Determining GaN nanowire polarity and its influence on light emission in the scanning electron microscope

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Abstract

The crystal polarity of non-centrosymmetric wurtzite GaN nanowires is determined non-destructively in the scanning electron microscope using electron backscatter diffraction (EBSD). The impact of the nanowire polarity on light emission is then investigated using cathodoluminescence (CL) spectroscopy. EBSD can determine polarity of non-centrosymmetric crystals by interrogating differences in the intensity distribution of bands of the EBSD pattern associated with semi-polar planes. Experimental EBSD patterns from an array of GaN nanowires are compared with theoretical patterns produced using dynamical electron simulations to reveal whether they are Ga or N-polar or, as in several cases, of mixed polarity. CL spectroscopy demonstrates the effect of the polarity on light emission, with spectra obtained from nanowires of known polarity revealing a small but measureable shift (≈28 meV) in the band edge emission energy between those with Ga and N polarity. We attributed this energy shift to a difference in impurity incorporation in nanowires of different crystal polarity. This approach can be employed to non-destructively identify polarity in a wide range of non-centrosymmetric nanoscale material systems and provide direct comparison with their luminescence.
LanguageEnglish
Pages3863-3870
Number of pages8
JournalNano Letters
Volume19
Issue number6
Early online date30 Apr 2019
DOIs
Publication statusPublished - 12 Jun 2019

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Light emission
Nanowires
light emission
polarity
nanowires
Electron microscopes
Electron diffraction
electron microscopes
Scanning
scanning
Cathodoluminescence
Diffraction patterns
Crystals
Spectroscopy
cathodoluminescence
electrons
diffraction patterns
Luminescence
crystals
Impurities

Keywords

  • nanowires
  • polarity
  • electron diffraction
  • SEM
  • GaN
  • cathodoluminescence
  • electron backscatter diffraction
  • EBSD
  • spectroscopy

Cite this

@article{71175f3ef2014301bdd375e1ce6d5e8a,
title = "Determining GaN nanowire polarity and its influence on light emission in the scanning electron microscope",
abstract = "The crystal polarity of non-centrosymmetric wurtzite GaN nanowires is determined non-destructively in the scanning electron microscope using electron backscatter diffraction (EBSD). The impact of the nanowire polarity on light emission is then investigated using cathodoluminescence (CL) spectroscopy. EBSD can determine polarity of non-centrosymmetric crystals by interrogating differences in the intensity distribution of bands of the EBSD pattern associated with semi-polar planes. Experimental EBSD patterns from an array of GaN nanowires are compared with theoretical patterns produced using dynamical electron simulations to reveal whether they are Ga or N-polar or, as in several cases, of mixed polarity. CL spectroscopy demonstrates the effect of the polarity on light emission, with spectra obtained from nanowires of known polarity revealing a small but measureable shift (≈28 meV) in the band edge emission energy between those with Ga and N polarity. We attributed this energy shift to a difference in impurity incorporation in nanowires of different crystal polarity. This approach can be employed to non-destructively identify polarity in a wide range of non-centrosymmetric nanoscale material systems and provide direct comparison with their luminescence.",
keywords = "nanowires, polarity, electron diffraction, SEM, GaN, cathodoluminescence, electron backscatter diffraction, EBSD, spectroscopy",
author = "G. Naresh-Kumar and J. Bruckbauer and A. Winkelmann and X. Yu and B. Hourahine and Edwards, {P. R.} and T. Wang and C. Trager-Cowan and Martin, {R. W.}",
year = "2019",
month = "6",
day = "12",
doi = "10.1021/acs.nanolett.9b01054",
language = "English",
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number = "6",

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T1 - Determining GaN nanowire polarity and its influence on light emission in the scanning electron microscope

AU - Naresh-Kumar, G.

AU - Bruckbauer, J.

AU - Winkelmann, A.

AU - Yu, X.

AU - Hourahine, B.

AU - Edwards, P. R.

AU - Wang, T.

AU - Trager-Cowan, C.

AU - Martin, R. W.

PY - 2019/6/12

Y1 - 2019/6/12

N2 - The crystal polarity of non-centrosymmetric wurtzite GaN nanowires is determined non-destructively in the scanning electron microscope using electron backscatter diffraction (EBSD). The impact of the nanowire polarity on light emission is then investigated using cathodoluminescence (CL) spectroscopy. EBSD can determine polarity of non-centrosymmetric crystals by interrogating differences in the intensity distribution of bands of the EBSD pattern associated with semi-polar planes. Experimental EBSD patterns from an array of GaN nanowires are compared with theoretical patterns produced using dynamical electron simulations to reveal whether they are Ga or N-polar or, as in several cases, of mixed polarity. CL spectroscopy demonstrates the effect of the polarity on light emission, with spectra obtained from nanowires of known polarity revealing a small but measureable shift (≈28 meV) in the band edge emission energy between those with Ga and N polarity. We attributed this energy shift to a difference in impurity incorporation in nanowires of different crystal polarity. This approach can be employed to non-destructively identify polarity in a wide range of non-centrosymmetric nanoscale material systems and provide direct comparison with their luminescence.

AB - The crystal polarity of non-centrosymmetric wurtzite GaN nanowires is determined non-destructively in the scanning electron microscope using electron backscatter diffraction (EBSD). The impact of the nanowire polarity on light emission is then investigated using cathodoluminescence (CL) spectroscopy. EBSD can determine polarity of non-centrosymmetric crystals by interrogating differences in the intensity distribution of bands of the EBSD pattern associated with semi-polar planes. Experimental EBSD patterns from an array of GaN nanowires are compared with theoretical patterns produced using dynamical electron simulations to reveal whether they are Ga or N-polar or, as in several cases, of mixed polarity. CL spectroscopy demonstrates the effect of the polarity on light emission, with spectra obtained from nanowires of known polarity revealing a small but measureable shift (≈28 meV) in the band edge emission energy between those with Ga and N polarity. We attributed this energy shift to a difference in impurity incorporation in nanowires of different crystal polarity. This approach can be employed to non-destructively identify polarity in a wide range of non-centrosymmetric nanoscale material systems and provide direct comparison with their luminescence.

KW - nanowires

KW - polarity

KW - electron diffraction

KW - SEM

KW - GaN

KW - cathodoluminescence

KW - electron backscatter diffraction

KW - EBSD

KW - spectroscopy

U2 - 10.1021/acs.nanolett.9b01054

DO - 10.1021/acs.nanolett.9b01054

M3 - Article

VL - 19

SP - 3863

EP - 3870

JO - Nano Letters

T2 - Nano Letters

JF - Nano Letters

SN - 1530-6984

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ER -