Acoustic and dynamic force microscopy with ultrasonic probes

Ultrasonic quartz resonators with quality factors >5000 allow one to probe surface morphologies directly, i.e., without any additional sensors determining the vertical position of the probing tip. With tip radii of several tenths of a micrometer, hydrodynamic friction forces dominate the tip/surface interaction. while, by using sharp atomic force microscopy tips glued onto rod-shaped 1 MHz length extension quartz resonators, the conventional dynamical quasi noncontact atomic force microscopy mode is obtained. This allows one to resolve atomically sized structures on mica in air. The ultrasonic sensors with spring moduli of 3000 to 400 000 N/m exhibit an extremely high sensitivity allowing one to probe even monomolecular organic layers without destruction. (C) 1996 American Vacuum Society.