Neon ion bombardment on silicon surfaces

Under UHV conditione, c-Si (111), (110), (100) surfaces have been bombarded at room temperature and normal incidence, by Ne+ ions. Using spectroscopic ellipsometry (1.55.5 eV), the implantation processes were continuously recorded. The results of the optical measurements are compared with the relation: (ε 2 Ep)q = c(E - Eoo ), in which Tauc takes p = 2, q = 1/2, Davis and Mott p = 2, q = 1/3 and Cody p = 0, q = 1/2, for 1.5−3.0 eV. Applying the least-squares method to the results of the ellipsometric measurements we find that they can be described most satisfactorily by using the model of Davis and Mott. The thickness of the amorphous silicon layer, both during and at the end of bombardment, is calculated from the same optical measurements and compared with the predicted ion range. The growth of the amorphous layer can be described by a simple mathematical model (microscopic surface roughness). On termination of the bombardment we observe a partial restoration of the amorphous layer at room temperature, which may be easily interpreted in terms of the Davis and Mott model.