Parallel carbon nanotube quantum dots and their interactions. 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. 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. 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. Nanotube quantum dot transport with spinorbit coupling and. The noise detection is based on photon assisted tunneling in a superconductorinsulatorsuperconductor junction.
Because these devices are so short, we can explore fundamental mesoscopic physics, engineer tuneable nanoelectromechanical systems nems and create ultrashort transistors. Quantum transport in carbon nanotubes semantic scholar. The magnetoresistance of these spinvalves were measured at lowtemperatures and as a function of the charge state of the quantum dots. This master thesis describes the fabrication steps and complications of. In a quantum dot electrons are made to tunnel onebyone through. Emmett thesis submitted to the faculty of the graduate school of vanderbilt university in partial ful. The ratio of lifetimes of the highcurrent state to the lowcurrent state changes exponentially with respect to the gatevoltage, and also. The sample is first evaporated under one angle dark, then oxidized. A novel strategy for the fabrication of multiwall carbon nanotube. Pdf parallel carbon nanotube quantum dots and their. Churchill 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.
Quantum dot modified multiwall carbon nanotubes the. This thesis presents research into spintransport in carbon nanotube quantum dots. Local gate control in carbon nanotube quantum devices. Quantum dot josephson junctions in the kondo regime. Noncollinear spinorbit magnetic elds in a bent carbon nanotube. Quantum dots seem to be ideal devices in which to observe quantum phase transitions. Quantum dots 2 quantum dot qd is a conducting island of a size comparable to the fermi wavelength in all spatial directions. The current emission noise of a carbon nanotube quantum dot in the kondo regime is measured at frequencies. This project will investigate carbon nanotube devices with. 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. Electron transistors sets and carbon nanotube double quantum dots with narrow top. Accessing the quantum world through electronic transport in. In single quantum dots defined in short lengths of nanotube, the energy levels associated.
The second set of experiments concerns carbon nanotube double quantum dots. Exact calculations are combined with a simple model to provide an intuitive and accurate description of singleparticle and interaction effects. Currentvoltage characteristics of suspended carbon nanotube quantum dots show an additional series of steps equally spaced in. While tio2 nanotube arrays cosensitized with cds and pbs quantum dots can achieve water splitting under visible light excitation, the use of quantum dots is limited by the relatively slow interfacial hole transfer rate and low internal quantum efficiencies in the visible region. 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. This thesis describes the design, fabrication, and characterization of a photo.
Shotnoise detection in a carbon nanotube quantum dot. Often called the artificial atoms, however the size is much bigger 100 nm for qds versus 0. All in all, i can affirm that the research into cnt qds has reached a reasonable level of. We precisely extract the tunnel coupling and identify the molecular states by the sequentialtunneling line shape of the resonances in di. 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. The locations of single wall carbon nanotube quantum dots were. Analysis of random telegraph noise observed in semiconducting. 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. Purcellenhanced quantum yield from carbon nanotube. Pdf kramers polarization in strongly correlated carbon. Asgrown carbon nanotube quantum dots with superconducting contacts. 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.
A study by physicists at the technische universitaet muenchen has shown how nanotubes can. The observed values are nevertheless already significantly below g 2. Outline of thesis the problem statement behind this thesis was the following. Chem library, imperial college of science, technology and medicine, uk. An electronic version of this thesis, including color figures, is available at. Local gate control in carbon nanotube quantum devices abstract this thesis presents transport measurements of carbon nanotube electronic devices operated in the quantum regime. Gatedefined quantum dots on carbon nanotubes request pdf. The experiments presented in this thesis show that carbon nanotube nt electronic structure can be tuned by mechanical stretching and by magnetic fields. In the last chapter we present a fabrication procedure for defining nanotube quantum dots with controllable barriers. This thesis presents experimental attempts towards advances in the field of quantum computation using carbon nanotube based quantum dot devices and highfrequency techniques. We demonstrate tunable tunnel coupling of the double dot and quantify the strength of the tunneling using the charge sensor.
Characterization of conjugated quantum dots and carbon nanotube qd. Carbon nanotube superconducting quantum interference device. A superconducting quantum interference device squid with singlewalled carbon nanotube cnt josephson junctions is presented. A carbon nanotube quantum dot cnt qd is a small region of a carbon nanotube in which electrons are confined. Highly tunable hole quantum dots in sige shellcore nanowires. Ferromagnetically contacted carbon nanotube\ud quantum dots.
This way it was possible to extend the system to form a double quantum dot. Ferromagnetically contacted carbon nanotube quantum dots. 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 phase transition in a singlemolecule quantum dot.
Reaction scheme of manual solidphase synthesis of synthetic crt peptide. 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. We study the twoelectron eigenspectrum of a carbonnanotube double quantum dot with spinorbit coupling. The exposed resist is removed from the substrate by immersing the sample in. Using an electromigration procedure which we recently developed, we generate 10 nmscale singlewall carbon nanotube quantum dot swcntqd transistors. Ultrashort carbon nanotube quantum dot transistors.
Asgrown carbon nanotube quantum dots with superconducting. I, shirin ghaderi, certify that the work presented in this thesis is my own. Master thesis hybrid devices based on carbon nanotubes. In this thesis, the fundamentals of quantum dots in carbon nanotubes are. Enhanced photoelectrochemical performance of quantum dot. There are various ways of producing swnts, which are briefly discussed later. Quantum dots in gated nanowires and nanotubes abstract this thesis describes experiments on quantum dots made by locally gating onedimensional quantum wires. Carbon nanotubes can be used as quantum bits for quantum computers. These fascinating electromechanical and magnetic effects are quantified using.
Also, a small coupling is found between orbitals with opposite magnetic moments leading to anticrossing behaviour at zero. Physics of very small bandgap carbon nanotube quantum dots. Carbon nanotube quantum dots tu delft repositories. Scanning gate imaging of two coupled quantum dots in single. Electronhole symmetry in a semiconducting carbon nanotube quantum dot. Semiconductor nanocrystals, or quantum dots, are crystalline semiconductors on a size scale from 1. We next chose parameters which concerns the nanotube dot region. For nanotube quantum dot we adopted the dependence. Quantum confinement in each junction induces a discrete quantum dot. Pdf quantum transport in carbon nanotubes researchgate. Thermoelectric transport in nanoscale materials joshua p. Fabrication and characterization of a quantum dotsensitized solar cell by kevin j. 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. Pdf carbon nanotubes are a versatile material in which many aspects of condensed.
In this thesis, we fabricate silicongermanium coreshell nanowire on bottom gate. In the first nanotube experiment, spindependent transport through the double dot is compared in two sets of devices. Tuning the band structure of carbon nanotubes ethan davis minot, ph. Lastly, the areas of the quantum dot not covered by the etch mask are chemically etched away poole. Single electron transistors and carbon nanotube double quantum. Lately, the emphasis of carbon nanotube quantum dot research is shifting towards defining nanotube quantum dots with tunable barriers. Rey jila, university of colorado and national institute of standards and technology, boulder, colorado 803090440, and. Andreev and spin transport in carbon nanotube quantum dot. Much of the following thesis will be devoted to the quantum dot behavior of. Quantum dots form during the epitaxial growth of two semiconductors having two different lattice constants. In atoms the attractive forces are exerted by the nuclei, while in qds by background charges. First, such gatetuneable artificial atoms offer a high degree.
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