In this study, we demonstrated experimentally and theoretically that the charge transport mechanism in amorphous Hf$_{0.5}$Zr$_{0.5}$O$_2$ is phonon-assisted tunneling between traps like in HfO$_2$ and ZrO$_2$. The thermal trap energy of 1.25 eV and
optical trap energy of 2.5 eV in Hf$_{0.5}$Zr$_{0.5}$O$_2$ were determined based on comparison of experimental data on transport with different theories of charge transfer in dielectrics. A hypothesis that oxygen vacancies are responsible for the charge transport in Hf$_{0.5}$Zr$_{0.5}$O$_2$ was discussed.
In this study, we demonstrated experimentally that formation of chains and islands of oxygen vacancies in hafnium sub-oxides (HfO$_x$, $x<2$) leads to percolation charge transport in such dielectrics. Basing on the model of {E}fros-Shklovskii percola
tion theory good quantitative agreement between the experimental and theoretical data of current-voltage characteristics were achieved. Based on the percolation theory suggested model shows that hafnium sub-oxides consist of mixtures of metallic Hf nanoscale clusters of 1-2 nm distributed onto non-stoichiometric HfO$_x$. It was shown that reported approach might describe low resistance state current-voltage characteristics of resistive memory elements based on HfO$_x$.
In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the charge transport in HfO$_2$. Basing on the model of phonon-assisted tunneling between traps, and assuming that the electron traps are oxygen
vacancies, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics were achieved. The thermal trap energy of 1.25 eV in HfO$_2$ was determined based on the charge transport experiments.
A promising candidate for universal memory, which would involve combining the most favourable properties of both high-speed dynamic random access memory (DRAM) and non-volatile flash memory, is resistive random access memory (ReRAM). ReRAM is based o
n switching back and forth from a high-resistance state (HRS) to a low-resistance state (LRS). ReRAM cells are small, allowing for the creation of memory on the scale of terabits. One of the most promising materials for use as the active medium in resistive memory is hafnia (HfO$_2$). However, an unresolved physics is the nature of defects and traps that are responsible for the charge transport in HRS state of resistive memory. In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the HRS charge transport in resistive memory elements based on HfO$_2$. We also demonstrated that LRS transport occurs through a mechanism described according to percolation theory. Based on the model of multiphonon tunneling between traps, and assuming that the electron traps are oxygen vacancies, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics were achieved. The thermal excitation energy of the traps in hafnia was determined based on the excitation spectrum and luminescence of the oxygen vacancies. The findings of this study demonstrate that in resistive memory elements using hafnia, the oxygen vacancies in hafnia play a key role in creating defects in HRS charge transport.
