Fluence dependence of the interband critical points in ion-implanted silicon

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Fluence ( Φ) dependence of interband critical points (CPs) can help to monitor the variation of band structure in crystalline–amorphous (c–a) silicon interfaces under ion implantation. Silicon wafers 〈1 0 0〉 were implanted in the range of 200–900 keV with Si, Ar, Kr and Xe ions with different fluences. The techniques used and the 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 Δ and amplitude ratio Ψ) [1,2]. The observed structures are analyzed by fitting the second-derivative spectra for complete line shape for both real and imaginary parts of the dielectric function d 2 ε/d ω 2 with analytic critical point line shapes. The interband critical point parameters (strength, threshold energy, broadening and excitonic phase angle) have been considered. The variations of these parameters were used to monitor crystalline–amorphous transformation. Obtained results of unimplanted crystals were in fair agreement with previously published data [3–13].