Fabrication of Thermally Stable Ultra-High Density Particle-in-Cavity Nanostructure with Tunable Size and Density

This work reports a simple and effective method to fabricate large scale particle-in-cavity (PIC) nanostructure with tunable size from 10-100 nm. By using pre-patterned anodized alumina template (AAO) as a mask for reactive ion etching, the hexagonally ordered nanoporous structure can be transferred onto various substrates including glass, ITO-coated glass, and silicon. With the protection of an organic polystyrene layer, the AAO template can be easily transferred with great consistency and minimal contamination. This method also provides versatility in fabricating multiple unique nanostructures depending on the choice of gas used for RIE. Additionally, the nanoparticles can be deposited into nano-cavities using a variety of techniques such as e-beam evaporation, sputtering with annealing or spincoating of pre-made nanoparticle suspension. Furthermore, Au PIC nanostructure has demonstrated excellent thermal stability compared to Au nanoparticles deposited on flat surface. This method provides great potential not only for the investigation of nanopatterning and nanoparticle assembly but also for enhanced surface Raman scattering and many nanowire based devices including sensors, electronics and photovoltaics.