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Structural and compositional evolutions of InxAl1-xN core-shell nanorods grown on Si(111) substrates by reactive magnetron sputter epitaxy
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0001-9140-6724
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
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2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 21, 215602- p.Article in journal (Refereed) Published
Abstract [en]

Catalystless growth of InxAl1-xN core-shell nanorods have been realized by reactive magnetron sputter epitaxy onto Si(111) substrates. The samples were characterized by scanning electron microscopy, x-ray diffraction, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. The composition and morphology of InxAl1-xN nanorods are found to be strongly influenced by the growth temperature. At lower temperatures, the grown materials form well-separated and uniform core-shell nanorods with high In-content cores, while a deposition at higher temperature leads to the formation of an Al-rich InxAl1-xN film with vertical domains of low In-content as a result of merging Al-rich shells. The thickness and In content of the cores (domains) increase with decreasing growth temperature. The growth of the InxAl1-xN is traced to the initial stage, showing that the formation of the core-shell nanostructures starts very close to the interface. Phase separation due to spinodal decomposition is suggested as the origin of the resultant structures. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber textured to an epitaxial growth with an epitaxial relationship of InxAl1-xN[0001]//Si[111] and InxAl1-xN[11 (2) over bar0]//Si[1 (1) over bar0] by removing the native SiOx layer from the substrate.

Place, publisher, year, edition, pages
IOP Publishing: Hybrid Open Access , 2015. Vol. 26, no 21, 215602- p.
Keyword [en]
InAlN; core-shell; nanorods; sputtering; MSE; STEM; EDX
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-118979DOI: 10.1088/0957-4484/26/21/215602ISI: 000354598800010PubMedID: 25944838OAI: oai:DiVA.org:liu-118979DiVA: diva2:818179
Note

Funding Agencies|Swedish Research Council (VR) [621-2012-4420]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program; Knut and Alice Wallenberg Foundation

Available from: 2015-06-08 Created: 2015-06-05 Last updated: 2017-12-04
In thesis
1. Magnetron Sputter Epitaxy of Group III-Nitride Semiconductor Nanorods
Open this publication in new window or tab >>Magnetron Sputter Epitaxy of Group III-Nitride Semiconductor Nanorods
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The III-nitride semiconductors family includes gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), and related ternary and quaternary alloys. The research interest on this group of materials is sparked by the direct bandgaps, and excellent physical and chemical properties. Moreover, the ternary alloys (InGaN, InAlN and AlGaN) present the advantage of bandgap tuning, giving access to the whole visible spectrum, from near infrared into deep ultraviolet wavelengths. The intrinsic properties of III-nitride materials can be combined with characteristical features of nanodimension and geometry in nanorod structures. Moreover, nanorods offer the advantage of avoiding problems arising from the lack of native substrates, like lattice and thermal expansion, film – substrate mismatch.

The growth and characterization of group III-nitride semiconductos nanorods, namely InAlN and GaN nanorods, is presented in this thesis. All the nanostructures were grown by employing direct-current reactive magnetron sputter epitaxy. InxAl1−xN self-assembled, core-shell nanorods on Si(111) substrates were demonstrated. A comprehensive study of temperature effect upon the morphology and composition of the nanorods was realized. The radial nanorod heterostructure consists of In-rich cores surrounded by Al-rich shells with different thicknesses. The spontaneous formation of core-shell nanorods is suggested to originate from phase separation due to spinodal decomposition. As the growth temperature increase, In desorption is favored, resulting in thicker Al-rich shells and larger nanorod diameters.

Both self-assembled and selective-area grown GaN nanorods are presented. Self-assembled growth of GaN nanorods on cost-effective substrates offers a cheaper alternative and simplifies device processing. Successful growth of high- quality GaN (exhibiting strong bandedge emission and high crystalline quality) on conductive templates/substrates such as Si, SiC, TiN/Si, ZrB2/Si, ZrB2/SiC, Mo, and Ti is supported by the possibility to be used as electrodes when integrated in optoelectronic devices.

The self-assembled growth leads to mainly random nucleation, resulting in nanorods with large varieties of diameters, heights and densities within a single growth run. This translates into non-uniform properties and complicates device processing. These problems can be circumvented by employing selective-area growth. Pre-patterned substrates by nano-sphere lithography resulted in GaN nanorods with controlled length, diameter, shape, and density. Well-faceted c-axis oriented GaN nanorods were grown directly onto the native SiOx layer inside nano-opening areas, exhibiting strong bandedge emission at room- temperature and single-mode lasing. Our studies on the growth mechanism revealed a different growth behavior when compared with selective-area grown GaN nanorods by MBE and MOCVD. The time-dependent growth series helped define a comprehensive growth mechanism from the initial thin wetting layer formed inside the openings, to the well-defined, uniform, hexagonal NRs resulted from the coalescence of multiple initial nuclei.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 38 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1788
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-141595 (URN)10.3384/lic.diva-141595 (DOI)9789176854396 (ISBN)
Presentation
2017-10-13, Planck, Campus Valla, Linköping, 13:15 (English)
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Available from: 2017-10-02 Created: 2017-10-02 Last updated: 2017-10-11Bibliographically approved

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Serban, AlexandraPersson, Per O AJunaid, JunaidHultman, LarsBirch, JensHsiao, Ching-Lien

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