三维原子探针的电场结构模拟研究

Simulation of the electric field structure of a three-dimensional atom probe

本文针对目前世界上被广泛使用的局部电极原子探针的样品及局部电极几何结构,通过有限元方法,结合多物理场仿真技术,研究了局部电极与针状样品的距离z、样品尖端曲率半径ρ、局部电极的入口直径φ、厚度w、开口角度α和入口长度h等参数对样品尖端附近的局部电场的影响。模拟结果表明:当z与φ的取值满足z/φ≥1时,既能在样品尖端得到较高的蒸发电场强度,又能降低局部电极对离子轨迹的影响;局部电极的厚度w和开口角度α的取值对样品尖端的电场影响较小;增大局部电极入口长度h的值有利于提高样品尖端电场强度;随着原子的蒸发(样品尖端曲率半径ρ增大),为维持原子蒸发所需的电场强度,施加在样品上的电压V与样品尖端的曲率半径ρ成正比,且所需维持的电场强度越高,施加的电压V越大。

This article employed the finite element method and multiphysics simulation to analyze the structure of a local electrode atom probe.The impact of various parameters,including inlet diameter(φ),thickness(w),opening angle(α),entrance length(h)of the local electrode,the radius of curvature(ρ)of the specimen,and the distance(z)between the local electrode and the needle-shaped specimen on the local electric field structure near the apex of a specimen,was investigated.The result indicated that a higher evaporation electric field strength was achieved at the apex of the specimen,and the influence of local electrode on ion trajectories was reduced when the ratio of distance(z)to inlet diameter(φ)satisfied z/φ≥1.Specifically,the thickness(w)and opening angle(α)of the local electrode had a minimal impact on the electric field at the apex of the specimen.In contrast,the increase of the entrance length(h)of the local electrode improved the electric field strength at the apex of the specimen.Moreover,the radius of curvature(ρ)of the specimen increased as atoms continued to evaporate from the specimen surface.The electric field(V)applied to the specimen was proportional to the radius of curvature(ρ)of the specimen to maintain the required electric field intensity.The higher intensity of electric field corresponded to the greater applied electric field(V).