Quantum Molecular Dynamics Study on Energy Transfer to the Secondary Electron in Surface Collision Process of an Ion

It is well known that an emission of secondary electrons is observed in an ion collision process to a surface, such as the focused ion beam (FIB) process. However, the physical effect of secondary electron emission to energy and mass transfer is seldom considered and there are few examples of analysis of the secondary electron emission. It is one of interesting problems as an extreme small scale energy transfer problem how energy is transferred to the electron emitted from the surface by ionic collisions. In the present study the quantum molecular dynamics method was applied to an energy transfer problem to an electron during ionic surface collision process in order to elucidate how energy of ionic collision transfers to the emitted electrons. The energy transfer paths to the electron was discussed during the collision process of an ion with changing the interaction between the electron and ions and that between the electron and surface molecules by the quantum molecular dynamics method. Effects of various physical parameters, such as the collision velocity and interaction strength between the observed electron and the classical particles to the energy transfer to the electron were investigated by the quantum molecular dynamics method when the potassium ion was collided with the surface so as to elucidate the energy path to the electron and the predominant factor of energy transfer to the electron. Effects of potential energy between the ion and the electron and that between the surface molecule and the electron to the electronic energy transfer were shown in the present paper. The energy transfer to the observed secondary electron through the potential energy term between the ion and the electron was much dependent on the ion collision energy although the energy increase to the observed secondary electron was not monotonous through the potential energy between the ion and surface molecules with the change of the ion collision energy.