Proximity field nanopatterning of azopolymer thin films.

A method for inscribing surface relief gratings in azopolymer thin films via proximity field nanopatterning is reported. Azopolymers prepared by ring opening metathesis polymerization were cast as thin films and brought into conformal contact with transparent polydimethylsiloxane phase masks. Irradiation of the film surface through the phase masks induces mass transport of azopolymer that generates surface relief structures on the basis of the intensity modulation of the light by structures on the phase mask.

Three-dimensional nanofabrication with elastomeric phase masks.

This Feature Article reviews recent work on an optical technique for fabricating, in a single exposure step, three-dimensional (3D) nanostructures with diverse structural layouts. The approach, which we refer to as proximity field nanopatterning, uses conformable, elastomeric phase masks to pattern thick layers of transparent, photosensitive materials in a conformal contact mode geometry. Aspects of the optics, the materials, and the physical chemistry associated with this method are outlined.

Thick, three-dimensional nanoporous density-graded materials formed by optical exposures of photopolymers with controlled levels of absorption.

Three-dimensional (3D) intensity distributions generated by light passing through conformal phase masks can be modulated by the absorption property of photosensitive materials. The intensity distributions have extremely long depth of focus, which is proportional to the size of the phase masks, and this enables one to pattern thick (approximately 100 microm), nanoporous structures with precise control of grade density. Various density-graded 3D structures that result from computational modeling are demonstrated.

Molded transparent photopolymers and phase shift optics for fabricating three dimensional nanostructures.

This paper introduces approaches that combine micro/nanomolding, or nanoimprinting, techniques with proximity optical phase mask lithographic methods to form three dimensional (3D) nanostructures in thick, transparent layers of photopolymers. The results demonstrate three strategies of this type, where molded relief structures in these photopolymers represent (i) fine (<1 microm) features that serve as the phase masks for their own exposure, (ii) coarse features (>1 microm) that are used with phase masks to provide access to large structure dimensions, and (iii) fine structures that are used together phase masks to achieve large, multilevel phase modulations. Several examples are provided, together with optical modeling of the fabrication process and the transmission properties of certain of the fabricated structures.