Enhanced uniformity in arrays of electroless plated spherical gold nanoparticles using tin presensitization

Gold nanoparticle arrays created with electroless gold plating provide a unique means of transforming nanocylinders usually formed in electron beam lithography to spherical nanoparticles. Alone, electroless gold plating is not selective to the substrate and results in the formation of a gold film on all exposed surfaces of an electron beam patterned sample, including the electron resist. Undesired gold plating occurred near patterned features on the substrate surface, which was reduced by increasing post-spin-coat cure time. When the electron resist is removed, some nanocylinders break off with the gold film, leaving partial cylinders or holes in the patterned elements. By presensitizing the substrate surface with tin, gold cylinders may be selectively deposited to the substrate surface without forming a film on the electron resist. Tin presensitized arrays were produced with 47.1 +/- 7.4 nm radius gold nanoparticles with an interparticle distance of 646.0 +/- 12.4 nm. Defects from sheared, missing, and redeposited Au particles associated with the resist removal were minimized, resulting in enhanced size and shape uniformity of pillars and arrays. Hollow particles were eliminated, and relative standard deviation in particle size was reduced by 7.4% on average, while elongation was reduced 12.3% when astigmatism was eliminated.