Origin of the anomalous piezoelectric response in wurtzite Sc$_x$Al$_{1-x}$N alloys

TL;DR

This study uncovers the intrinsic origin of the extraordinary piezoelectric response in Sc$_x$Al$_{1-x}$N alloys, linking it to atomic response changes and phase competition, guiding future high-performance piezoelectric material design.

Contribution

It reveals the intrinsic mechanism behind the 400% piezoelectric enhancement in Sc$_x$Al$_{1-x}$N alloys through quantum mechanical calculations and phase analysis.

Findings

Intrinsic origin of the anomalous piezoelectric response identified.

Softening of elastic constant C33 linked to response change.

Energy landscape flattening due to phase competition observed.

Abstract

The origin of the anomalous, 400% increase of the piezoelectric coefficient in Sc$_x$Al$_{1-x}$N alloys is revealed. Quantum mechanical calculations show that the effect is intrinsic. It comes from a strong change in the response of the internal atomic coordinates to strain and pronounced softening of C$_{33}$ elastic constant. The underlying mechanism is the flattening of the energy landscape due to a competition between the parent wurtzite and the so far experimentally unknown hexagonal phases of the alloy. Our observation provides a route for the design of materials with high piezoelectric response.