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    Characterization of porous poly-silicon as a gas sensor

    , Article Sensors and Actuators, B: Chemical ; Volume 100, Issue 3 , 2004 , Pages 341-346 ; 09254005 (ISSN) Iraji Zad, A ; Rahimi, F ; Chavoshi, M ; Ahadian, M. M ; Sharif University of Technology
    Porous poly-silicon (PPS) is a cheaper alternative to single crystal porous silicon and is a favorable choice for making gas sensors. In this study, porous poly-silicon samples were prepared using different HF concentrations and the structural and gas-sensing properties were studied. The topography of the surface was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The variation of electrical conductivity of the samples in the presence of dry air-diluted acetone, ethanol and methanol showed that for a constant etching current, the sensitivity was highest for samples prepared in 13% HF solution. The structure of the films in the optimum HF... 

    Si/Si, Si/SiO2 and SiO2/SiO2 fusion wafer bonding

    , Article Scientia Iranica ; Volume 10, Issue 4 , 2003 , Pages 477-480 ; 10263098 (ISSN) Motieifar, A ; Rashidian, B ; Sharif University of Technology
    Sharif University of Technology  2003
    The wafer bonding process has many applications in the fabrication of microelectronic, optoelectronic, power and micromachined devices. In this article, fusion bonding of silicon wafers and study of their interface are reported for the first time in Iran. Also, the bonding of two silicon wafers, with one (or both) of the wafers having a thermally grown silicon dioxide layer, has been performed and tested. © Sharif University of Technology, October 2003  

    Development of the tigre compton telescope for intermediate-energy gamma-ray astronomy

    , Article IEEE Transactions on Nuclear Science ; Volume 50, Issue 2 , 2003 , Pages 251-257 ; 00189499 (ISSN) O'Neill, T. J ; Bhattacharya, D ; Polsen, M ; Zych, A. D ; Samimi, J ; Akyuz, A ; Sharif University of Technology
    Gamma-ray observations in the low and medium energy range (0.1-100 MeV) with sufficiently sensitive telescopes will provide unique insights into many outstanding high-energy astrophysics questions. The University of California, Riverside (UCR) Tracking and Imaging Gamma-Ray Telescope (TIGRE) Compton gamma-ray telescope uses multilayers of silicon strip detectors to, for the first time, track the Compton electron and CsI(Tl)-photodiode detectors to measure the scattered photon energy. By combining the Compton telescope's inherent imaging capability with improved background discrimination, a larger field-of-view and improved spectral and spatial resolutions, a significant improvement in... 

    Design and modeling of a semiconductor laser by employing silicon carbide polymers (6H-SiC, 3C-SiC and 4H-SiC)

    , Article Asian Journal of Chemistry ; Volume 24, Issue 5 , May , 2012 , Pages 2177-2179 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    We present an edge emitting laser structure employing silicon carbide polymers only. In this structure, 3C-SiC well embedded in 6H-SiC barriers are used as the active region, which is sandwiched between the 6H-SiC mirror at the top and bottom of structure. The basic design goal is to use only silicon carbide polymers and decrease the threshold current and stable optical wavelength of the lasers with silicon carbide polymers. This paper provides key results of the device characteristics, including the light power versus electrical current and the optical wavelength versus current  

    Analysis and design of semiconductor laser with silicon carbide polymers (6H-SiC and 3C-SiC)

    , Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 7 , 2011 , Pages 1060-1063 ; 19918178 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    In the present work, a new structure of the strained quantum-well (QW) laser diode is designed and simulated. In this structure, the active region consists of tow 6H-SiC barrier and 3C-SiC quantum well (QW)which is sandwiched between two layers of 6H-SiC that can be interpreted in terms of a type-II heterostructure character and a built-in electric field due to the pyroel ectricity of 6H using an industrial-based numerical simulator. The basic design goal was to decrease the threshold current by using only silicon carbide polymers. We could obtain a working model at stable optical wavelength of 0.83μm. This paper provides key results of the device characteristics, including the light power... 

