Control of Material Damping in High-Q Membrane Microresonators

TL;DR

This paper investigates how material loss affects the quality factors of high-Q membrane resonators and demonstrates that patterning metal coatings can significantly reduce damping, leading to ultrahigh Q membranes at room temperature.

Contribution

It introduces a theoretical model linking material loss to Q and shows how patterning metal films enhances membrane quality factors.

Findings

Material loss impacts membrane Q factors significantly.

Patterned metal coatings can reduce damping.

Fabricated ultrahigh-Q membranes at room temperature.

Abstract

We study the mechanical quality factors of bilayer aluminum/silicon-nitride membranes. By coating ultrahigh-Q Si3N4 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-Si3N4 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.