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1. Mode-dependent scaling of nonlinearity and linear dynamic range in a NEMS resonator

   https://doi.org/10.1063/5.0215566  

   Ma, M; Welles, N; Svitelskiy, O; Yanik, C; Kaya, I I; Hanay, M S; Paul, M R; Ekinci, K L (August 2024, Applied Physics Letters)

   Even a relatively weak drive force is enough to push a typical nanomechanical resonator into the nonlinear regime. Consequently, nonlinearities are widespread in nanomechanics and determine the critical characteristics of nanoelectromechanical systems' (NEMSs) resonators. A thorough understanding of the nonlinear dynamics of higher eigenmodes of NEMS resonators would be beneficial for progress, given their use in applications and fundamental studies. Here, we characterize the nonlinearity and the linear dynamic range (LDR) of each eigenmode of two nanomechanical beam resonators with different intrinsic tension values up to eigenmode n = 11. We find that the modal Duffing constant increases as n4, while the critical amplitude for the onset of nonlinearity decreases as 1/n. The LDR, determined from the ratio of the critical amplitude to the thermal noise amplitude, increases weakly with n. Our findings are consistent with our theory treating the beam as a string, with the nonlinearity emerging from stretching at high amplitudes. These scaling laws, observed in experiments and validated theoretically, can be leveraged for pushing the limits of NEMS-based sensing even further. 

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2. Two-dimensional FePS3 nanoelectromechanical resonators with local-gate electrostatic tuning at room temperature

   https://doi.org/10.1063/5.0243387  

   Wang, Yunong; Yousuf, S_M_Enamul Hoque; Zhang, Xiao-Xiao; Feng, Philip X-L (December 2024, Journal of Applied Physics)

   Nanoelectromechanical systems (NEMS) enabled by two-dimensional (2D) magnetic materials are promising candidates for exploring ultrasensitive detection and magnetostrictive phenomena, thanks to their high mechanical stiffness, high strength, and ultralow mass. The resonance modes of such vibrating membrane NEMS can be probed optically and also manipulated mechanically via electrostatically induced strain. Electrostatic frequency tuning of 2D magnetic NEMS resonators is, thus, an important means of investigating magneto-mechanical coupling mechanisms. Toward realizing magneto-mechanical coupled devices, we build circular drumhead iron phosphorus trisulfide (FePS3) NEMS resonators with different diameters (3–7 μm). Here, we report on experimental demonstration of tunable antiferromagnet FePS3 drumhead resonators with the highest fractional frequency tuning range up to Δf/f0 = 32%. Combining experimental results and analytical modeling of the resonance frequency scaling, we attain quantitative understanding of the elastic behavior of FePS3, including the transition from “membrane” to “plate” regime, with built-in tension (γ) ranging from 0.1 to 2 N/m. This study not only offers methods for investigating mechanical properties of ultrathin membranes of magnetic 2D materials but also provides important guidelines for designing future high-performance magnetic NEMS resonators. 

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3. Design Principles for Noncentrosymmetric Materials

   https://doi.org/10.1146/annurev-matsci-080921-110002  

   Huai, Xudong; Tran, Thao T. (July 2023, Annual Review of Materials Research)

   Noncentrosymmetric (NCS) materials feature an exciting array of functionalities such as nonlinear optical (NLO) responses and topological spin textures (skyrmions). While NLO materials and magnetic skyrmions display two different sets of physical properties, their design strategies are deeply connected in terms of atomic-scale precision, structural customization, and electronic tunability. Despite impressive progress in studying these systems separately, a joint road map for navigating the chemical principles for NCS materials remains elusive. This review unites two subtopics of NCS systems, NLO materials and magnetic skyrmions, offering a multifaceted narrative of how to translate the often-abstract fundamentals to the targeted functionalities while inviting innovative approaches from the community. We outline the design principles central to the desired properties by exemplifying relevant examples in the field. We supplement materials chemistry with pertinent electronic structures to demonstrate the power of the fundamentals to create systems integration relevant to foreseeable societal impacts in frequency-doubling instrumentation and spin-based electronics. 

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4. Atomistic Insights into Elemental Two-Dimensional Materials and Their Heterostructures

   https://doi.org/10.1146/annurev-physchem-082423-124941  

   Rajak, Soumyajit; Schultz, Jeremy F; Li, Linfei; Jiang, Nan (April 2025, Annual Review of Physical Chemistry)

   Inspired by the success of graphene, two-dimensional (2D) materials have been at the forefront of advanced (opto-)nanoelectronics and energy-related fields owing to their exotic properties like sizable bandgaps, Dirac fermions, quantum spin Hall states, topological edge states, and ballistic charge carrier transport, which hold promise for various electronic device applications. Emerging main group elemental 2D materials, beyond graphene, are of particular interest due to their unique structural characteristics, ease of synthetic exploration, and superior property tunability. In this review, we present recent advances in atomic-scale studies of elemental 2D materials with an emphasis on synthetic strategies and structural properties. We also discuss the challenges and perspectives regarding the integration of elemental 2D materials into various heterostructures. 

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5. Temperature Compensated Graphene Nanomechanical Resonators

   https://doi.org/10.1002/adfm.202415708  

   Lee, Jaesung; Chiu, Hsin‐Ying; Zhao, Liang; Shan, Jie; Feng, Philip X‐L (June 2025, Advanced Functional Materials)

   We report the experimental demonstration of temperature compensated bilayer graphene two‐dimensional (2D) nanomechanical resonators operating in temperature range of 300 to 480 K. By using both microspectroscopy and scanning spectromicroscopy techniques, spatially visualized undriven thermomechanical motion is conveniently used to monitor both the resonance frequency and temperature of the device via noise thermometry while the device is photothermally agitated. Thanks to engineerable naturally integrated temperature compensation of the graphene and gold clamps that minimize variations of built‐in tension in a wide temperature range, very small linear TCfs of ≈−39 and −84 ppm K^−1 are achieved in the graphene nanomechanical resonators. The measured TCfs are orders of magnitude smaller than those in other 2D resonant nanoelectromechanical systems (NEMS). The intricately coupled thermal tuning and strain effects are further examined, elucidating that TCf can be further improved by optimizing device dimensions, which can be exploited for engineering highly stable NEMS resonators and oscillators for signal transduction and sensing applications. 

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