Local oxidation of titanium thin films using an atomic force microscope under static and pulsed voltages

Scanning probe microscope tip-induced local oxidation is a promising tool for the fabrication of nanometre-scale structures and devices. In this study, oxide line patterns were fabricated on the surface of a titanium thin film using a conductive atomic force microscope (AFM). Geometrical characters of the oxide line patterns and their dependence on the exposure parameters in fabricating, i.e. the applied voltage amplitude and duration, ambient humidity, AFM set point value, and the mode of applied voltage, are investigated. The dependence of the oxide width on the applied voltage duration was found to have two distinct growth rates and a two-stage growth model was proposed to account for it. Application of pulsed voltages was proved to be an efficient method for suppressing the growth of oxide width by repeatedly breaking the directional transport of OH- ions in the process of oxidation. A line-width of 8 nm was achieved with an optimized pulsed voltage. Based on the experimental results, optimal controlling of exposure parameters to improve the fabricating resolution and reliability are discussed.