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breakdown-voltage
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Fabrication of gas ionization sensor using carbon nanotube arrays grown on porous silicon substrate
, Article Sensors and Actuators, A: Physical ; Volume 162, Issue 1 , 2010 , Pages 24-28 ; 09244247 (ISSN) ; Iraji Zad, A ; Razi, F ; Mortazavi, S. Z ; Sharif University of Technology
2010
Abstract
We fabricated gas sensors based on field ionization from multiwalled carbon nanotube (MWCNT) arrays grown on porous silicon templates. MWCNTs were grown through thermal chemical vapor deposition. We measured breakdown voltages, discharge and pre-discharge currents of the device for various gases in different concentrations. Our gas ionization sensors (GIS) presented good sensitivity, selectivity and short response time. The GISs based on porous substrates showed higher discharge current and good mechanical stability in comparison to those which were fabricated on polished silicon substrates. Additionally, we applied a high electric field to align CNTs. This increased the pre-breakdown...
The effect of growth parameters on photo-catalytic performance of the MAO-synthesized TiO2 nano-porous layers
, Article Materials Chemistry and Physics ; Volume 120, Issue 2-3 , 2010 , Pages 582-589 ; 02540584 (ISSN) ; Golestani Fard, F ; Moshfegh, A. Z ; Sharif University of Technology
2010
Abstract
In this research, the effect of applied voltage and electrolyte concentration on structure, chemical composition, optical properties, and especially photo-catalytic activity of the TiO2 layers containing micro/nano-sized pores are discussed. TiO2 layers were synthesized by micro arc oxidation (MAO) process using different electrolyte concentrations and applied voltages. Surface structure of the layers was studied by scanning electron microscope (SEM); furthermore, energy dispersive spectrophotometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques were employed to determine phase structure and chemical composition of the layers. Photo-activity of the...
High voltage SnO2 varistors prepared from nanocrystalline powders
, Article Journal of Materials Science: Materials in Electronics ; Volume 21, Issue 2 , 2010 , Pages 199-205 ; 09574522 (ISSN) ; Shojaee, S. A ; Nemati, A ; Sani, M. A. F ; Sharif University of Technology
2010
Abstract
In this study, SnO 2-based varistors were prepared from mechanically activated nanocrystalline powders. Nanocrystalline powders were derived by subjecting the initial powders to intensive high-energy activation with different times and ball to powder ratio. The effect of activation parameters on the powder properties and sintering temperature, as well as microstructural, micro-electrical and macro-electrical properties of the final specimens was evaluated. Varistors derived from high-energy mechanical activation exhibit a higher density (98.3% relative density) and more refined microstructure upon sintering at 1,300 °C in comparison varistors prepared from conventional powders. Breakdown...
Design of a Wide Band Power Amplifier for Power DAC
, M.Sc. Thesis Sharif University of Technology ; Sharifbakhtiar, Mehrdad (Supervisor)
Abstract
Today’s radio transmitters must be able to send information in several standards. One problem involved in these wide band electronic systems lies in its end part, ie power amplifier. To have a broad band width either switching must be made among several power amplifiers with narrow band width (tuned) or the transistor part of power amplifier must be the same and single and selection be made only among matching networks. In this thesis, a power amplifier with broad band width without requiring a matching network has been designed and laid out. Also considering the low breakdown voltage of the gate oxide of the today’s standard CMOS transistors, it is very difficult to get a high output power...
Investigation of breakdown voltage in InAIAs/InGaAs/InP HEMTs with different structures
, Article IEICE Electronics Express ; Volume 7, Issue 19 , 2010 , Pages 1447-1452 ; 13492543 (ISSN) ; Faez, R ; Hoseini, H. R ; Sharif University of Technology
Abstract
InAlAs/InGaAs/InP high electron mobility transistors have higher mobility comparing to structures without indium. But existence of indium causes smaller Eg and as a result smaller breakdown voltage. However, increasing percentage of indium results in higher mobility and as a result higher current and transconductance. Therefore decreasing percentage of indium causes higher breakdown voltage at the sometime lower transconductance. One of the most important parameters that limit maximum output power of transistor is breakdown voltage. In this paper, InAIAs/InGaAs/InP HEMTs with different structures are simulated and a structure with a good transconductance and breakdown voltage is introduced