AFM-tip-induced and current-induced local oxidation of silicon and metals

Abstract

Here we discuss two different processes that can be used to locally oxidize silicon or metals and are promising for the fabrication of model nanoelectronic devices. The first in- volves oxidation induced by a negatively biased conducting atomic force microscope (AFM) tip. We examine the kinet- ics and mechanism of this process and how factors such as the strength of the electric field, thickness of the oxide, and ambient humidity affect its rate and resolution. Weak ionic currents are detected, pointing to the electrochemical charac- ter of the process. Very fast initial oxidation rates are found to slow down dramatically as a result of the build up of stress and the reduction of the electric field strength. The lateral resolution is found to be largely determined by the defocus- ing of the electric field by a water film, surrounding the tip, whose extent is a function of ambient humidity. The second approach involves local oxidation induced by high current densities generated by forming constrictions in the current- carrying sample. This novel local oxidation process can be used to generate thin oxide tunneling barriers of 10- 50 nm.