Sharif Digital Repository

Nowadays, thin film alloy deposition has much importance. These alloys are used for various opto-electronic device applications such as liquid crystal displays, flat panel displays, plasma displays, solar cells and computer memories. Exact control of elements ratio in alloy is one of the important issues in deposition of thin film alloys. In alloy deposition with electron beam gun method from its elements, uniformity improvement of each layer is a way to maintain elements ratio in different parts of sample. This uniformity has much importance especially in optical coatings such as high quality antireflection coatings, highly selective filters and low loss reflectance coatings. In this... 

For years, in thermionic emission, a great deal of scientists’s effort has been devoted to the search for low work function materials with high melting temperature. In this way, high brightness and long life are the central targets of emission material investigations. In addition, high current density and low power consumption are the guiding principles for some applications.
In first part of this thesis, basic electron emission theories, fabrication methods of thermionic emission, effect of different parameters on the electron emission properties of thermionic emitters and applications of them are investigated. After setting up fabrication methods of S type cathode, in the second part... 

Porous thin films have becom very atractive due to their applications in many types of electronic and optical devices. There are several methods for deposition of such films. Chemical method for deposition of nanoporous thin films are relatively simple, but usually hard to control. In this thesis, chemical deposition of thin porous Molybden films is reported. In addition, an available sputtering system has been modified and, controlled porosity thin films were then deposited on glass and silicon substrates using GLAD method.These films have been characerized, and compared with chemically deposited porous thin films  

The need for integration of electron guns together with thermal considerations of thermionic cathodes has led to design new cold cathode guns based on field emission phenomenon. In first part of this thesis, basic field emission theories, fabrication methods of field emitter arrays, effect of different parameters on the field emission properties of field emitter arrays and applications of these arrays are investigated. After setting up fabrication methods of nano-tip field emitters, in the second part of thesis, Si nano-tips and Si field emitter arrays are fabricated using of thermal oxidation of silicon substrate, lithography, and chemical etching of silicon oxide and silicon substrate. Si... 

In the first part of this thesis, limitations on magnetic field distribution are studied. After that methods of creating high gradient magnetic field and limitations on it is discussed. In the second part, magnetic properties of materials and the effect of particle shape and size on these properties are studied. In this part a comprehensive analysis on demagnetizing field inside magnetic bodies is also conducted and its dependence on material susceptibility and shape is discussed. At the end of this part the effect of particle shape and size on its hysteresis loop is demonstrated theoretically, practically and by computer simulation. In order to ... 

Transparent conductive materials have been widely used in semiconductor technology. Among them all, Indium tin oxide (ITO) has been utilized as electrodes in liquid crystal displays, solar cells, heat reflecting films and gas sensors.In general, the desired properties of transparent conductive oxides are high conductance and transmission. However, due to the complexity of ITO molecular structure, the film properties strongly depend on the depositon parameters.In first part of this thesis, physical properties and electrical characteristic of ITO films, different deposition techniques, and effects of deposition parameters (substrate temperature, pressure, power, etc. ) on film properties are... 

Today, in order to reach atomic scale resolution, novel nanolithography methods, known as unconventional nanolithography, have been presented, since conventional methods, including photolithography and scanning beam lithography are fundamentally unable to fulfill this need. In this work, a specific type of unconventional lithography, known as scanning probe lithography, is presented. Scanning probe lithography takes advantage of the interactions between a very sharp probe and the sample in nanoscale distances to control this distance, and hence enable the modification of the sample using this sharp probe. In mechanical scanning probe lithography, the probe is used mechanically to change the... 

The purpose of this thesis is construction of a characterization system, for plasmonic nanoparticles. plasmonic nanoparticles are metallic particles in nanometer scale, which can confine the electromagnetic field, in their induced electric dipole, in a wide range of frequency. This optical property lead to many applications such as, medicine cancer therapy, controlled releasing of drugs, solar cells and interconnections in integrated photonic circuits.Since, optical properties are the most important properties of plasmonic nanoparticles, we need a system to characterize them optically. There are different ways of optical characterization, which need a common tools, including light sources,... 

Carbon nanotubes, due to their extraordinary electronic and physical properties, have attracted much attention in the last decade. Some of their potential applications are in CNT-field effect transistor, field emission devices, physical and chemical sensors, micro and Nanoelectromechanical systems and Nano antenna. In this thesis, we have first reviewed some features of carbon nanotubes and the advantages of PECVD method compared with thermal CVD. In the second part the role of some of the materials (such as H2/NH3/C2H4) in CNT growth are studied. We created a square pattern on the silicon wafer by photolithography. Afterwards, titanium and nickel deposition is done on the mentioned pattern.... 

