3C-SiC中嬗变原子(Mg、Be、Al)对He间隙原子迁移行为影响的第一性原理研究

First-principle Calculations of the Effect of Transmutation Atoms(Mg,Be,Al)Doping on the He Atom Migration in 3C-SiC Interval

辐照条件下固体嬗变原子对立方碳化硅(3C-SiC)基体内氦泡形成过程中的作用尚不明确。本文基于密度泛函理论研究了Mg、Be、Al这三种固体嬗变原子对He间隙原子在3C-SiC基体内的形成能以及迁移行为的影响。计算发现,He原子在3C-SiC基体中主要稳定于由Si或C原子组成的四面体间隙中,且易于在相邻间隙间迁移。当嬗变原子浓度从0增至5%(物质的量分数)时,碳四面体间隙位点的He原子形成能先是骤降、然后随着固体原子浓度的增大而线性改变,而硅四面体间隙位点的He原子形成能则是和固体原子浓度呈多次函数关系。同时,三种固体原子也使He原子的迁移势垒和扩散系数发生明显改变,He原子从C原子间隙迁移到Si原子间隙的迁移势垒随着固体原子浓度的升高而线性降低、扩散系数逐渐增大;从Si原子间隙迁移到C原子间隙的迁移势垒与浓度呈多次函数关系,扩散系数与势垒曲线反相关。无论哪种路径和掺杂浓度,固体原子的加入都促进了He原子的迁移,这为气泡的成核生长提供了有利条件。

The role of solid transmutation atoms in the formation of irradiation-induced He bubbles in the cubic silicon carbide(3C-SiC)matrix is unclear.The effects of Mg,Be,Al atom on the formation energies(Efs)and diffusion behavior of He in the 3C-SiC matrix were studied using the density functional theory.The calculation results show that the He atom is mainly stable in the tetrahedral gap composed of Si or C atoms in the 3C-SiC matrix,and it is easier to migrate between adjacent gaps.When the transmutation atomic concentration increases from 0 to 5 at.%,the formation energy of the He atom in the TC carbon tetrahedral gap first plummets and then linearly changes with the increase of the solid atomic concentration,while the formation energy of the He atom in the silicon tetrahedral gap is a function of the concentration of solid atoms.Three solid atoms increases gradually,and the migration barrier of the He atom from Si interstice to C interstice is a function of concentration of many times,and the diffusion coefficient is inversely correlated with the barrier curve.Regardless of the path and doping concentration,the addition of solid atoms promotes the migration of He atoms,which provides favorable conditions for the nucleation growth of bubbles.