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1 - Transistors based on gallium nitride (GaN), growth techniques, and nanostructures
Hamidreza Ravanbakhsh Leila ShekariGallium nitride(GaN) is a material with a wide and straight band gap of 3.39eV. This semiconductor has the crystal structure of Wurtzite as one of the most stable phases of matter in environmental conditions. This material and its alloys have a low intrinsic charge carr أکثرGallium nitride(GaN) is a material with a wide and straight band gap of 3.39eV. This semiconductor has the crystal structure of Wurtzite as one of the most stable phases of matter in environmental conditions. This material and its alloys have a low intrinsic charge carrier density due to their wide band gap, but on the other hand, they have significant charge transfer properties. These include high electron mobility of about 1300cm2/Vs and usability in high-temperature applications due to its very high thermal conductivity. They also have a saturation velocity of about 2.5*107cm/S and a high breakdown electric field of about 3.5MV/cm compared to 0.3MV/cm for silicon. This paper discussed about the most important GaN crystal growth methods, such as Ammonothermal, Hydride Vapor Phase Epitaxy(HVPE), Sodium flux(Na-flux), Metal-Organic Chemical Vapor Deposition(MOCVD) and Molecular Beam Epitaxy(MBE). Each of these methods has its own advantages and drawbacks and is used in research and industrial fields. MOCVD and MBE techniques are more widely used than other techniques, and due to larger throughput and larger wafer size, MOCVD, is widely used in industrial applications. According to the articles, which were discussed in this paper, countries such as the United States, Japan, and Germany, among other countries, have focused more on these two methods. The most common nanostructures obtained from the studied methods are nanowires, quantum wells, quantum wires, quantum dots, and GaN nanoparticles. This paper mentioned that nanowires and quantum wells are the most widely used morphologies in the structure of GaN-based transistors. Over the past few years, countries such as the United States, South Korea, India, China, and Germany have focused more on the growth of widely used GaN nanostructures. تفاصيل المقالة -
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2 - Employing constant photocurrent method for the study of defects in silicon thin films
Hitendra K. Malik Sucheta Juneja Sushil KumarAbstractDifferent optical characterization techniques have been performed on a series of microcrystalline silicon thin films deposited using very high-frequency-assisted plasma-enhanced chemical vapor deposition process. The constant photocurrent method has been employe أکثرAbstractDifferent optical characterization techniques have been performed on a series of microcrystalline silicon thin films deposited using very high-frequency-assisted plasma-enhanced chemical vapor deposition process. The constant photocurrent method has been employed to study the defects states in density of states spectra of hydrogenated microcrystalline silicon thin films. The photocurrent measurements demonstrate anisotropy in the optoelectronic properties of the material. We have analyzed the optical absorption coefficient from UV spectroscopy and with the help of constant photocurrent method. The spectra have been analyzed in broad region and are presented for both the cases, i.e., surface and bulk light scatterings. The spectra were interpreted in terms of disorder, resulting defect density, crystalline/amorphous volume fractions and material morphology. The subgap-related parameters such as absorption coefficient, characteristic energy E0 of tail states and density of subgap defect states together with an estimate of the bandgap of silicon films prepared at various crystalline fractions have also been estimated. The density of localized tail states is found to fall exponentially toward the gap with band tail width of about 110 meV. تفاصيل المقالة -
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3 - Memory effect in silicon nitride deposition using ICPCVD technique
