Nano silicon particles can be become nano fibre under low energy electron beam bombarding. The formation of the nano silicon fibre include two stages. At first, on the nano silicon particle surface many ...Nano silicon particles can be become nano fibre under low energy electron beam bombarding. The formation of the nano silicon fibre include two stages. At first, on the nano silicon particle surface many silicon atoms are gasified, then these silicon atoms deposit in the place where have more charge on account of the static electrical absorption and the point effect of the charge accumulation , these atoms grow into non crystalline silicon fibres. The second stage is the non crystalline silicon fibres crystallizing. Its crystallizing temperature is about 180℃. The growth mechanism of the nano silicon fibre is vapour solid mode.展开更多
Increasing the density and thickness of electrodes is required to maximize the volumetric energy density of lithium-ion batteries for practical applications.However,dense and thick electrodes,especially highmass-conte...Increasing the density and thickness of electrodes is required to maximize the volumetric energy density of lithium-ion batteries for practical applications.However,dense and thick electrodes,especially highmass-content(>50 wt%) silicon anodes,have poor mechanical stability due to the presence of a large number of unstable interfaces between the silicon and conducting components during cycling.Here we report a network of mechanically robust carbon cages produced by the capillary shrinkage of graphene hydrogels that can contain the silicon nanoparticles in the cages and stabilize the silicon/carbon interfaces.In situ transmission electron microscope characterizations including compression and tearing of the structure and lithiation-induced silicon expansion experiments,have provided insight into the excellent confinement and buffering ability of this interface-strengthened graphene-caged silicon nanoparticle anode material.Consequently,a dense and thick silicon anode with reduced thickness fluctuations has been shown to deliver both high volumetric(>1000 mAh cm^-3) and areal(>6 mAh cm^-2)capacities together with excellent cycling capability.展开更多
An epitaxial SixGey layer on a silicon substrate was quantitatively evaluated using rocking curve (RC) and reciprocal space map (RSM) obtained by powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (E...An epitaxial SixGey layer on a silicon substrate was quantitatively evaluated using rocking curve (RC) and reciprocal space map (RSM) obtained by powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) in conjunction with transmission electron microscopy (TEM), and EDS in conjunction with scanning electron microscopy (SEM). To evaluate the relative deviation of the quantitative analysis results obtained by the RC, RSM, SEM/EDS, and TEM/EDS methods, a standard sample comprising a Si0.7602Ge0.2398 layer on a Si substrate was used. The correction factor (K-factor) for each technique was determined using multiple measurements. The average and standard deviation of the atomic fraction of Ge in the Si0.7602Ge0.2398 standard sample, as obtained by the RC, RSM, TEM/EDS, and SEM/EDS methods, were 0.2463 ± 0.0016, 0.2460 ± 0.0015, 0.2350 ± 0.0156, and 0.2433 ± 0.0059, respectively. The correction factors for the RC, RSM, TEM/EDS, and SEM/EDS methods were 0.9740, 0.9740, 1.0206, and 0.9856, respectively. The SixGey layer on a silicon substrate was quantitatively evaluated using the RC, RSM, and EDS/TEM methods. The atomic fraction of Ge in the epitaxial SixGey layer, as evaluated by the RC and RSM methods, was 0.1833 ± 0.0007, 0.1792 ± 0.0001, and 0.1631 ± 0.0105, respectively. After evaluating the results of the atomic fraction of Ge in the epitaxial layer, the error was very small, i.e., less than 3%. Thus, the RC, RSM, TEM/EDS, and SEM/EDS methods are suitable for evaluating the composition of Ge in epitaxial layers. However, the thickness of the epitaxial layer, whether the layer is strained or relaxed, and whether the area detected in the TEM and SEM analyses is consistent must be considered.展开更多
