Sharif Digital Repository

In this paper effect of Nitrogen and Boron doping on the quantum conductance of semiconductor carbon nanotubes is investigated. Calculations are performed using density function theory in conjunction with Green function techniques and the quantum conductance is calculated. Transmission and conductance of the electronic devices in nanometer scale depend on band structure and density of states. Our results show that quantum conductance of semiconductor carbon nanotube is increased by replacing Nitrogen and Boron in its structure. The value of increasing conductance depends on the type of impurity. It is greater for Nitrogen doping in comparison with Boron. Effect of strain on the quantum... 

Graphene -a two-dimensional monolayer of graphite- was realized for the first time in 2004.Owing to its physical extra ordinary properties, graphene has attracted growing interest in research from fundamental physics to electronics, spintronics, and thermoelectrics. Importantly, it is an attractive material for electronics and spintronics due to its specific physical properties such as high electron mobility and gate tunable carrier concentration. Furthermore,achievement of room-temperature spin transport with relatively long spin relaxation time makes graphene nanoribbons the best candidate for spintronics. Based on the theoretical predictions, the weak spin-orbit interaction in graphene... 

Cold plasma has many applications in micro electronics industry. In this study, several examples of widely used plasmas systems have been investigated. First, the theory and physics of each type of plasma has been studied. Then the applications of each type have been discussed. Finally, the accuracy of the statements has been investigated using COMSOL multi physics software. In 1&2 D simulations the effects of all macroscopic parameters on plasma properties and its behavior have been investigated. In the design of plasma excitation source, plasma impedance is a very important parameter for maximum power transfer. Plasma impedance has been calculated with COMSOL software. Different modes of... 

Cold plasma due to its special properties has many applications in the microelectronics industry. At the beginning of this study, a few examples of widely used plasmas and the requirements for driving their power sources have been investigated. To generate and characterize plasma, various topologies of DC power supply construction, including high-voltage low-current power supplies called multipliers and low-voltage high-voltage power supplies called converters, have been reviewed and compared.Circuit for pulse generating for plasma application has also been proposed and investigated. In the simulation section, after introducing, reviewing, and compareing the common types of simulators, the... 

As the traditional MOSFET is reaching to its scaling limit, it is crucial to find an alternative. Single Electron Devices have shown promising features, such as nano-scale dimensions and extremely low power consumption that can lead to new generation of integrated circuits. In this thesis we have presented an analytical study of metallic single electron devices, particularly single electron transistors (SET). We have illustrated our study with some major logic applications of SET. The main goal of this thesis is to develop simulation software for single electron circuits, comparable with the well-known commercial software “SIMON”, which can provide steady-state and transient analysis of the... 

Quantum-Dot Cellular Automata (QCA) is a novel field of nanotechnology which is being designed and implemented in molecular scales. It has major advantageous over transistor based technology such as: low power consumption, high information transition speed, small size and high density. It has been shown that conventional transistor based circuits can be implemented in this nanotechnology with less complexity. Furthermore, binary circuits can be implemented in QCA technology since QCA cells have only two independent and equivalent states. So, QCA provides appropriate space for computational circuits. The aim of computational circuits design is to achieve small size and high speed processors.... 

The main power source of many space systems, are solar panels which are mainly affected from irradiance, temperature and particles radiation and an electronic solar panel simulator is a power-supply system that simulates the output of the solar panel. This system by processing of input data such as environment conditions, panel specifications and etc, simulate panel behavior and it can set the IV curve of the panel in different conditions. In this thesis, after introducing electronic solar panel simulators (chapter one), photovoltaic cells (chapter two) and space environment and its effects on space systems (chapter three), modeling solar panel based on the equivalent circuit of a solar...