Resolving Mechanical Properties and Morphology Evolution of Free‐Standing Ferroelectric Hf_0.5Zr_0.5O₂

Advances in creating polar structures in atomic‐layered hafnia‐zirconia (Hf_xZr_1−xO₂) films not only augurs extensive growth in studying ferroelectric nanoelectronics and neuromorphic devices, but also spurs opportunities for exploring novel integrated nanoelectromechanical systems (NEMS). Design and implementation of Hf_xZr_1−xO₂ NEMS transducers necessitates accurate knowledge of elastic and electromechanical properties. Up to now, all experimental approaches for extraction of morphological content, elastic, and electromechanical properties of Hf_xZr_1−xO₂ are based on solidly mounted structures, highly stressed films, and electroded architectures. Unlike Hf_xZr_1−xO₂ layers embedded in electronics, NEMS transducers require free‐standing structures with highly contrasted mechanical boundaries and stress profiles. Here, a nanoresonator‐based approach for simultaneous extraction of Young's modulus and residual stress in free‐standing ferroelectric Hf_0.5Zr_0.5O₂ films is presented. High quality factor resonance modes of nanomechanical resonators created in predominantly orthorhombic Hf_0.5Zr_0.5O₂ films are measured using nondestructive optical transduction. Further, the evolution of morphology during creation of free‐standing Hf_0.5Zr_0.5O₂ structures is closely mapped using X‐ray diffraction measurements, clearly showing transformation of ferroelectric orthorhombic to nonpolar monoclinic phase upon stress relaxation. The extracted Young's modulus of 320.0 ± 29.4 GPa and residual stress of σ = 577.4 ± 24.1 MPa show the closest match with theoretical calculations for orthorhombic Hf_0.5Zr_0.5O₂.