A megahertz nanomechanical resonator with room temperature quality factor over a million

We demonstrate the fabrication and operation of high aspect ratio tensile stressed silicon nitride string resonators. We explore the parameter space of small cross sections, on the order of $100\mathrm{nm}$ , and long lengths up to $325\mu \mathrm{m}$ , demonstrating that such high aspect ratio resonators can be made with standard wet release processing using a material with internal tensile stress. Room temperature quality factors exceed one million at frequencies above $1\mathrm{MHz}$ . The utility of such high quality factor flexural resonators to probe the interaction of high frequency nanoscale devices with rarefied gases is demonstrated.