Sunil Kumar D. S. Rawal Hitendra K. Malik Rajeev Sanwal S. A. Khan Seema VinayakAbstractIn this study, a plasma-based low-temperature, low-pressure SiN film deposition is investigated for device applications. Ammonia, nitrogen and silane are being used for optimization of the quality of SiN film for device passivation by ICPCVD. Characterization of أکثرAbstractIn this study, a plasma-based low-temperature, low-pressure SiN film deposition is investigated for device applications. Ammonia, nitrogen and silane are being used for optimization of the quality of SiN film for device passivation by ICPCVD. Characterization of SiN film is done using elastic recoil detection analysis, AFM, FTIR and ellipsometry. The effect of previous process parameters on subsequent process is called memory effect, which has been investigated by all the characterization techniques. During deposition, this effect has been observed for the same parameters that are used to maintain the stoichiometry of the film. It has been observed that some of the residues of gases used for SiN deposition remain present even after the deposition in the chamber and are carried over for the next deposition process and alter the film property, though parameters such as flow rate, temperature, pressure and time remain fixed. This memory effect alters the film surface roughness and stoichiometry thus affecting device characteristics after passivation. تفاصيل المقالة -
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4 - Effect of Catalyst on the Growth of Diamond-like Carbon by HFCVD
M. Aghaie M. Ghoranneviss Z. PurrajabiDiamond like carbon (DLC) film was grown by hot filament chemical vapor deposition (HFCVD)technique. In the present work, we investigated the quality of the DLC films groew on the substratesthat were coated with various metal nanocatalysts (Au and Ni). A combination of أکثرDiamond like carbon (DLC) film was grown by hot filament chemical vapor deposition (HFCVD)technique. In the present work, we investigated the quality of the DLC films groew on the substratesthat were coated with various metal nanocatalysts (Au and Ni). A combination of CH4/Ar/H2 rendersthe growth of carbon nanostructures technique (diamond like carbon). The utilized samples werecharacterized by the scanning electron microscopy (SEM) and Raman spectroscopy techniques. تفاصيل المقالة -
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5 - Evaluation of the Effect of Ni-Co NPs for the Effective Growth of Carbon Nanotubes by TCVD System
Sepideh Sadat Madani Karim Zare Mahmood GhorannevissA systematic study was conducted to understand the influences of catalyst combination as Ni-Co NPs on carbon nanotubes (CNTs) grown by Chemical Vapor Deposition (TCVD). The DC-sputtering system was used to prepare Co and Ni-Co thin films on silicon substrate. Ni- Co أکثرA systematic study was conducted to understand the influences of catalyst combination as Ni-Co NPs on carbon nanotubes (CNTs) grown by Chemical Vapor Deposition (TCVD). The DC-sputtering system was used to prepare Co and Ni-Co thin films on silicon substrate. Ni- Co nanoparticles were used as metal catalyst for growing carbon nanotubes from acetylene (C2H2) gas in 850 ̊ C during 15 min. Carbon nanotubes grown on Co and Ni-Co deposited on Si substrates was characterized by Field Emission Scanning Electron Microscopy (FESEM) and Raman spectroscopy. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the nickel and cobalt nanocatalysts deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface morphology of the nanocatalysts. It was found that by the addition of Ni NPs thin layer on Si substrate for Co NPs catalyst, density of the grown CNTs is much decreased in comparison to Co NPs on Si substrate. تفاصيل المقالة -
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6 - Optimization The High Speed Machining of Hardened AISI 4140 Steel Using Vapor Deposited Cutting Tools (Wear and Roughness)
Mehdi Jalali Azizpour Ata FardaghaieIn this study, the main cutting parameters of high speed machining (HSM) including cutting speed, feed rate, depth of cut as well as deposition method were optimized using genetic algorithm considering the average surface roughness (Ra) of work piece and flank wear (Vb) أکثرIn this study, the main cutting parameters of high speed machining (HSM) including cutting speed, feed rate, depth of cut as well as deposition method were optimized using genetic algorithm considering the average surface roughness (Ra) of work piece and flank wear (Vb) of CVD and PVD coated tool criteria in high speed turning of hardened AISI 4140 Steel. Standard L18 orthogonal array has been used for the design of experiment (DOE) applying Taguchi approach. Multiple linear regression model applying Minitab, was used to determine the relationship and interaction between machining parameters and outputs. For genetic algorithm(GA) optimization, the average was applied as a functional output of design of