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Materials 2018, 11(7), 1140;

Hybrid Top-Down/Bottom-Up Fabrication of a Highly Uniform and Organized Faceted AlN Nanorod Scaffold

Centre of Nanoscience & Nanotechnology & Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK
Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK
Author to whom correspondence should be addressed.
Received: 12 June 2018 / Revised: 29 June 2018 / Accepted: 2 July 2018 / Published: 5 July 2018
(This article belongs to the Special Issue III-Nitrides Semiconductor Research in the UK and Ireland)
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As a route to the formation of regular arrays of AlN nanorods, in contrast to other III-V materials, the use of selective area growth via metal organic vapor phase epitaxy (MOVPE) has so far not been successful. Therefore, in this work we report the fabrication of a highly uniform and ordered AlN nanorod scaffold using an alternative hybrid top-down etching and bottom-up regrowth approach. The nanorods are created across a full 2-inch AlN template by combining Displacement Talbot Lithography and lift-off to create a Ni nanodot mask, followed by chlorine-based dry etching. Additional KOH-based wet etching is used to tune the morphology and the diameter of the nanorods. The resulting smooth and straight morphology of the nanorods after the two-step dry-wet etching process is used as a template to recover the AlN facets of the nanorods via MOVPE regrowth. The facet recovery is performed for various growth times to investigate the growth mechanism and the change in morphology of the AlN nanorods. Structural characterization highlights, first, an efficient dislocation filtering resulting from the ~130 nm diameter nanorods achieved after the two-step dry-wet etching process, and second, a dislocation bending induced by the AlN facet regrowth. A strong AlN near band edge emission is observed from the nanorods both before and after regrowth. The achievement of a highly uniform and organized faceted AlN nanorod scaffold having smooth and straight non-polar facets and improved structural and optical quality is a major stepping stone toward the fabrication of deep UV core-shell-based AlN or AlxGa1-xN templates. View Full-Text
Keywords: AlN; nanorod; displacement Talbot lithography; etching; MOVPE; TEM; cathodoluminescence AlN; nanorod; displacement Talbot lithography; etching; MOVPE; TEM; cathodoluminescence

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Coulon, P.-M.; Kusch, G.; Fletcher, P.; Chausse, P.; Martin, R.W.; Shields, P.A. Hybrid Top-Down/Bottom-Up Fabrication of a Highly Uniform and Organized Faceted AlN Nanorod Scaffold. Materials 2018, 11, 1140.

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