Contact mode near-field microscope

A novel non-optical contact technique of tip-sample distance control for the near-field microscopy has been realized. A tuning fork, which is built with two piezotubes on the common base, is used as a sensor. The tapered fiber attached to one of the tubes serves as a probe. The sensor is resonantly excited using an autogenerator circuit, which maintains the amplitude of the tip oscillations at the value of 0.1–10 nm. The dither amplitude is controlled using the piezocurrent. When the probe is in contact with the surface the current is decreased. Using this effect the probe may be held in permanent contact during scanning. The optical and height images of a diffraction grating obtained using a photon scanning tunneling microscope equipped with the new sensor are presented.