Electrical SPM-based nanofabrication techniques

Abstract

Scanning probe microscopes (SPM) have been envisaged and applied from the beginning as tools both to image surfaces with unprecedented resolution and to interact with surfaces like an extension of the operator's fingertips. The prototype for electrical SPM certainly was the scanning tunneling microscope (STM). For the purpose of this chapter we do not consider mechanical nano-machining, i.e., scratching with the tunneling-tip, as a form of electrical SPM, despite the mechanical contact between tip and specimen surface being induced by low tunneling voltages and high current set-points. Applying a voltage of a few 10 V to the tip, McCord and Pease [1] succeeded in writing lines of contamination on bare silicon that protected the substrate during the subsequent etch. Line widths below 50 nm were achieved. Contamination lines were already observed before on metallic glass [2]. Later, Okawa and Aono [3] were able to induce the formation of polymeric nanowires on a graphite substrate covered by a monolayer of a diacetylene compound by applying voltage pulses to the STM tip. Positioning single xenon atoms on a nickel (110) surface at cryogenic temperatures, as demonstrated by Eigler [4], or removing a single atom from a MoS2 crystal to create, according to the Guinness World Records book, the smallest hole in the world, as shown by Heckl, mark the ultimate forms of nanofabrication possible with the STM. So far, however, most application-or device-directed nanofabrication by SPM takes place on a scale of molecules to several dozen nanometers. © 2007 Springer Science+Business Media, LLC.