2010 Volume 45 Issue 4 Pages 237-242
Atomic force microscopy (AFM) has been used for imaging of nanoscale structures at solid/liquid interfarces due to its capability of operation in liquid. However, the performance of liquid-environment AFM has been significantly inferior to that of ultrahigh vacuum AFM that is used for atomic-scale imaging of surface structures and propoerties as well as for atom-by-atom manipulation. The atomic-scale imaging techniques used in ultrahigh vacuum has been realized by operating AFM in frequency modulation mode (FM-AFM) while the use of FM-AFM in liquid was considered to be very difficult. In 2005, however, a method to overcome this difficulty was developed and thereby true atomic resolution FM-AFM imaging in liquid was realized. This achievement triggered subsequent remarkable advances in liquid-environment AFM, enabling molecular- and atomi-scale imaging of biomolecules and hydration layers. In this article, basic principle of liquid-environment FM-AFM and its recent applications are described.