| 1. |
- Popok, Vladimir, 1966, et al.
(author)
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Stopping of energetic cobalt clusters and formation of radiation damage in graphite
- 2009
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In: Physical Review B. ; 80:20
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Journal article (peer-reviewed)abstract
- The interaction of energetic (up to 200 eV/atom) size-selected Con clusters with HOPG is studied both experimentally and theoretically. Etching of the radiation damage areas introduced by cluster impacts provides a measure of the depth to which the collision cascades are developed and allowes a comparison of these data with the molecular dynamics simulations. Good agreement between the experimental results and modelling is obtained. It is shown that the projected range of the cluster constituents can be linearly scaled with the projected momentum (the cluster momentum divided by surface impact area). With decrease of cluster energies to ca. 10 eV/atom the transition from implantation to pinning is suggested. It is found that even after quite energetic impacts residual clusters remain intact in the shallow graphite layer. These clusters can catalyse reaction of atmospheric oxygen with damaged graphite areas under the thermal heating that leads to the formation of narrow (5-15 nm) random in shape surface channels (trenches) in the top few graphene layers. Thus, small imbedded Co nanoparticles can be used as a processing tool for graphene.
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| 2. |
- Samela, J., et al.
(author)
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Argon cluster impacts on layered silicon, silica, and graphite surfaces
- 2007
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In: European Physical Journal D. ; 43, s. 181-184
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Journal article (peer-reviewed)abstract
- Seven structures of covalently bonded materials are used as targets of 6 keV Ar12 cluster bombardment in classical molecular dynamics simulations. Energy deposition, cratering and Ar ranges are compared and remarkable differences are found between the structures. In particular, bombardment of a thin 2 nm silica layer on top of the Si(111) surface is shown to behave quite differently from bombardment of pure Si.
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| 3. |
- Samela, J., et al.
(author)
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Origin of complex impact craters on native oxide coated silicon surfaces
- 2008
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In: Physical Review B. ; 77
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Journal article (peer-reviewed)abstract
- Crater structures induced by impact of keV-energy Ar cluster ions on silicon surfaces are measured with atomic force microscopy. Complex crater structures consisting of a central hillock and outer rim are observed more often on targets covered with a native silicon oxide layer than on targets without the oxide layer. To explain the formation of these complex crater structures, classical molecular dynamics simulations of Ar cluster impacts on oxide coated silicon surfaces, as well as on bulk amorphous silica, amorphous Si, and crystalline Si substrates, are carried out. The diameter of the simulated hillock structures in the silicon oxide layer is in agreement with the experimental results, but the simulations cannot directly explain the height of hillocks and the outer rim structures when the oxide coated silicon substrate is free of defects. However, in simulations of 5 keV/atom Ar12 cluster impacts, transient displacements of the amorphous silicon or silicon oxide substrate surfaces are induced in an approximately 50 nm wide area surrounding the impact point. In silicon oxide, the transient displacements induce small topographical changes on the surface in the vicinity of the central hillock. The comparison of cluster stopping mechanisms in the various silicon oxide and silicon structures shows that the largest lateral momentum is induced in the silicon oxide layer during the impact; thus, the transient displacements on the surface are stronger than in the other substrates. This can be a reason for the higher frequency of occurrence of the complex craters on oxide coated silicon.
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