Temperature-Dependent Ferroelectric Properties of Pristine and Defective ScₓAl₁₋ₓN: Insights from Ab Initio Molecular Dynamics

Scandium-doped wurtzite aluminum nitride (ScₓAl_1-xN) has recently attracted significant attention as a promising nitride ferroelectric with enhanced piezoelectric and polarization responses compared to conventional AlN. Despite extensive studies at zero temperature, the finite-temperature behavior and mechanisms governing ferroelectric-to-paraelectric transitions remain limited. In this work, we employ large-scale ab initio molecular dynamics (AIMD) simulations to investigate the temperature-dependent ferroelectric properties of ScₓAl₁_₋ₓN over a temperature range of (300 - 4000) K. Our results show a systematic decrease in polarization with increasing temperature, with atomic displacements approaching a paraelectric-like configuration (u ≈ 0.5) at higher temperatures, suggesting a possible transition region. Furthermore, we introduce nitrogen vacancies (V_N) to examine defect-mediated polarization behavior and its influence on phase stability. These simulations aim to clarify how intrinsic defects modify local atomic displacements, affect polarization switching, and potentially lower the transition temperature relative to pristine ScₓAl₁_₋ₓN. The findings provide microscopic insight into temperature-dependent ferroelectricity in nitride systems and establish a foundation for defect engineering in high-temperature ferroelectric and piezoelectric devices.