Resistive switching and charge accumulation in Hf0.5Zr0.5O2 nanoparticles

Abstract

We revealed the resistive switching, negative differential resistance and charge accumulation effects in Hf0.5Zr0.5O2 nanopowders sintered by the auto-combustion sol-gel method and annealed at temperatures from 500°C to 800°C. The fraction of the orthorhombic phase, determined by the X-ray diffraction (XRD), decreases from 91 vol.% to 7 vol.% with an increase in the annealing temperature from 600°C to 800°C. The electron paramagnetic resonance (EPR) spectra reveal the great amount of oxygen vacancies in the annealed samples, at that the decrease of the orthorhombic phase fraction (observed with an increase in the annealing temperature) correlates with a decrease in the intensity of EPR spectral lines associated with the oxygen vacancies and impurities. This indicates the participation of oxygen vacancies and other defects in the formation of the orthorhombic phase in the Hf0.5Zr0.5O2 powders. To explain the results of electrophysical measurements, we compare the features of the current-voltage characteristics with the phase composition of the Hf0.5Zr0.5O2 powders and with the peculiarities of their EPR spectra. The analysis allows us to relate the resistive switching and charge accumulation observed in Hf0.5Zr0.5O2 nanopowders with the appearance of the ferroelectric-like polar regions in the orthorhombic phase of the nanoparticles, which agrees with the calculations performed in the framework of Landau-Ginzburg-Devonshire approach and density functional theory.