A Novel Non-Optical Method Of Tip-Sample Distance Regulation Based On Shear Force In Scanning Near-Field Optical Microscopy

In this paper a novel method for tip-sample distance regulation based on shear-force is presented. A semicircular piezo-electric ceramic plate is used as the excitation as wall as detection element, the electrode of which is divided into three segments. The first segment is excited by a generator and the second one is used to fix the fiber tip. The induced voltage on the third segment is used to detect the tip-sample distance. The approach curves show that it is very sensitive and the tip-sample distance can be regulated below 5 nm. Experimental results indicate that when the sample is covered with liquid the approach curve is different fi om that in the air. In addition, during experiments we found that at some resonant frequency the approach curve is different from the conventional shape. The phenomenon, if proved reliable, can be used to realize automatic and rapid tip-sample approach as well as small-scale distance regulation.