The fractal patterns in implanted samples are observed. Possible correlation of fractal patterns with the annealing temperature and the electrical activation ratio are given. The formation and growth process of fracta...The fractal patterns in implanted samples are observed. Possible correlation of fractal patterns with the annealing temperature and the electrical activation ratio are given. The formation and growth process of fractal patterns are compared for implanted layers both in silicon and in SiO2/GaAsP during thermal annealing. The mechanism of formation and growth process of fractal pattern is discussed.展开更多
As a wide-bandgap semiconductor, 4H-SiC is an ideal material for high-power and high-frequency devices, and plays an increasingly important role in developing our country’s future electric vehicles and 5G techniques....As a wide-bandgap semiconductor, 4H-SiC is an ideal material for high-power and high-frequency devices, and plays an increasingly important role in developing our country’s future electric vehicles and 5G techniques. Practical applications of SiCbased devices largely depend on their mechanical performance and reliability at the micro-and nanoscales. In this paper, singlecrystal [0001]-oriented 4H-SiC nanopillars with the diameter ranging from ~200 to 700 nm were microfabricated and then characterized by in situ nanomechanical testing under SEM/TEM at room temperature. Loading-unloading compression tests were performed, and large, fully reversible elastic strain up to ~6.2% was found in nanosized pillars. Brittle fracture still occurred when the max strain reached ~7%, with corresponding compressive strength above 30 GPa, while in situ TEM observation showed few dislocations activated during compression along the [0001] direction. Besides robust microelectromechanical system(MEMS), flexible device and nanocomposite applications, the obtained large elasticity in [0001]-oriented 4H-SiC nanopillars can offer a fertile opportunity to modulate their electron mobility and bandgap structure by nanomechanical straining,the so called "elastic strain engineering", for novel electronic and optoelectronic applications.展开更多
针对目前物理建模方法参数获取困难、行为建模方法需要大量实验数据的问题,该文提出两种简单易用的考虑温度影响的Si C JFET功率器件Saber环境建模方法。模型I基于Saber软件提供的JFET模板实现,问题的难点转化为如何准确提取建模对象Si ...针对目前物理建模方法参数获取困难、行为建模方法需要大量实验数据的问题,该文提出两种简单易用的考虑温度影响的Si C JFET功率器件Saber环境建模方法。模型I基于Saber软件提供的JFET模板实现,问题的难点转化为如何准确提取建模对象Si C JFET的相关模板参数;模型II根据器件厂商提供的Si C JFET的PSpice模型,在Saber环境中搭建相应的电路实现,问题的难点转化为如何分析透彻器件厂商提供的模型中各参数的物理意义,并如何调整这些参数使其能准确模拟建模对象的静态和动态特性。该文详细阐述两种仿真模型的特点及具体实现方法,并从静态特性和动态特性两个方面,从仿真和实验两个角度,验证两种仿真模型的正确性和有效性,比较两种建模方法的适用性。展开更多
文摘Nano silicon particles can be become nano fibre under low energy electron beam bombarding. The formation of the nano silicon fibre include two stages. At first, on the nano silicon particle surface many silicon atoms are gasified, then these silicon atoms deposit in the place where have more charge on account of the static electrical absorption and the point effect of the charge accumulation , these atoms grow into non crystalline silicon fibres. The second stage is the non crystalline silicon fibres crystallizing. Its crystallizing temperature is about 180℃. The growth mechanism of the nano silicon fibre is vapour solid mode.
基金the National Natural Science Foundation of China(51872195)the National Science Fund for Distinguished Young Scholars of China(51525204)+1 种基金JSPS KAKENHI(20K05281)the Beijing Natural Science Foundation(2192061)。
文摘Increasing the density and thickness of electrodes is required to maximize the volumetric energy density of lithium-ion batteries for practical applications.However,dense and thick electrodes,especially highmass-content(>50 wt%) silicon anodes,have poor mechanical stability due to the presence of a large number of unstable interfaces between the silicon and conducting components during cycling.Here we report a network of mechanically robust carbon cages produced by the capillary shrinkage of graphene hydrogels that can contain the silicon nanoparticles in the cages and stabilize the silicon/carbon interfaces.In situ transmission electron microscope characterizations including compression and tearing of the structure and lithiation-induced silicon expansion experiments,have provided insight into the excellent confinement and buffering ability of this interface-strengthened graphene-caged silicon nanoparticle anode material.Consequently,a dense and thick silicon anode with reduced thickness fluctuations has been shown to deliver both high volumetric(>1000 mAh cm^-3) and areal(>6 mAh cm^-2)capacities together with excellent cycling capability.
