Schematic illustration of the selective gold metallization. MPTMS coated substrates are selectively treated with pure water followed by gold nanoparticle deposition to obtain patterned gold arrays, which act as seeds for subsequent electroless plating.
Top-view images showing a substrate (a) during water treatment with droplets of different sizes, (b) after deposition of gold nanoparticles, and (c) after electroless metallization. The colour scheme in different images does not exactly reflect the true colours.
SEM images showing the distribution of gold nanoparticles in three different regions after adsorption: (bottom right) WT area, (top right) non-WT area, and (top left) the boundary between both regions. The large scale overview (bottom left) shows the entire circular area, which was in contact with the water droplet.
SEM images showing the morphology in three different regions after electroless deposition for 30 min on the patterned gold nanoparticle arrays: (top right) non-WT area, (bottom right) WT area, and (top left) the boundary between both regions. The large scale overview (bottom left) shows the complete circular area, which was in contact with the water droplet prior to deposition of nanoparticles.
SEM images showing the morphology of the samples for different electroless plating times: panel A (5 min), panel B (10 min), panel C (15 min), panel D (20 min), panel E (25 min), panel F (30 min). The right column depicts the boundary between seeded (non-WT) and seedless (WT) parts, while the middle and left columns show the seeded area, at different levels of magnification.
SEM images revealing the distribution (left) and morphology (right) of the clusters on the WT part of a sample after 30 min electroless deposition.
Measured thickness (a) and conductivity (b) of electroless grown gold films as a function of plating time. The dashed lines are a guide to the eye; the dotted line in (b) represents the conductivity value for bulk gold.
Ellipsometry spectra, i.e., and Δ as a function of photon energy, of electroless deposited gold films on oxide coated silicon substrates for different plating times. Red lines correspond to samples with only gold nanoparticles, while the green, blue, and magenta spectra correspond to electroless deposition times of 5 min, 10 min, and 20 min, respectively. The black dashed lines represent calculated spectra for bulk gold.
Real (top) and imaginary (bottom) parts of the pseudo-dielectric functions before electroless gold deposition (red line) and after gold growth for 5 min (green), 10 min (blue), and 20 min (magenta), acquired by direct inversion of the spectra in Fig. 8 . The dashed lines represent the bulk dielectric function as tabulated by Johnson and Christy. 50
Comparison of the pseudo-dielectric function after 20 min electroless growth (magenta symbols; see also Fig. 9 ) to calculations using the Drude model (solid line; Eq. (1) ) and the approximation for negligible scattering rates (dashed lines; Eq. (2) ). Log-log plots of and are shown in the top and bottom panels, respectively.
Typical size range of metallic clusters on the seedless WT area for different deposition times.
Measured sheet resistance, thickness, and calculated conductivity of deposited gold films on the seeded, non-WT part as a function of electroless plating time.
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