In this paper, a new multi-frequency excitation method based on combination resonance is introduced to enhance the non-contact atomic force microscopy performance. In combination resonance, excitation frequencies are selected so that summation/subtraction of excitation frequencies is close to the natural frequencies of the microcantilever. Due to the nonlinear nature of this method, the probe response to excitation is very sensitive to change in tip-sample forces. This could be used to generate high-resolution compositional mapping and topographical images of the surface. The present study reveals that both amplitude and phase shift of the combination resonance are sensitive to change in parameters such as Hamaker constant, damping coefficient, Young’s modulus and tip-sample initial distance. It is observed that because of high sensitivity to Hamaker constant a small change in the surface material leads to considerable variations in amplitude and phase shift. This sensitivity is employed to improve compositional mapping of the surface materials. It is also found out that the response amplitude in the combination resonance is very sensitive to change in the tip-sample initial distance. This sensitivity may be used to reduce the vertical noise and increase image resolution, especially in environments with low quality factors. Overall, using this technique the image contrast increases significantly and high resolution compositional mapping of surfaces is achieved.

本文介绍了一种基于组合共振的多频激励方法，以提高非接触原子力显微镜的性能。在组合谐振中，选择激励频率，以使激励频率的总和/减法接近微悬臂梁的固有频率。由于这种方法的非线性特性，探头对激发的响应对尖端采样力的变化非常敏感。这可用于生成高分辨率的成分映射和表面的地形图像。本研究表明，组合共振的振幅和相移都对诸如Hamaker常数，阻尼系数，杨氏模量和尖端样品初始距离等参数的变化敏感。可以看出，由于对Hamaker常数的高度敏感性，表面材料的微小变化会导致幅度和相移的显着变化。该灵敏度用于改善表面材料的成分映射。还发现，组合共振中的响应幅度对尖端样本初始距离的变化非常敏感。此灵敏度可用于减少垂直噪声并提高图像分辨率，尤其是在质量因数较低的环境中。总体而言，使用该技术，图像对比度显着提高，并且可以实现表面的高分辨率成分映射。该灵敏度用于改善表面材料的成分映射。还发现，组合共振中的响应幅度对尖端样本初始距离的变化非常敏感。此灵敏度可用于减少垂直噪声并提高图像分辨率，尤其是在质量因数较低的环境中。总体而言，使用该技术，图像对比度显着提高，并且可以实现表面的高分辨率成分映射。该灵敏度用于改善表面材料的成分映射。还发现，组合共振中的响应幅度对尖端样本初始距离的变化非常敏感。此灵敏度可用于减少垂直噪声并提高图像分辨率，尤其是在质量因数较低的环境中。总体而言，使用该技术，图像对比度显着提高，并且可以实现表面的高分辨率成分映射。