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Metastable YAlN and ScAlN thin films: growth and characterization
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

ScxAl1-xN and YxAl1-xN thin films were deposited in a ultra high vacuum system using reactive magnetron co-sputtering from elemental Al, Sc and Y targets in Ar/N2. Their mechanical, electrical, optical, and piezoelectrical properties were investigated with the help of transmission electron microscopy, xray diffraction, ellipsometry, I-V and C-V measurements, and two different techniques for piezoelectric characterization: piezoresponse force microscopy and double beam interferometry. Compared to AlN, improved electromechanical coupling and increase in piezoelectric response was found in ScxAl1-xN/TiN/Al2O3 structures with Sc content up to x=0.2. Microstructure of the films had a stronger influence on piezoelectric properties than the crystalline quality, which affected the leakage currents. YxAl1-xN thin films show a formation of solid solution up to x=0.22. Lattice constants obtained experimentally are in good agreement with theoretical predictions obtained through first principle (ab initio) calculations using density-functional formalism. The mixing enthalpy for wurtzite, cubic, and layered hexagonal phases of the YxAl1-xN system was also calculated.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. , p. 46
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1524
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-76474DOI: 10.3384/lic.diva-76474Local ID: LIU-TEK-LIC-2012:9ISBN: 978-91-7519-934-4 (print)OAI: oai:DiVA.org:liu-76474DiVA, id: diva2:514730
Supervisors
Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2021-12-29Bibliographically approved
List of papers
1. Increased electromechanical coupling in w-ScxAl1-xN
Open this publication in new window or tab >>Increased electromechanical coupling in w-ScxAl1-xN
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2010 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 11, p. 112902-Article in journal (Refereed) Published
Abstract [en]

AlN is challenged as the material choice in important thin film electroacoustic devices for modern wireless communication applications. We present the promise of superior electromechanical coupling (kt2), in w−ScxAl1−xN by studying its dielectric properties. w−ScxAl1−xN (0≤x≤0.3) thin films grown by dual reactive magnetron sputtering exhibited low dielectric losses along with minor increased dielectric constant (ε). Ellipsometry measurements of the high frequency ε showed good agreement with density function perturbation calculations. Our data show that kt2 will improve from 7% to 10% by alloying AlN with up to 20 mol % ScN.

 

National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-59839 (URN)10.1063/1.3489939 (DOI)000282032900055 ()
Note
Original Publication: Gunilla Wingqvist, Ferenc Tasnadi, Agne Zukauskaite, Jens Birch, Hans Arwin and Lars Hultman, Increased electromechanical coupling in w-ScxAl1-xN, 2010, Applied Physics Letters, (97), 11, 112902. http://dx.doi.org/10.1063/1.3489939 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2010-09-27 Created: 2010-09-27 Last updated: 2021-12-29Bibliographically approved
2. Microstructure and Dielectric Properties of Piezoelectric Magnetron Sputtered w-ScxAl1-xN thin films
Open this publication in new window or tab >>Microstructure and Dielectric Properties of Piezoelectric Magnetron Sputtered w-ScxAl1-xN thin films
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2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 9, p. 093527-Article in journal (Refereed) Published
Abstract [en]

Piezoelectric wurtzite ScxAl1-xN (x=0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al2O3(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. Samples grown at 400 °C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN samples grown at 800 °C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x≥0.2 when substrate temperature is increased from 400 to 800 °C. The piezoelectric response of epitaxial ScxAl1-xN films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x=0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-76471 (URN)10.1063/1.4714220 (DOI)000304109900044 ()
Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2021-12-29Bibliographically approved
3. YxAl1-xN Thin Films
Open this publication in new window or tab >>YxAl1-xN Thin Films
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2012 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 45, no 42, p. 422001-Article in journal (Refereed) Published
Abstract [en]

Reactive magnetron sputtering was used to deposit YxAl1-xN thin films, 0≤x≤0.22, onto Al2O3(0001) and Si(100) substrates. X-ray diffraction and analytical electron microscopy show that the films are solid solutions. Lattice constants are increasing with Y concentration, in agreement with ab initio calculations. Spectroscopic ellipsometry measurements reveal a band gap decrease from 6.2 eV (x=0) down to 4.9 eV (x=0.22). Theoretical investigations within the special quasirandom structure approach show that the wurtzite structure has the lowest mixingenthalpy for 0≤x≤0.75.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2012
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-76472 (URN)10.1088/0022-3727/45/42/422001 (DOI)000309766700001 ()
Note

funding agencies|Linkoping Linnaeus Initiative on Nanoscale Functional Materials (LiLiNFM)||Swedish Research Council (VR)|349-2008-6582|FCT Portugal|SFRH/BPD/66818/2009|VR|2010-3848|Swedish Governmental Agency for Innovation Systems (VINNOVA)|2011-03486|

Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2023-12-28Bibliographically approved

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