A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an ...A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an atomic scale. The results show that when the cutting edge radius decreases in the nanometric grinding process with the same cut-depth and grinding speed, the depth of the damage layers and the potential energy between the silicon atoms decrease too. Also, when the cut depth increases, both the depth of the damage layers and the potential energy between silicon atoms increase. When the grinding speed is between 20 and 200m/s,the depth of the damage layers does not change much with the increase of the grinding speed under the same cutting edge radius and cut depth conditions. This means that the MD simulation is not sensitive to changes in the grinding speed, and thus increasing the grinding speed properly can shorten the sion,the subsurface damage of monocrystal silicon is silicon atoms, which is verified by the ultra-precision simulation time and enlarge the simulation scale. In conclumainly based on the change of the potential energy between grinding and CMP experiments.展开更多
In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves,...In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.展开更多
The effect of the parameters on the open-circuit voltage, V_(OC) of a-Si:H/c-Si heterojunction solar cells was explored by an analytical model. The analytical results show that V_(OC) increases linearly with the logar...The effect of the parameters on the open-circuit voltage, V_(OC) of a-Si:H/c-Si heterojunction solar cells was explored by an analytical model. The analytical results show that V_(OC) increases linearly with the logarithm of illumination intensity under usual illumination. There are two critical values of the interface state density(D_(it)) for the open-circuit voltage(V_(OC)), D_(it)^(crit,1) and D_(it)crit,2(a few 1010 cm^(-2)·e V^(-1)). V_(OC) decreases remarkably when D_(it) is higher than D_(it)^(crit,1). To achieve high V_(OC), the interface states should reduce down to a few 1010 cm^(-2)·e V^(-1). Due to the difference between the effective density of states in the conduction and valence band edges of c-Si, the open-circuit voltage of a-Si:H/c-Si heterojunction cells fabricated on n-type c-Si wafers is about 22 mV higher than that fabricated on p-type c-Si wafers at the same case. V_(OC) decreases with decreasing the a-Si:H doping concentration at low doping level since the electric field over the c-Si depletion region is reduced at low doping level. Therefore, the a-Si:H layer should be doped higher than a critical value of 5×10^(18) cm^(-3) to achieve high V_(OC).展开更多
A brilliant purple octahedral single crystal is hydrothermally synthesized by the reaction of CoCl26H2O, H3BO3 and H3PO4 in NaOH aqueous solution of CH3(CH2)15N(CH3)3Br, and its crystal structure has been characterize...A brilliant purple octahedral single crystal is hydrothermally synthesized by the reaction of CoCl26H2O, H3BO3 and H3PO4 in NaOH aqueous solution of CH3(CH2)15N(CH3)3Br, and its crystal structure has been characterized by single-crystal X-ray diffraction. The compound, NaCo(H2O)2BP2O8稨2O (Mr = 336.72), belongs to hexagonal, space group P6122 with a = 9.447(5), c = 15.83(1) , V = 1223(1) 3, Dc = 2.742 g/cm3, Z = 6, F(000) = 1002 and m = 2.606 mm-1. The three-dimensional framework in the compound is built up from the linkage tetrahedral ribbons, in which the BO4 and PO4 tetrahedra alternate with CoO6 octahedra. The sodium ions and water molecules are located within the free thread of the helical ribbons.展开更多
Three-dimensional molecular dynamics simulations are carried out to study the mechanism of nanometric processing of ion implanted monocrystalline silicon surfaces. Lattice transformation is observed during implantatio...Three-dimensional molecular dynamics simulations are carried out to study the mechanism of nanometric processing of ion implanted monocrystalline silicon surfaces. Lattice transformation is observed during implantation and nano-indentation using radial distribution function and geometric criterion damage detection. Nano-indentation is simulated to study the changes of mechanical property. Implantation analysis shows the existence of amorphous phase. Indentation process shows the lattice evolution, which is beneficial for reducing fractures during processing. The indentation results reveal the reduction of brittleness and hardness of the implanted surface. The ion fluence is in direct proportion to the damage, and inverse to the hardness of the material. Experiments of ion implar, tation, nanoindentation, nano-scratching and nanometric cutting were carried out to verify the simulation results.展开更多
Non-contact atomic force microscopy（nc-AFM） atomic-scale imaging process of monocrystalline silicon surface using capped single-wall carbon nanotube tip is simulated by molecular dynamic method. The simulation resuh...Non-contact atomic force microscopy（nc-AFM） atomic-scale imaging process of monocrystalline silicon surface using capped single-wall carbon nanotube tip is simulated by molecular dynamic method. The simulation resuhs show that the nc-AFM imaging force mainly comes from the C-Si and C-C chemical covalent bonding forces, especially the former, the nonbonding Van der Waals force change is small during the range of stable imaging height. When the tip-surface distance is smaller than the stable imaging height, several neighboring carbon atoms at the tip apex are attracted, and some of them jump onto the sample surface. Finally the tip apex configuration is destroyed with the tip indenting further.展开更多
