Dynamic-mode AFM in liquid
In contact-mode atomic force microscopy (AFM) , a tip is laterally scanned with its apex in contact with a surface, which often causes damage or deformation of the sample. In addition, contact-mode AFM requires the use of a soft cantilever, leading to an instability known as jump-to-jump contact. Namely, when a force gradient in the z direction exceeds the spring constant (k) of a cantilever during a tip approach, the tip suddenly jumps to the surface. Thus, it is often impossible either to measure force (Ft) or control the vertical tip position (zt) near a surface. This often hinders true atomic-resolution imaging. Besides, owing to the use of a DC deflection of a cantilever for the tip-sample distance regulation, it is often difficult to achieve good long-term stability.