Açıkgöz Hande N, Shin Dong Hoon, van der Knijff Inge C, Katan Allard J, Yang Xiliang, Steeneken Peter G, Verbiest Gerard J, Caneva Sabina
Department of Precision and Microsystems Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands.
Department of Electronics and Information Engineering, Korea University, Sejong 30019, Republic of Korea.
ACS Nano. 2025 Apr 15;19(14):14044-14052. doi: 10.1021/acsnano.4c18508. Epub 2025 Apr 1.
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.
基于二维（2D）材料的高频声学器件正在成为新兴平台，用于设计和操纵声波的时空响应，以应用于下一代传感和非接触式驱动。然而，传统的驱动方法不能应用于所有二维材料，存在频率限制或受衬底相互作用的影响。因此，需要一种通用的高频片上驱动技术。在此，我们证明表面声波（SAW）可以通过用高频（375 MHz）瑞利波激发悬浮的石墨烯膜并使用原子力声学显微镜（AFAM）映射产生的振动场，来有效地驱动悬浮的二维材料，从而能够在没有衬底干扰的情况下直接可视化波的传播。从支撑的石墨烯传播到悬浮的石墨烯的声波，由于有效弯曲刚度的降低，其声波波长从10μm减小到约2μm，导致悬浮石墨烯上的波速降低。通过激光光热驱动（0 - 100 MHz）和表面声波驱动（375 MHz）改变激发频率，我们观察到相速度从约160 m/s变化到约700 m/s。这种行为与平板理论预测的悬浮石墨烯膜中声波的非线性色散一致。因此，膜的几何形状和弯曲刚度在调制声波模式和波长方面起着关键作用。这种表面声波驱动和原子力声学显微镜可视化相结合的方案，增进了对纳米尺度极限下声传输的理解，并为在二维材料表面进行片上图案化和传输的局部波场操纵提供了一条途径。
