Patterned 3D assembly of Au nanoparticle on silicon substrate by colloid lithography

We patterned self-assembly monolayer of protecting organic shell for ca. 3–4-nm gold nanoparticles directly onto a Si substrate by using very large-scale integration process involving electron beam lithography and oxygen plasma treatment. AuNPs assembled from colloid solution to construct a patterned bottom layer of dense lines and square dots including resolution from 200 nm to 10 μm through the patterned protecting organic shell on a large area. The nanowire and nanodots of 3D AuNP assemblies were fabricated by cross-linking AuNPs layer-by-layer through dithiol groups as a linker, so-called bottom-up construction. The interparticle distances among the AuNPs decreased with constructed layers of 3D AuNP assemblies, causing the significant change in electrical resistivities of nanowires. Semiconducting property of the nanowires of AuNP assembly for 1–10 constructed layers was obtained by the resistivities under applying various voltages. In addition, the cross-linking of 3D AuNP assemblies merged as insolated AuNP clusters after thermal treatment at 140 °C demonstrated significant change in morphology and resistivity. The key feature of this approach is the manipulation of AuNPs as nanowires with temperature-dependent effect and semiconducting property, which could function as a nanosensor to minimize the device.