CRYSTAL TO AMORPHOUS TRANSITION OF SI AND AR IMPLANTED SILICON USING SINGLE-EFFECTIVE OSCILLATOR MODEL

Complex dielectric function was used to calculate refractive index and optical dispersion parameters for silicon wafers implanted with Si and Ar ions with different fluences. Energies of 200 and 800 keV were used, in order to relate ion implantation parameters with lattice perturbation. Single-effective oscillator energy, average strength of the interband optical transition, zero frequency (static) refractive index, moments of e(E) dispersion spectra, plasma angular frequency, lattice energy, the contribution of the free carriers and Urbach energy were obtained on the basis of the single-effective oscillator model proposed by Wemple and DiDomenico to monitor crystalline-amorphous transformation.
Used experimental techniques and damage profiles have been demonstrated elsewhere(1). Real and imaginary parts of the dielectric constant were calculated from the recently measured ellipsometric parameters (phase difference D and amplitude ratio y ) (1,2).
Progressive increase in the absorption coefficient magnitude below fundamental edge, oscillator energy E0, and oscillator average strength Ed with increasing ion fluence is primarily a defect formation effect, which produce a perturbation to the periodic potential of the crystal resulting a localized states in the band gap. The suggested mechanism can account for the decrease of both lattice energy (El) and N/m* behavior. Decrease of static refractive index in the low fluencies interpreted as a decrease in the dangling bonds which attributed to restructuring of the bonds. With increase of fluence the dangling bonds increased denoting formation of clusters together and increasing its mean size up to a percolation threshold. Increasing Urbach energy as a function of fluencies was observed and interpreted from the point view of Mott–Anderson transition.