Gatedefined quantum dots on carbon nanotubes request pdf. Electronhole symmetry in a semiconducting carbon nanotube quantum dot. Quantum confinement in each junction induces a discrete quantum dot. Purcellenhanced quantum yield from carbon nanotube. Carbon nanotube quantum dots 3 in order to observe the rich physics of charge transport through quantum dots, though, it is necessary to introduce tunnel barriers at those interfaces, which will decrease the transmission t thesis submitted to the faculty of the graduate school of vanderbilt university in partial fulfillment of the requirements for the degree of master of science in chemistry december, 2010 nashville, tennessee approved.
This thesis presents research into spintransport in carbon nanotube quantum dots. Single electron transistors and carbon nanotube double quantum. Parallel carbon nanotube quantum dots and their interactions. A novel strategy for the fabrication of multiwall carbon nanotube.
Analysis of random telegraph noise observed in semiconducting. In single quantum dots defined in short lengths of nanotube, the energy levels associated. Because these devices are so short, we can explore fundamental mesoscopic physics, engineer tuneable nanoelectromechanical systems nems and create ultrashort transistors. In the last chapter we present a fabrication procedure for defining nanotube quantum dots with controllable barriers. The noise detection is based on photon assisted tunneling in a superconductorinsulatorsuperconductor junction. This project will investigate carbon nanotube devices with. All in all, i can affirm that the research into cnt qds has reached a reasonable level of. These fascinating electromechanical and magnetic effects are quantified using. Reaction scheme of manual solidphase synthesis of synthetic crt peptide. The second set of experiments concerns carbon nanotube double quantum dots. Quantum phase transition in a singlemolecule quantum dot. The ratio of lifetimes of the highcurrent state to the lowcurrent state changes exponentially with respect to the gatevoltage, and also.
In summary, we have investigated random telegraph noise observed in semiconducting cnt quantum dot. Sputtered permalloy electrodes designed with shape anisotropy were used to contact carbon nanotubes grown by chemicalvapour deposition in lateral spinvalve structures. In atoms the attractive forces are exerted by the nuclei, while in qds by background charges. Thermoelectric transport in nanoscale materials joshua p. Tuning the band structure of carbon nanotubes ethan davis minot, ph. The structural and optical properties of cntqd heterostructures are characterized by electron microscopy. Outline of thesis the problem statement behind this thesis was the following.
For nanotube quantum dot we adopted the dependence. Pdf parallel carbon nanotube quantum dots and their. Using this technique, complex nanostructures such as quantum dot arrays can be created. In the first nanotube experiment, spindependent transport through the double dot is compared in two sets of devices. Master thesis hybrid devices based on carbon nanotubes. Rey jila, university of colorado and national institute of standards and technology, boulder, colorado 803090440, and. We study the twoelectron eigenspectrum of a carbonnanotube double quantum dot with spinorbit coupling. Andreev and spin transport in carbon nanotube quantum dot.
A quantum dot qd is defined between two argon ion induced defects, revealing quantized states with a large level spacing in the conduction and valence bands. Different quantum dots qds with narrow size distributions were covalently coupled to carbon nanotubes cnts and silicacoated cnts in a simple, uniform, and controllable manner. Quantum dot modified multiwall carbon nanotubes the. Asgrown carbon nanotube quantum dots with superconducting contacts. Currentvoltage characteristics of suspended carbon nanotube quantum dots show an additional series of steps equally spaced in. We demonstrate tunable tunnel coupling of the double dot and quantify the strength of the tunneling using the charge sensor. Lately, the emphasis of carbon nanotube quantum dot research is shifting towards defining nanotube quantum dots with tunable barriers. Physics of very small bandgap carbon nanotube quantum dots. Characterization of conjugated quantum dots and carbon nanotube qd. A study by physicists at the technische universitaet muenchen has shown how nanotubes can.
Two coupled single wall carbon nanotube quantum dots in a multiple quantum dot system were characterized by using a low temperature scanning gate microscopy sgm technique, at a temperature of 170mk. This thesis presents experimental attempts towards advances in the field of quantum computation using carbon nanotube based quantum dot devices and highfrequency techniques. Electron transistors sets and carbon nanotube double quantum dots with narrow top. Churchill quantum dots in gated nanowires and nanotubes abstract this thesis describes experiments on quantum dots made by locally gating onedimensional quantum wires. The motivation behind using carbon nanotubes lies with the fact that they provide a priori confinement in two dimensions, making the quantum dot fabrication procedure simpler. Quantum dots in gated nanowires and nanotubes abstract this thesis describes experiments on quantum dots made by locally gating onedimensional quantum wires. Molecular statesin carbon nanotube double quantum dots.
