Mapping of Lateral Vibration Amplitude of the Tip at a Sub-Atomic Level in Contact Mode Atomic Force Microscopy

T. Kawagishi, A.Kato, Y. Hoshi, and H. Kawakatsu

Institute of Industrial ScienceﾅCUniversity of Tokyo
4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

The amplitude of torsional resonance vibration of a rectangular cantilever was mapped as the sample was raster scanned in x and y. It was observed that the amplitude of the resonance vibration was different between HOPG, Mica, silicon, silicondioxide thin film and bulk silicondioxide. Contrast image was obtained in a sample of SiO2 protrusions on Si substrate by mapping the variations of resonance vibration amplitude (approximately 10 pmp-p, 420 kHz) employing a lock-in-voltmeter/amplifier. Amplitude mapping was also operated in the same sample by the active excitation of the cantilever by a shear piezo (typical value: 100 pmp-p, 470 kHz). Active excitation made the image acquisition more stable and reproducible than passive excitation. The experiments demonstrated the possibility of detecting changes occurring due to surface oxidation of silicon.