Fabrication of quasiperiodic nanostructures with EUV interference lithography.

We demonstrate the fabrication and analysis of well-ordered high-resolution quasiperiodic nanostructures with feature sizes down to a few tens of nanometers using extreme ultraviolet interference lithography. A well-controlled mask manufacturing process for producing high quality transmission diffraction masks enables simple and fast fabrication of highly ordered 2D quasiperiodic structures using 5- and 8-beam interference setups.

A wide-angle antireflection surface for the visible spectrum.

A surface consisting of periodically arranged nanopyramids producing wide-angle broad-band antireflection properties is presented. The reflectance of silicon dioxide is reduced below 0.45% over the visible spectral range (380-760 nm) for viewing angles from 0 degrees to 40 degrees . The surface is designed by using rigorous diffraction theory and fabricated first in silicon by exploiting its strong crystalline orientation and by using the wet etching process. The structure is transferred from silicon to transparent silicon dioxide by using nano-imprint lithography and proportional reactive ion etching.

Liquid phase deposition of polymers on arbitrary shaped surfaces and their suitability for e-beam patterning.

We present a straightforward low cost liquid phase deposition method to coat arbitrary-shaped dielectric substrates with uniform electron beam sensitive polymer films. Furthermore, we investigate the use of electron beam lithography to pattern the coated pre-form substrates. The polymers studied are poly-methyl-methacrylate with different molecular weights, poly(methyl methacrylate-co-ethyl acrylate) and methyl methacrylate. The polymer coverage over the whole surface area is shown to be uniform and the thickness of the film dependent on the concentration of the polymer liquid used. As the uniform polymer layer is deposited on non-flat surfaces, we show that with an electron beam various surfaces, e.g. microlens arrays, can be re-patterned accurately with nanoscale features. Furthermore, we show the required dose for electron beam exposure to be dependent on the concentration and on the molecular weight of the polymer used.