  It is crucial to have a good phenomenological model of electronic stopping
power for modeling the physics of ion implantation into crystalline silicon. In
the spirit of the Brandt-Kitagawa effective charge theory, we develop a model
for electronic stopping power for an ion, which can be factorized into (i) a
globally averaged effective charge taking into account effects of close and
distant collisions by target electrons with the ion, and (ii) a local charge
density dependent electronic stopping power for a proton. This phenomenological
model is implemented into both molecular dynamics and Monte Carlo simulations.
There is only one free parameter in the model, namely, the one electron radius
rs0 for unbound electrons. By fine tuning this parameter, it is shown that the
model can work successfully for both boron and arsenic implants. We report that
the results of the dopant profile simulation for both species are in excellent
agreement with the experimental profiles measured by secondary-ion mass
spectrometry(SIMS) over a wide range of energies and with different incident
directions. We point out that the model has wide applicability, for it captures
the correct physics of electronic stopping in ion implantation. This model also
provides a good physically-based damping mechanism for molecular dynamics
simulations in the electronic stopping power regime, as evidenced by the
striking agreement of dopant profiles calculated in our molecular dynamics
simulations with the SIMS data.
