liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
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.
Show others and affiliations
2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 21, p. 215602-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, p. 215602-
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, id: 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: 2018-05-03
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. p. 38
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)
Opponent
Supervisors
Available from: 2017-10-02 Created: 2017-10-02 Last updated: 2017-10-11Bibliographically approved
2. Self-Assembled and Selective-Area Growth of Group III-Nitride Semiconductor Nanorods by Magnetron Sputter Epitaxy
Open this publication in new window or tab >>Self-Assembled and Selective-Area Growth of Group III-Nitride Semiconductor Nanorods by Magnetron Sputter Epitaxy
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The III-nitride semiconductor family includes gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), and the 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 characteristic features of nanodimension and geometry in nanorod structures. Moreover, nanorods offer the advantage of avoiding problems arising from the lack of native substrates with film/substrate lattice and thermal expansion mismatch.

The growth and characterization of group III-nitride semiconductor nanorods, namely InAlN and GaN nanorods, is presented in this Thesis. All the nanostructures were grown by employing direct-current reactive magnetron sputter epitaxy. The results include the growth and study of both self-assembled and site-controlled grown nanorods.

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 increases, In desorption is favored, resulting in thicker Al-rich shells and larger nanorod diameters. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber-textured to an epitaxial growth by removing the native SiOx layer from the substrate.

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 influence of growth temperature upon the resulting size and optical properties of the nanorods was investigated. By applying a kinetic model, average diffusion length was calculated in correlation with growth temperature in order to explain the nanorods’ morphology evolution.

The self-assembled growth leads to 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 nanosphere lithography resulted in GaN nanorods with controlled length, diameter, shape, and density. Well-faceted caxis oriented GaN nanorods were grown directly onto the native SiOx layer inside opening areas exhibiting strong bandedge emission at room-temperature and single-mode lasing. 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 nanorods resulted from the coalescence of multiple initial nuclei.

Although nanosphere lithography is a fast and cheap patterning method, it does not offer the control on the size, position or density. The growth parameters were transferred onto focused ion beam lithography - patterned substrates which offers more control on the design. Focused ion beam lithography optimization included tailoring of the milling current (2-50 pA) and milling time (5-50 s). The patterning process optimisation enabled the minimization of mask and substrate damage, the key to attain uniform, welldefined, single, and straight nanorods. Destruction of the mask results in selective-area growth failure, while damage of the substrate surface promotes inclined nanorods grown into the openings, owning to random oriented nucleation. At lower growth temperatures (950 °C) nanostructures resulted from the coalescence of multiple, tilted, and irregular nanorods are observed. The tilting of the nanorods is reduced when increasing the growth temperature to 980 °C resulting in single and straight nanorods. The partial pressure of the Ar/N2 working gas was also varied for achieving selectivity and single nanorods, and study the growth behaviour. By increasing the amount of Ar in the working gas from 0 to 50%, we observe a transition of the target from a nitridized to metallic-state, affecting the sputtering conditions of the GaN nanorods. The change in the sputtering and deposition conditions influences the growth selectivity, coalescence, and growth rates. By balancing these effects, the selective growth of faceted, single nanorods was achieved.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. p. 47
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1935
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-147647 (URN)10.3384/diss.diva-147647 (DOI)9789176853085 (ISBN)
Public defence
2018-06-08, Schrödinger, E324, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2018-05-03Bibliographically approved

Open Access in DiVA

fulltext(2136 kB)233 downloads
File information
File name FULLTEXT01.pdfFile size 2136 kBChecksum SHA-512
7628d4f9ac7d3b18825b6db7faa9d3a26355cb2066e0b68e5783990fc068839d90af258d95d8480ad7a7b3ad50f1c100b19496a79b2a3d1006b0b25f708eb0b5
Type fulltextMimetype application/pdf

Other links

Publisher's full textPubMed

Authority records BETA

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

Search in DiVA

By author/editor
Serban, AlexandraPersson, Per O AJunaid, JunaidHultman, LarsBirch, JensHsiao, Ching-Lien
By organisation
Thin Film PhysicsFaculty of Science & EngineeringDepartment of Physics, Chemistry and BiologyThe Institute of Technology
In the same journal
Nanotechnology
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 233 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 345 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf