Fabrication of micromechanical tunneling probes and actuators on a silicon chip

Simultaneous visual control of tip position is indispensable for in-situ observation of nanoscopic phenomena at the tunneling gap. In this paper we propose a one-chip tunneling control device, which is small enough to load on a standard sample holder of the transmission electron microscope (TEM). Tunneling probes and micro actuators have been successfully integrated on a 2.4 x 2.4-mm(2)-chip by silicon micromachining technique. A pair of sharp silicon tips is obtained by the combination of stress-induced oxidation and selective etching of silicon oxide. Typical dimensions of the tips are 10 nm in radius and I mum in length with a 200-nm-initial gap. An electrostatically operated comb-drive actuator is used to close the gap with a voltage around 100 V. The tunneling tips are suspended over a through hole in the base substrate, and the tunneling gap can be observed by TEM. We found that clear images could be obtained without distortion or shift due to the driving voltage applied to the integrated actuator.