Tracing interfacical nanocrystalline grain defects(NCGD)formation inducing electrical characteristic degradation in thermal remains a challenging issue for polycrystalline silicon(poly-Si)stable and reliable applicati...Tracing interfacical nanocrystalline grain defects(NCGD)formation inducing electrical characteristic degradation in thermal remains a challenging issue for polycrystalline silicon(poly-Si)stable and reliable application in engineering.Here,we present a microelectromechanical systems(MEMS)unit,which is composed of tunnel oxide passivating contact poly-Si tandem layer.It is a pioneering work to explore poly-Si NCGD performance in the thermal cycle,which includes three case periods and lasts 2 years.We obtain the thermal expansion deformation of poly-Si and demonstrate it with the thermal cycle finite element model(TC-FEM).Then,we reveal the key factor to be carrier mobility decay,in which the nanocrystal finite element model(NC-FEM)predicts grain displacement(GD)increasing,otherwise electronic mobility data is measured and determined by the Hall method.Specifically,dislocation defection accumulation is induced by grain refinement(GR),grain size(GS),and grain boundary(GB)increasing.Moreover,multiple twinning phenomena are displayed with three-dimensional(3D)structural reconstruction,which provides the basis for the formation of new grains and substantiates the GR phenomena.The periodic lattice strain induces deep trap accumulation and chemical degradation during operation,which restricts the carrier mobility.Ultimately,the electron-hole’s scattering probability is enhanced,promoting the decrease in conductivity.These findings differ from the conventional poly-Si electrical properties changing mechanisms,which enrich our understanding of NCGD in poly-Si materials.Additionally,we obtain insights into the resistance drift and carrier transport mechanisms and unravel the structural and mechanistic hierarchical twinning processes governed by defects.The findings of this work can have significant implications for the stability and reliability of poly-Si field-effect transistors or the pursuit of high-efficiency tandem solar cells.展开更多
The effects of two different symmetric tilt grain boundaries （GBs）, ∑13[001]（230） GB and ∑17[001]（140） GB, on displacement cascade processes in tungsten were investigated using molecular dynamics simulations. ...The effects of two different symmetric tilt grain boundaries （GBs）, ∑13[001]（230） GB and ∑17[001]（140） GB, on displacement cascade processes in tungsten were investigated using molecular dynamics simulations. By quantifying the number of interstitials and vacancies surviving after irradiation with the kinetic energy of primary knock-on atom energies of 1, 3 and 5 keV, respectively, in these simulations, it is found that the GBs have dual nature for radiation-induced defects： They absorb interstitials while leaving more vacancies to survive in the grains. The net effect is that the number of total surviving defects in the GB system is not always less than that in the single crystal. These defect behaviors are understood by quantitatively analyzing the recovery fraction of irradiation-induced defects, the time to reach steady state and the mobility of vacancies and interstitials. It is also found that the ∑17 GB is a more effective sink of radiation-induced point defects than the ∑13 GB. One of the main reasons is that the ∑17 GB has a higher GB energy.展开更多
We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an i...We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an interstitial helium atom to the grain boundary plane is the strongest among all sites around the plane. The He_N defect is much more stable in nickel bulk than in the grain boundary plane. Besides, the binding energy of an interstitial helium atom to a vacancy is stronger than that to a grain boundary plane. The binding strength between the grain boundary and the HeN defect increases with the defect size. Moreover, the binding strength of the HeN defect to the Σ3（112）[110] grain boundary becomes much weaker than that to other grain boundaries as the defect size increases.展开更多
This paper investigates crystalline orientation in monolike silicon wafers and its effect on solar cell performance. Monolike silicon wafers from two different bricks cut from interior and corner region of an ingot we...This paper investigates crystalline orientation in monolike silicon wafers and its effect on solar cell performance. Monolike silicon wafers from two different bricks cut from interior and corner region of an ingot were compared. The mono grain in the interior brick is nearly perfect, but there are some large oblong shaped sub-grains in the corner brick. The large sub-grains at corner brick wafers are oriented at (311), instead of (100) orientation. The (311) grains contain high density of dislocation and cannot be effectively textured by alkaline solution, therefore lowering the cell efficiency significantly. There is about 0.86% (abs) cell efficiency reduction on the monolike cells that contain large sub-grains.展开更多
Both radiation-induced excess vacancies and solute-interstitials may enhance solute diffusion. The radiation-enhanced solute diffusion promotes the kinetic process of equilibrium segregation. This effect is especially...Both radiation-induced excess vacancies and solute-interstitials may enhance solute diffusion. The radiation-enhanced solute diffusion promotes the kinetic process of equilibrium segregation. This effect is especially considerable in the low temperature range. As a complement to modelling of radiation-induced non-equilibrium segregation, the radiation-created vacancy and solute-interstitial-accelerated equilibrium grain boundary solute segregation were theoretically treated. The models were applied to phosphorus segregation in α-Fe subjected to neutron irradiation.展开更多
The VTLLS microscopy studies were made on high purity gold and commercial grade zinc grains in a temperature range of 30-230?C. Differential area ω and surface activity Sa were estimated from photomicrographs. The ω...The VTLLS microscopy studies were made on high purity gold and commercial grade zinc grains in a temperature range of 30-230?C. Differential area ω and surface activity Sa were estimated from photomicrographs. The ω vs dT/dt (rate of heating) curve was seen to differ from those of silver and titanium. The nature of curve between normalized ω and dT/dt was seen to be non-exponential. The characteristic relation between sectorized differential area ωsec and mean temperature was examined. The present study further establishes the simplicity and versatility of the VTLLS technique, in studying the defect-sub-structure of metal particles such as Au and Zn in presence of an imposed temperature gradient in a reasonable way. As such an attempt was made to connect the ω and defect-sub-structure related parameters.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFB3204100)the National Natural Science Foundation of China(No.U20A20168)a grant from the Guoqiang Institute,Tsinghua University.
