Preparation of random stamps for thermal nanoimprint

Abstract

Tailoring of surfaces or interfaces by patterning is a well-known approach used for the improvement of optical and electrical properties of thin film optical devices, and nanoimprint is a strong candidate to realise this at low cost over large areas. For such purposes we provide stamps with random texture. Contamination masking is used instead of lithography to further reduce the costs. Reactive ion etching in SF6/O2 at high oxygen content is effective to provide pyramidal structures of about 300-500nm in height. Loading affects the etch result and has to be considered when establishing a process suitable for large area processing. The geometry of the pyramids is characterised by SEM and AFM measurements, and also by thermal imprint to show the shape of the grooves in between the pyramids. Optical characterisation in a single-axis goniometer-type set-up documents a substantial broadening of the angular distribution of the intensity of the reflected light compared to a flat surface, well suited for the purpose envisaged.