Computer modeling and electron microscopy of silicon surfaces irradiated by cluster ion impacts

A hybrid molecular dynamics model has been applied for modeling impacts of Ar and decaborane clusters, with energies ranging from 25 to 1500 eV/atom, impacting Si surfaces. Crater formation, sputtering, and the shapes of craters and rims were studied. Our simulation predicts that on a Si(1 0 0), craters are nearly triangular in cross-section, with the facets directed along the close-packed (1 1 1) planes. The Si(1 0 0) craters exhibit four fold symmetry. The craters on Si(1 1 1) surface are well rounded in cross-section and the top-view shows a complicated six fold or triangular image. The simulation results for individual gas cluster impacts were compared with experiments at low dose (10¹⁰ ions/cm² charge fluence) for Ar impacts into Si(1 0 0) and Si(1 1 1) substrate surfaces. Atomic force microscopy and cross-sectional high-resolution transmission electron microscope imaging of individual gas cluster ion impacts into Si(1 0 0) and Si(1 1 1) substrate surfaces revealed faceting properties of the craters and are in agreement with the theoretical prediction. The sputtering yield from Si(1 0 0) surfaces bombarded with B₁₀ cluster ions, with total energy of 1-15 keV, was also calculated. The results of this study will be helpful for the research and development of a new low-damage gas cluster ion beam process technology.