun. 2 (2018), 115023) F.1 Introduction F.2 Theory F.3 Results F.4 Summary and conclusions 3 Ongoing work 4 Summary and outlook 4.1 Summary 4.2 Outlook 5 Appendix 5.1 Bandstructure of graphene 5.2 Quantum transport theory and Landauer-Büttiker formula References List of figures List of tables Acknowledgement Selbstständigkeitserklärung Curriculum vitae List of publications