Nanooptical Substrates for Resonance-Enhanced Gold Growth

Metal lines grown by photocatalysis from solution and dissolved by chemical dissolution are a promising technical approach to mimic the growth and pruning of long-range axonal connections in neuromorphic computing architectures. We investigate a metal line growth approach on the surface of a photoactive titanium dioxide layer. In order to achieve a light-stimulus dependent metal growth nanooptical templates with different nanostructured lines are suggested. Nanostructures allow for resonance-enhancement of the illumination as a function of wavelength, incidence angle, and polarization. Periodic grating nanostructures with grating periods of 170 nm to 210 nm in $500-\mu \mathrm{m}$ squares and 20-period triangular arrangements for excitation in the UV are investigated. The resonant optical enhancement is characterized by deposition of an emitter material with the absorption maximum matching the excitation laser at 355 nm and fluorescence in the visible spectrum. Resonance enhancement is demonstrated experimentally for the designed nanooptical substrates. Photocatalytic gold-growth experiments are presented exhibiting enhanced gold growth on the nanostructured regions compared to the unstructured regions.