Close-packed gold-nanocrystal assemblies deposited with complete selectivity into lithographic trenches

A study was conducted to demonstrate the deposition of close-packed gold-nanocrystal assemblies with complete selectivity into lithographic trenches. The study demonstrated that the deposition is 100% selective to the trenches, with close packing of the nanocrystals obtained uniformly across all the patterned features. The corralled close-packed assemblies were imaged by high-resolution scanning electron microscopy (HRSEM). The experimental set-up for nanocrystal assembly consisted of parallel gold-coated copper electrodes, which were completely immersed in a solution of gold nanoparticle in toluene. The patterned wafer was attached to the negative electrode, using a copper clamp, which ensured robust electrical connection between the highly doped silicon substrate and the gold electrode. It was observed that the gold particles have a net positive charge and are attracted to the negative electrode under the influence of an electric field of 200 V.