Thermal evolution of the morphology, structure, and optical properties of multilayer nanoperiodic systems produced by the vacuum evaporation of SiO and SiO$_2$

The alternate vacuum evaporation of SiO and SiO$_2$ from separate sources is used to produce amorphous $a$-SiO$_x$/SiO$_2$ multilayer nanoperiodic structures with periods of 5–10 nm and a number of layers of up to 64. The effect of annealing at temperatures $T_a$ = 500–1100$^\circ$C on the structural and optical properties of the nanostructures is studied. The results of transmission electron microscopy of the samples annealed at 1100$^\circ$C indicate the annealing-induced formation of vertically ordered quasiperiodic arrays of Si nanocrystals, whose dimensions are comparable to the $a$-SiO$_x$-layer thickness in the initial nanostructures. The nanostructures annealed at 1100$^\circ$C exhibit size-dependent photoluminescence in the wavelength range 750–830 nm corresponding to Si nanocrystals. The data on infrared absorption and Raman scattering show that the thermal evolution of structural and phase state of the SiO$_x$ layers with increasing annealing temperature proceeds through the formation of amorphous Si nanoinclusions with the subsequent formation and growth of Si nanocrystals.