Mechanical Mode Imaging of a High-Q Hybrid hBN/Si₃N₄ Resonator

Abstract

We image and characterize the mechanical modes of a 2D drum resonator made of hBN suspended over a high-stress Si3N4 membrane. Our measurements demonstrate hybridization between various modes of the hBN resonator and those of the Si3N4 membrane. The measured resonance frequencies and spatial profiles of the modes are consistent with finite-element simulations based on idealized geometry. Spectra of the thermal motion reveal that, depending on the degree of hybridization with modes of the heavier and higher-quality-factor Si3N4 membrane, the quality factors and the motional mass of the hBN drum modes can be shifted by orders of magnitude. This effect could be exploited to engineer hybrid drum/membrane modes that combine the low motional mass of 2D materials with the high quality factor of Si3N4 membranes for optomechanical or sensing applications.

Radiation pressure backaction on a hexagonal boron nitride nanomechanical resonator

“…Any hybridization between the heavy SiN membrane and the hBN drum will result in an increase of the effective mass of the hBN resonator. 47 This is the upper limit of the effective mass of pure ideal hBN drum modes. From our data we observe that the effective masses measured outside the circular drum (orange markers) stay close to the theoretical limit for SiN, which is what we expect as no hybridization should occur.…”

“…All this suggests that these modes, undetectable on the SiN membrane, originate purely from the hBN circular resonator or result from hybridization between the modes intrinsic to the hBN drum-head and the SiN membrane ones. 47,54 To further investigate the degree of hybridization, we measure the effective mass of all modes starting from the fundamental mode of the SiN membrane at 137.2 kHz until 1.7 MHz.…”

“…The former can be improved by using high stress Si 3 N 4 as a support for the hBN drums, pushing the Si 3 N 4 resonances to higher frequencies and allowing resolution of the distinct mode shapes; the latter by using more gentle transfer mechanisms like a wet transfer. 47 The setup presented in this work is very versatile: a careful design of the mirror coatings and the use of multi mode fibers for the input mirror would enable the incorporation of several wavelengths, enabling photoluminiscence experiments on-site. This will open the door to new ways of studying the strain dependence of hBN defects with an additional control of the mechanical properties through light, and a new step forward toward the realization of spin-optomechanics with this 2D material.…”

Radiation Pressure Backaction on a Hexagonal Boron Nitride Nanomechanical Resonator

“…We identify the mechanical resonances by systematic characterization in a standard Michelson interferometer. Following the work from Jaeger et al, 50 we use the experimentally determined effective mass to characterize the degree of mechanical hybridization of the hBN resonator with the mechanical modes of the SiN stripe supporting the flake (Supporting Information). We observe a series of mechanical modes between 1500 kHz and 1700 kHz that are localized in the circular hBN resonator and possess effective masses more than 1 order of magnitude below that of pure SiN modes, which we identify as hybridized modes with a strong hBN character.…”

“…The former can be improved by using high stress Si 3 N 4 as a support for the hBN drums, pushing the Si 3 N 4 resonances to higher frequencies and allowing resolution of the distinct mode shapes, the latter by using more gentle transfer mechanisms like a wet transfer. 50 The setup presented in this work is very versatile: a careful design of the mirror coatings would enable the incorporation of several wavelengths, enabling photoluminescence experiments on-site. This will open the door to new ways of studying the strain dependence of hBN defects with an additional control of the mechanical properties through light and a new step forward toward the realization of spin-optomechanics with this van der Waals material.…”