Sharif Digital Repository

Concept of Truth is the most fundamental concept in any intellectual activity. Knowledge systems are distinguished, above all, by their different viewpoint about truth and different criteria which they present for determining truth. Phenomenology, that its motto is returning to things as such, should introduce a definition of truth free from the presuppositions which lie in the definitions (implied or expressed ones) of it in most knowledge systems. In this project, we try to clarify concept of truth as correlation of transcendental act in philosophy of Husserl, and also study antecedents and consequents of this conception. In this project we investigate the place of the idea of “truth” in... 

This study considers the Cartesian masculinization of thought and objectivity applying Susan Bordo's viewpoint. It has been manifested here that contents in Descartes's thoughts, especially in meditations, are emerged from a historical-cultural context which also reflect the psychological condition and a reaction to that. Accordingly, Cartesian dualism emphasizing on distance and detachment, paves a way to a mechanistic view to the world; in the other hand Cartesian distinction and clearness would result in objectivity through the philosophical reconstruction of the self and the world and through making dominance and mastery. Dynamic objectivity, historical-cultural reconsideration of... 

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  

Nowadays electron beams have extensive applications in electon-optic devices such as microwave devices, electron microscopes and flat displays. So shaping and confinment of electron beams is of great importance. In the other hand, scaling of electron emitters to atomic limit causes new chalanges in reliability and beam shaping. Designing electron optic devices for nanoscale emitters needs great knowledge regarding materials properties and electron optic systems behavior in nano scale. In this study, beside providing basic optics of electron beam and effects Of external electronmagnetic fields, properties of electron optical devices
Considering nano scale limitations is considered. In... 

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... 

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... 

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... 

The fabrication of future electronic and optical devices will require advanced nanofabrication techniques that realize high spatial resolution and high precision in controlling size and position, and that are applicable to various materials. Near-field CVD (NF-CVD) was proposed to solve these problems with no need to perform nanolithography prcesses. NFCVD system has two major subsystems, first vacuum chamber and gas distribution system for delivering parent gases to the chamber and second, a nanopositiong system to keep the probe and the sample in the constant systems.In this dissertation we have set up a piezoelectric nanopositiong system and its driver modules. The positioning accuracy... 

The need for better characterization systems (electron microscopes) and high resolution lithography systems, have made electron beams systems an interesting choice for research and development. In fact, all of the above applications require ideal electron beams (beams with minimum energy spread, maximum current density, and minimum spotsize), and electron-optic lenses (simple lenses with minimum aberration). In this research, theoretical aspects of electron emission and lens systems are reviewed. Field emission array (FEA) electron guns are introduced as electron sources with minimum energy spread, and a new simulation method is presented in order to minimize the complexity, and reduce the... 

In the fabrication of semiconductor devices, uniformity of thin films has many important influences on optical and electrical properties of the device. many attempts have been done on the enhancement of the uniformity of thin films so far. In this thesis, first the effect of angular variation of source with respect to the target on uniformity in the evaporation coating system has been studied, then an in situ positioning system for substrate has been designed and fabricated. After finding the thickness’s profile for Ag and Cu in Electron Beam Gun system, we studied the motion pattern of the target for improving the uniformity. This positioning system can be used to any coating systems. in... 

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... 

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... 

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... 

An inconsistency between the circular symmetric geometry of conventional optical imagers and the geometry of long linear sensors used in today line scan cameras, results in suboptimal separate design of optics and electronics of scanner systems. In this thesis two new imaging methods namely Foveated scanning (FS) and Linear Fovea (LF) are proposed to tackle this problem and to design lenses that are better matched to linear sensors. Both techniques are based on the known Foveated Imaging (FI) scheme and are employed to enlarge the one dimensional resolved field of view (RFOV) of conventional lenses and to permit prioritized performance on a Line-of-Interest (LOI) in the image plane where the... 

Despite ongoing progress in the field of nanophotonics, characterizing and identifying optical interactions in the deep subwavelength dimensions have remained challenging. The inability of conventional optical microscopy in nanoscale imaging, due to diffraction limit, was the main stimulus for research on new characterizing methods with the capability of non-destructive high-resolution imaging in which the sample preparation is not required. To achieve this goal, scanning probe microscopes are introduced to extract valuable high spatial harmonics from near field measurements on the sample. In this thesis, by focusing on the probe-sample interaction, the near field behavior of the plasmonic... 

The main objective of this thesis is to investigate the scaling laws of electrical breakdown and the devices that use it as the main current-passage mechanism. To achieve this goal, first, the physical phenomena involved in electrical breakdown and the mechanisms that cause electrical breakdown in different environments have been investigated. It is determined which phenomena become more important with down scaling and which phenomena lose their importance, and how the electrical breakdown mechanism changes based on the importance of these phenomena. In the second step, spark gap switches that use electrical breakdown as the main current-passage mechanism have been introduced, and dependence... 

Ion sources have changed significantly since ion implantation was first used commercially. High beam current and good performance with long lifetime are the keys in an ion source. Freeman ion sources are facing challenges such as the short lifetime of the filament, the single charge of the extracted ions. In the third chapter, these challenges and solutions for them are described. In this thesis, while examining different types of ion sources and comparing them with the combination and simulation of Freeman Varian 300XP ion source performance, an improved Freeman ion source is also presented. Also, the results obtained through simulation using Comsol 6.1 software and MATLAB program have been...