The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Anand V Patwardhan - One of the best experts on this subject based on the ideXlab platform.
-
Reduction of p-nitrotoluene by aqueous Ammonium Sulfide: Anion exchange resin as a triphasic catalyst
Chemical Engineering Journal, 2007Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reduction of p- nitrotoluene (PNT) by aqueous Ammonium Sulfide was carried out using a triphasic (liquid–liquid–solid) catalyst, anion exchange resin (AER). The maximum enhancement factor of about 57 was observed with 20% (w/v) loading of AER. The reaction was observed to be kinetically controlled with apparent activation energy of 49.8 kJ/mol. The rate of reduction of PNT was established to be proportional to the square of the concentration of Sulfide and to the cube of the concentration of PNT. Based on the detailed kinetic study, an empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data. The developed model predicted the PNT conversions reasonably well.
-
reaction of benzyl chloride with Ammonium Sulfide under liquid liquid phase transfer catalysis reaction mechanism and kinetics
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reaction between benzyl chloride and aqueous Ammonium Sulfide was carried out in an organic solvent – toluene, using tetrabutylAmmonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl Sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH3/H2S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction.
-
Reaction of benzyl chloride with Ammonium Sulfide under liquid–liquid phase transfer catalysis: Reaction mechanism and kinetics
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reaction between benzyl chloride and aqueous Ammonium Sulfide was carried out in an organic solvent – toluene, using tetrabutylAmmonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl Sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH3/H2S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction.
-
kinetics of the reduction of nitrotoluenes by aqueous Ammonium Sulfide under liquid liquid phase transfer catalysis
Applied Catalysis A-general, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reduction of nitrotoluenes (o-, m- and p-) using aqueous Ammonium Sulfide as the reducing agent was carried out in an organic solvent, toluene, under liquid–liquid mode with a phase transfer catalyst (PTC), tetrabutylAmmonium bromide (TBAB). The selectivity of toluidines was found to be 100%. The reaction rate of m-nitrotoluene was found to be highest among the three nitrotoluenes, followed by p- and o-nitrotoluene. The effects of different parameters, such as speed of agitation, temperature, ammonia concentration, elemental sulfur loading, catalyst concentration, Sulfide concentration and concentration of nitrotoluene, on the conversion and reaction rate of nitrotoluene were studied to establish the mechanism of the reaction. The rate of reaction of nitrotoluene was found to be proportional to the concentration of catalyst, to the square of the concentration of Sulfide and to the cube of the concentration of nitrotoluene. The apparent activation energy for this kinetically controlled reaction was estimated as 19.43, 21.45 and 25.54 kcal/mol for ONT, PNT and MNT, respectively. A generalized empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data for the three nitrotoluenes.
-
Kinetics of the reduction of nitrotoluenes by aqueous Ammonium Sulfide under liquid–liquid phase transfer catalysis
Applied Catalysis A: General, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reduction of nitrotoluenes (o-, m- and p-) using aqueous Ammonium Sulfide as the reducing agent was carried out in an organic solvent, toluene, under liquid–liquid mode with a phase transfer catalyst (PTC), tetrabutylAmmonium bromide (TBAB). The selectivity of toluidines was found to be 100%. The reaction rate of m-nitrotoluene was found to be highest among the three nitrotoluenes, followed by p- and o-nitrotoluene. The effects of different parameters, such as speed of agitation, temperature, ammonia concentration, elemental sulfur loading, catalyst concentration, Sulfide concentration and concentration of nitrotoluene, on the conversion and reaction rate of nitrotoluene were studied to establish the mechanism of the reaction. The rate of reaction of nitrotoluene was found to be proportional to the concentration of catalyst, to the square of the concentration of Sulfide and to the cube of the concentration of nitrotoluene. The apparent activation energy for this kinetically controlled reaction was estimated as 19.43, 21.45 and 25.54 kcal/mol for ONT, PNT and MNT, respectively. A generalized empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data for the three nitrotoluenes.
Ming-kwei Lee - One of the best experts on this subject based on the ideXlab platform.
