title: Control of material damping in high-Q membrane microresonators.
abstract: We study the mechanical quality factors of bilayer aluminum-silicon-nitride membranes. By coating ultrahigh-Q Si(3)N(4) membranes with a more lossy metal, we can precisely measure the effect of material loss on Q's of tensioned resonator modes over a large range of frequencies. We develop a theoretical model that interprets our results and predicts the damping can be reduced significantly by patterning the metal film. Using such patterning, we fabricate Al-Si(3)N(4) membranes with ultrahigh Q at room temperature. Our work elucidates the role of material loss in the Q of membrane resonators and informs the design of hybrid mechanical oscillators for optical-electrical-mechanical quantum interfaces.
authors.affiliation: JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309, USA.
authors.forename: P-L
authors.initials: PL
authors.lastname: Yu
authors.forename: T P
authors.initials: TP
authors.lastname: Purdy
authors.forename: C A
authors.initials: CA
authors.lastname: Regal