experiments. The results of GA for smaller- the better quality characterization shows the optimum roughness of 1.107 mm and optimum flank wear of 0.461mm. The confirmation tests were carried out in order to validate the response of predicted optimum condition. The results of validation test show a good agreement between obtained optimum condition and the results of genetic algorithm. The analysis of variance was used in order to obtain the contribution of each factor on the output statistically. ANOVA results indicated that the cutting speed and cut depth are the most effective factors on the flank wear by 37.02 and 27.80 percent contribution respectively. The most effective factors on surface roughness were feed rate and cutting speed by 82.49 and 10.50 percent contribution respectively. Stereoscopy and Scanning electron microscopy was used to evaluate the wear mechanism and topography of worn surface. تفاصيل المقالة -
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7 - Effect of Deposition Time on the Morphological Features and Structure of DLC Coatings on Aluminuim-T6 by PACVD
seyed mohammad mahdi shafiei Hamed raeiesifard kameleh JafariDiamond like Carbon (DLC) was deposited on aluminum substrate using Plasma Assisted Chemical Vapor Deposition (PACVD) route. Spattering, the surface was activated before deposition for increasing adhesion. Deposition time was varied from 60 minutes to 5 hours. Deposit w أکثرDiamond like Carbon (DLC) was deposited on aluminum substrate using Plasma Assisted Chemical Vapor Deposition (PACVD) route. Spattering, the surface was activated before deposition for increasing adhesion. Deposition time was varied from 60 minutes to 5 hours. Deposit was characterized using with grazing incidence X-ray diffraction and atomic force microscope. The mechanical property was measured using microhardness and roughness tester. The analysis showed that the deposit consisted of columnar growth of submicron and micron meter scale. Compared to substrate material, deposit showed higher hardness and roughness. These results show that growth of DLC layer includes three stages. The first stage is primary growth of nuclei, and then these nuclei join together in second stage. In third stage, secondary growth of these nuclei happens. تفاصيل المقالة -
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8 - Characterization of DLC Thin Films Deposited by DC-Pulsed PACVD using Methane Precursor
seyed mohammad mahdi shafiei Hamed raeiesifardIn this work, Diamond Like Carbon (DLC) thin films were deposited on aluminum alloy 6061 by Plasma-Assisted Chemical Vapor Deposition (PACVD). Nitiding prior to coated leads to appropriate hardness gradient and it can greatly improve the mechanical properties of the coa أکثرIn this work, Diamond Like Carbon (DLC) thin films were deposited on aluminum alloy 6061 by Plasma-Assisted Chemical Vapor Deposition (PACVD). Nitiding prior to coated leads to appropriate hardness gradient and it can greatly improve the mechanical properties of the coatings. The composition, crystalline structure and phase of the films were investigated by Grazing Incidence X-ray Diffraction (GIXRD). Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were employed to observe the morphology and structure of the film. The DLC layer exhibited a columnar structure. The adhesion force between the film and the aluminum alloy 6061 was 30.8 Mpa. The DLC film was determined by the pull of test. The hardness of the DLC film was 12.75 Gpa. The improvement of the adhesion DLC was attributed to a less gradient hardness configuration. In addition, the mean friction coefficient of the films was about 0.2 determined by nanoindentation test. According to the results, the high and unique hardness of this coating leads to increase of the wear resistance and thus the useful life of parts. تفاصيل المقالة -
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9 - Department of Mechanical Engineering, Islamic Azad University, Roudehen Branch Tehran, Iran
