Evidence for reversible oxygen ion movement during electrical pulsing: enabler of the emerging ferroelectricity in binary oxides

Abstract

Ferroelectric HfO2-based materials and devices show promising potential for advancing emerging information technology but face challenges with inadequate electrostatic control, degraded reliability, and serious variation for EOT (effective oxide thickness) scaling. We demonstrate a novel interface-type switching strategy to realize ferroelectric characteristics in atomic-scale amorphous binary oxide films, which are formed in oxygen-deficient conditions by atomic layer deposition (ALD) at low temperatures. This approach can avoid the shortcomings of reliability degradation and gate leakage increment in scaling poly-crystalline doped HfO2-based films. Through theoretical modeling and experimental characterization, we show that: 1) Emerging ferroelectricity exists in the ultrathin oxide system due to microscopic ion migration in the switching process. 2) These ferroelectric binary oxide films are governed by the interface-limited switching mechanism, which can be attributed to the oxygen vacancy migration and the surface defect related to electron (de)trapping. 3) Transistors featuring ultrathin amorphous dielectrics, used for nonvolatile memory applications with an operating voltage reduced to ±1 V, have also been experimentally demonstrated. These findings suggest that the strategy is a promising approach to realizing the next-generation CMOS with scalable ferroelectric material.