By employing the dielectric continuum model and Loudon＇s uniaxial crystal model, the interface optical （IO） phonon modes in a freestanding quasi-one-dimensional （Q1D） wurtzite rectangular quantum wire are derived...By employing the dielectric continuum model and Loudon＇s uniaxial crystal model, the interface optical （IO） phonon modes in a freestanding quasi-one-dimensional （Q1D） wurtzite rectangular quantum wire are derived and analyzed. Numerical calculation on a freestanding wurtzite GaN quantum wire is performed. The resulte reveal that the dispersion frequencies of IO modes sensitively depend on the geometric structures of the Q1D wurtzite rectangular quantum wires, the free wave-number kz in z-direction and the dielectric constant of the nonpolar matrix. The degenerating behavior of the IO modes in Q1D wurtzite rectangular quantum wire has been clearly observed in the case of small wave-number kz and Iarge ratio of length to width of the rectangular crossing profile. The limited frequency behaviors of IO modes have been analyzed deeply, and detailed comparisons with those in wurtzite planar quantum wells and cylindrical quantum wires are also done. The present theories can be looked on as a generalization of that in isotropic rectangular quantum wires, and it can naturally reduce to the case of Q1D isotropic quantum wires once the anisotropy of the wurtzite material is ignored.展开更多
Molecular dynamics simulations are employed to study the nanometric machining process of single crystal nickel. Atoms from different machining zones had different atomic crystal structures owing to the differences in ...Molecular dynamics simulations are employed to study the nanometric machining process of single crystal nickel. Atoms from different machining zones had different atomic crystal structures owing to the differences in the actions of the cutting tool. The stacking fault tetrahedral was formed by a series of dislocation reactions, and it maintained the stable structure after the dislocation reactions. In addition, evidence of crystal transition and recovery was found by analyzing the number variations in different types of atoms in the primary shear zone, amorphous region, and crystalline region. The effects of machining speed on the cutting force, chip and subsurface defects, and temperature of the contact zone between the tool and workpiece were investigated. The results suggest that higher the machining speed, larger is the cutting force. The degree of amorphousness of chip atoms and the depth and extent of subsurface defects increase with the machining speed. The average friction coefficient first decreases and then increases with the machining speed because of the temperature difference between the chip and machining surface.展开更多
Single crystalline Bi2O3 nanosheets have been synthesized by the surfactant assisted solvothermal method, using oleic acid and sodium dodecyl benzene sulfonate （SDBS） as compound surfactants. The thickness of Bi2O3 ...Single crystalline Bi2O3 nanosheets have been synthesized by the surfactant assisted solvothermal method, using oleic acid and sodium dodecyl benzene sulfonate （SDBS） as compound surfactants. The thickness of Bi2O3 nanosheets is 40--70 nm with a monoclinic crystal structure. High-resolution transmission electron microscopy observation reveals that （ 345 ） lattice plane of the single crystal is parallel to the surface of the nanosheets. The cooperative effect of oleic acid encapsulated SDBS is the key to form single crystalline a-Bi2O3 nanosheets with a preferred growth orientation. An obvious blue shift of the single crystalline Bi2O3 nanosheets with a preferred surface （ 34-5 ） is observed due to quantum confinement effects in thickness and optical anisotropy.展开更多
文摘A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an atomic scale. The results show that when the cutting edge radius decreases in the nanometric grinding process with the same cut-depth and grinding speed, the depth of the damage layers and the potential energy between the silicon atoms decrease too. Also, when the cut depth increases, both the depth of the damage layers and the potential energy between silicon atoms increase. When the grinding speed is between 20 and 200m/s,the depth of the damage layers does not change much with the increase of the grinding speed under the same cutting edge radius and cut depth conditions. This means that the MD simulation is not sensitive to changes in the grinding speed, and thus increasing the grinding speed properly can shorten the sion,the subsurface damage of monocrystal silicon is silicon atoms, which is verified by the ultra-precision simulation time and enlarge the simulation scale. In conclumainly based on the change of the potential energy between grinding and CMP experiments.
