A micromachined unit for tunnel current control

Tunneling current which passes through a small gap, in the order of 1 nm, between a sample and a sharpened metallic tip is extremely sensitive to the length of the gap. This phenomenon has been utilized for a scanning tunneling microscope (STM) which takes a topographic image of a sample surface, by using the variation of the tunneling current with atomic scale resolution. While controlled in the scale of atoms, a conventional STM has a scale of several centimeters. This paper deals with the development of an ultimately small tunneling unit using micromachining. Since the present unit has one degree-of-freedom, it cannot be used as an STM as itself but can be used as a displacement detector of a microstructure such as an AFM (Atomic Force Microscope) probe. The design, fabrication and performance of the micromachined tunneling unit is reported