Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nanoscale. 2018 Jan 25;10(4):1598-1606. doi: 10.1039/c7nr08116b.
Full three dimensional (3D) simulations of ion implantation are necessary in a wide range of nanoscience and nanotechnology applications to capture the increasing effect of ion leakage out of surfaces. Using a recently developed 3D Monte Carlo simulation code IM3D, we first quantify the relative error of the 1D approach in three applications of nano-scale ion implantation: (1) nano-beam for nitrogen-vacancy (NV) center creation, (2) implantation of nanowires to fabricate p-n junctions, and (3) irradiation of nano-pillars for small-scale mechanical testing of irradiated materials. Because the 1D approach fails to consider the exchange and leakage of ions from boundaries, its relative error increases dramatically as the beam/target size shrinks. Lastly, the "Bragg peak" phenomenon, where the maximum radiation dose occurs at a finite depth away from the surface, relies on the assumption of broad beams. We discovered a topological transition of the point-defect or defect-cluster distribution isosurface when one varies the beam width, in agreement with a previous focused helium ion beam irradiation experiment. We conclude that full 3D simulations are necessary if either the beam or the target size is comparable or below the SRIM longitudinal ion range.
在广泛的纳米科学和纳米技术应用中，需要对离子注入进行全三维（3D）模拟，以捕捉表面外逸离子的增强效应。我们使用最近开发的 3D 蒙特卡罗模拟代码 IM3D，首次在纳米尺度离子注入的三个应用中量化了 1D 方法的相对误差：（1）用于氮空位（NV）中心创建的纳米束，（2）用于制造 p-n 结的纳米线注入，以及（3）用于对辐照材料进行小规模机械测试的纳米柱辐照。由于 1D 方法未能考虑边界处离子的交换和逸出，因此随着束/靶尺寸的缩小，其相对误差会急剧增加。最后，“布拉格峰”现象，即最大辐射剂量出现在离表面有限深度处，依赖于宽束的假设。我们发现，当改变束宽时，点缺陷或缺陷团簇分布等位面会发生拓扑转变，这与之前的聚焦氦离子束辐照实验结果一致。我们得出结论，如果束或靶的尺寸与 SRIM 纵向离子射程可比或小于该射程，则需要进行全 3D 模拟。
