The Nano-dot Effect And The Diamond-Like Carbon Formation Induced By The Impact Of Highly Charged Ion

The HCI has huge potential energy which equals to the sum of the ionization energy of the specific electron. When HCI approaches the solid surface, the huge amount of potential energy is released into the outmost layer of surface in an area about 100 nm3. Therefore, an area with extremely high power density is formed and many new effects have been observed, such as potential sputtering and nanostructure on the surface. Considering the advantages of HCI interaction with solid surface, it has been thought as a new powerful tool for surface analysis and surface modification. In this paper, the nano-dots on KBr surface and the Diamond-Like Carbon on HOPG surface produced by HCIs were observed.Xe21+ ions were used to bombard the KBr(001) surface, and the nano-hillocks on irradiated surface were observed by AFM. The distribution density of the nano-hillocks on the sample is consistent with estimated total ion fluence. This is against with the widely reported nano-pits on KBr surface, the reason is thought that higher kinetic energy Xeq+ ions are used in this work. More electronic defects is produced in deeper region of target for higher kinetic energy, so the diffuse of "color center" to the surface is easier to prohibited, the aggregation of defects under the surface may induce the arise of nano-hillock. The nano-hillocks on KBr have similar size with other alkali halide surface, such as CaF2, LiF, and BaF2.Raman and X-ray photoelectron spectroscopy (XPS) measurements have also been performed on the Highly Oriented Pyrolytic Graphite (HOPG) following Xeq+(q=5～26) ions irradiation with different fluence. The results show the electronic structure transition from sp2 to sp3 hybridization, which represent the formation of Diamond-Like Carbon (DLC) on HOPG. An obvious evolution of the transition dependent on the charge state and the fluence of the impact ions were found. The DLC production is thought to relate to intense potential energy deposition, due to the local High-temperature and High-pressure environment the surface structure could be strongly changed.