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Error Estimation and Enhanced Stiffness Sensitivity in Contact Resonance Force Microscopy with a Multiple Arbitrary Frequency Lock-In Amplifier (MAFLIA)



Erin Flater, Arya Mugdha, Saurabh Gupta, William Hudson, Abbigail Fahrenkamp, Jason Killgore, Jesse Wilson


In contact resonance force microscopy and related dynamic atomic force microscopy methods, an accurate description of the real-time cantilever dynamics is essential to the mapping of local material properties, such as viscoelasticity, piezo response, and chemical composition. Stiffness and damping variations of the tip-sample contact result in variations in the cantilever's resonance frequency and quality factor as it scans a sample of interest. When measuring characteristics of the resonance, generally, there is a tradeoff between full spectral coverage, best obtained by sweeping the amplitude versus frequency response in the time or frequency domain, and high-speed information, obtained by observing the cantilever response at one or two discrete frequencies, that may be required to track a resonance frequency that changes spatially. Here, we introduce a low-cost multifrequency lock-in amplifier system with up to eight simultaneous independent excitation and detection frequencies, for use in contact resonance. We show how the multifrequency approach can measure contact resonance frequency, quality factor, amplitude, and phase during imaging, with high precision and error estimation, without the need for frequency-tracking feedback. We show using a wood composite sample that this multifrequency approach can determine resonance frequency and quality factor, and associated uncertainty. Using a micromachined microbridge, we show a novel means of increasing the stiffness range for nanomechanical sensing by dividing the eight lock-in frequencies to monitor two or four simultaneous eigenmodes, each of which is optimized for sensitivity in a particular stiffness regime. Overall, we show how multifrequency lock-in amplifiers with observation frequency chosen to coincide with an expected eigenmode's contact resonance can benefit the characterization of strongly heterogeneous samples, while maintaining fast measurement speed.
Measurement Science & Technology


atomic force microscopy, nanomechanics, field programmable gate array


Flater, E. , Mugdha, A. , Gupta, S. , Hudson, W. , Fahrenkamp, A. , Killgore, J. and Wilson, J. (2020), Error Estimation and Enhanced Stiffness Sensitivity in Contact Resonance Force Microscopy with a Multiple Arbitrary Frequency Lock-In Amplifier (MAFLIA), Measurement Science & Technology (Accessed June 20, 2024)


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Created May 28, 2020, Updated October 12, 2021