Fabrication and characterization of silicon nanowire scanning probes

Abstract

Many researchers hold the view of silicon nanowires as a potential constituent for future nano-sensors and devices, owing to their electrical, mechanical and optical properties and inherent small diameters. Within the scope of potential silicon nanowire applications, high aspect ratio bottom-up grown silicon nanowires can be applied in scanning atomic force microscopy (AFM). In general, to fabricate silicon nanowire-based devices, nanowires are either synthesized directly in regions of interest or transferred to a device substrate. Fabricating a single silicon nanowire-based device using bottom-up grown silicon nanowires is still challenging and elaborate, as it is currently realized by applying advanced and sophisticated techniques such as focused-ion-beam deposition for confining the growth area. Also, current silicon nanowire integration techniques require still further development towards large-scale production and industrialization, as the main criteria including reproducibility, cost-effectiveness and control over the nanowire position and orientation were not met. The main goal of the thesis is a realization of a low-cost and facile approach for silicon nanowire integration based on both, growth and assembly strategies. Unlike the reported techniques and methods for fabrication of nanowire scanning probes, advanced and sophisticated approaches shall be avoided. In this work, silicon nanowires are applied in atomic force microscopy (AFM) probes as a scanning tip, by integrating silicon nanowires into fabricated micro-sized Si3N4-cantilevers. In order to realize a single silicon nanowire via the bottom-up growth, a new strategy is proposed by applying the contact printing method and regrowing silicon nanowires from the gold particles at the tip of the contact printed nanowires. In principle, by contact printing silicon nanowires into a region of interest (here on the tip region of cantilevers), the gold particles at the tip of the nanowires can be employed again as catalyst to yield silicon nanowire scanning tips. Beside the fabrication, characterization of the fabricated probes is also one of the thesis goals. The characterizations are targeted by testing the fabricated probes in AFM and comparing it to a pyramidal silicon tip. Furthermore, the mechanical behaviors of silicon nanowire tips on micro-cantilevers, including the silicon nanowire softness and oscillation behavior, are studied.