Process-dependent ferroelectric and memristive properties in polycrystalline Ca:HfO2-based devices

Abstract

Memristors are considered key building blocks for developing neuromorphic or in-memory computing hardware. Here, we study the ferroelectric and memristive response of Pt/Ca:HfO2/Pt devices fabricated on silicon by spincoating from chemical solution deposition followed by a pyrolysis step and a final thermal treatment for crystallization at 800°C for 90 s. For pyrolysis temperature of 300°C, the annealed samples are ferroelectric while for 400°C a dielectric behavior is observed. For each case, we found a distinct, forming-free, memristive response. Ferroelectric devices can sustain polarization switching and memristive behavior simultaneously. Aided by numerical simulations, wedescribe the memristive behavior of ferroelectric devices arising from oxidemetal Schottky barriers modulation by both the direction of the electrical polarization and oxygen vacancy electromigration. For non-ferroelectric samples, only the latter effect controls the memristive behavior.