Resonant laser excitation for nanoscale photocatalytic gold growth on patterned templates

Resonant excitation of nanooptical templates offers great advantages for localized photocatalytic activity. We present a design, fabrication and characterization of nanostructured TiO₂ to mimic the dynamic behavior of growth of long-range axonal connections in neuromorphic computing architectures. We use the photocatalytic activity of the TiO₂ to reduce gold particles from a precursor solution and influence the localized gold growth with light-dependent field enhancements inside the TiO₂. Nanooptical templates with different grating parameters are suggested to individually control the formation of metal lines on the surface. We show with an optical probe that resonant excitation with a UV laser is achieved with the nanostructures. 150 nm of DPVBi is used as an emissive layer on top of the patterned TiO₂ to visualize the field enhancement. The experiments show an emission increase for selected grating periods depending on the excitation setup. For nanostructures with only a few lateral repetitions, the quality factor of the resonance wavelength is lower which leads to a broader range of grating periods that resonantly increase the emission of DPVBi. We perform growth experiments and find dense coverage of gold particles on the nanostructured lines, if excited resonantly. For non-resonant excitation and on planar TiO₂ areas, gold particles are sparsely scattered. These results show that local manipulation of dynamic growth characteristics is achieved.