Ferroelectric-HfO2/Oxide Interfaces, Oxygen Distribution Effect and Implications for Device Performance

TL;DR

This paper explores the atomic-scale electronic structures of ferroelectric HfO2 interfaces with oxides, revealing how interface effects influence device performance, especially regarding depolarizing fields and oxygen distribution.

Contribution

It provides a detailed analysis of ferroelectric HfO2/dielectric interfaces, highlighting the impact of oxygen distribution and depolarizing fields on ferroelectric properties and device implications.

Findings

Strong depolarizing fields at interfaces can be detrimental or beneficial depending on device context.

Asymmetric oxygen distribution induces polarity, affecting ferroelectric behavior.

Annealing and defect formation can mitigate some interface-induced effects.

Abstract

Atomic-scale understanding of HfO2 ferroelectricity is important to help address many challenges in developing reliable and high-performance ferroelectric HfO2 (fe-HfO2) based devices. Though investigated from different angles, a factor that is real device-relevant and clearly deserves more attention has largely been overlooked by previous research, namely, the fe-HfO2/dielectric interface. Here, we investigate the electronic structures of several typical interfaces formed between ultrathin fe-HfO2 and oxide dielectrics in the sub-3-nm region. We find that interface formation introduces strong depolarizing fields in fe-HfO2, which is detrimental for ferroelectric polarization but can be a merit if tamed for tunneling devices, as recently demonstrated. Asymmetric oxygen distribution-induced polarity, intertwined with ferroelectric polarization or not, is also investigated as a relevant interfacial effect in real device. Though considered detrimental from certain aspects, such as inducing build-in field (independent of ferroelectric polarization) and exacerbating depolarization (intertwined with ferroelectric polarization), it can be partly balanced out by other effects, such as annealing (extrinsic) and polarity-induced defect formation (intrinsic). This work provides insights into ferroelectric-HfO2/dielectric interfaces and some useful implications for the development of devices.