The Nano-dot Effect Induced By Impact Of Highly Charged Xe^q+ Ion On The Mica Surface

Due to its characteristic of possessing high potential energy, the interaction of highly charged ion(HCI) with solid surface will induce many novel physical effects. Thus, many labs in the world have performed a lot of researches on the physics of highly charged ions. At present, the investigation of physics of HCI has been expanded to atomic physics, plasma physics and surface physics. Furthermore, the nano-modification by the HCI bombarding the solid surface, especially the nano-structure effect has attracted people's great interest.At this work, the Xe^q+(q=30,35) was used to bombard the mica, following the nano-hillocks on mica surface were observed by AFM, and the width and height were measured, respectively. The area density of the nano-hillocks is consistent with estimated total ion fluence on the sample. The results thus show the dependence between the volume of the nano-hillock and potential energy of HCI. The Coulomb explosion model was applied to understand the formation of nanostructure.The highly anisotropic nature of mica could play a very important role to produce nano-defect due to HCI impact. When the HCI approaches to the mica surface, the removal of electrons from the lattice will happen. Due to stripping large electrons from the layers, two layers of positively charged ions, together with a layer of cations K⁺ between them will be created to form a three-layer charged structure. Therefore, a strong charged region on the surface will be formed. An estimation of electrostatic energy in the charged region was made. The result indicates that the Coulomb energy of a surface charged region is larger than the bonding energy of interlayer. In this case, ionic bonds are thus destroyed, leading to delamination of the layer. Therefore, the hillocks will be created in the local region of the surface. In the calculation of nanodot size as well as regarding the contribution of the kinetic energy, the results are almost consistent with the experimental results. Although the model is simple, it helps to understand the mechanism of the formation of nanostructure.