Optical Lever Measurement Accuracy for Off-ResonanceAtomic Force Microscopy

[摘要] This research evaluates measurement accuracy in optical lever-based atomic forcemicroscopy (AFM) for off-resonance conditions and parameter variations. Under controlledconditions and correct calibration, AFM provides researchers with the abilityto accurately observe and manipulate matter on the micro- and nano-scale. Accuracyof imaging and nano-manipulation operations are directly correlated to theaccuracy with which the displacement of the probe is measured. The optical levermethod, a common displacement measurement technique employed in AFM, calculatesprobe displacement based on a calibration that assumes a consistent responseprofile throughout operation. Off-resonance excitation and tip-sample interactionforces during intermittent contact mode AFM can alter this response profile. Standardtapping-mode operation at the fundamental frequency is observed to be robustto changes in effective stiffness, maintaining accurate measurements for all laser spotpositions considered. A nominal laser spot position between Xp = 0.5 and 0.6 is determinedto most accurately predict displacement for off-resonance excitation duringboth free response and intermittent contact condit ions. Measurement accuracy foroff-resonance tapping- mode is more directly correlated to changes introduced to theinteraction force profile than choice of spot position.

[发布机构] Rice University

[效力级别] engineering