Contact mode near-field microscope

A novel non-optical contact technique of tip-sample distance control for th e near-field microscopy has been realized. A tuning fork, which is built wi th two piezotubes on the common base, is used as a sensor. The tapered fibe r attached to one of the tubes serves as a probe. The sensor is resonantly excited using an autogenerator circuit, which maintains the amplitude of th e tip oscillations at the value of 0.1-10 nm. The dither amplitude is contr olled 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 perma nent contact during scanning. The optical and height images of a diffractio n grating obtained using a photon scanning tunneling microscope equipped wi th the new sensor are presented. (C) 1999 Elsevier Science B.V. All rights reserved.