-
Electrical characterization of liquid‐phase‐deposited SiON on (NH4)2S‐treated GaAs
physica status solidi (a), 2013Co-Authors: Chih-feng Yen, Jung-chan Lee, Chi-hsuan Cheng, Ming-kwei LeeAbstract:The electrical characteristics of liquid-phase-deposited (LPD) silicon oxynitride film on Ammonium-Sulfide-treated p-type (100) gallium arsenide (GaAs) substrate were investigated. Hydrofluosilicic acid, ammonia, and boric acid aqueous solutions were used as precursors. The electrical characteristics of silicon oxynitride film are a function of the boric acid volume in the growth solution and much improved on GaAs substrate with Ammonium-Sulfide treatment. The leakage currents can reach 1.24 × 10−7 and 7.85 × 10−7 A cm−2 at ±0.5 MV cm−1. The lowest interface state density and the dielectric constant are 3.32 × 1011 cm−2 eV−1 and 4.74, respectively.
-
Characterization of enhancement-mode n-channel sulfur-treated InP MOSFET with liquid phase deposition-TiO2 gate oxide
Journal of Vacuum Science & Technology B Nanotechnology and Microelectronics: Materials Processing Measurement and Phenomena, 2012Co-Authors: Chih-feng Yen, Ming-kwei LeeAbstract:TiO2 films were prepared with aqueous solutions of hexafluorotitanic acid and boric acid on an InP substrate with an Ammonium Sulfide treatment. The films showed greatly enhanced electrical characteristics compared to those prepared without the Ammonium Sulfide treatment. The leakage currents of the resulting TiO2/InP capacitor reached 2.1 × 10−7 and 7.4 × 10−7 A/cm2 at ±0.5 MV/cm. The dielectric constant and the effective oxide charges were 43 and −2 × 1011 C/cm2, respectively. The interface state density was 3.6 × 1011 cm−2 eV−1. The fabricated enhancement-mode n-channel InP MOSFET exhibited good electrical characteristics with a maximum gm of 43 mS/mm and electron mobility of 348 cm2/Vs.
-
Thin TiO 2 grown by metal-organic chemical vapor deposition on (NH 4 ) 2 S x -treated InP
Applied Physics A, 2011Co-Authors: Ming-kwei Lee, Chih-feng Yen, Shih-chen ChiuAbstract:The electrical characteristics of thin TiO2 films prepared by metal–organic chemical vapor deposition grown on a p-type InP substrate were studied. For a TiO2 film of 4.7 nm on InP without and with Ammonium Sulfide treatment, the leakage currents are 8.8×10−2 and 1.1×10−4 A/cm2 at +2 V bias and 1.6×10−1 and 8.3×10−4 A/cm2 at −2 V bias. The lower leakage currents of TiO2 with Ammonium Sulfide treatment arise from the improvement of interface quality. The dielectric constant and effective oxide charge number density are 33 and 2.5×1013 cm2, respectively. The lowest mid-gap interface state density is around 7.6×1011 cm−2 eV−1. The equivalent oxide thickness is 0.52 nm. The breakdown electric field increases with decreasing thickness in the range of 2.5 to 7.6 nm and reaches 9.3 MV/cm at 2.5 nm.
-
Improvement in Electrical Characteristics of Low-Pressure Chemical-Vapor-Deposited SiNx Dielectric Layer on GaN Substrate by Ammonium Sulfide Treatment
Japanese Journal of Applied Physics, 2009Co-Authors: Ming-kwei Lee, Cheng-yuan LeeAbstract:The electrical characteristics of low-pressure chemical-vapor-deposited SiNx on GaN and Ammonium Sulfide-treated GaN substrate were investigated. Upon Ammonium Sulfide treatment, the leakage current densities of SiNx/GaN were reduced from 1.82 ×10-9 to 2 ×10-10 A/cm2 and from 4.44 ×10-9 to 1.6 ×10-9 A/cm2 under electric fields of ±1 MV/cm, respectively. The negative effective oxide charges were improved from -1.39 ×1013 to -4.1 ×1012 C/cm2. The Ammonium Sulfide treatment improves the interface and film qualities of SiNx/GaN.
