الفهرس 
THEORETICAL MODEL
Thermoelectric energy conversionOnly 14 pages are availabe for public view
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Abstract
The purpose of the current thesis is to explore the characteristics of quantum carrier transport of a single walled carbon nanotube quantum dot field-effect-transistor (SWCNTFET) subjected to both a magnetic field and an ac-field (mid infrared region). The effect of tensile strain for zigzag, chiral and armchair SWCNTs will be taken into consideration. Also, it is interesting to investigate the thermoelectric effect, that is, Seebeck and Peltier coefficients in the present different types of strained single walled carbon nanotube quantum dot field effect transistor (SWCNTFET) under the influence of an ac-field with frequency in the mid infrared region and magnetic field. This nanodevice can be modeled as follows: SWCNT in the form of quantum dot is connected to two metallic leads. These two metallic leads operate as a drain and a source. In this three-terminal device, the conducting substance acts as the gate electrode. Governing the Switching and the electrostatics of the carbon nanotube channel is realized by using another metallic gate. The back gate controls the substances at the carbon nanotube quantum dot/metal contact. Landauer-Buttiker formula using to deduce the electric current. Also by using the WKB approximation method, the photon-assisted tunneling probability is deduced. The strained band gap energy for all types of SWCNT is expressed in terms of the induced tensile strain. This band gap energy depends on the chiral indices for every type (armchair, zigzag, chiral) of the single walled carbon nanotube. In our calculations, we consider different chiral indices for every type of SWCNT.
Numerical calculations are performed for the strained energy band gap for zigzag, chiral and armchair SWCNTs. Also, the chiral angle and the diameter are computed for them. Results that for some metallic SWCNT with certain chiral indices shows a metallic SWCNT to semiconducting SWCNT transition. The variation of energy band gap of all types of SWCNT with strain might be due to breaking the bond symmetry due to curvature of nanotube.
Numerical calculations are performed for the current for zigzag, chiral and armchair SWCNT quantum dots under the influence of the frequency of an induced ac-field in the mid-infrared region and magnetic field and its variation with the external tensile strain. from the analysis of the results obtained in this thesis we notice from the computation of tunneled electrons’ mean free path that the quantum electronic transport through the present investigated SWCNT quantum dot nanodevice can be described as ballistic and obeys the coulomb blockade phenomenon. Also, results show that a periodic oscillation of the current with the strain for all armchair, zigzag and chiral SWCNTs quantum dot nanodevice. These oscillations are Coulomb blockade oscillation. Also, according to the present model of single walled carbon nanotube quantum dot nanodevice, the interaction of the tunneled electrons with the induced ac-field leads to photon-mediated transmission resonances. The interplay between the induced photons and the tunneled electrons leads to what it is known as Fano-resonance. The observed periodic oscillation of the current with strain for all types of armchair, zigzag and chiral SWCNTs quantum dot nanodevices might be operated as single electron transistor. Results of the present thesis are found concurrent with those in literature. Our results show that SWCNT quantum dot nanodevice might be applied in the field of soft and flexible nanoelectronics. Also, the present investigated nanodevice could be used as a photo-nanoscopic device for frequencies in the THz region and it could be applied in many applications in imaging systems, microwave communications and nanoelectromechanical devices for strain sensing in nanostructure materials.
The thermoelectric Seebeck and Peltier effects of the armchair, zigzag and chiral SWCNT quantum dot nanodevice are investigated, taking into consideration of certain value of applied tensile strain and induced ac-field with frequency in THz rang. Numerical calculations are performed for both Seebeck and for Peltier coefficients for the present investigated nanodevice of all types of SWCNT. The present results for both Seebeck & Peltier coefficients show that the induced far-infrared radiation introduces new photon-mediated conduction channels in the devices. Results show that both Seebeck & Peltier coefficients have random oscillations as a function of gate voltages in the Coulomb blockade regime for all types of SWCNTs quantum dots. Also, the values of both Seebeck and Peltier coefficients are enhanced mainly due to the induced tensile strain, so as the strain also has important effect on the sub-band edges of the electron band structure by smoothing the steps in the electron transmission function. Also, results show that the three types of single walled carbon nanotube quantum dot are a good thermoelectric nanodevice for energy harvesting (Seebeck effect) and coolers for nanoelectronic devices (Peltier effect).