Ferroelectricity in hafnium oxide thin films

TLDR

Ferroelectric hafnium oxide is ideally suited for ferroelectric field‑effect transistors and capacitors because of its excellent compatibility with silicon technology. The authors fabricated 10‑nm‑thick SiO₂‑doped hafnium oxide films with less than 4 mol % SiO₂. They found that crystalline phases with ferroelectric behavior can be formed in these films, and mechanical encapsulation suppresses the monoclinic phase while promoting an orthorhombic phase that exhibits a distinct piezoelectric response and remanent polarization above 10 µC/cm² at a coercive field of 1 MV/cm, confirming ferroelectricity.

Abstract

We report that crystalline phases with ferroelectric behavior can be formed in thin films of SiO2 doped hafnium oxide. Films with a thickness of 10 nm and with less than 4 mol. % of SiO2 crystallize in a monoclinic/tetragonal phase mixture. We observed that the formation of the monoclinic phase is inhibited if crystallization occurs under mechanical encapsulation and an orthorhombic phase is obtained. This phase shows a distinct piezoelectric response, while polarization measurements exhibit a remanent polarization above 10 μC/cm2 at a coercive field of 1 MV/cm, suggesting that this phase is ferroelectric. Ferroelectric hafnium oxide is ideally suited for ferroelectric field effect transistors and capacitors due to its excellent compatibility to silicon technology.