S.M.M. Shafiei H. RaeisifardPlasma-assisted chemical vapor deposition method was used to construct a diamond-like carbon coating on aluminum substrate 6061-T6. Sedimentation was carried out using CH4 as a process gas at different temperatures of 250-300 Celsius with constant flow rate and power. R أکثرPlasma-assisted chemical vapor deposition method was used to construct a diamond-like carbon coating on aluminum substrate 6061-T6. Sedimentation was carried out using CH4 as a process gas at different temperatures of 250-300 Celsius with constant flow rate and power. Raman spectroscopy was used to describe these samples. Raman analysis of DLC coatings at different temperatures has been done in detail for two different wavelengths of stimulation of 514 and 785 nm and the results are shown in this paper. Peak changes were observed in both D and G peaks of Raman spectrum with increasing sediment temperature, indicating the formation of compressive strain in DLC coatings at high temperatures. Scattering is observed at both D and G peaks for different wavelengths of excitation, indicating that the DC coating is hydrogenated. It seems that the degree of hydrogenation of DLC coating decreases due to sediment temperature. The study of nano-indentation with increasing sediment temperature shows a marginal increase in hardness. تفاصيل المقالة -
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10 - The Growth of Multilayer Graphene over MCM-41 by CVD Method in Atmospheric Pressure: metal–Free Nanocatalyst
Majid Masoumi Alimorad Rashidi Saeed Sadeghpour Mohammad Mehdi ChoolaeiGraphene films were fabricated over synthesized MCM-41 nanocatalyst by chemical vapor deposition method, and the reaction was carried in atmospheric pressure at 750˚C . Acetylene gas used as carbon precursor and the synthesis reaction took place at hydrogen atmosphere . أکثرGraphene films were fabricated over synthesized MCM-41 nanocatalyst by chemical vapor deposition method, and the reaction was carried in atmospheric pressure at 750˚C . Acetylene gas used as carbon precursor and the synthesis reaction took place at hydrogen atmosphere . Mesoporous MCM-41 was synthesized at room temperature using wet chemical method . The synthesized metal free catalyst was characterized by XRD and N2 adsorption isotherms. The catalytically synthesized graphene layers were characterized by Raman spectroscopy, scanning electron microscopy ( SEM ), and transmission electron microscopy ( TEM ) . The results indicated the favorable effect of MCM-41 with high BET surface area ( 908.76 m2/g ) as an active metal free nanocatalyst for fabricating graphene layers with high level of purity and homogeneity . Because of simplicity, easy purification, and high yield of graphene synthesis offered by this method , it is possible to use it in larger scales . تفاصيل المقالة -
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11 - The Growth of Diamond-like Carbon Nano-Structures: Investigation of the Affecting Factors
Morasa Amani Malkeshi karim Zare Mahmood Ghoranneviss Zohreh Ghorannevis Omid moradiUsing DC-Plasma Enhanced Chemical Vapour Deposition (PECVD) system, the impact of pure Co onthe growth of diamond-like carbon (DLC) nano-structures were investigated. In this study, Acetylene(C2H2) was diluted in H2 and used as the reaction gas and Cobalt (Co) nano-part أکثرUsing DC-Plasma Enhanced Chemical Vapour Deposition (PECVD) system, the impact of pure Co onthe growth of diamond-like carbon (DLC) nano-structures were investigated. In this study, Acetylene(C2H2) was diluted in H2 and used as the reaction gas and Cobalt (Co) nano-particles were used asthe catalyst. The effect of preparing Co catalyst at temperatures of 240°C and 350°C and growthconditions was studied. The results showed that the Co catalyst sputtering at 350°C temperature hasa significant impact on purity, morphology, and synthesized diamond-like carbon nano-structures.This research was conducted to investigate the effect of catalyst preparation and growth conditions.Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used tocharacterize the diamond-like carbon nano-structures produced under different conditions. تفاصيل المقالة -
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12 - The Growth of Multilayer Graphene over MCM-41 by CVD Method in Atmospheric Pressure: metal–Free Nanocatalyst
Majid Masoumi Ali Morad Rashidi Mohammadmehdi Choolaei Saeed SadeghpourGraphene films were fabricated over synthesized MCM-41 nanocatalyst by chemical vapordeposition method, and the reaction was carried in atmospheric pressure at 750˚C. Acetylenegas used as a carbon precursor and the synthesis reaction took place in hydrogen atmosphere.Me أکثرGraphene films were fabricated over synthesized MCM-41 nanocatalyst by chemical vapordeposition method, and the reaction was carried in atmospheric pressure at 750˚C. Acetylenegas used as a carbon precursor and the synthesis reaction took place in hydrogen atmosphere.Mesoporous MCM-41 was synthesized at room temperature, using wet chemical method. Thesynthesized metal free catalyst was characterized by XRD and N2 adsorption isotherms. Thecatalytically synthesized graphene layers were characterized by Raman spectroscopy, scanningelectron microscopy (SEM), and transmission electron microscopy (TEM). The results indicatedthat the favorable effect of MCM-41 with high BET surface area (908.76 m2/g) as an activemetal free nanocatalyst for fabricating graphene layers with high level of purity and homogeneity.Because of simplicity, easy purification, and high yield of graphene synthesis offered bythis method, it is possible to use it in larger scales. تفاصيل المقالة -
