FAST, HIGH-RESOLUTION ATOMIC-FORCE MICROSCOPY USING A QUARTZ TUNING FORK AS ACTUATOR AND SENSOR

We report a new method of achieving tip-sample distance regulation in an atomic force microscope (AFM). A piezoelectric quartz tuning fork s erves as both actuator and sensor of tip-sample interactions, allowing tip-sample distance regulation without the use of a diode laser or di ther piezo. Such a tuning fork has a high spring constant so a dither amplitude of only 0.1 nm may be used to perform AFM measurements. Tuni ng-fork feedback is shown to operate at a noise level as low as that o f a cantilever-based AFM. Using phase-locked-loop control to track exc ursions in the resonant frequency of a 32 kHz tuning fork, images are acquired at scan rates which are fast enough for routine AFM measureme nts. Magnetic force microscopy using tuning-fork feedback is demonstra ted. (C) 1997 American Institute of Physics.