Peculiarities of the electron structure of nanosized ion-implanted layers in silicon

The effect of implantation of Ba, P, B, and alkali element ions with a low energy ($E_0<$ 5 keV) on the electron structure of a thin surface region of $p$- and $n$-type Si(111) single crystals is investigated by photoelectron and secondary electron-electron spectroscopy. It is shown that irrespective of the ion species, high-dose ion implantation leads to a sharp narrowing of the band gap in silicon, which can be explained by overlapping of the wavefunctions of electrons of impurity atoms and the formation of the impurity subband overlapping with the allowed band. After implantation thermal annealing, SiP, BaSi, and SiB$_3$ films of nano-sized thickness are obtained for the first time. Optimal regimes of ion implantation and subsequent annealing for the formation of silicide films are determined, and their electron structure is investigated.