Insight into the dynamics of electrons ejected by energetic ions in silicon and its relation to the basics of the inelastic thermal spike model

A Monte Carlo (MC) event-by-event scheme is used to calculate the temporal and spatial characteristics of electrons in silicon excited by penetrating energetic ions. The ions pass the active region of the device within ∼0.01 fs while interacting with the electrons and leaving behind them a wake of δ-electrons and their cascading secondaries. All electrons with energies Ee > 4 eV slow down to Ee ≤ 4 eV within a time interval of few femtoseconds to hundreds of picoseconds. They are then considered as stopped. Below 4 eV, their interaction with phonons becomes dominant. The results of our simulations help to understand the peculiarities of the processes which take place at these short times. It also becomes clear that one can use the inelastic thermal spike (i-TS) model only several picoseconds after the passing of the ion, and thereby avoid the deeply non-equilibrium stage of ion track evolution which is a serious problem for this model. The calculations, done using our data for the electron-phonon interactions, enable us to find the limits of using the electron-phonon coupling parameter as a constant value (independent of the electronic temperature) in the i-TS model. The latter is a key parameter of the i-TS model. Our analysis also determines the accuracy of other input parameters when the i-TS model is used in combination with molecular dynamics calculations.