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Abstract
Recent advance of nanotechnology has stimulated much interest in the study of quantum transport in mesoscopic nanoscale devices. The aim of the present thesis is to investigate the quantum transport properties of a mesoscopic device under the influence of an ac-field, i.e., the important role in the photon-assisted charge carrier transport. A model for such mesoscopic devices proposed as follow:
Two metal contacts are deposited on the carbon nanotube quantum dot to serve as source and drain electrodes. The conducting substrate is the gate electrode in this three-terminal mesoscopic device. Another metallic gate is used to govern the electrostatics and the switching of carbon nanotube channel. The substrate at the carbon nanotube quantum dot contacts are controlled by the back gate. Both effects of the photons of an ac-field and magnetic field are investigated. The photon-assisted tunneling probability is deduced by solving Dirac equation. Then the current is deduced according to Landauer-Buttiker formula. The quantum capacitance for the device is deduced in terms of the density of states. Numerical calculations are performed for the dependence of the current on the magnetic field, photon energy, gate voltage and source-drain voltage.
Oscillatory behavior of the current is observed which is due to the Coulomb blockade oscillations. It was found, also, that the peak heights of the dependence of the current on the parameters under study are strongly affected by the interplay between the tunneled electrons and the photon energy. This interplay affects on the sidebands resonance.
The results obtained in the present thesis are found to be in concordant with those in the literature, which confirms the correctness of the proposed model. This study is valuable for nanotechnology applications, e.g., photo-detector devices and solid state quantum computing systems and quantum information processes.