Sample-and-Hold Operation in Kelvin Probe Force Microscopy

概要

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To achieve a more accurate determination of surface potential in Kelvin probe force microscopy (KFM), we have proposed and demonstrated a sample-and-hold operation of KFM (SH-KFM), in which a sample-and-hold (S/H) circuit is inserted between an optical deflection sensor and a lock-in amplifier, to sample the deflection signal at a tapping frequency. Owing to the sampling operation, the cantilever bending due to the electrostatic force can be extracted at a desired phase in the tapping oscillation by intentional tuning of a time delay for sampling. We performed SH-KFM measurements on InAs quantum dots, and successfully observed a very clear site dependence of the potential with a large contrast. The results also indicated that the spatial resolution in the potential images was estimated to be better than 10 nm, and that the amplitude of an ac modulation bias in KFM could be reduced to 10 mVp–p without any remarkable degradation of the potential images.
2005-08-15