Aharonov-Bohm oscillations in ballistic graphene rings
| Autor: | Dauber, Jan |
|---|---|
| Přispěvatelé: | Stampfer, Christoph, Bluhm, Jörg Hendrik |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Quantenkohärenz
Klein tunneling nanotechnology graphene nanostructures nanotechnology mesoscopic physics Aharonov-Bohm effect Klein tunneling phase-coherent transport quantum decoherence Hall effect sensor Graphen Nanostrukturen Nanotechnologie Mesoskopische Physik Aharonov-Bohm-Effekt Kleinsches Paradoxon phasenkohärenter Transport Quantenkohärenz Hall-Sensoren Kleinsches Paradoxon graphene Hall effect sensor Nanostrukturen Aharonov-Bohm effect Condensed Matter::Mesoscopic Systems and Quantum Hall Effect phasenkohärenter Transport Graphen phase-coherent transport Hall-Sensoren nanostructures quantum decoherence Aharonov-Bohm-Effekt Mesoskopische Physik ddc:530 mesoscopic physics Nanotechnologie |
| Zdroj: | Aachen 1 Online-Ressource (v, 131 Seiten) : Illustrationen (2018). doi:10.18154/RWTH-2019-02353 = Dissertation, RWTH Aachen University, 2018 |
| DOI: | 10.18154/RWTH-2019-02353 |
| Popis: | Dissertation, RWTH Aachen University, 2018; Aachen 1 Online-Ressource (v, 131 Seiten) : Illustrationen (2018). = Dissertation, RWTH Aachen University, 2018 This thesis focuses on the electrical transport characteristics of graphene nanostructures at low temperatures and investigates several effects related to mesoscopic physics. Graphene provides an ideal host material for quantum engineering with its outstanding electronic properties and QED-like physics as well as the feasibility of pattering of sub-micron devices. Mesoscopic systems are formed when sample dimensions are on the order of characteristic length scales of electron transport. They are the fundament for the observation of size quantization, quantum interference effects, ballistic transport and many more phenomena. Graphene nanoribbons on SiO2 are fabricated from mechanical exfoliation of graphite and structured by lithography and dry etching. The transport properties are studied by low temperature transport measurements before and after a short treatment with hydrofluoric acid (HF). The chemical interactions of HF with the SiO2 substrate and the edges of nanoribbons lead to the observation of a significantly reduced disorder potential in transport measurements. In the next experiment an Aharonov-Bohm (AB) ring is fabricated from exfoliated graphene, which is fully encapsulated in exfoliated hexagonal boron nitride (hBN). The device is assembled by a dry transfer process based on van der Waals forces providing an excellent sample quality. Magnetotransport measurements show AB conductance oscillations at low B fields and exhibit signatures of magnetic focusing effects in the intermediate field range demonstrating quasi-ballistic transport. A subsequent experiment studies phase-coherent transport in a ring with a partial top gate made from chemical vapor deposition (CVD) grown graphene and fully encapsulated in exfoliated hBN. For unipolar charge carrier configurations, AB oscillations and higher harmonics are observed and quantum decoherence is investigated by bias voltage and temperature dependent measurements indicating a quasi-ballistic mesoscopic system. In bipolar settings, the interplay of AB oscillations and Klein tunneling leads to phase-coherent transport in an electron-hole system. The final experiment demonstrates the fabrication and the characterization of Hall sensor elements based on hBN/graphene/hBN heterostructures. In Hall measurements these devices achieve current- and voltage-related sensitivities of up to 5700 V/(AT) and 3 V/(VT), respectively. These results outperform state of the art Si and III/V semiconductor Hall sensor devices and show the high potential of hBN/graphene/hBN heterostructures for commercial applications. Published by Aachen |
| Databáze: | OpenAIRE |
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