Presentation Information
[10a-E308-7]Molecular Dynamics Origin of FM-AFM Images of Anchored Alkyl Chains
〇Rikuo Suzuki1, Ryo Miyata2, Satoru Inoue3, Yoshiaki Sugimoto4, Tatsuo Hasegawa2, Hiroyuki Matsui1 (1.ROEL, Yamagata U., 2.U. Tokyo, 3.INOEL, Yamagata U., 4.GSFS, U. Tokyo)
Keywords:
Anchored alkyl chain,FM-AFM,Molecular dynamics simulation
This study clarifies the molecular origin of frequency modulation atomic force microscopy (FM-AFM) images of surface-anchored alkyl chains through classical molecular dynamics (MD) simulations. While FM-AFM can visualize organic molecules, it remained unclear whether the images reflect static molecular shapes or time-averaged distributions under thermal fluctuations. To resolve this, all-atom MD simulations were conducted on a Ph-BTBT-Cn mixed thin film to calculate the mean force distribution by scanning a nanoparticle probe. Both experimental FM-AFM and simulated results revealed a characteristic donut-shaped contrast. The dark, repulsive center aligns with the root carbon atom where the spatial existence probability is high, whereas the bright, attractive periphery corresponds to the flexible chain ends. Consequently, it is concluded that the features in FM-AFM images directly correlate with the spatial existence probability, representing the distribution of degrees of freedom driven by the thermal fluctuations of the chains.