Highly Sensitive Electrostatic Force Detection Using Small Amplitude Frequency-Modulation Atomic Force Microscopy in the Second Flexural Mode

Abstract

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 Kelvin-probe 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. [DOI: 10.1380/ejssnt.2011.146]