Reproducible Patterning of Single Au Nanoparticles on Silicon Substrates by Scanning Probe Oxidation and Self-Assembly

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This paper describes a rational approach for reproducibly patterning single Au nanoparticles, 15-20-nm diameter, on silicon wafer substrates. The approach uses scanning probe oxidation (SPO) to pattern silicon oxide nanodomain arrays on silicon substrates modified with octadecyltrimethoxysilane (OTS). It was usually found using aminopropyltrimethoxysilane (APS) that Au nanoparticles only assembled at the domain boundaries probably because of asymmetrically distributed hydroxyl groups. To generate uniformly distributed hydroxyl groups on oxide domains, we employed a two-step treatment to etch and oxidize the substrate. With this treatment, oxide domains consistently attached Au nanoparticles to maximum capacity. Single Au nanoparticles were readily patterned by fabricating oxide nanodomains with a diameter below 30 nm. We also investigated the deposition of APS on OTS monolayers, which resulted in the assembly of Au nanoparticles outside of the oxide domains, and proposed two alternative methods to inhibit it.