We propose a novel scheme of highly sensitive electrostatic force detection using a small oscillation amplitude of a cantilever in the second flexural mode of frequency-modulation atomic force microscopy, which is useful for Kelvinprobe force microscopy (KFM) and electrostatic force microscopy (EFM). In this novel scheme, the cantilever is mechanically oscillated at the second flexural resonance frequency with a small oscillation amplitude, while the electrostatic force detection is carried out at the first flexural resonance frequency. Because of the reduced average tip-sample distance and the low spring constant and high quality factor of the first flexural mode, the sensitivity for electrostatic force detection becomes very high. We calculated signal-to-noise ratios (SNRs) for the proposed scheme and conventional schemes, and found that the SNR of the proposed scheme is higher than that of conventional schemes. We also performed KFM/EFM measurements using the proposed and conventional schemes on metal phthalocyanine thin films.

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