Dual AC Resonance Tracking Piezoresponse Force Microscopy for Crosstalk-free Measurements - August 24

Lecture to be given at IVC-18 Conference, Beijing Tues. Aug. 24 3-4pm Rm 202 This patent pending dual-excitation method used in Atomic Force Microscopy allows the cantilever to be operated at or near resonance for techniques where conventional phase locked loops are not stable. The potential of the conductive cantilever is the sum of two oscillating voltages with frequencies at or near the same resonance. The resulting cantilever deflection is digitized and then sent to two separate lock-in amplifiers, each referenced to one of the drive signals. By measuring the amplitudes at these two frequencies, it is possible to measure changes in the resonance behavior and furthermore, to track the resonant frequency. Specifically, by driving at one frequency below resonance (A1), and another above (A2), A2-A1 gives an error signal that the ARC2™ controller uses to track the resonance frequency changes. Additional information on the technique can be found in the application note "Piezoresponse Force Microscopy with Asylum Research AFMs" at http://www.asylumresearch.com/Applications/PFMAppNote/PFMAppNote.shtml.