title: Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating.
abstract: We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.
authors.affiliation: Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: By Marcel
authors.initials: BM
authors.lastname: Rey
authors.affiliation: ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future Industries Institute, University of South Australia , Mawson Lakes, 5095, Australia.
authors.forename: Roey
authors.initials: R
authors.lastname: Elnathan
authors.affiliation: Department of Physical Electronics, Fleischman Faculty of Engineering, Tel-Aviv University , Tel-Aviv 69978, Israel.
authors.forename: Ran
authors.initials: R
authors.lastname: Ditcovski
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, 52056, Aachen, Germany.
authors.forename: Karen
authors.initials: K
authors.lastname: Geisel
authors.affiliation: Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Michele
authors.initials: M
authors.lastname: Zanini
authors.affiliation: Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.|Biocolloid and Fluid Physics Group, Applied Physics, University of Granada , 18071 Granada, Spain.
authors.forename: Miguel-Angel
authors.initials: MA
authors.lastname: Fernandez-Rodriguez
authors.affiliation: Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Vikrant V
authors.initials: VV
authors.lastname: Naik
authors.affiliation: Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich , Gloriastrasse 35, ETZ F76, CH-8092 Zurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Frutiger
authors.affiliation: Institute of Physical Chemistry, RWTH Aachen University , Landoltweg 2, 52056, Aachen, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Richtering
authors.affiliation: Department of Physical Electronics, Fleischman Faculty of Engineering, Tel-Aviv University , Tel-Aviv 69978, Israel.
authors.forename: Tal
authors.initials: T
authors.lastname: Ellenbogen
authors.affiliation: ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future Industries Institute, University of South Australia , Mawson Lakes, 5095, Australia.
authors.forename: Nicolas H
authors.initials: NH
authors.lastname: Voelcker
authors.affiliation: Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich , Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland.
authors.forename: Lucio
authors.initials: L
authors.lastname: Isa
mesh_terms: D008670:Metals / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D053770:Nanowires / Q000737:chemistry*; D055095:Optics and Photonics; D012825:Silicon / Q000737:chemistry*
chemical_list: D008670:Metals; D012825:Silicon
keywords: 2D photonic crystals; Vertically aligned nanowires; fluid interfaces; microgels; nanoscale patterning; optical cavities