    Topology specialization for networks-on-chip in the dark silicon era

    , Article Advances in Computers ; Volume 110 , 2018 , Pages 217-258 ; 00652458 (ISSN); 9780128153581 (ISBN) Modarressi, M ; Sarbazi Azad, H ; Sharif University of Technology
    Academic Press Inc  2018
    Following Moore's law, the number of transistors on chip has grown exponentially for decades. This growing transistor count, coupled with recent architecture and compiler advances, has resulted in an unprecedented exponential performance increase of computers. With the end of Dennard scaling, however, the power required to operate all transistors at the full performance level simultaneously grows across the technology generations. Consequently, chips will keep an increasing fraction of transistors power gated or dark to remain within the power envelope. The power-gated part of the chip, known as dark silicon, is expected to comprise a significant portion of the die real estate in new... 

    Modified antisolvent method for improving the performance and stability of triple-cation perovskite solar cells

    , Article ACS Omega ; Volume 6, Issue 1 , 2021 , Pages 172-179 ; 24701343 (ISSN) Samadpour, M ; Golchini, A ; Abdizadeh, K ; Heydari, M ; Forouzandeh, M ; Saki, Z ; Taghavinia, N ; Sharif University of Technology
    American Chemical Society  2021
    Antisolvent crystallization is known as an effective approach for the deposition of pinhole-free solution-processed perovskite layers for high-performance solar cells. Here, we introduce a modified antisolvent dripping method by adding tetra ethyl orthosilicate (TEOS) into chlorobenzene as a conventional antisolvent. Through TEOS modification, perovskite solar cells show efficiencies as high as 16% with more than 85% retention after 290 h storage at ambient conditions in comparison to 20% in pristine cells. This significant enhancement in efficiency and stability mainly related to the decrement of the density of surface defects, which is confirmed by considerably enhanced photoluminescence... 

    An investigation of the silicon role on austenite recrystallization

    , Article Materials Letters ; Volume 56, Issue 6 , 2002 , Pages 984-989 ; 0167577X (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Sharif University of Technology
    The role of silicon on austenite recrystallization was investigated using hot compression experiments on a low carbon and a high silicon steel samples. The models were proposed to describe the hot deformation behavior of metals regarding dynamic recovery. The rate of static recrystallization was found lower in the silicon steel in comparison with low carbon steel. Silicon was found to produce a lower rate of dynamic recovery due to its effect on the austenite staking fault energy  

    A DFT study of carbon monoxide adsorption on a Si4 nano-cluster

    , Article Molecular Physics ; Volume 107, Issue 17 , 2009 , Pages 1805-1810 ; 00268976 (ISSN) Nahali, M ; Gobal, F ; Sharif University of Technology
    Using the gradient-corrected hybrid density functional method of Predew, Burke, and Ernzerhof (PBEPBE) and the new hybrid meta-density functional method of Truhlar (MPW1B95), the geometry, adsorption energy, vibrational frequency, and charge distribution of carbon monoxide adsorption on a Si4 nano-cluster has been studied. Taking into account spin multicipility in the calculations, a new stable structure of CO absorbed on the Si4 cluster has been found, in addition to the previously reported structures. Exhaustive vibrational frequency analysis of optimized structures shows that some of the formerly reported structures have imaginary vibrational frequencies and are not proper stable... 

    Morphological features of silicon rich phase in powder thixoformed spray atomized hyper-eutectic Al-Si alloy

    , Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 493-498 ; 10120394 (ISSN); 9771012039401 (ISBN) Kiani, M ; Aashuri, H ; Nategh, S ; Foroughi, A ; Narimannezhad, A ; Khosravani, A ; Sharif University of Technology
    Trans Tech Publications Ltd  2008
    Microstructural evolution of the spray atomized and powder thixoformed hyper-eutectic A390 aluminum alloy was investigated. The spray atomized powder revealed homogeneous and very fine silicon particles distribution, due to the rapid solidification of the alloy. The semi-solid powders were extruded into a closed die cavity through a hole for the plastic deformation of the powder particles. A drop forge of 45kg weight at different heights was used in this investigation. Remarkable rearrangement and growth of the silicon rich phase was revealed in the final stage  

    Effect of nanoparticle content on the microstructural and mechanical properties of nano-SiC dispersed bulk ultrafine-grained Cu matrix composites [electronic resource]

    , Article Journal of Materials & Design ; December 2013, Volume 52, Pages 881–887 Akbarpour, M. R ; Salahi, E ; Alikhani Hesari, F ; Kim, H. S ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    In this study, the microstructural and mechanical features of monolithic pure Cu and Cu matrix nanocomposites reinforced with three different fractions (2, 4, and 6 vol%) of SiC nanoparticles (n-SiC) fabricated via a combination of high energy mechanical milling and hot pressing techniques were investigated. The fabricated composites exhibited homogeneous distribution of the n-SiC with few porosities. It was found that the grain refinement, the planar features within the grains, and the lattice strains increase with increase in the n-SiC content. The yield and compressive strengths of the nanocomposites were significantly improved with increases in the n-SiC content up to 4 vol%; then they... 

