Mechanisms for the deposition of nanometer-sized structures from organic fluids using the scanning tunneling microscope

Abstract

We have formed nanometer-sized structures on graphite surfaces by the application of voltage pulses to the tunneling tip of a scanning tunneling microscope. This work pursues a line of a study initiated by Foster et al. [Nature 331, 324 (1988)]. The structures we formed in this way range from 1 nm2 to at least 100 nm2 in size. We have successfully formed these structures using a variety of tip materials (W, PtIr) and methods of manufacture (etched, ion milled, mechanically formed).We have formed structures in air, and in the presence of dimethyl phthalate and decane. We have observed a 3–4 V threshold for structure formation. We have not observed any strong dependence on pulse length in the range of 200 ns to 2 μs. Monitoring the current and tip position as a function of time proved to be a useful diagnostic technique. A likely mechanism for the formation of these structures is the deposition of tip material onto the surface.