Composition and electronic structure of hidden nanoscale phases and layers of BaSi$_2$ formed in the near-surface of Si

For the first time, nanoscale phases and layers of BaSi$_2$ were obtained by implantation of Ba$^+$ ions with an energy of $E_0$ = 20–30 keV in the surface layer of Si(111). In particular, it is shown that at a dose of $D\approx$ 10$^{15}$ cm$^{-2}$ nanophases with a band gap $E_g\approx$ 0.85 eV are formed, and at $D\approx$ 10$^{17}$ cm$^{-2}$ a BaSi$_2$ nanolayer with $E_g$ = 0.67 eV. The composition and structure of the barium disilicide nanostructure were investigated by light absorption spectroscopy by Auger electron spectroscopy, and the X-ray surface morphology was studied by scanning electron microscopy. The optimal modes of ion implantation and annealing for obtaining nanoscale phases and layers of BaSi$_2$ in the near-surface region of Si have been established. Using the method of light absorption spectroscopy, the band gap and the degree of coverage of the layer with BaSi$_2$ nanophases were estimated. It has been shown that at a dose of $D\approx$ 10$^{17}$ cm$^{-2}$ the nanolayer of BaSi$_2$.