-
High-Quality SiO2 Grown on (NH4)2Sx-Treated GaAs by Liquid Phase Deposition
Japanese Journal of Applied Physics, 2008Co-Authors: Ming-kwei Lee, Chih-feng YenAbstract:The electrical characteristics including current–voltage, capacitance–voltage, hysteresis loops, and interface state density of liquid-phase-deposited silicon dioxide (LPD-SiO2) films on the p-type (100) gallium arsenide (GaAs) substrate with and without Ammonium Sulfide treatments were investigated. The aqueous solution of hydrofluosilicic acid and boric acid was used as the growth solution for silicon dioxide films. The GaAs substrate with Ammonium Sulfide treatment shows improved electrical characteristics. The electrical characteristics depend on the boric acid concentration in the growth solution. The leakage currents can reach 3.95 ×10-8 and 1.01 ×10-7 A/cm2 under positive and negative electric fields at 0.5 MV/cm, respectively. The interface state density is 9.34 ×1010 cm-2 eV-1 at an energy of 0.69 eV from the valence band.
Meimei Z Tidrow - One of the best experts on this subject based on the ideXlab platform.
-
Ammonium Sulfide passivation of Type-II InAs/GaSb superlattice photodiodes
Applied Physics Letters, 2004Co-Authors: Aaron Gin, Andrew Hood, A Bajowala, Manijeh Razeghi, Yajun Wei, V. R. Yazdanpanah, Meimei Z TidrowAbstract:We report on the surface passivation of Type-II InAs/GaSb superlattice photodetectors using various Ammonium Sulfide solutions. Compared to unpassivated detectors, zero-bias resistance of treated 400 μm×400 μm devices with 8 μm cutoff wavelength was improved by over an order of magnitude to ∼20 kΩ at 80 K. Reverse-bias dark current density was reduced by approximately two orders of magnitude to less than 10 mA/cm2 at −2 V. Dark current modeling, which takes into account trap-assisted tunneling, indicates greater than 70 times reduction in bulk trap density for passivated detectors.
-
Ammonium Sulfide passivation of type ii inas gasb superlattice photodiodes
Applied Physics Letters, 2004Co-Authors: Andrew Hood, A Bajowala, Vahid Yazdanpanah, Manijeh Razeghi, Meimei Z TidrowAbstract:We report on the surface passivation of Type-II InAs/GaSb superlattice photodetectors using various Ammonium Sulfide solutions. Compared to unpassivated detectors, zero-bias resistance of treated 400 μm×400 μm devices with 8 μm cutoff wavelength was improved by over an order of magnitude to ∼20 kΩ at 80 K. Reverse-bias dark current density was reduced by approximately two orders of magnitude to less than 10 mA/cm2 at −2 V. Dark current modeling, which takes into account trap-assisted tunneling, indicates greater than 70 times reduction in bulk trap density for passivated detectors.
Sunil K Maity - One of the best experts on this subject based on the ideXlab platform.
-
A new mechanistic model for liquid-liquid phase transfer catalysis: Reaction of benzyl chloride with aqueous Ammonium Sulfide
Chemical Engineering Science, 2009Co-Authors: Sunil K Maity, Sujit Sen, Narayan C. PradhanAbstract:Abstract A new mechanistic model for reactions involving two liquid phases and a homogeneous phase transfer catalyst (PTC) has been developed based on extraction mechanism considering the equilibrium of catalyst and active catalysts at the interface. The proposed kinetic model considers thermodynamic framework based aqueous phase ionic equilibrium and the separate contributions of non-PTC and PTC-enhanced reactions towards the overall reactions. The developed model was then applied to an industrially important reaction of benzyl chloride with aqueous Ammonium Sulfide for synthesis of dibenzyl Sulfide and benzyl mercaptan. The kinetic parameters of the developed model were estimated at different temperatures using an indigenously developed non-linear regression technique based on modified Levenberg–Marquardt algorithm. Sensitivity analysis was then performed under various experimental conditions using the estimated parameters and the results were compared with experimental observations. A good agreement was observed between experimental and calculated values with proper trends of the results.
