Densely Packed Arrays of Ultra‐High‐Aspect‐Ratio Silicon Nanowires Fabricated using Block‐Copolymer Lithography and Metal‐Assisted Etching

Abstract

Metal‐assisted etching is used in conjunction with block‐copolymer lithography to create ordered and densely‐packed arrays of high‐aspect‐ratio single‐crystal silicon nanowires with uniform crystallographic orientations. Nanowires with diameters and spacings down to 19 nm and 10 nm, respectively, are created as either continuous carpets or as carpets within trenches. Wires with aspect ratios up to 220 are fabricated, and capillary‐induced clustering of wires is eliminated through post‐etching critical point drying. The wires are single crystals with 〈100〉 axis directions. The distribution of wire diameters is narrow and closely follows the size distribution of the block copolymer, with a standard deviation of 3.12 nm for wires of mean diameters 22.06 nm. Wire arrays formed in carpets and in channels have hexagonal order with good fidelity to the block copolymer pattern. Fabrication of wires in topographic features demonstrates the ability to accurately control wire placement. Wire arrays made using this new process will have applications in the creation of arrays of photonic and sensing devices.

Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity

“…The NWs clump together at their tips, due to van der Waals or electrostatic charges on the newly formed surfaces, facilitated by capillary forces present during drying after liquid immersion. 50,51 A lower degree of surface etching compared to underlying porosity, however, would also cause a similar effect. Additionally, as detailed further on, the reduction of the Ag þ to Ag 0 also has a spatial consideration since n-type NWs more readily reduce ionic Ag, allowing for a greater areal deposition of the metal per unit time on the surface of the Si.…”

A Facile Route for the Large Scale Fabrication of Graphene Oxide Papers and Their Mechanical Enhancement by Cross-linking with Glutaraldehyde

“…However, the drop casting method is fascinating and can be considered as a more suitable route for the large scale production of GO papers. Comparing with the general polymer film systems, such as PVA [38], PU [39], etc., the mechanical properties of GO papers are encouraging, and show potential applications in many fields. In order to enhance the mechanical properties of the obtained GO papers, GA has been added in the GO aqueous suspension with different concentrations during the process of GO papers fabrication.…”

Fabrication of high aspect ratio silicon micro-/nano-pore arrays and surface modification aiming at long lifetime liquid-infused-type self-cleaning function

“…In this case, piranha treatment was used to clean and to produce hydroxyl groups on the structured surfaces. Because of using liquid environment for the hydroxylation, stiction phenomenon, the free-ends of nanostructures get together due to the meniscus attraction of the rinse solution during evaporation process, often occurs (Chang et al, 2009, Moronuki et al, 2016b. This problem was reduced by using the same method as as fabrication of high AR structures (Balasundaram et al, 2012, Moronuki et al, 2016b.…”