High Quality Factors in Superlattice Ferroelectric Hf_0.5Zr_0.5O₂ Nanoelectromechanical Resonators

The discovery of ferroelectricity and advances in creating polar structures in atomic-layered hafnia-zirconia (HfZr_1-O₂) films spur the exploration of using the material for novel integrated nanoelectromechanical systems (NEMS). Despite its popularity, the approach to achieving high quality factors (Qs) in resonant NEMS made of HfZr_1-O₂ thin films remains unexplored. In this work, we investigate the realization of high Qs in Hf_0.5Zr_0.5O₂ nanoelectromechanical resonators by stress engineering via the incorporation of alumina (Al₂O₃) interlayers. We fabricate nanoelectromechanical resonators out of the Hf_0.5Zr_0.5O₂-Al₂O₃ superlattices, from which we measure Qs up to 171,000 and frequency-quality factor products (f × Q) of >10¹¹ Hz through electrical excitation and optical detection schemes at room temperature in vacuum. The analysis suggests that clamping loss and surface loss are the limiting dissipation sources and f × Q > 10¹² Hz is achievable through further engineering of anchor structure and built-in stress.