Hopping conductivity in multilayer nanostructures {[(Co$_{40}$Fe$_{40}$B$_{20}$)$_{34}$(SiO$_2$)$_{66}$]/[ZnO]}$_n$

The structure and electrical properties of multilayer thin films {[(Co$_{40}$Fe$_{40}$B$_{20}$)$_{34}$(SiO$_2$)$_{66}$]/[ZnO]}$_n$ with different thickness of ZnO interlayers are studied. It was found that the (Co$_{40}$Fe$_{40}$B$_{20}$)$_{34}$(SiO$_2$)$_{66}$ composite interlayers are amorphous, and the ZnO interlayers are hexagonal crystalline with the structure of $P6_3mc$ symmetry group. The temperature dependence of the specific electrical resistance of multilayer nanostructures {[(Co$_{40}$Fe$_{40}$B$_{20}$)$_{34}$(SiO$_2$)$_{66}$]/[ZnO]}$_n$ at the temperature range of 80 – 280 K obeys the “1/4” law, which is interpreted as Mott type hopping conductivity along the ZnO interlayers. In this case, the dependence of specific electrical resistance of the reference zinc oxide films at the noted temperatures is described by the logarithmic law $\rho(T)\propto\ln T$, which indicates the presence of interference effects. The reference nanocomposites demonstrates the “1/2” mechanism, which is explained within the framework of the Efros–Shklovsky conductivity mechanism models and thermally activated tunneling. The effective density of electron states of multilayer nanostructures {[(Co$_{40}$Fe$_{40}$B$_{20}$)$_{34}$(SiO$_2$)$_{66}$]/[ZnO]}$_n$ nonlinearly increases with increasing zinc oxide layer thickness, which is associated with the presence of a thin layer of ZnO oxidized during the deposition process at the composite-ZnO interfaces.