Gentle imaging of soft materials in solution with amplitude modulation atomic force microscopy: Q control and thermal noise

Increasing the effective Q factor using feedback (Q control) decreases tip-sample interaction forces for amplitude modulation atomic force microscopy. However, the feedback loop amplifies thermal noise compromising the signal to noise ratio. Simulations, which include thermal excitations, reveal that average tip-sample forces scaled for signal to noise ratio remain roughly unchanged as Q factor changes for intrinsically low Q environments such as liquids. Furthermore, increased Q causes the tip-sample interaction to become sporadic and hinders consistent imaging. Thus, it is preferable to image with small amplitudes instead of higher effective Q factor.