# Semiconducting nonperovskite ferroelectric oxynitride designed ab initio

## TL;DR

This paper reports the discovery of new nonperovskite ferroelectric oxynitrides, TaON and NbON, with promising electronic and piezoelectric properties suitable for multifunctional applications, guided by ab initio calculations.

## Contribution

It introduces a novel class of ferroelectric oxynitrides with unique properties, expanding the design space for ferroelectric semiconductors using ab initio methods.

## Key findings

- TaON and NbON exhibit large remnant polarization.
- They have low switching barriers and negative piezoelectric effects.
- Both materials can absorb visible light and have high charge mobility.

## Abstract

Recent discovery of HfO2-based and nitride-based ferroelectrics that are compatible to the semiconductor manufacturing process have revitalized the field of ferroelectric-based nanoelectronics. Guided by a simple design principle of charge compensation and density functional theory calculations, we discover HfO2-like mixed-anion materials, TaON and NbON, can crystallize in the polar Pca21 phase with a strong thermodynamic driving force to adopt anion ordering spontaneously. Both oxynitrides possess large remnant polarization, low switching barriers, and unconventional negative piezoelectric effect, making them promising piezoelectrics and ferroelectrics. Distinct from HfO2 that has a wide band gap, both TaON and NbON can absorb visible light and have high charge carrier mobilities, suitable for ferroelectric photovoltaic and photocatalytic applications. This new class of multifunctional nonperovskite oxynitride containing economical and environmentally benign elements offer a platform to design and optimize high-performing ferroelectric semiconductors for integrated systems.