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
Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticl...Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories： nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly sum marized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.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Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories： nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly sum marized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.