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13 - Raman Analysis of DLC Nanostructure Coating on AL 6061-T6 Made by DC Pulsed- PACVD
Seyed Mohammad Mahdi Shafiei Hamed RaeiesifardPlasma assisted chemical vapor deposition (PACVD) technique was used to make a diamond-like carbon (DLC) coating on the Aluminum 6061- T6 substrate. The deposition was carried out using CH4 as the process gas, at different temperatures, 250°C and 300°C with cons أکثرPlasma assisted chemical vapor deposition (PACVD) technique was used to make a diamond-like carbon (DLC) coating on the Aluminum 6061- T6 substrate. The deposition was carried out using CH4 as the process gas, at different temperatures, 250°C and 300°C with constant power and flow rate. Characterization technique Raman spectroscopy was used to characterize these samples. Raman analysis of DLC coatings at different temperatures is carried out in detail for two different excitation wavelengths i.e. 514 and 785 nm and, results are presented in the paper. Blue shifts were observed in both D and G peaks of the Raman spectrum with an increase in deposition temperature, which indicates the formation of compressive strain in high-temperature deposited DLC coatings. Dispersion in both D and G peaks is observed for different excitation wavelengths suggesting that the coating is hydrogenated DLC. The degree of hydrogenation of the DLC coating appears to decrease for the deposition temperature. Nano-indentation study shows a marginal increase in hardness with an increase in deposition temperature. تفاصيل المقالة -
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14 - اثر اعمال نانو فیلم کربن شبه الماسی بر بازدهی سلولهای خورشیدی سیلیکونی
اکبر اسحاقی فخرالدین مجیری اسماعیل کرمی ایمان ابراهیم زادهلایه نازک کربن شبه الماسی به علت خاصیت ضد بازتابی که دارند به منظور افزایش بازدهی سلول های خورشیدی استفاده می گردد. در این تحقیق نانو فیلم کربن شبه الماسی با ضخامت 80 نانومتر بر سلول خورشیدی سیلیکونی نوع P به روش رسوب شیمیایی از فاز بخار تقویت شده با پلاسما (PECVD) از أکثرلایه نازک کربن شبه الماسی به علت خاصیت ضد بازتابی که دارند به منظور افزایش بازدهی سلول های خورشیدی استفاده می گردد. در این تحقیق نانو فیلم کربن شبه الماسی با ضخامت 80 نانومتر بر سلول خورشیدی سیلیکونی نوع P به روش رسوب شیمیایی از فاز بخار تقویت شده با پلاسما (PECVD) از مخلوط گازهای هیدروژن و متان لایه نشانی شد. خواص اپتیکی پوشش به وسیله دستگاه بیضی سنجی وUV-VIS-NIR Recording Spectro Photometer ارزیابی شد. بازدهی سلول خورشیدی قبل و بعد از لایه نشانی به وسیله دستگاه شبیه ساز خورشیدی مورد ارزیابی قرار گرفت. نتایج نشان داد با اعمال کربن شبه الماسی بر سلول های خورشیدی سیلیکونی، بازدهی به میزان بیش از 32 درصد افزایش می یابد. تفاصيل المقالة -
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15 - بررسی تاثیر پارامترهای مختلف بر سینتیک رسوبدهی پوشش SiC اعمال شده به روش CVD بر روی کامپوزیت کربن - کربن
ناصر حسینی حسین آقاجانیدر این پژوهش پس از اعمال پوشش SiC به روش رسوب دهی شیمیایی فاز بخار (CVD) بر روی کامپوزیت کربن-کربن، به بررسی تاثیر پارامترهای مختلف بر سینتیک رسوب دهی پرداخته شده است. به منظور بررسی فازی پوشش SiC از آنالیز XRD، ریز ساختار کامپوزیت کربن-کربن قبل و پس از اعمال پوشش SiC ا أکثردر این پژوهش پس از اعمال پوشش SiC به روش رسوب دهی شیمیایی فاز بخار (CVD) بر روی کامپوزیت کربن-کربن، به بررسی تاثیر پارامترهای مختلف بر سینتیک رسوب دهی پرداخته شده است. به منظور بررسی فازی پوشش SiC از آنالیز XRD، ریز ساختار کامپوزیت کربن-کربن قبل و پس از اعمال پوشش SiC از آنالیز SEM و بررسی فرآورده های جانبی فرآیند از آنالیز EDS استفاده شده است. بر این اساس تاثیر پارامترهای دما، ترکیب گاز ورودی، زمان و موقعیت نمونه در رآکتور بر سرعت رسوب دهی بررسی شد. نتایج نشان می دهد با تغییر پارامترهای رسوب دهی با توجه به تغییر مکانیزم رسوب دهی، سرعت آن تحت تاثیر قرار می گیرد. همچنین تصاویر SEM نشان می دهد اندازه بلورهای SiC و ضخامت پوشش در شرایط بهینه رسوب دهی به ترتیب حدود nm 300 و mμ3 است. در نهایت، تصویر SEM سطح کامپوزیت کربن-کربن قبل و بعد از اعمال پوشش SiC مقایسه شده است. تفاصيل المقالة
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