Enhanced higher-harmonic imaging in tapping-mode atomic force microscopy

Abstract

Cataloged from PDF version of article.Higher-harmonics generation in a tapping-mode atomic force microscope is a consequence of the nonlinear tip-sample interaction force. The higher harmonics contain important information about the materials’ nanomechanical properties. These harmonics can be significantly enhanced by driving the cantilever close to a submultiple of its resonant frequency. We present the results of enhanced higher-harmonic imaging experiments on several samples. The results indicate that enhanced higher harmonics can be utilized effectively for both material characterization and surface roughness analysis with a high signal-to-noise ratio.\ud © 2005 American Institute of Physic

Sensitivity vector fields for atomic force microscopes

“…Also, by enhancing and exploiting the dynamics of the higher harmonics, the resolution of AFM can be enhanced [2,3,15,21]. Stark showed [20,22] that the higher harmonics cannot be neglected in the analysis of the tapping-mode AFM.…”

Concentrated-mass cantilever enhances multiple harmonics in tapping-mode atomic force microscopy

“…4 Thus, in an attempt to access the tip-sample interaction which can be quantitatively related to the material properties, the higher-order harmonic components in the vibration spectrum of the tapping cantilevers have attracted particular attention in the recent years. [5][6][7][8][9][10] A more detailed imaging with a better contrast which reveals the variation in material properties was obtained with the higher-harmonic resonance signal than that with the fundamental one, [11][12][13] while theoretical investigations and numerical simulations revealed that the high-order harmonic components contain the information on elastic properties of the sample surface. 7,9,13 The high force sensitivity of higher harmonics or modes has been quantitatively examined by Lozano and Garcia.…”

“…3,12 While the cantilever is excited at or near its fundamental natural frequency to ensure a high-sensitive signal output of vibration amplitudes mainly corresponding to the fundamental eigenmode during the topography imaging, signal contributions from the higher harmonics of vibration amplitude are usually suppressed by the rapid decay of the frequency response curve of a continuum cantilever. 15 In fact, the frequency response curve only exhibits high peaks near the natural frequencies corresponding to each of the vibration eigenmodes, as shown in Fig.…”

Enhancing the multiple harmonics by step-like cantilever

“…A great number of efforts have been made to enhance the higher harmonic signals. The higher harmonics are enhanced by simultaneously exciting the first two modes of a cantilever, 14 or by driving the cantilever around a submultiple of the fundamental frequency, 8,15 or by exciting the torsional modes in a torsional harmonic cantilever. 16 Besides excitation, the geometry of cantilever can also be modified to enhance its response.…”