Forouhi–Bloomer analysis to study amorphization in Si

Single crystal Si (1 0 0) was irradiated with 120 keV Ar+ for fluences ranging from 6 × 1013 to 1 × 1016 ions/cm2 and the real and imaginary parts of the dielectric function were measured using a spectroscopic ellipsometer in the energy range 1.5–5 eV. The pseudodielectric functions of the irradiated specimens were analyzed using Forouhi–Bloomer model for the first time. It was found that a minimum of four absorption terms is required to obtain ‘good’ fits to the experimental data. The parameters of the fit show distinct behavior above and below amorphization threshold. This paper demonstrates that Forouhi–Bloomer interband model for pseudodielectric functions can be used to follow structural changes too.