Structure and electrical properties of (ZnO/SiO$_{2})_{25}$ thin films

Multilayer (ZnO/SiO$_{2})_{25}$ thin films with a bilayer thickness of 6 to 10 nm has been synthesized in a single deposition process. The structure of the films consist of nanocrystalline ZnO layers and layers of amorphous SiO$_2$. An analysis of the temperature dependences of the electrical resistivity, showed that a consistent change of the dominant conduction mechanism are realized in (ZnO/SiO$_{2})_{25}$ thin films at temperatures 77 – 300 K: variable length hopping mechanism in a narrow energy band near the Fermi level at temperatures 77 – 250 K changed by the thermal activated impurity conductivity at close to room temperatures. The density of localized states and the activation energy of impurity conductivity has been estimated. The effect of heat treatment on the structure and electrical properties of the synthesized films has been investigated. It was found that the chemical interaction between the ZnO and SiO$_2$ layers occurs at 580–600$^{\circ}$C. It accompanied by the destruction of the multilayer structure and the appearance of the chemical compound Zn$_{2}$SiO$_{4}$ with the tetragonal structure (I-42$d$ space group).