In‐Grain Ferroelectric Switching in Sub‐5 nm Thin Al0.74Sc0.26N Films at 1 V

Abstract

Abstract Analog switching in ferroelectric devices promises neuromorphic computing with the highest energy efficiency if limited device scalability can be overcome. To contribute to a solution, one reports on the ferroelectric switching characteristics of sub‐5 nm thin Al0.74Sc0.26N films grown on Pt/Ti/SiO2/Si and epitaxial Pt/GaN/sapphire templates by sputter‐deposition. In this context, the study focuses on the following major achievements compared to previously available wurtzite‐type ferroelectrics: 1) Record low switching voltages down to 1 V are achieved, which is in a range that can be supplied by standard on‐chip voltage sources. 2) Compared to the previously investigated deposition of ultrathin Al1−xScxN films on epitaxial templates, a significantly larger coercive field (Ec) to breakdown field ratio is observed for Al0.74Sc0.26N films grown on silicon substrates, the technologically most relevant substrate‐type. 3) The formation of true ferroelectric domains in wurtzite‐type materials is for the first time demonstrated on the atomic scale by scanning transmission electron microscopy (STEM) investigations of a sub‐5 nm thin partially switched film. The direct observation of inversion domain boundaries (IDB) within single nm‐sized grains supports the theory of a gradual domain‐wall driven switching process in wurtzite‐type ferroelectrics. Ultimately, this should enable the analog switching necessary for mimicking neuromorphic concepts also in highly scaled devices.

Keywords

• domains
• ferroelectrics
• neuromorphic computing
• scandium
• thin films