NIL processes and material characterization on transparent substrates for optical applications

Several nanoimprint lithography polymers have been investigated for optical applications. The objective was to establish which materials can be used as a permanent polymer coated on top of a glass substrate to provide nanostructures imprinted by nanoimprint lithography. 400 and 600 nm dots were realized in polystyrene, polymethylmethacrylate (PMMA), mr-I T85, and mr-I6000. The adhesion study shows that PMMA and mr-I6000 materials are the best candidates for demolding issues. Scanning electron microscopy characterization confirmed that PMMA structures are well defined, whereas dots printed in other polymers exhibit defects due to sticking issues which lead to local pattern deformation. Finally, optical characterization showed that the nonperfect profiles are a benefit in terms of light extraction. Polycarbonate sheets were also imprinted on one or two sides in order to study the influence of a double side patterning. It was also concluded that a double side imprinted device leads to an increase in the external efficiency.