Effects of the density of collision cascades: Separating contributions from dynamic annealing and energy spikes

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS

卷:267

Article; Proceedings Paper

Titov, A. I.¹  Karaseov, P. A.¹  Azarov, A. Yu.¹  Kucheyev, S. O.² 

[1] St Petersburg State Polytech Univ, Dept Phys Elect, St Petersburg 195251, Russia

[2] Lawrence Livermore Natl Lab, Livermore, CA 94551 USA

关键词: Ion implantation;    Cluster ions;    Molecular effect;    Collision cascades;    Silicon;    Si;   

DOI  :  10.1016/j.nimb.2009.05.033

来源: Elsevier

【 摘 要 】

We present a quantitative model for the efficiency of the molecular effect in damage buildup in semiconductors. Our model takes into account only one mechanism of the dependence of damage buildup efficiency on the density of collision cascades: nonlinear energy spikes. In our three-dimensional analysis, the volume of each individual collision cascade is divided into small cubic cells, and the number of cells that have an average density of displacements above some threshold value is calculated. We assume that such cells experience a catastrophic crystalline-to-amorphous phase transition, while defects in the cells with lower displacement densities have perfect annihilation. For the two limiting cases of heavy (500 keV/atom Bi-209) and light (40 keV/atom N-14) ion bombardment of Si, theory predictions are in good agreement with experimental data for a threshold displacement density of 4.5 at.%. For intermediate density cascades produced by small 2.1 keV/amu PFn clusters, we show that dynamic annealing processes entirely dominate cascade density effects for PF2 ions, while energy spikes begin contributing in the case of PF4 cluster bombardment. (C) 2009 Elsevier B.V. All rights reserved.

【 授权许可】

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