Self-aligned nucleation of gold onto templates with a nano-scale precision fabricated by scanning probe lithography

Nanostructures consisting of concentric Au circles with a nm-scale line thickness have been fabricated on silicon (Si) substrates based on electroless plating and by the use of scanning probe microscope as a lithographic tool. First, a micro-template was fabricated on a hexadecyl self-assembled monolayer (HD-SAM) covalently bonded to a Si(1 1 1) substrate by scanning probe anodization lithography in which the HD-SAM was locally degraded and the substrate Si was anodized along a trace of an conductive AFM-tip biased negatively to the grounded Si substrate. Anodic Si oxide formed by this local anodization process was then etched with HF in order to expose the Si surface under the anodic oxide layer. Consequently, a Si nanopattern surrounded with the HD-SAM identical to the anodic oxide pattern was formed. This Si nanopattern served as a template for fabricating a Au nanostructure by means of electroless plating. Due to the galvanic displacement of surface Si atoms with Au complex ions in a plating bath, Au started to nucleate on the exposed Si surface, while no nuclei was formed on the surrounding HD-SAM. Consequently, a Au nanostructure was formed through further Au deposition on the Au nuclei. The fabricated Au nanostructures are promising for applications emerging plasmonic functions.