Nowadays, silicon based devices especially carbon nanotubes received lots of attentions and advancement from researchers and industries. Because of amazing electrical and mechanical properties and wide range of applications, CNTs are received a lot of attention from nanoelectronics experts. There are lots of CNT growth methods such as: Arc Discharge, Laser Ablation, Surface Decomposition, CVD and PECVD.
In this thesis, we are going to use PECVD method to synthesis CNT. A typical PECVD system includes two parallel electrodes that have been packed in vacuum chamber and gases like argon, hydrogen and NH3 are introduced to chamber as a reactant gas.
In this thesis, firs we had fixed... 

With the increasing development of the semiconductor industry, the density integration of integrated circuits with affordable expenses has gained a special place between different researches. Nanolithography as a way to decrease the size of patterns has a significant contribution in integration of circuits. Scanning Probe Nanolithography (SPNL) is one of the most important nanolithography methods due to its ability to create patterns with an extremely high resolution and direct patterning. Scanning Near-field Optical Lithography (SNOL) has the advantages of the usage of optic such as non-direct effect on sample and the advantages of scanning systems such as high resolution. In first part of... 

Various applications of nanostructures in electronics, optoelectronics, MEMS, photonics and plasmonic make their fabrication an interesting research topic recently. Progress in nanotechnology depends on the capability to fabricate, position and interconnect nanometer-scale structures. The development of fabrication devices with nanoscales is mainly dependent on the existence of a suitable nanolithography approach. Patterning materials with nanoscale features aimed at improving integration and device performance faced several challenges. The limitation of conventional lithography systems including resolution related issues, operational costs and lack of flexibility to pattern organic and... 

In this project, different types of optical frequency selector devices are compared with each other and the factors limiting their behavior (losses, throughput, quality factor, etc.) are precisely analyzed. Change this behavior in near-field and far-field scales as well as the behavior of these devices in nano-dimensions are analyzed. Also, the main theoretical and technological limitations of different types of optical filters in far-field and near-field regimes are compared. In the following, the scaling behavior of different filter families in passing to nanometric dimensions is investigated and finally the limitations of the possibility of making the selected sample are analyzed. For... 

Plasma is a quasi-neutral gas consist of charged and neutral particles that manifest collective behavior. Plasma is an ionized gas in which all or a significant portion of its atoms have lost one or more electrons and become a set of positive ions and electrons. Plasma is one of the four primary states of matter. This project intends to generate plasma by a pulsed electric discharge in a gaseous environment. At first, in this project, the proper excitation circuits are collected and compared, then based on the feasibility of production, applicable methods are selected and constructed. The construction steps were such that the selected circuits were first simulated with the appropriate... 

Very dangerous gases are used in ion implanter machines. Opening and closing the valves of these gases can be very dangerous. In this project, these valves are inspected, monitored and opened and closed from a safe distance. To do this, we must monitor and control the above system by using the latest and most efficient technologies available and with the least delay. For accurate and precise monitoring, clear images should be obtained from the location and changes should be detected, and the device can be controlled very quickly with the necessary commands. To do this, one must have an accurate and comprehensive knowledge of processors and communication protocols, and also pay attention to... 

Nowadays, Diffractive lenses with the binary profile have extensive application in integrated optics and other areas photonics. These elements-because of their compatibility with integrated circuits fabrication methods- have easy and efficient fabrication processes. They also have low aberration and they offer vast degree of freedom in designing process. The main objective of this thesis is to present an effective method to analyze these binary lenses in three dimensions. From different vectorial analyses methods, Boundary Element Method (BEM) has been chosen because of its different advantages like appropriate precision and higher speed in comparison with other methods. Yet this method has... 

Diffractive optical elements with binary surface profile are of great importance in integrated optical applications. Being easy to fabricate and having high degree of freedom in design, such devices play an outstanding role in optical applications. Specifically, binary (multilevel) lenses are investigated in this dissertation. These lenses are fabricated through conventional IC fabrication methods (lithography, etching, …) and have an acceptable performance and small aberration with proper design. Different scalar and vectorial methods for the analysis of finite aperture diffractive optical elements have been investigated and advantages and disadvantages of each one have been discussed.... 

Charged particle lenses perform two types of operations. One purpose of lenses is to confine a beam, or maintain a constant or slowly varying radius. This is important in high-energy accelerators where particles must travel long distances through a small bore.A second function of lenses is to focus beams or compress them to the smallest possible radius. If the particles are initially parallel to the axis, a linear field lens aims them at a common point. Focusing leads to high particle flux or a highly localized beam spot. Focusing is important for applications such as scanning electron microscopy, ion microprobes, and ion-beam-induced inertial fusion. All modern lenses, have fully metal... 

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...