Local electrical characteristic of memristor structure in a high-resistance state obtained using electrostatic force microscopy: Fractal and multifractal dynamics of surface

A heterostructure BiFeO3/TiO2(Nt)Ti (BFOT) was obtained by the atomic layer deposition (ALD) method. After thermal treatment, the redistribution of Fe/Ti atoms forms an Aurivillius intermediate layered phase, and local charge capture centers are formed in the sample. Due to cationic non-stoichiometry, the BFO film exhibits p-type conductivity, while the nanotubes exhibit n-type conductivity due to oxygen vacancies. It was observed that lateral displacement of the sample can lead to ferroelectric switching, which can, in turn, affect the transition of the memristive structure from high-resistance (HRS) to low-resistance states (LRS). The hysteresis suppression tends to transition to an ohmic character and depends on the amplitude, frequency, and duration of the periodic signal. It has been found that compensation of static charge during resistive switching can affect the transport properties of the material. Fractal dimension analysis showed an acceleration of structure restructuring with increasing voltage, possibly contributing to the transition from an insulator to a metal in certain areas of the film volume. The joint analysis of piezoresponse force microscopy (PFM), electrostatic force microscopy (EFM), and fractal/multifractal dynamics showed a correlation between surface static charge and piezopotential. The new methodology described in this work can help understand the resistive switching processes in ferroelectric/ semiconductor memristive structures.

Automated summary

A heterostructure BiFeO3/TiO2(Nt)Ti (BFOT) with p-type conductivity in the BFO film and n-type conductivity in the nanotubes was obtained by the atomic layer deposition method. The redistribution of Fe/Ti atoms and the formation of Aurivillius intermediate layered phase and local charge capture centers were observed after thermal treatment. The ferroelectric switching and the transition of the memristive structure were affected by the lateral displacement of the sample and the properties of the periodic signal. The compensation of static charge during resistive switching and the acceleration of structure restructuring with increasing voltage were found to influence the transport properties of the material. The correlation between surface static charge and piezopotential was shown through the analysis of piezoresponse force microscopy, electrostatic force microscopy, and fractal/multifractal dynamics. This new methodology can contribute to the understanding of the resistive switching processes in ferroelectric/semiconductor memristive structures.