Local gate control in carbon nanotube quantum devices. Pdf carbon nanotubes are a versatile material in which many aspects of condensed. I, shirin ghaderi, certify that the work presented in this thesis is my own. Carbon nanotube superconducting quantum interference device. Measurement of quantum noise in a carbon nanotube quantum dot. Ferromagnetically contacted carbon nanotube quantum dots. Ferromagnetically contacted carbon nanotube\ud quantum dots. The observed values are nevertheless already significantly below g 2. Asgrown carbon nanotube quantum dots with superconducting. Shotnoise detection in a carbon nanotube quantum dot.
Fabrication and characterization of a quantum dotsensitized solar cell by kevin j. This thesis presents experimental attempts towards advances in the field of quantum computation using carbon nanotubebased quantum dot devices and highfrequency techniques. Often called the artificial atoms, however the size is much bigger 100 nm for qds versus 0. Exact calculations are combined with a simple model to provide an intuitive and accurate description of singleparticle and interaction effects. Accessing the quantum world through electronic transport in. Quantum transport in carbon nanotubes semantic scholar. Nanotube quantum dot transport with spinorbit coupling and. Atomistic modeling of graphene nanostructures and singleelectron quantum dots a thesis submitted to the faculty of purdue university by junzhe geng in partial ful llment of the requirements for the degree of master of science in electrical and computer engineering august 2012 purdue university west lafayette, indiana. Also, a small coupling is found between orbitals with opposite magnetic moments leading to anticrossing behaviour at zero. We next chose parameters which concerns the nanotube dot region. This master thesis describes the fabrication steps and complications of. Conductance measurements of carbon nanotubes containing gated local depletion regions exhibit plateaus as a function of gate voltage, spaced by approximately 1e2h, the quantum of conductance for a single nondegenerate mode.
Enhanced photoelectrochemical performance of quantum dot. Scanning gate imaging of two coupled quantum dots in single. Carbon nanotubes can be used as quantum bits for quantum computers. The experiments presented in this thesis show that carbon nanotube nt electronic structure can be tuned by mechanical stretching and by magnetic fields. In a quantum dot electrons are made to tunnel onebyone through. Quantum dots 2 quantum dot qd is a conducting island of a size comparable to the fermi wavelength in all spatial directions. The locations of single wall carbon nanotube quantum dots were. The current emission noise of a carbon nanotube quantum dot in the kondo regime is measured at frequencies. In this thesis, we fabricate silicongermanium coreshell nanowire on bottom gate. The sample is first evaporated under one angle dark, then oxidized.
Noncollinear spinorbit magnetic elds in a bent carbon nanotube. A carbon nanotube quantum dot cnt qd is a small region of a carbon nanotube in which electrons are confined. The magnetoresistance of these spinvalves were measured at lowtemperatures and as a function of the charge state of the quantum dots. A superconducting quantum interference device squid with singlewalled carbon nanotube cnt josephson junctions is presented. This thesis describes the design, fabrication, and characterization of a photo.
Quantum dots seem to be ideal devices in which to observe quantum phase transitions. Quantum dot josephson junctions in the kondo regime. Carbon nanotube quantum dots tu delft repositories. Request pdf gatedefined quantum dots on carbon nanotubes we report the realization of nanotube based quantum dot structures that use local electrostatic gating to produce individually. Local gate control in carbon nanotube quantum devices abstract this thesis presents transport measurements of carbon nanotube electronic devices operated in the quantum regime. This way it was possible to extend the system to form a double quantum dot. There are various ways of producing swnts, which are briefly discussed later. Semiconductor nanocrystals, or quantum dots, are crystalline semiconductors on a size scale from 1. Much of the following thesis will be devoted to the quantum dot behavior of. An onchip detection scheme for high frequency signals is used to detect noise generated by a quantum dot formed in a single wall carbon nanotube. In this thesis, the fundamentals of quantum dots in carbon nanotubes are. Ultrashort carbon nanotube quantum dot transistors.
Using an electromigration procedure which we recently developed, we generate 10 nmscale singlewall carbon nanotube quantum dot swcntqd transistors. Cornell university 2004 the experiments presented in this thesis show that carbon nanotube nt electronic structure can be tuned by mechanical stretching and by magnetic fields. The detailed mechanisms responsible for nanotube growth are still not fully. Emmett thesis submitted to the faculty of the graduate school of vanderbilt university in partial ful. In this thesis, we investigate carbon nanotube cnt quantum dot qd hybrid devices in which a single cnt is coupled either to superconducting s and normal metal n electrodes or to ferromagnetic f contacts by means of lowtemperature transport spectroscopy experiments. An electronic version of this thesis, including color figures, is available at. Pdf quantum transport in carbon nanotubes researchgate. Highly tunable hole quantum dots in sige shellcore nanowires. Highfrequency measurements of carbon nanotube quantum dots. First, such gatetuneable artificial atoms offer a high degree.
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