Greyscale 2D nanograting fabrication by multistep nanoimprint lithography and ion beam etching

The application of nanopatterned electrode materials is a promising method to improve the performance of thin-film optoelectronic devices such as organic light-emitting diodes and organic photovoltaics. Light coupling to active layers can be enhanced by employing individual nanopatterns specifically tailored to the device structure. During the development process typically a range of different nanopatterns need to be evaluated. Fabrication of each of these nanopatterns using electron-beam lithography is time and cost intensive, particularly for larger scale devices, due to the serial nature of electron beam writing. Here, we present a meth-od to generate nanopatterns of varying depth with different nanostructure designs from a single one-dimensional grating template structure with fixed grating depth. We employ multiple subsequent steps of UV nanoimprint lithography and ion beam etching to fabricate greyscale two-dimensional nanopatterns. After each imprint step, the imprint resist is cured and etched to maintain the structural conformity. In this work we present variable greyscale nanopatterning of the widely used electrode material indium tin oxide. We demonstrate the fabrication of periodic pillar-like nanostructures with different period lengths and heights in the two grating directions. The patterned films can be used either for immediate device fabrication or pattern reproduction by convention-al nanoimprint lithography. This parallel processing approach promises cost-efficient large-scale nanopattern variation for the device development process.