文摘Tracing interfacical nanocrystalline grain defects(NCGD)formation inducing electrical characteristic degradation in thermal remains a challenging issue for polycrystalline silicon(poly-Si)stable and reliable application in engineering.Here,we present a microelectromechanical systems(MEMS)unit,which is composed of tunnel oxide passivating contact poly-Si tandem layer.It is a pioneering work to explore poly-Si NCGD performance in the thermal cycle,which includes three case periods and lasts 2 years.We obtain the thermal expansion deformation of poly-Si and demonstrate it with the thermal cycle finite element model(TC-FEM).Then,we reveal the key factor to be carrier mobility decay,in which the nanocrystal finite element model(NC-FEM)predicts grain displacement(GD)increasing,otherwise electronic mobility data is measured and determined by the Hall method.Specifically,dislocation defection accumulation is induced by grain refinement(GR),grain size(GS),and grain boundary(GB)increasing.Moreover,multiple twinning phenomena are displayed with three-dimensional(3D)structural reconstruction,which provides the basis for the formation of new grains and substantiates the GR phenomena.The periodic lattice strain induces deep trap accumulation and chemical degradation during operation,which restricts the carrier mobility.Ultimately,the electron-hole’s scattering probability is enhanced,promoting the decrease in conductivity.These findings differ from the conventional poly-Si electrical properties changing mechanisms,which enrich our understanding of NCGD in poly-Si materials.Additionally,we obtain insights into the resistance drift and carrier transport mechanisms and unravel the structural and mechanistic hierarchical twinning processes governed by defects.The findings of this work can have significant implications for the stability and reliability of poly-Si field-effect transistors or the pursuit of high-efficiency tandem solar cells.
文摘The effects of two different symmetric tilt grain boundaries （GBs）, ∑13[001]（230） GB and ∑17[001]（140） GB, on displacement cascade processes in tungsten were investigated using molecular dynamics simulations. By quantifying the number of interstitials and vacancies surviving after irradiation with the kinetic energy of primary knock-on atom energies of 1, 3 and 5 keV, respectively, in these simulations, it is found that the GBs have dual nature for radiation-induced defects： They absorb interstitials while leaving more vacancies to survive in the grains. The net effect is that the number of total surviving defects in the GB system is not always less than that in the single crystal. These defect behaviors are understood by quantitatively analyzing the recovery fraction of irradiation-induced defects, the time to reach steady state and the mobility of vacancies and interstitials. It is also found that the ∑17 GB is a more effective sink of radiation-induced point defects than the ∑13 GB. One of the main reasons is that the ∑17 GB has a higher GB energy.
基金Project supported by the Program of International S&T Cooperation,China(Grant No.2014DFG60230)the National Basic Research Program of China(Grant No.2010CB934504)+2 种基金Strategically Leading Program of the Chinese Academy of Sciences(Grant No.XDA02040100)the Shanghai Municipal Science and Technology Commission,China(Grant No.13ZR1448000)the National Natural Science Foundation of China(Grant Nos.91326105 and 21306220)
文摘We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an interstitial helium atom to the grain boundary plane is the strongest among all sites around the plane. The He_N defect is much more stable in nickel bulk than in the grain boundary plane. Besides, the binding energy of an interstitial helium atom to a vacancy is stronger than that to a grain boundary plane. The binding strength between the grain boundary and the HeN defect increases with the defect size. Moreover, the binding strength of the HeN defect to the Σ3（112）[110] grain boundary becomes much weaker than that to other grain boundaries as the defect size increases.
文摘This paper investigates crystalline orientation in monolike silicon wafers and its effect on solar cell performance. Monolike silicon wafers from two different bricks cut from interior and corner region of an ingot were compared. The mono grain in the interior brick is nearly perfect, but there are some large oblong shaped sub-grains in the corner brick. The large sub-grains at corner brick wafers are oriented at (311), instead of (100) orientation. The (311) grains contain high density of dislocation and cannot be effectively textured by alkaline solution, therefore lowering the cell efficiency significantly. There is about 0.86% (abs) cell efficiency reduction on the monolike cells that contain large sub-grains.
基金This work was partly supported by the N ational N atural Science Foundation of China(project title:Nonequilibrium Grain Boundary Segregation Kinetics and Brittle Intergran-ular Fracturegrant No.50331020).
文摘Both radiation-induced excess vacancies and solute-interstitials may enhance solute diffusion. The radiation-enhanced solute diffusion promotes the kinetic process of equilibrium segregation. This effect is especially considerable in the low temperature range. As a complement to modelling of radiation-induced non-equilibrium segregation, the radiation-created vacancy and solute-interstitial-accelerated equilibrium grain boundary solute segregation were theoretically treated. The models were applied to phosphorus segregation in α-Fe subjected to neutron irradiation.
文摘The VTLLS microscopy studies were made on high purity gold and commercial grade zinc grains in a temperature range of 30-230?C. Differential area ω and surface activity Sa were estimated from photomicrographs. The ω vs dT/dt (rate of heating) curve was seen to differ from those of silver and titanium. The nature of curve between normalized ω and dT/dt was seen to be non-exponential. The characteristic relation between sectorized differential area ωsec and mean temperature was examined. The present study further establishes the simplicity and versatility of the VTLLS technique, in studying the defect-sub-structure of metal particles such as Au and Zn in presence of an imposed temperature gradient in a reasonable way. As such an attempt was made to connect the ω and defect-sub-structure related parameters.
