High- <i>Q</i> membrane resonators using ultra-high-stress crystalline TiN films

High-quality-factor (Q) mechanical resonators are essential components for precise sensing and control of mechanical motion at a quantum level. While amorphous materials such as SiN have been widely used in high-Q mechanical resonators utilizing stress-induced dissipation dilution, crystalline materials have emerging potential to achieve higher quality factors by combining low intrinsic loss and high tensile stress. In this paper, we demonstrate high-Q membrane resonators using ultra-high-stress crystalline TiN. Our membrane resonator exhibits a tensile stress exceeding 2.3 GPa and a quality factor of Q=8.0×106 at 2.2 K. By estimating the dilution factor, we infer that our TiN resonator has an intrinsic quality factor comparable to that of SiN membrane resonators. With its ultra-high stress and crystalline properties, our TiN films can serve as a powerful tool for opto- and electromechanical systems, offering highly dissipation-diluted mechanical resonators.