Atomic force microscope–force mapping and profiling on a sub 100-Å scale

A modified version of the atomic force microscope is introduced that enables a precise measurement of the force between a tip and a sample over a tip-sample distance range of 30–150 Å. As an application, the force signal is used to maintain the tip-sample spacing constant, so that profiling can be achieved with a spatial resolution of 50 Å. A second scheme allows the simultaneous measurement of force and surface profile; this scheme has been used to obtain material-dependent information from surfaces of electronic materials.