文摘In this article, the electrochemical performance of the electrodes of zinc polycrystal, Zn（002） and Zn（100） single crystals were studied by the Tafel line extrapolation of the potentio-dynamic polarization curves, the cyclic voltammetry and the charge/discharge experiment. The results shows that in 6.0 mol·L^-1 KOH solution the corrosion rate of Zn polycrystal, Zn（100） and Zn（002） single crystals decreases in turn; and the reversibility and the charge/discharge performance of Zn single crystal was superior to Zn polycrystal. The dendrite growth of the surface of Zn polycrvstal was easier than Zn single crystal during the stages of charge/discharge.
基金Project(11374094)supported by the National Natural Science Foundation of ChinaProject(2013HZX23)supported by Natural Science Foundation of Hunan University of Technology,ChinaProject(2015JJ3060)supported by Natural Science Foundation of Hunan Province of China
文摘The effect of the parameters on the open-circuit voltage, V_(OC) of a-Si:H/c-Si heterojunction solar cells was explored by an analytical model. The analytical results show that V_(OC) increases linearly with the logarithm of illumination intensity under usual illumination. There are two critical values of the interface state density(D_(it)) for the open-circuit voltage(V_(OC)), D_(it)^(crit,1) and D_(it)crit,2(a few 1010 cm^(-2)·e V^(-1)). V_(OC) decreases remarkably when D_(it) is higher than D_(it)^(crit,1). To achieve high V_(OC), the interface states should reduce down to a few 1010 cm^(-2)·e V^(-1). Due to the difference between the effective density of states in the conduction and valence band edges of c-Si, the open-circuit voltage of a-Si:H/c-Si heterojunction cells fabricated on n-type c-Si wafers is about 22 mV higher than that fabricated on p-type c-Si wafers at the same case. V_(OC) decreases with decreasing the a-Si:H doping concentration at low doping level since the electric field over the c-Si depletion region is reduced at low doping level. Therefore, the a-Si:H layer should be doped higher than a critical value of 5×10^(18) cm^(-3) to achieve high V_(OC).
基金NNSFC (No. 20173017) and State Key Basic Program (No. G2000048)
文摘A brilliant purple octahedral single crystal is hydrothermally synthesized by the reaction of CoCl26H2O, H3BO3 and H3PO4 in NaOH aqueous solution of CH3(CH2)15N(CH3)3Br, and its crystal structure has been characterized by single-crystal X-ray diffraction. The compound, NaCo(H2O)2BP2O8稨2O (Mr = 336.72), belongs to hexagonal, space group P6122 with a = 9.447(5), c = 15.83(1) , V = 1223(1) 3, Dc = 2.742 g/cm3, Z = 6, F(000) = 1002 and m = 2.606 mm-1. The three-dimensional framework in the compound is built up from the linkage tetrahedral ribbons, in which the BO4 and PO4 tetrahedra alternate with CoO6 octahedra. The sodium ions and water molecules are located within the free thread of the helical ribbons.
