Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafe
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NANO EXPRESS
Open Access
Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on silicon wafers Therese Gorisse1,2*, Ludovic Dupré2, Pascal Gentile2, Mickael Martin1, Marc Zelsmann1 and Denis Buttard2,3
Abstract In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard −oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm−2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors. Keywords: Anodic alumina oxide, Nanoimprint lithography, Templates, Chemical vapour deposition, Nanowires, Silicon, Hexagonal array, Defect-free
Background Low-cost and versatile fabrication of functional nanostructures, for example for nanowires, nanocrystals or nanotubes, becomes of great importance in an increasing number of potential commercial devices [1-6]. In this context, the general approach of directed self-assembly (DSA) seems to be favoured by a high number of scientists and engineers because it uses natural properties and top-down methods to create nanostructures already positioned and organised. As an example, DSA was introduced in the International Technology Roadmap for Semiconductors in 2007. The most common DSA approach consists of organising di-block copolymer features [7] in lithographically created topographical [8] or chemical [9] templates. Another promising DSA approach is the use of anodic aluminium oxide (AAO) as templates for the growth of * Correspondence: [email protected] 1 CNRS/UJF-Grenoble1/CEA LTM, 17 rue des Martyrs, Grenoble 38054, France 2 SiNaPS Lab - SP2M, UMR-E CEA/UJF-Grenoble 1, INAC, Grenoble 38054, France Full list of author information is available at the end of the article
nanoobjects [10]. An electrochemical oxidation of aluminium in acid solutions will naturally produce a highly dense, roughly triangular array of nanopores in alumina [11]. By varying experimental parameters as acid electrolyte, the applied voltage or the anodization time, geometrical characteristics of the porous membrane can be adjusted. In particular, the diameter, the depth of
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