Mechanistic analysis from molecular-dynamics simulations: keV-particle-induced desorption from Si{001}

Abstract

We have developed a method for interpreting and classifying mechanisms from molecular-dynamics simulations. The reason for this effort is that molecular-dynamics simulations contain a wealth of information regarding the microscopic details of atomic motions. It is at best tedious, however, to extract all of the essential information in very complex processes. In particular, we are interested in particle ejection due to the keV-particle bombardment. Our method isolates the motion of the last two collisions, which we depict in a single frame showing the time sequence of the positions of the three atoms involved. The remainder of the atoms are shown at their initial positions. These atoms give the perspective of the entire system but small or irrelevant displacements do not distract from the key motions. This method is utilized to elucidate the structure-sensitive mechanisms of keV-particle bombardment of the I001I face of diamond-lattice crystals. We have observed that two mechanisms are responsible for the major features of the angular distributions, namely, the 6& and the 53 mechanisms. The two mechanisrns are characterized by the difference in the number of layers of the atoms involved in the final momentum transfer.

The Correlation between Ion Beam/Material Interactions and Practical FIB Specimen Preparation

“…Multiple methodologies have been applied in the area of computer modeling~Bier-sack and Haggmark, 1980;Guinan and Kinney, 1982;Adesida and Karapiperis, 1982;Garrison et al, 1994;Sanders et al, 1994;Rosencrance et al, 1995! ;however, as Lindhard, Scharff, and Schiott~LSS!…”

Atomic placement of Al on the GaAs {001}c(4×4)reconstruction determined by angle-resolved secondary-ion mass spectrometry

“…This trend of shifting polar angle with energy is indicative of the ejected particle being drawn towards the surface by an attractive interaction. 41,42 Changes in the Al ϩ ion polar distributions versus Al coverage are shown in Fig. 5͑a͒.…”

“…Molecular dynamics simulations of the keV bombardment process are useful in determining desorption mechanisms from crystalline solids. 38,41,43 In particular, detailed mechanistic study has shown that atoms in a diamond lattice eject via two primary mechanisms. First, the closest atom in the layer just below the surface layer may cause desorption via nearest-neighbor collision (⌬ 1 mechanism͒.…”

“…It has been shown in previous studies that the Si PES adequately, though only qualitatively, describes the angular distributions of GaAs and Al/GaAs systems because the desorption mechanisms are more dependent on atomic positions than on mass or chemical environments of the atoms in the lattice. 25,27,35,36,41,45 Three different Al adsorption sites on the c(4ϫ4) reconstruction, shown in Fig. 1, were modeled with MD calculations using a Si ͕001͖ c(4ϫ4) reconstruction to identify desorption patterns of adsorbate and surface atoms.…”

Molecular dynamics simulation of ion bombardment on hydrogen terminated Si(001)2×1 surface

“…22 Garrison and co-workers used MD to study physical sputtering of silicon by rare-gas ions. 23,24 More recently, MD studies of the interactions between halogen ions and silicon surface have provided a deeper understanding of silicon reactive ion etching. [25][26][27][28][29] In addition, systematic MD investigations have been carried out to understand interactions between reactive neutral species and silicon surface.…”