基金Supported by the National Basic Research Program of China("973" Program,No.2011CB706703)
文摘Three-dimensional molecular dynamics simulations are carried out to study the mechanism of nanometric processing of ion implanted monocrystalline silicon surfaces. Lattice transformation is observed during implantation and nano-indentation using radial distribution function and geometric criterion damage detection. Nano-indentation is simulated to study the changes of mechanical property. Implantation analysis shows the existence of amorphous phase. Indentation process shows the lattice evolution, which is beneficial for reducing fractures during processing. The indentation results reveal the reduction of brittleness and hardness of the implanted surface. The ion fluence is in direct proportion to the damage, and inverse to the hardness of the material. Experiments of ion implar, tation, nanoindentation, nano-scratching and nanometric cutting were carried out to verify the simulation results.
文摘Non-contact atomic force microscopy（nc-AFM） atomic-scale imaging process of monocrystalline silicon surface using capped single-wall carbon nanotube tip is simulated by molecular dynamic method. The simulation resuhs show that the nc-AFM imaging force mainly comes from the C-Si and C-C chemical covalent bonding forces, especially the former, the nonbonding Van der Waals force change is small during the range of stable imaging height. When the tip-surface distance is smaller than the stable imaging height, several neighboring carbon atoms at the tip apex are attracted, and some of them jump onto the sample surface. Finally the tip apex configuration is destroyed with the tip indenting further.
基金The project supported by the Science and Technology Project of Advanced Academy of Guangzhou City under Grant No. 2060. The author acknowledges the detailed and valuable discussions with Prof. J.J. Shi.
文摘By employing the dielectric continuum model and Loudon＇s uniaxial crystal model, the interface optical （IO） phonon modes in a freestanding quasi-one-dimensional （Q1D） wurtzite rectangular quantum wire are derived and analyzed. Numerical calculation on a freestanding wurtzite GaN quantum wire is performed. The resulte reveal that the dispersion frequencies of IO modes sensitively depend on the geometric structures of the Q1D wurtzite rectangular quantum wires, the free wave-number kz in z-direction and the dielectric constant of the nonpolar matrix. The degenerating behavior of the IO modes in Q1D wurtzite rectangular quantum wire has been clearly observed in the case of small wave-number kz and Iarge ratio of length to width of the rectangular crossing profile. The limited frequency behaviors of IO modes have been analyzed deeply, and detailed comparisons with those in wurtzite planar quantum wells and cylindrical quantum wires are also done. The present theories can be looked on as a generalization of that in isotropic rectangular quantum wires, and it can naturally reduce to the case of Q1D isotropic quantum wires once the anisotropy of the wurtzite material is ignored.
基金supported by the National Natural Science Foundation of China(Grant Nos,51375082)
文摘Molecular dynamics simulations are employed to study the nanometric machining process of single crystal nickel. Atoms from different machining zones had different atomic crystal structures owing to the differences in the actions of the cutting tool. The stacking fault tetrahedral was formed by a series of dislocation reactions, and it maintained the stable structure after the dislocation reactions. In addition, evidence of crystal transition and recovery was found by analyzing the number variations in different types of atoms in the primary shear zone, amorphous region, and crystalline region. The effects of machining speed on the cutting force, chip and subsurface defects, and temperature of the contact zone between the tool and workpiece were investigated. The results suggest that higher the machining speed, larger is the cutting force. The degree of amorphousness of chip atoms and the depth and extent of subsurface defects increase with the machining speed. The average friction coefficient first decreases and then increases with the machining speed because of the temperature difference between the chip and machining surface.
基金supported by the National Natural Science Foundation of China (Grant Nos.50431030 and 50871054)the Outstanding Scholar Supporting Program of NUST
文摘Single crystalline Bi2O3 nanosheets have been synthesized by the surfactant assisted solvothermal method, using oleic acid and sodium dodecyl benzene sulfonate （SDBS） as compound surfactants. The thickness of Bi2O3 nanosheets is 40--70 nm with a monoclinic crystal structure. High-resolution transmission electron microscopy observation reveals that （ 345 ） lattice plane of the single crystal is parallel to the surface of the nanosheets. The cooperative effect of oleic acid encapsulated SDBS is the key to form single crystalline a-Bi2O3 nanosheets with a preferred growth orientation. An obvious blue shift of the single crystalline Bi2O3 nanosheets with a preferred surface （ 34-5 ） is observed due to quantum confinement effects in thickness and optical anisotropy.