    Validity and size-dependency of cauchy–born hypothesis with Tersoff potential in silicon nano-structures

    , Article Computational Materials Science ; Volume 63 , October , 2012 , PP. 168–177 Khoei, A. R. (Amir Reza) ; Dormohammadi, H. (Hossein) ; Sharif University of Technology
    One of the most popular constitutive rules that correlate the continuum and atomic properties in multi-scale models is the Cauchy–Born (CB) hypothesis. Based on this constitutive law of continuum media, it assumes that all atoms follow the deformation subjected to the boundary of crystal. In this paper, the validity and failure of CB hypothesis are investigated for the silicon nano-structure by comparison of the continuum and atomic properties. In the atomistic level, the stresses and position of atoms are calculated using the molecular dynamics (MD) simulation based on the Tersoff inter-atomic potential. The stresses and strains are compared between the atomistic and continuous media to... 

    A temperature-related boundary Cauchy-Born method for multi-scale modeling of silicon nano-structures

    , Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Vol. 378, issue. 5-6 , 2014 , pp. 551-560 ; ISSN: 03759601 Khoei, A. R ; Dormohammadi, H ; Aramoon, A ; Sharif University of Technology
    The surface, edge and corner effects have significant influences in the electrical and optical properties of silicon nano-structures. In this paper, a novel hierarchical temperature-related multi-scale model is presented based on the boundary Cauchy-Born method to investigate not only the surface but also the edge and corner effects in thermal properties of diamond-like structures such as silicon nano-structures at finite temperature. A combined finite element method and molecular dynamics are respectively employed in macro- and micro-scale levels. The temperature-related Cauchy-Born rule is applied using the Helmholtz free energy, as the energy density of equivalent continua relating to the... 

    Analysis of the various elements of heat sources in silicon carbide polymers (6H-SiC and 3C-SiC) semiconductor laser

    , Article Asian Journal of Chemistry ; Volume 24, Issue 5 , 2012 , Pages 2333-2335 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    In the present paper, we investigated the various elements of heat sources within a silicon carbide polymers (6H-SiC and 3C-SiC) semiconductor laser. The device employs 3C-SiC quantum well (QW) which is sandwiched between two layers of 6H-SiC as cladding regions that can be interpreted in terms of a type-II heterostructure character and a built-in electric field due to the pyroelectricity of 6H using a numerical simulator. The basic design goal was the study of the various elements of heat sources, including the Joule heat power, the Peltier-Thomson heat power and the recombination heat power  

    Growth of ZNO nanostructures on porous silicon and oxidized porous silicon substrates

    , Article Brazilian Journal of Physics ; Volume 41, Issue 2-3 , 2011 , Pages 113-117 ; 01039733 (ISSN) Rajabi, M ; Dariani, R. S ; Iraji Zad, A ; Sharif University of Technology
    We have investigated an oxidation of substrate effect on structural morphology of zinc oxide (ZnO) rods. ZnO rods are grown on porous silicon (PS) and on thermally oxidized porous silicon substrates by carbothermal reduction of ZnO powder through chemical vapour transport and condensation. Porous silicon is fabricated by electrochemical etching of silicon in hydrofluoric acid solution. The effects of substrates on morphology and structure of ZnO nanostructures have been studied. The morphology of substrates is studied by atomic force microscopy in contact mode. The texture coefficient of each sample is calculated from X-ray diffraction data that demonstrate random orientation of ZnO rods on... 