文摘An epitaxial SixGey layer on a silicon substrate was quantitatively evaluated using rocking curve (RC) and reciprocal space map (RSM) obtained by powder X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) in conjunction with transmission electron microscopy (TEM), and EDS in conjunction with scanning electron microscopy (SEM). To evaluate the relative deviation of the quantitative analysis results obtained by the RC, RSM, SEM/EDS, and TEM/EDS methods, a standard sample comprising a Si0.7602Ge0.2398 layer on a Si substrate was used. The correction factor (K-factor) for each technique was determined using multiple measurements. The average and standard deviation of the atomic fraction of Ge in the Si0.7602Ge0.2398 standard sample, as obtained by the RC, RSM, TEM/EDS, and SEM/EDS methods, were 0.2463 ± 0.0016, 0.2460 ± 0.0015, 0.2350 ± 0.0156, and 0.2433 ± 0.0059, respectively. The correction factors for the RC, RSM, TEM/EDS, and SEM/EDS methods were 0.9740, 0.9740, 1.0206, and 0.9856, respectively. The SixGey layer on a silicon substrate was quantitatively evaluated using the RC, RSM, and EDS/TEM methods. The atomic fraction of Ge in the epitaxial SixGey layer, as evaluated by the RC and RSM methods, was 0.1833 ± 0.0007, 0.1792 ± 0.0001, and 0.1631 ± 0.0105, respectively. After evaluating the results of the atomic fraction of Ge in the epitaxial layer, the error was very small, i.e., less than 3%. Thus, the RC, RSM, TEM/EDS, and SEM/EDS methods are suitable for evaluating the composition of Ge in epitaxial layers. However, the thickness of the epitaxial layer, whether the layer is strained or relaxed, and whether the area detected in the TEM and SEM analyses is consistent must be considered.
基金Project supported by the National Natural Science Foundation of China.
文摘The fractal patterns in implanted samples are observed. Possible correlation of fractal patterns with the annealing temperature and the electrical activation ratio are given. The formation and growth process of fractal patterns are compared for implanted layers both in silicon and in SiO2/GaAsP during thermal annealing. The mechanism of formation and growth process of fractal pattern is discussed.
基金supported by Hong Kong Research Grant Council (RGC)(Grant No. U11207416)City University of Hong Kong (Grant No.7005234)National Natural Science Foundation of China under the Excellent Young Scientists Fund (Grant No. 11922215)。
文摘As a wide-bandgap semiconductor, 4H-SiC is an ideal material for high-power and high-frequency devices, and plays an increasingly important role in developing our country’s future electric vehicles and 5G techniques. Practical applications of SiCbased devices largely depend on their mechanical performance and reliability at the micro-and nanoscales. In this paper, singlecrystal [0001]-oriented 4H-SiC nanopillars with the diameter ranging from ~200 to 700 nm were microfabricated and then characterized by in situ nanomechanical testing under SEM/TEM at room temperature. Loading-unloading compression tests were performed, and large, fully reversible elastic strain up to ~6.2% was found in nanosized pillars. Brittle fracture still occurred when the max strain reached ~7%, with corresponding compressive strength above 30 GPa, while in situ TEM observation showed few dislocations activated during compression along the [0001] direction. Besides robust microelectromechanical system(MEMS), flexible device and nanocomposite applications, the obtained large elasticity in [0001]-oriented 4H-SiC nanopillars can offer a fertile opportunity to modulate their electron mobility and bandgap structure by nanomechanical straining,the so called "elastic strain engineering", for novel electronic and optoelectronic applications.
文摘针对目前物理建模方法参数获取困难、行为建模方法需要大量实验数据的问题,该文提出两种简单易用的考虑温度影响的Si C JFET功率器件Saber环境建模方法。模型I基于Saber软件提供的JFET模板实现,问题的难点转化为如何准确提取建模对象Si C JFET的相关模板参数;模型II根据器件厂商提供的Si C JFET的PSpice模型,在Saber环境中搭建相应的电路实现,问题的难点转化为如何分析透彻器件厂商提供的模型中各参数的物理意义,并如何调整这些参数使其能准确模拟建模对象的静态和动态特性。该文详细阐述两种仿真模型的特点及具体实现方法,并从静态特性和动态特性两个方面,从仿真和实验两个角度,验证两种仿真模型的正确性和有效性,比较两种建模方法的适用性。
