Frequency fluctuations in silicon nanoresonators

TL;DR

This paper investigates unexpected large frequency fluctuations in silicon nanoresonators, revealing they are intrinsic and not due to measurement errors, challenging existing assumptions about frequency stability limits.

Contribution

The study introduces a new method to identify intrinsic frequency fluctuations in silicon nanoresonators, demonstrating their unexpectedly high level and questioning current stability models.

Findings

Frequency fluctuations are larger than thermomechanical noise limits.

The fluctuations are intrinsic and not caused by measurement system.

Current models underestimate the level of frequency fluctuations.

Abstract

Frequency stability is key to performance of nanoresonators. This stability is thought to reach a limit with the resonator's ability to resolve thermally-induced vibrations. Although measurements and predictions of resonator stability usually disregard fluctuations in the mechanical frequency response, these fluctuations have recently attracted considerable theoretical interest. However, their existence is very difficult to demonstrate experimentally. Here, through a literature review, we show that all studies of frequency stability report values several orders of magnitude larger than the limit imposed by thermomechanical noise. We studied a monocrystalline silicon nanoresonator at room temperature, and found a similar discrepancy. We propose a new method to show this was due to the presence of frequency fluctuations, of unexpected level. The fluctuations were not due to the instrumentation system, or to any other of the known sources investigated. These results challenge our current understanding of frequency fluctuations and call for a change in practices.