Photo-electrochemical deposition of platinum on TiO₂ with resolution of twenty nanometers using a mask elaborated with electron-beam lithography

We report the patterning of Pt on a TiO₂-rutile single crystal (the fundamental absorption band starts at 396 nm) by direct deposition from a water solution of H₂PtCl₆ (10-20 mmol/dm³) using laser beam writing at 390-396 nm, or by Hg-lamp illumination (i-line at 365 nm). Pt deposition was corroborated by microchemical analysis. A resolution of the Pt pattern down to 20-30 nm was achieved. To create a Pt pattern with resolution of twenty nanometers, we employed a mask elaborated with electron-beam (EB) drawing lithography. The mask was transparent to the writing illumination. The Pt was reduced from the solution by laser scanning over resist-covered regions, while the pattern was formed in the openings of the resist. Separation of the growth and illumination regions, typically, by 0.5-2 μm, facilitates the deposition of reproducible, high-aspect-ratio patterns. It is demonstrated that Pt was deposited through a process of diffusion on the light-excited carriers. The possibility of fabrication of a three-dimensional Pt pattern by the overgrowth of the resist is discussed.