Annealing-induced evolution of the structural and morphological properties of a multilayer nanoperiodic SiO$_x$/ZrO$_2$ system containing Si nanoclusters

The structural and morphological properties of nanoperiodic structures produced by the alternate vacuum evaporation of SiO and ZrO$_2$ followed by annealing at temperatures of 500–1100$^\circ$C are studied by the transmission electron microscopy of a transverse cross section. Upon annealing at temperatures below 700$^\circ$C, the layers are amorphous. Upon annealing at 900$^\circ$C and 1000$^\circ$C, nanocrystals separated by twinned boundaries or amorphous regions are formed in the ZrO$_2$ layers. The formation of Si nanocrystals in the SiO$_x$ layers occurs upon annealing at 1000$^\circ$C and 1100$^\circ$C. At 1100$^\circ$C, because of the reaction between SiO$_x$ and ZrO$_2$, spherical Si$_x$Zr$_y$O$_z$-type nanocrystals are formed in place of the ZrO$_2$ layers; the nanocrystal diameters exceed the initial layer thickness. The annealing-induced structural evolution is consistent with the previously considered behavior of the optical and luminescence properties of the system.