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 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.

Nanoscale investigation of bulk heterojunction organic solar cell by scanning capacitance force microscopy

“…As the reference signal of SCFM is related to the primary resonance frequency, the signal-tonoise (S=N) ratio of the F 3ω component was improved. 25) In addition, the high-sensitivity frequency modulation detection capability could be impaired by the electrostatic force component in the cantilever vibration when V mod was applied to the sample. To resolve this issue, we stabilized the cantilever vibration by cutting off the electrostatic force in the cantilever deflection signal using a high-pass filter in the FM detector, as the KFM=SCFM reference signal was set to the secondary resonance.…”

Nanoscale observation of organic thin film by atomic force microscopy

“…However, since the modulation frequency of the electrostatic force component of KFM is set to the primary resonance frequency, the signal-to-noise (S=N) ratio improves. 23) In terms of the vibration frequency of the cantilever, because the electrostatic force component is noise, in this study we cut off the electrostatic force component of KFM using a Butterworth filter, and using this signal as the input signal to the PLL ensured a stable cantilever vibration.…”