Experimental investigation of damping factors in 20% scandium-doped aluminum nitride laterally vibrating resonators

This paper reports experimental investigation of damping factors for 20% Scandium-doped Aluminum Nitride (ScAlN) laterally vibrating resonators (LVRs). ScAlN films for LVRs are very promising since they enable greater electromechanical coupling (kt2) than undoped AlN films (∼ 2X for 20% doping), but have generally exhibited lower quality factors (Qs) [1,2]. This work is the first to study what damping factors impact the performance of these devices and provide preliminary design guidelines to attain high Qs. Different ScAlN LVR geometries are analyzed and devices tested in air, under vacuum, and at cryogenic temperatures (11 K). Anchor losses and thermoelastic damping (TED) are evaluated and compared to AlN LVRs. Similarities in thermal scaling of Qs in ScAlN resonators indicate that the source of TED is similar to AlN devices.