The dependence of the parameters of energy bands on the depth of the ion-doped layer for Si implanted with ions Ba⁺

The physicochemical properties of near-surface layers of Si implanted with low-energy (E₀≤5 keV) Ba⁺ ions have been investigated by ultraviolet photoelectron spectroscopy and secondary emission spectroscopy. It was found that at E₀=0.5 keV the dependence of the concentration of Ba⁺ atoms on the depth d has a stepwise character. Up to d≈25-30 Å, the C_Ba practically does not change and is ∼50-55 at.%. Starting from d≈25-30 Å, with an increase in the depth, C_Ba decreases and at d≈80 Å does not exceed 1–2 at.%, therefore, in this region, the band parameters and the density of states in valence electrons change. The observed changes are explained both by the formation of chemical bonds between the Ba and Si atoms and the emergence of new electronic states in the band gap due to the presence of unbound barium and silicon atoms.