Features in the formation of Ge/Si multilayer nanostructures under ion-beam-assisted crystallization

A method of combined ion-beam crystallization of the Ge/Si multilayer nanostructures is proposed. Using atomic-force microscopy and electron microscopy, we observed the formation of an array of germanium quantum dots with lateral dimensions $\langle$a$\rangle$ = 12–15 nm at the following conditions: silicon-substrate temperature $T$ = 330–350$^\circ$C, ion-beam energies $E_{\mathrm{Ge}^+}$ = 30–40 eV, $E_{\mathrm{Ar}^+}^0$ = 230–240 eV (primary pulsed defect formation mode), $E_{\mathrm{Ar}^+}$ = 130–140 eV (permanent diffusion stimulation mode), and ion-beam fluences, $f_{\mathrm{Ge}^+}$ = 1.5 $\times$ 10$^{14}$ cm$^{-2}$ s$^{-1}$, $f_{\mathrm{Ar}^+}$ = 5 $\times$ 10$^{12}$ cm$^{-2}$ s$^{-1}$. The Raman spectroscopy data indicate the experimental possibility of low-temperature ion-stimulated growth of the spacer layers of silicon ($T$ = 420–450$^\circ$C, $E_{\mathrm{Ar}^+}$ eV, $E_{\mathrm{Si}^+}$ eV, $f_{\mathrm{Si}^+}$ $\times$ 10$^{14}$ cm$^{-2}$ s$^{-1}$) and the formation of multilayer structures with Ge$_x$Si$_{1-x}$ quantum dots ($x >$ 0.85).