Mapping of lateral vibration of the tip in atomic force microscopy at the torsional resonance of the cantilever

• Published in: Ultramicroscopy Vol. 91; no. 1; pp. 37 - 48
• Main Authors: Kawagishi, Takayoshi, Kato, Atsushi, Hoshi, Yasuo, Kawakatsu, Hideki
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2002; Elsevier Science
• Subjects: Atomic force microscopes; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; Micromechanical devices and systems; Physics; Scanning probe microscopes, components and techniques; 018, 032; Atomic force microscopy; Microscope tips; Resonance; Self-assembled layers; Piezoelectric devices; Experimental study; Scanning mode; Microelectromechanical device; Bending vibration
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/S0304-3991(02)00080-3

Lateral vibration of the tip in atomic force microscopy was mapped at the torsional resonance of the cantilever by attaching a shear piezo element at the base of the cantilever or under the sample. Fixed frequency excitation and self-excitation of torsional motion were implemented. The lateral vibration utilized as measured by an optical lever was in the order of 10 pm to 3 nm, and its frequency approximately 450 kHz for a contact-mode silicon nitride cantilever. The amplitude and phase of the torsional motion of the cantilever was measured by a lock-in-amplifier or a rectifier and plotted in x and y as the sample was raster scanned. The imaging technique gave contrast between graphite terraces, self-assembled monolayer domains, silicon and silicon dioxide, graphite and mica. Changing contrast was observed as silicon islands oxidized in atmosphere, showing that the imaging technique can detect change in lateral tip mobility due to changes occurring near the surface. Torsional self-excitation showed nanometric features of self-assembled monolayer islands due to different lateral dissipation. Dependence of torsional resonance frequency on excitation amplitude, and contrast change due to driving frequency around resonance were observed.