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Curved-Lattice Epitaxial Growth of InxAl1-xN Nanospirals with Tailored Chirality
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.ORCID iD: 0000-0002-6371-0638
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-3203-7935
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
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2015 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 1, 294-300 p.Article in journal (Refereed) Published
Abstract [en]

Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth (CLEG) of uniform coatings of single-crystalline InxAl1-xN nanospirals. The nanospirals are formed by sequentially stacking segments of curved nanorods on top of each other, where each segment is incrementally rotated around the spiral axis. By controlling the growth rate, segment length, rotation direction, and incremental rotation angle, spirals are tailored to predetermined handedness, pitch, and height.  The curved morphology of the segments is a result of a lateral compositional gradient across the segments while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties as well. Left- and right-handed nanospirals, tailored with 5 periods of 200 nm pitch, as confirmed by scanning electron microscopy, exhibit uniform spiral diameters of ~80 nm (local segment diameters of ~60 nm) with tapered hexagonal tips.  High resolution electron microscopy, in combination with nanoprobe energy dispersive X-ray spectroscopy and valence electron energy loss spectroscopy, show that individual nanospirals consist of an In-rich core with ~15 nm-diameter hexagonal cross-section, comprised of curved basal planes. The core is surrounded by an Al-rich shell with a thickness asymmetry spiraling along the core. The ensemble nanospirals, across the 1 cm2 wafers, show high in-plane ordering with respect to shape, crystalline orientation, and direction of compositional gradient. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the CLEG nanospiral-coated wafers. In that, the polarization state is shown to be dependent on the handedness of the nanospirals and the wavelength of the incident light in the ultraviolet-visible region.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015. Vol. 15, no 1, 294-300 p.
Keyword [en]
InAlN, nanospirals, chirality, sputtering, CLEG, GLAD, STEM, VEELS
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-112512DOI: 10.1021/nl503564kISI: 000348086100047PubMedID: 25427233OAI: oai:DiVA.org:liu-112512DiVA: diva2:767192
Projects
Growth of Metastable Ternary Group III-Nitride Semiconductor Nanostructures by unique design concepts and doping
Funder
Swedish Research Council, 621-2012-4420
Available from: 2014-12-01 Created: 2014-12-01 Last updated: 2017-12-05

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