Large-scale molecular dynamics simulations of cluster impact and erosion processes on a diamond surface

Single Ar-n or (CO2)(n) (nsimilar or equal to960) cluster impacts on a diamond (111) surface are studied by large-scale molecular dynamics simulations in order to investigate highly energetic cluster-surface interactions. For a cluster impact energy E-a of 100 keV, a hemispherical crater and multilayered shockwaves are observed. Rebounding hot fluidized carbon material is seen to replenish the transient crater very quickly, with a central peak appearing as a long time phenomenon in the case of a CO2 cluster impact. Transient craters develop also for lower impact energies of 30less than or equal toE(a)less than or equal to75 keV while only an elastic deformation is observed for E-a=10 keV. The volume of the transient crater is approximately proportional to E-a while the volume of the plastically deformed region and the kinetic energy transfer via the shockwave are linear functions of E-a minus a threshold energy of about 10 keV. At an impact energy of 100 keV, the number of carbon atoms emitted from the target is much larger for a CO2 cluster impact than for an Ar cluster impact with a factor of about 3.35. The reactive enhancement of the surface erosion in the CO2 case is also proven by a strong CO signal in the spectrum of the emitted fragments. On the other hand, the surface of the relaxed crater is more densely packed and smoother in the case of the Ar cluster impact.