Dissipation measurements of vacuum-operated single-crystal silicon microresonators

Abstract

The quality factors of vacuum-operated single-crystal silicon microresonators have been measured, to identify their important sources of mechanical loss when medium-related loss is absent. The microresonators are torsional structures consisting of beams of width ≈ 0.7 μm, fabricated by reactive-ion etching from a single-crystal silicon substrate. For torsional microresonators having Q-factors around 50 000, doping-impurity and support-related losses do not seem to be significant. Rather, it appears that losses originating from beam surfaces, which are dry-etched, are important. This etched-surface loss can be halved by thermal oxidation, resulting in microresonators with Q-values consistently in the range 80 000–100 000. A model for this surface-related loss is presented.