Theoretical understanding of the in-plane tensile strain effects on enhancing the ferroelectric performance of HfZrO and ZrO thin films.

In-plane tensile strain was reported to enhance the ferroelectricity of HfZrO thin films by promoting the formation of a polar orthorhombic (PO-) phase. However, its origin remains yet to be identified unambiguously, although a strain-related thermodynamic stability variation was reported. This work explores the kinetic effects that have been overlooked to provide a precise answer to the problem, supplementing the thermodynamic calculations.

Study of a charge transition-driven resistive switching mechanism in TiO-based random access memory density functional theory.

The nature of the conducting filament (CF) with a high concentration of oxygen vacancies (Vs) in oxide thin film-based resistive random access memory (RRAM) remains unclear. The Vs in the CF have been assumed to be positively charged (V) to explain the field-driven switching of RRAM, but V clusters in high concentration encounter Coulomb repulsion, rendering the CF unstable. Therefore, this study examined the oxidation state of Vs in the CF and their effects on the switching behavior density functional theory calculations using a Pt/TiO/Ti model system.

Reversible transition between the polar and antipolar phases and its implications for wake-up and fatigue in HfO-based ferroelectric thin film.

Atomic-resolution Cs-corrected scanning transmission electron microscopy revealed local shifting of two oxygen positions (O and O) within the unit cells of a ferroelectric (HfZr)O thin film. A reversible transition between the polar Pbc2 and antipolar Pbca phases, where the crystal structures of the 180° domain wall of the Pbc2 phase and the unit cell structure of the Pbca phase were identical, was induced by applying appropriate cycling voltages. The critical field strength that determined whether the film would be woken up or fatigued was ~0.