Ultraviolet nanoimprint lithography for the fabrication of ordered nanostructures, integrated optics and electronic devices

Nanoimprint lithography (NIL) is a lithographic technique that allows the patterning of substrates with nanostructures over large areas with high density. NIL relies on the simplicity of mechanically deforming a polymeric resist layer by a patterned mold. The generated thickness contrast is used for pattern transfer into the substrate. The silicon-germanium (Si-Ge) material system is a model system for the Stranski-Krastanow growth mode. By combining the self-assembly of SiGe islands with a pre-patterning of the growth substrate, an ordered SiGe island growth is achieved. Both, a position-control of the SiGe islands and an improvement of their homogeneity and emission efficiency is accomplished. Ultraviolet NIL (UV-NIL) was developed for the pit-patterning of substrates, in particular of Si substrates. The periodically patterned substrates were used for investigations of the ordered growth of SiGe islands by molecular-beam epitaxy. Furthermore, the work towards integrating such ordered SiGe islands into a two-dimensional photonic crystal slab was pursued, demanding a second imprinted layer precisely aligned to the first one. Then, for the fabrication of {111}-faceted Si pits, the anisotropic etchant tetramethylammonium hydroxide and UV-NIL were used and a pre-defined positioning of nanocrystals inside such pits was achieved. Moreover, pyramidal nanoimprint molds were fabricated via a remastering process and in comparison to a standard imprint and pattern transfer process, a substantial size reduction of the resulting pit and line patterns in Si was demonstrated