    Molecular dynamics study of the thermal expansion coefficient of silicon

    , Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 380, Issue 48 , 2016 , Pages 4039-4043 ; 03759601 (ISSN) Nejat Pishkenari, H ; Mohagheghian, E ; Rasouli, A ; Sharif University of Technology
    Elsevier, B. V  2016
    Due to the growing applications of silicon in nano-scale systems, a molecular dynamics approach is employed to investigate thermal properties of silicon. Since simulation results rely upon interatomic potentials, thermal expansion coefficient (TEC) and lattice constant of bulk silicon have been obtained using different potentials (SW, Tersoff, MEAM, and EDIP) and results indicate that SW has a better agreement with the experimental observations. To investigate effect of size on TEC of silicon nanowires, further simulations are performed using SW potential. To this end, silicon nanowires of different sizes are examined and their TEC is calculated by averaging in different directions ([100],... 

    Revisiting processor allocation and application mapping in future CMPs in dark silicon era

    , Article Advances in Computers ; Volume 110 , 2018 , Pages 35-81 ; 00652458 (ISSN); 9780128153581 (ISBN) Hoveida, M ; Aghaaliakbari, F ; Jalili, M ; Bashizade, R ; Arjomand, M ; Sarbazi Azad, H ; Sharif University of Technology
    Academic Press Inc  2018
    With technology advances and the emergence of new fabrication and VLSI technologies, current and future chip multiprocessors (CMPs) are expected to have tens to hundreds of processing elements and Gigabytes of on-chip caches, which are connected by a high bandwidth network-on-chip (NoC). Unfortunately, due to limited power budget of a computing system, specially for its processing element(s), it is impossible to keep all cores, caches, and network elements working at highest voltage level—that would resulted in dark silicon computing era, where by employing system-level or architecture-level techniques, one can keep a great portion of a CMP elements OFF (or in dim mode) to meet the power... 

    Computational investigation of gas detection and selectivity on TiS3 nanoflakes supported by experimental evidence

    , Article Physical Chemistry Chemical Physics ; Volume 20, Issue 39 , 2018 , Pages 25458-25466 ; 14639076 (ISSN) Aryanpour, M ; Rafiefard, N ; Hosseini Shokouh, H ; Fardindoost, S ; Iraji Zad, A ; Sharif University of Technology
    Royal Society of Chemistry  2018
    Titanium trisulfide (TiS3), a transition metal chalcogenide, bears the potential to replace silicon, when taking the form of nanoflakes, due to its favorable band gap and optical response. In this paper, we investigate the response of TiS3 nanoflakes to gas detection through a careful quantum computational approach and a few succinct measurements. The computations are benchmarked and compared with a relevant experiment at each step, where their results/conclusions are discussed. The most stable surface of TiS3 particles is determined as (001), in agreement with the literature. The adsorption of 5 gas molecules is characterized through formulating and estimating their adsorption intensity... 

    The effect of oxidation of macroporous silicon on carbon nanotubes growth by TCVD method

    , Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 37, Issue 6 , 2007 , Pages 489-492 ; 15533174 (ISSN) Mortazavi, S. Z ; Iraji zad, A ; Taghavi, N. S ; Reyhani, A ; Sharif University of Technology
    Carbon nanotubes (CNTs) were grown on deposited Ni on macroporous silicon by thermal chemical vapor deposition (TCVD) method using CH4 as the reaction gas. Macroporous silicon was fabricated by electrochemical etching of P-type silicon in organic electrolytes. The effect of oxidation of porous silicon (PS) on growth rate, morphology and structure of CNTs has been studied. The SEM micrographs and Raman spectra indicated that the nanotubes grown on the oxidized PS are more homogeneous and regular than those grown on the pristine PS and growth rate of CNTs grown on oxidized PS higher than those grown on pristine PS. In addition, the CNTs grown on the non-oxidized PS have different morphology... 

    Palladium plating on macroporous/microporous silicon: application as a hydrogen sensor

    , Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 37, Issue 5 , 2007 , Pages 377-380 ; 15533174 (ISSN) Rahimi, F ; Iraji Zad, A ; Razi, F ; Sharif University of Technology
    Porous silicon samples are obtained by electrochemical method on n-type wafers in room light. Scanning electron microscopy showed that the porous structure consisted of macropores under a thin microporous layer. Placing the samples in Pd-electroless solution causes the crakes inside the microporous layer and growth of the palladium particles in these crakes. However, removing the microporous layer by KOH solution with an ultrasonically assisted process makes the growth of rather uniform palladium particles on the surface in electroless plating. Variation of the electrical resistance in the presence of diluted hydrogen at room temperature revealed that the best samples have the ability to...