High aspect ratio constructive nanolithography with a photo-dimerizable molecule.

A major challenge in constructive nanolithography is the preservation of the lateral resolution of a monolayer-thick template pattern while amplifying it to a structure with a thickness above 10 nm. So far, the most successful approach to achieve this is surface-initiated polymerization (SIP) from e-beam structured monolayer templates in a multistep process. However, spreading of the polymer on the substrate leads to a rapid line-widening. Therefore, structures with lateral resolutions well below 100 nm and thicknesses above 10 nm (aspect ratio: 0.1) were not reported yet. Our approach of photoinduced, constructive, reversible nanolithography, is based on nanografting within a coumarin-derivative thiol (CDT) solution using the tip of an atomic force microscope (AFM). By photodimerization and the formation of disulfide bonds, the CDT polymerizes in a single-step process. We demonstrate the highest lateral resolution in constructive nanolithography at thicknesses above 10 nm (40 nm lateral resolution at 12 nm thickness, aspect ratio: 0.3).