Fabrication of Ni mold for nanoimprint lithography by combining two supercritical fluid-based deposition technologies

Abstract

Hollow-core toroidal micro-cavities are obtained by self-rolling of double-layer (polyvinyl pyridine/polystyrole) polymer films. Rolling of the bilayer is due to preferential swelling of polyvinyl pyridine in water solution of dodecyl benzene sulfonic acid. The tube formation proceeds from a circular opening in the film made by photolithography or by mechanical scratching. Toroid equilibrium dimensions are determined by the balance of the elastic energy relaxation via the film scrolling and the work of the in-plane stretching that is due to increasing radius of the toroid. The principle features of the micro-toroid formation process are captured by a simple analytical model. The inner walls of the cavities can be made metal coated. For this aim, the polymer bilayer can be metallized by vacuum sputtering prior to lithographic patterning and rolling of the bilayer. The toroids with metallic inner surfaces are promising for the future research as IR-frequency range resonators.

Synthesis of Metal Nanostructures Using Supercritical Carbon Dioxide: A Green and Upscalable Process

“…[189] Very recently, it has been shown that SCFD of Ni on polymer resists can be achieved by depositing a thin layer of Pd first as shown in Figure 12. [190] Deposition of the Pd film was achieved by supercritical fluid impregnation (SCFI) at 150 °C. The advantage of this method is the low process temperature (>200 °C) which is essential as the photoresist is sensitive to temperature.…”