Enhanced Uniformity in Arrays of Electroless Plated Spherical Gold Nanoparticles Using Tin Presensitization

Abstract

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.

Coupled dipole plasmonics of nanoantennas in discontinuous, complex dielectric environments

“…3(a). Fabricated lattices of AuNS appeared to be more cutoff than embedded in SEM analysis, consistent with previous observations [52]. Fig.…”

“…A square lattice of AuNS with radii of 80 nm was lithographed using electron-beam lithography (EBL) and metallized by electroless plating [21,52]. Briefly, ITOcovered glass (300 nm ITO thickness) was sensitized with SnCl 2 .…”

“…Simulated modes that corresponded to observed features included LSPR (square), lattice-shifted plasmon (circle), diffraction (diamond), and CLR (triangle). Simulations were based on physical features observed by SEM analysis; e.g., AuNS appeared cut-off [52]. Attributions were assigned based on changes in feature location and bandwidth after immersion in water, e.g., LSPR peaks red-shift less and broaden more relative to coupled resonances in response to a change in local dielectric [22].…”

Reductive spectrophotometry of divalent tin sensitization on soda lime glass

“…TFA concentrations of 30, 68, and 90 mM were tested at sensitization concentration and time of 26 mM and 30 s, respectively. TFA was used instead of HCl during sensitization, due to reports indicating tin (II)-TFA sensitization was effective for subsequent EL plating of uniform gold films with features closely resembling sputtered gold films [7,13,29,30,34,39]. However, tin sensitization in the presence of TFA may reduce tin (II) on substrates, and produce larger grain size and higher pK a (0.23) than HCl (−7.0) [13].…”

“…It has been used to prepare submicron electrical interconnects [2], polystyrene/silver (PS/Ag) microspheres for filling applications in anisotropic conductive films [3], reductive platinum (Pt) catalyst [4], silicon and germanium semiconductors with copper (Cu) nanofilms [5], and functionalized polymer surfaces with gold (Au) nanoparticles [6]. EL Au plating was recently used to create ordered arrays of metal nanoparticles [1,7]. Such arrays support coupling between lattice diffraction with localized surface plasmons for use in functional waveguides [8], nanoantennae [9], enhanced fluorescence sensors [10], biosensors [11], or surface enhanced Raman spectroscopy (SERS) [12].…”