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Graphene transport and dual-gate devices : 그래핀의 수송현상과 이중 게이트 소자 연구
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | 박영우 | - |
dc.contributor.author | 남영우 | - |
dc.date.accessioned | 2017-07-14T00:57:40Z | - |
dc.date.available | 2017-07-14T00:57:40Z | - |
dc.date.issued | 2014-02 | - |
dc.identifier.other | 000000016876 | - |
dc.identifier.uri | https://hdl.handle.net/10371/121517 | - |
dc.description | 학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2014. 2. 박영우. | - |
dc.description.abstract | This thesis contains experimental studies on electronic transport properties of graphene with the Aharonov-Bohm (AB) effect, thermopower (TEP) measurements, dual-gated graphene field effect devices, and quantum Hall effect (QHE).
First, in an effort to enhance the AB effect in graphene, we place either superconducting-metal (aluminium) or normal-metal (gold) mirrors on the graphene rings. A significant enhancement of the phase coherence effect is conferred from the observation of the third harmonic of the AB oscillations. The superconducting contribution to the AB effect by the aluminium (Al) mirrors is unclear. Instead, we believe that a large mismatch of Fermi velocity between graphene and the mirror materials can account for the enhancement. Second, TEP measurement is performed on wrinkled inhomogeneous graphene grown by chemical vapour deposition (CVD). The gate-dependent TEP shows a large electron-hole asymmetry while resistance is symmetric. In high magnetic field and low temperature, we observe anomalously large TEP fluctuations and an insulating quantum Hall state near the Dirac point. We believe that such behaviors could be ascribed to the inhomogeneity of CVD-graphene. Third, dual-gated graphene field effect devices are made using two gates | - |
dc.description.abstract | top- and back-gates. In particular, the top gate is made of Al deposited directly onto the middle part of the graphene channel. Naturally formed Al2O3 at the interface between Al and graphene can be facilitated for the top-gate dielectric layer. When the Al top-gate is floating, a double-peak structure accompanied by hysteresis appears in the graphene resistance versus back-gate voltage curve. This can be attributed to the finite resistance of top-gate dielectric and the coupling between the two gates.
Lastly, we notice that the QHE is very robust in CVD-graphene grown on platinum. The effect is observed not only in high- but also low-mobility inhomogeneous graphene decorated with disordered multilayer patches. | - |
dc.description.tableofcontents | Abstract I
List of figures VII List of tables XI 1. Introduction 1 1.1 Graphene 2 1.2 Purpose and scope of this thesis 5 2. Concepts 7 2.1 Aharonov-Bohm (AB) effect 7 2.2 Thermopower (TEP) 10 2.3 Graphene p-n-p junctions and graphene-metal contact 14 3. Experimental techniques 17 3.1 Microfabrication of graphene devices 17 3.2 Graphene growth by chemical vapour deposition (CVD) 19 4. The Aharonov-Bohm (AB) effect in graphene rings with metal mirrors 21 4.1 Introduction 21 4.2 AB-ring devices and experimental details 22 4.3 Raman spectrum and Coulomb blockade effect 23 4.4 AB oscillations with Al T- and Al L-mirrors 25 4.5 AB oscillations with Al L-mirrors and without mirrors 29 4.6 AB oscillations with Au T- mirrors, Au L-mirrors and without mirrors 30 4.7 Conclusions 31 5. Unusual thermopower (TEP) of inhomogeneous graphene grown by chemical vapour deposition 33 5.1 Introduction 33 5.2 The thermopower device and experimental details 35 5.3 AFM and Raman mapping 36 5.4 Gate voltage dependence of resistance and thermopower 37 5.5 Simulation of inhomogeneity effect using simple mesh 39 5.6 Quantum Hall effect (QHE) 41 5.7 Magneto thermopower 42 5.8 Conclusions 44 6. Graphene p-n-p junctions made of naturally oxidized thin aluminium films 45 6.1 Introduction 45 6.2 The graphene p-n-p device and experimental details 46 6.3 Al oxidation at the interface with graphene 47 6.5 Double-peak structure in the transfer curve when Al top gate is floating 50 6.6 Circuit model to account for the hysteresis in the double-peak structure 53 6.7 Conclusions 55 7. Quantum Hall effect in graphene decorated with disordered multilayer patches 57 7.1 Introduction 57 7.2 Graphene growth on platinum by CVD 59 7.3 Transfer curves and Raman mapping 60 7.4 Quantum Hall effect (QHE) 63 7.5 Unusual ν = 0 quantum Hall state 66 7.5 Conclusions 67 8. Summary 69 References 71 국문 초록 81 | - |
dc.format | application/pdf | - |
dc.format.extent | 4493365 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | graphene | - |
dc.subject | electron transport | - |
dc.subject | Aharonov-Bohm effect | - |
dc.subject | thermopower | - |
dc.subject | chemical vapour deposition | - |
dc.subject | dual-gated graphene field effect devices | - |
dc.subject | quantum Hall effect | - |
dc.subject.ddc | 523 | - |
dc.title | Graphene transport and dual-gate devices | - |
dc.title.alternative | 그래핀의 수송현상과 이중 게이트 소자 연구 | - |
dc.type | Thesis | - |
dc.contributor.AlternativeAuthor | Youngwoo Nam | - |
dc.description.degree | Doctor | - |
dc.citation.pages | XII, 80 | - |
dc.contributor.affiliation | 자연과학대학 물리·천문학부(물리학전공) | - |
dc.date.awarded | 2014-02 | - |
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