-
Reduction of p-nitrotoluene by aqueous Ammonium Sulfide: Anion exchange resin as a triphasic catalyst
Chemical Engineering Journal, 2007Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reduction of p- nitrotoluene (PNT) by aqueous Ammonium Sulfide was carried out using a triphasic (liquid–liquid–solid) catalyst, anion exchange resin (AER). The maximum enhancement factor of about 57 was observed with 20% (w/v) loading of AER. The reaction was observed to be kinetically controlled with apparent activation energy of 49.8 kJ/mol. The rate of reduction of PNT was established to be proportional to the square of the concentration of Sulfide and to the cube of the concentration of PNT. Based on the detailed kinetic study, an empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data. The developed model predicted the PNT conversions reasonably well.
-
reaction of benzyl chloride with Ammonium Sulfide under liquid liquid phase transfer catalysis reaction mechanism and kinetics
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reaction between benzyl chloride and aqueous Ammonium Sulfide was carried out in an organic solvent – toluene, using tetrabutylAmmonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl Sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH3/H2S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction.
-
Reaction of benzyl chloride with Ammonium Sulfide under liquid–liquid phase transfer catalysis: Reaction mechanism and kinetics
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reaction between benzyl chloride and aqueous Ammonium Sulfide was carried out in an organic solvent – toluene, using tetrabutylAmmonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl Sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH3/H2S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction.
-
kinetics of the reduction of nitrotoluenes by aqueous Ammonium Sulfide under liquid liquid phase transfer catalysis
Applied Catalysis A-general, 2006Co-Authors: Sunil K Maity, Narayan C. Pradhan, Anand V PatwardhanAbstract:Abstract The reduction of nitrotoluenes (o-, m- and p-) using aqueous Ammonium Sulfide as the reducing agent was carried out in an organic solvent, toluene, under liquid–liquid mode with a phase transfer catalyst (PTC), tetrabutylAmmonium bromide (TBAB). The selectivity of toluidines was found to be 100%. The reaction rate of m-nitrotoluene was found to be highest among the three nitrotoluenes, followed by p- and o-nitrotoluene. The effects of different parameters, such as speed of agitation, temperature, ammonia concentration, elemental sulfur loading, catalyst concentration, Sulfide concentration and concentration of nitrotoluene, on the conversion and reaction rate of nitrotoluene were studied to establish the mechanism of the reaction. The rate of reaction of nitrotoluene was found to be proportional to the concentration of catalyst, to the square of the concentration of Sulfide and to the cube of the concentration of nitrotoluene. The apparent activation energy for this kinetically controlled reaction was estimated as 19.43, 21.45 and 25.54 kcal/mol for ONT, PNT and MNT, respectively. A generalized empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data for the three nitrotoluenes.
Chih-feng Yen - One of the best experts on this subject based on the ideXlab platform.
-
Electrical characterization of liquid‐phase‐deposited SiON on (NH4)2S‐treated GaAs
physica status solidi (a), 2013Co-Authors: Chih-feng Yen, Jung-chan Lee, Chi-hsuan Cheng, Ming-kwei LeeAbstract:The electrical characteristics of liquid-phase-deposited (LPD) silicon oxynitride film on Ammonium-Sulfide-treated p-type (100) gallium arsenide (GaAs) substrate were investigated. Hydrofluosilicic acid, ammonia, and boric acid aqueous solutions were used as precursors. The electrical characteristics of silicon oxynitride film are a function of the boric acid volume in the growth solution and much improved on GaAs substrate with Ammonium-Sulfide treatment. The leakage currents can reach 1.24 × 10−7 and 7.85 × 10−7 A cm−2 at ±0.5 MV cm−1. The lowest interface state density and the dielectric constant are 3.32 × 1011 cm−2 eV−1 and 4.74, respectively.
