Signatures of two-level defects in the temperature-dependent damping of nanomechanical silicon nitride resonators

The damping rates of high quality factor nanomechanical resonators are well beyond intrinsic limits. Here,we explore the underlying microscopic loss mechanisms by investigating the temperature-dependent dampingof the fundamental and third harmonic transverse flexural mode of a doubly clamped silicon nitride string. Itexhibits characteristic maxima reminiscent of two-level defects typical for amorphous materials. Coupling tothose defects relaxes the momentum selection rules, allowing energy transfer from discrete long-wavelengthresonator modes to the high frequency phonon environment.     «

The damping rates of high quality factor nanomechanical resonators are well beyond intrinsic limits. Here,we explore the underlying microscopic loss mechanisms by investigating the temperature-dependent dampingof the fundamental and third harmonic transverse flexural mode of a doubly clamped silicon nitride string. Itexhibits characteristic maxima reminiscent of two-level defects typical for amorphous materials. Coupling tothose defects relaxes the momentum selection rules, allowing energy trans...     »