Images and force measurements taken by an atomic‐force microscope (AFM) depend greatly on the properties of the spring and tip used to probe the sample’s surface. In this article, we describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AFM tip. Our procedure uses the AFM itself and does not require additional equipment.
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The AFM and tips were purchased from Park Scientific Instruments (1171 Borregas Ave., Sunnyvale, CA 94089). The software controlling the force-spectrum routine was modified to acquire 4096 points per measurement. Note that, as delivered, the feedback circuit controlling vertical displacement of the piezoelectric tube scanner cannot be disabled. The result is that the voltage applied across the piezo differs from the imposed value by about one volt (over a range of 300 V full scale). The extra, uncontrollable voltage may be removed by grounding the appropriate “fast feedback” line of the DB25 connector joining the SFM probe module to the main control unit. We thank V. Croquette for alerting us to this peculiarity of the Park AFM.
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© 1993 American Institute of Physics.
1993
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