Fabrication of large-area ordered arrays of nanoparticles on patterned substrates
Many potential applications in nanotechnology require virtually defect-free arrays of nanometre-scale particles over large areas. Guided self-assembly of colloidal particles on patterned templates has been shown to produce ordered arrays of colloidal particles. However, there is a need to extend this technique to particles measuring much less than 50 nm in size and to develop robust fabrication techniques that would lead to defect-free, large-area arrays. We have investigated the use of the dip-coating technique to assemble one- and zero-dimensional arrays on patterned templates using particles with diameters in the 15–50 nm range. Substrates with high-resolution groove or hole patterns were prepared with extreme-ultraviolet interference lithography (EUV-IL). Particle arrays with low defect density were achieved by adapting the deposition conditions (particle concentration, pH, dip speed and orientation). The experimental findings are explained with a model that describes the relative influences of the contributing forces in the assembly process. The driving force behind the assembly is found to be the capillary forces that organize the particles with respect to the pattern on the substrate and each other. The process does not seem to impose any inherent limitations on the defect density or the size of the particle arrays.