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Electron Energy Loss Spectroscopy of III-Nitride Semiconductors
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-3203-7935
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This Licentiate Thesis covers experimental and theoretical investigations of the bulk plasmon response to different compositions and strain states of group III-nitride materials. Investigated materials were grown using magnetron sputtering epitaxy and metal organic chemical vapour deposition and studied by Rutherford backscattering spectrometry, X-ray diffraction, electron microscopy and electron energy loss spectroscopy (EELS).

It is shown that low-loss EELS is a powerful method for a fast compositional determination in AlxIn1-xN system. The bulk plasmon energy of the investigated material system follows a linear relation with respect to lattice parameter and composition in unstrained layers.

Furthermore, the effect of strain on the bulk plasmon peak position has been investigated by using low-loss EELS in group III-nitrides. We experimentally determine the AlN bulk plasmon peak shift of 0.156 eV per 1% volume change. The AlN peak shift was corroborated by full potential calculations (Wein2k), which reveal that the bulk plasmon peak position of III-nitrides varies near linearly with unit cell volume variations.

Finally, self-assembled ternary Al1-xInxN nanorod arrays with variable In concentration have been realized onto c-plane sapphire substrates by ultra-high-vacuum magnetron sputtering epitaxy with Ti0.21Zr0.79N or VN seed layer assistance. The nanorods exhibit hexagonal cross-sections with preferential growth along the Al1-xInxN c-axis. A coaxial rod structure with higher In concentration in the core was observed by scanning transmission electron microscopy in combination with low-loss EELS.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2011. , 47 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1487
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-67985Local ID: LIU-TEK-LIC-2011:26ISBN: 978-91-7393-161-8OAI: oai:DiVA.org:liu-67985DiVA: diva2:414798
Presentation
2011-06-01, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-05-04 Created: 2011-05-04 Last updated: 2016-08-31Bibliographically approved
List of papers
1. Standard-free composition measurements of Alx In1–xN by low-loss electron energy loss spectroscopy
Open this publication in new window or tab >>Standard-free composition measurements of Alx In1–xN by low-loss electron energy loss spectroscopy
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2011 (English)In: physica status solidi (RRL) – Rapid Research Letters, ISSN 1862-6270, Vol. 5, no 2, 50-52 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate a standard-free method to retrieve compositional information in Alx In1–xN thin films by measuring the bulk plasmon energy (Ep), employing electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Two series of samples were grown by magnetron sputter epitaxy (MSE) and metal organic vapor phase epitaxy (MOVPE), which together cover the full com- positional range 0 ≤ x ≤ 1. Complementary compositional measurements were obtained using Rutherford backscattering spectroscopy (RBS) and the lattice parameters were obtained by X-ray diffraction (XRD). It is shown that Ep follows a linear relation with respect to composition and lattice parameter between the alloying elements from AlN to InN allowing for straightforward compositional analysis.

Place, publisher, year, edition, pages
Wiley, 2011
Keyword
AlInN;low-loss EELS;thin films;compositional analysis
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65816 (URN)10.1002/pssr.201004407 (DOI)000288178300002 ()
Note
This is the pre-peer reviewed version of the following article: Justinas Palisaitis, Ching-Lien Hsiao, Muhammad Junaid, Mengyao Xie, Vanya Darakchieva, Jean-Francois Carlin, Nicolas Grandjean, Jens Birch, Lars Hultman and Per O.Å. Persson, Standard-free composition measurements of AlxIn1-xN by low-loss electron energy loss spectroscopy, 2011, physica status solidi (RRL) – Rapid Research Letters, (5), 2, 50-52. http://dx.doi.org/10.1002/pssr.201004407 Copyright: Wiley Available from: 2011-02-21 Created: 2011-02-21 Last updated: 2016-08-31
2. Effect of strain on low-loss electron energy loss spectra of group III-nitrides
Open this publication in new window or tab >>Effect of strain on low-loss electron energy loss spectra of group III-nitrides
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2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 24, 245301- p.Article in journal (Refereed) Published
Abstract [en]

Low-loss EELS was used to acquire information about the strain state in group III-nitrides. Experimental and theoretical simulation results show that the bulk plasmon peak position varies near linearly with unit cell volume variations due to strain. A unit cell volume change of 1% results in a bulk plasmon peak shift of 0.159 eV, 0.168 eV, and 0.079 eV for AlN, GaN, and InN, respectively, according to simulations. The AlN peak shift was experimentally corroborated with a peak shift of 0.156 eV, where the applied strain caused a 1% volume change. It is also found that while the bulk plasmon energy can be used as a measure of the composition in a III-nitride alloy for relaxed structures, the presence of strain significantly affects such a measurement. The strain has a lower impact on the peak shift for Al(1-x)InxN (3% compositional error per 1 % volume change) and In(1-x)GaxN alloys compared to significant variations for Al(1-x)GaxN (16% compositional error for 1% volume change). Hence low-loss studies off III-nitrides, particularly for confined structures, must be undertaken with care and understanding.

Place, publisher, year, edition, pages
American Physical Society, 2011
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-67981 (URN)10.1103/PhysRevB.84.245301 (DOI)000297767800004 ()
Available from: 2011-05-04 Created: 2011-05-04 Last updated: 2016-08-31Bibliographically approved
3. Composition tunable Al1-xInxN nanorod arrays grown by ultra-high-vacuum magnetron sputter epitaxy
Open this publication in new window or tab >>Composition tunable Al1-xInxN nanorod arrays grown by ultra-high-vacuum magnetron sputter epitaxy
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2011 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Self-assembled ternary Al1-xInxN nanorod arrays with variable In concentration, 0.10 ≤ x ≤ 0.32 have been realized onto c-plane sapphire substrates by ultra-high-vacuum magnetron sputter epitaxy with Ti0.21Zr0.79N or VN seed layers assistance. The formation of nanorods was very sensitive to the applied seed layer. Without proper seed layer assistance a continuous Al1-xInxN film was grown. The nanorods exhibit hexagonal crosssections with preferential growth along the c axis. A coaxial rod structure with higher In concentration in the core was observed by (scanning) transmission electron microscopy in combination with low-loss electron energy loss spectroscopy and energy dispersive xray spectroscopy. 5 K cathodoluminescence spectroscopy of Al0.86In0.14N nanorods revealed band edge emission at ~5.46 eV, which was accompanied by a strong defectrelated emission at ~ 3.38 eV.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-67983 (URN)
Available from: 2011-05-04 Created: 2011-05-04 Last updated: 2016-08-31Bibliographically approved

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