-
Characterization of enhancement-mode n-channel sulfur-treated InP MOSFET with liquid phase deposition-TiO2 gate oxide
Journal of Vacuum Science & Technology B Nanotechnology and Microelectronics: Materials Processing Measurement and Phenomena, 2012Co-Authors: Chih-feng Yen, Ming-kwei LeeAbstract:TiO2 films were prepared with aqueous solutions of hexafluorotitanic acid and boric acid on an InP substrate with an Ammonium Sulfide treatment. The films showed greatly enhanced electrical characteristics compared to those prepared without the Ammonium Sulfide treatment. The leakage currents of the resulting TiO2/InP capacitor reached 2.1 × 10−7 and 7.4 × 10−7 A/cm2 at ±0.5 MV/cm. The dielectric constant and the effective oxide charges were 43 and −2 × 1011 C/cm2, respectively. The interface state density was 3.6 × 1011 cm−2 eV−1. The fabricated enhancement-mode n-channel InP MOSFET exhibited good electrical characteristics with a maximum gm of 43 mS/mm and electron mobility of 348 cm2/Vs.
-
Thin TiO 2 grown by metal-organic chemical vapor deposition on (NH 4 ) 2 S x -treated InP
Applied Physics A, 2011Co-Authors: Ming-kwei Lee, Chih-feng Yen, Shih-chen ChiuAbstract:The electrical characteristics of thin TiO2 films prepared by metal–organic chemical vapor deposition grown on a p-type InP substrate were studied. For a TiO2 film of 4.7 nm on InP without and with Ammonium Sulfide treatment, the leakage currents are 8.8×10−2 and 1.1×10−4 A/cm2 at +2 V bias and 1.6×10−1 and 8.3×10−4 A/cm2 at −2 V bias. The lower leakage currents of TiO2 with Ammonium Sulfide treatment arise from the improvement of interface quality. The dielectric constant and effective oxide charge number density are 33 and 2.5×1013 cm2, respectively. The lowest mid-gap interface state density is around 7.6×1011 cm−2 eV−1. The equivalent oxide thickness is 0.52 nm. The breakdown electric field increases with decreasing thickness in the range of 2.5 to 7.6 nm and reaches 9.3 MV/cm at 2.5 nm.
-
High-Quality SiO2 Grown on (NH4)2Sx-Treated GaAs by Liquid Phase Deposition
Japanese Journal of Applied Physics, 2008Co-Authors: Ming-kwei Lee, Chih-feng YenAbstract:The electrical characteristics including current–voltage, capacitance–voltage, hysteresis loops, and interface state density of liquid-phase-deposited silicon dioxide (LPD-SiO2) films on the p-type (100) gallium arsenide (GaAs) substrate with and without Ammonium Sulfide treatments were investigated. The aqueous solution of hydrofluosilicic acid and boric acid was used as the growth solution for silicon dioxide films. The GaAs substrate with Ammonium Sulfide treatment shows improved electrical characteristics. The electrical characteristics depend on the boric acid concentration in the growth solution. The leakage currents can reach 3.95 ×10-8 and 1.01 ×10-7 A/cm2 under positive and negative electric fields at 0.5 MV/cm, respectively. The interface state density is 9.34 ×1010 cm-2 eV-1 at an energy of 0.69 eV from the valence band.
-
Electrical Characteristics of Liquid-Phase-Deposited Titanium Oxide Films on ( NH4 ) 2S x -Treated InP Substrate
Journal of The Electrochemical Society, 2007Co-Authors: Ming-kwei Lee, Jung-jie Huang, Chih-feng YenAbstract:The electrical characteristics of liquid-phase-deposited titanium oxide films on Ammonium-Sulfide-treated p-type InP(100) substrate were investigated. The aqueous solutions of hexafluorotitanic acid and boric acid were used as the starting materials. For InP substrate without Ammonium Sulfide treatment, the electrical characteristics of titanium oxide films are poor. For InP substrate with Ammonium Sulfide treatment, the electrical characteristics are much improved. The leakage currents can reach 2 X 10 -7 and 7 X 10 -7 A/cm 2 under positive and negative electric fields at 0.5 MV/cm. The dielectric constant and the effective oxide charges are 40 and -2 X 10 11 C/cm 2 , respectively. The interface state density is 8 X 10 11 cm -2 eV -1 at the energy of 0.78 eV from the edge of valence band.