In atomically thin membranes, strain couples strongly to electrons, phonons, and photons. Although strain originating from uniform or global deformation has been widely studied, the impact of spatially localized mechanical perturbations on strain distribution remains less explored. Here, we investigate how localized tungsten carbide deposition via focused electron-beam-induced deposition (FEBID) modifies the strain landscape in suspended monolayer graphene membranes. Using spatially resolved mechanical resonance mode shape mapping and Raman spectroscopy, supported by finite element simulations, we find that the central deposit acts as a mechanically coupled local perturbation that redistributes the pre-existing strain into a more radially symmetric configuration with reduced angular anisotropy around the deposit. These findings demonstrate that FEBID-based local deposition can serve as a lithography-free approach for controlled strain modulation in suspended graphene, offering a practical platform for studying strain-coupled phenomena and designing strain-controlled nanoelectromechanical and optoelectronic systems. ... Read more

Crystal defects in hexagonal boron nitride (hBN) are emerging as versatile nanoscale optical probes with a wide application profile, spanning the fields of nanophotonics, biosensing, bioimaging, and quantum information processing. However, generating these crystal defects as reliable optical emitters remains challenging due to the need for deterministic defect placement and precise control of the emission area. Here, we demonstrate an approach that integrates microspheres with hBN crystal lattices to enhance both hBN defect generation and optical signal readout. This technique harnesses microspheres to amplify light–matter interactions at the nanoscale through two mechanisms: focused femtosecond (fs) laser irradiation into a photonic nanojet (PNJ) for highly localized defect generation and enhanced light collection via the whispering gallery mode (WGM) effect. Our microsphere-assisted defect generation method reduces the emission area by a factor of 5 and increases the fluorescence collection efficiency by approximately 10 times compared to microsphere-free samples. These advancements in defect generation precision and signal collection efficiency open new possibilities for optical emitter manipulation in hBN, with potential applications in quantum technologies and nanoscale sensing. ... Read more

High-frequency acoustic devices based on two-dimensional (2D) materials are emerging platforms to design and manipulate the spatiotemporal response of acoustic waves for next-generation sensing and contactless actuation applications. Conventional actuation methods, however, cannot be applied to all 2D materials, are frequency-limited or influenced by substrate interactions. Therefore, a universal, high-frequency, on-chip actuation technique is needed. Here, we demonstrate that surface acoustic waves (SAWs) can efficiently actuate suspended 2D materials by exciting suspended graphene membranes with high-frequency (375 MHz) Rayleigh waves and mapping the resulting vibration field with atomic force acoustic microscopy (AFAM), enabling direct visualization of wave propagation without substrate interference. Acoustic waves traveling from supported to suspended graphene experience a reduction in acoustic wavelength from 10 μm to ∼2 μm due to the decrease in effective bending rigidity, leading to a decrease in wave velocity on suspended graphene. By varying the excitation frequency through laser photothermal actuation (0-100 MHz) and SAW excitation (375 MHz), we observed a phase velocity change from ∼160 m/s to ∼700 m/s. This behavior is consistent with the nonlinear dispersion of acoustic waves, as predicted by plate theory, in suspended graphene membranes. The geometry and bending rigidity of the membrane thus play key roles in modulating the acoustic wave pattern and wavelength. This combined SAW actuation and AFAM visualization scheme advances the understanding of acoustic transport at the nanoscale limit and provides a route toward the manipulation of localized wavefields for on-chip patterning and transport over 2D materials surfaces. ... Read more