Charge-Induced Dynamics in Hexagonal Boron Nitride Nanoelectromechanical Resonators

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Hexagonal boron nitride (hBN) is a large bandgap dielectric material with potential applications in nanoelectromechanical systems (NEMS).
• Actuation of insulating nanostructures typically requires conductive layers, limiting their integration and functionality.

Purpose of the Study:

• To demonstrate electrostatic actuation of insulating hBN nanodrums without a conductive layer.
• To investigate the charge dynamics and defect physics within hBN using nanomechanical resonators.
• To explore the potential of hBN nanodrums for novel NEMS-based sensors.

Main Methods:

• Fabrication of hexagonal boron nitride (hBN) nanodrums.
• Utilizing a non-uniform electric field for electrostatic actuation.
• Measuring resonance frequency and its dispersion with applied DC bias voltage.
• Conducting band-bending analysis and wavelength-dependent optical excitation.

Main Results:

• Successful electrostatic actuation of insulating hBN nanodrums was achieved.
• An unconventional linear resonance frequency dispersion with applied DC bias was observed.
• Bias-dependent frequency drift indicated slow charge dynamics in hBN.
• Deep defect states in hBN were identified, exhibiting bias and photoassisted ionization, leading to asymmetric charge buildup.

Conclusions:

• Electrostatically driven hBN nanodrums provide a sensitive platform for studying charge dynamics and defect physics in insulating 2D materials.
• This research opens avenues for developing novel NEMS-based sensors and charge-controlled mechanical devices.