Surface Adsorbate Fluctuations and Noise in Nanoelectromechanical Systems

Kavli Nanoscience Institute, Mail Code 114-36, California Institute of Technology, Pasadena, California 91125, United States.
Nano Letters (Impact Factor: 13.59). 03/2011; 11(4):1753-9. DOI: 10.1021/nl2003158
Source: PubMed


Physisorption on solid surfaces is important in both fundamental studies and technology. Adsorbates can also be critical for the performance of miniature electromechanical resonators and sensors. Advances in resonant nanoelectromechanical systems (NEMS), particularly mass sensitivity attaining the single-molecule level, make it possible to probe surface physics in a new regime, where a small number of adatoms cause a detectable frequency shift in a high quality factor (Q) NEMS resonator, and adsorbate fluctuations result in resonance frequency noise. Here we report measurements and analysis of the kinetics and fluctuations of physisorbed xenon (Xe) atoms on a high-Q NEMS resonator vibrating at 190.5 MHz. The measured adsorption spectrum and frequency noise, combined with analytic modeling of surface diffusion and adsorption-desorption processes, suggest that diffusion dominates the observed excess noise. This study also reveals new power laws of frequency noise induced by diffusion, which could be important in other low-dimensional nanoscale systems.

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    • "No specific experimental result has come to our notice that targets revealing solvation dominated sorption–desorption behavior. Nearly all vapor interaction related investigations that have come to our notice visualize adsorption at discrete surface sites with characteristic entrapment energies and desorption through activated barrier and/or fluctuation by surface diffusion across sensitive region lateral boundary [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43]. The adsorption–desorption models in these studies also predict Lorentzian noise spectrum [33] [37], and surface diffusion models predict S Á (F) ∼ F −0.5 and S Á (F) ∼ F −1.5 behavior [36]. "
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