Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The C...Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The CoSi 2/Si Schottky contacts are measured with the current-voltage and capacitance-voltage (I-V/C-V) techniques within the range of temperature from 90K to room temperature.The measured I-V characteristics have been analyzed with a model based on the inhomogeneity in Schottky barrier height,i.e.,at high temperatures (≥～200K) or low temperatures but with a large bias,the I-V curves can be described by using the thermionic emission theory with a Gaussian distributed barrier height over the whole junction,while at low temperatures and with a small bias,the current is dominated by some small patches with low barrier height.It results in a plateau-like section in the low temperature I-V curves around 10 -7 A.At room temperature,the barrier height of polycrystalline CoSi 2/Si deduced from the I-V curve is about 0 57eV.For epitaxial CoSi 2,the barrier height depends on its final annealing temperature and increases from 0 54eV to 0 60eV with the annealing temperature increasing from 700℃ to 900℃.展开更多
Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent,...Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.展开更多
文摘Polycrystalline and epitaxial CoSi 2 films are formed on the n-Si (111) substrates by solid state reaction of the as-deposited Co single-layer and Co/Ti bilayer with Si,respectively at different annealing phase.The CoSi 2/Si Schottky contacts are measured with the current-voltage and capacitance-voltage (I-V/C-V) techniques within the range of temperature from 90K to room temperature.The measured I-V characteristics have been analyzed with a model based on the inhomogeneity in Schottky barrier height,i.e.,at high temperatures (≥～200K) or low temperatures but with a large bias,the I-V curves can be described by using the thermionic emission theory with a Gaussian distributed barrier height over the whole junction,while at low temperatures and with a small bias,the current is dominated by some small patches with low barrier height.It results in a plateau-like section in the low temperature I-V curves around 10 -7 A.At room temperature,the barrier height of polycrystalline CoSi 2/Si deduced from the I-V curve is about 0 57eV.For epitaxial CoSi 2,the barrier height depends on its final annealing temperature and increases from 0 54eV to 0 60eV with the annealing temperature increasing from 700℃ to 900℃.
基金Supported by the National Natural Science Foundation of China(No.20076019)the Natural Science Foundation of Guang-dong Province(No.000444).
文摘Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.
