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Microstructure and Dielectric Properties of Piezoelectric Magnetron Sputtered w-ScxAl1-xN thin films
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-3203-7935
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
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2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 9, 093527- p.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. Vol. 111, no 9, 093527- p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-76471DOI: 10.1063/1.4714220ISI: 000304109900044OAI: oai:DiVA.org:liu-76471DiVA: diva2:514700
Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Metastable YAlN and ScAlN thin films: growth and characterization
Open this publication in new window or tab >>Metastable YAlN and ScAlN thin films: growth and characterization
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. 46 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1524
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-76474 (URN)10.3384/lic.diva-76474 (DOI)LIU-TEK-LIC-2012:9 (Local ID)978-91-7519-934-4 (ISBN)LIU-TEK-LIC-2012:9 (Archive number)LIU-TEK-LIC-2012:9 (OAI)
Supervisors
Available from: 2012-04-10 Created: 2012-04-10 Last updated: 2016-08-31Bibliographically approved
2. Metastable ScAlN and YAlN Thin Films Grown by Reactive Magnetron Sputter Epitaxy
Open this publication in new window or tab >>Metastable ScAlN and YAlN Thin Films Grown by Reactive Magnetron Sputter Epitaxy
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Metastable ScxAl1-xN and YxAl1-xN thin films were deposited in an ultra high vacuum system using reactive magnetron sputter epitaxy from elemental Al, Sc, and Y targets in Ar/N2 gas mixture. Their structural, electrical, optical, mechanical, and piezoelectrical properties were investigated by using the transmission electron microscopy, x-ray diffraction, spectroscopic ellipsometry, I-V and C-V measurements, nanoindentation, 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. Decreasing the growth temperature down to 400 °C improved the microstructure and crystalline quality of the material. Microstructure of the films had a stronger influence on piezoelectric properties than the crystalline quality, which affected the leakage currents. When x was increased from x=0 to x=0.3, the hardness and reduced Young’s modulus Er showed a decrease from 17 GPa to 11 GPa, and 265 GPa down to 224 GPa, respectively. In ScxAl1-xN/InyAl1-yN superlattices, ScxAl1-xN layers negative lattice mismatched to In-rich InyAl1-yN were found to be stable at higher Sc concentration (x=0.4) than lattice-matched or positive lattice mismatched layers, confirmed by first principle (ab initio) calculations using density-functional formalism.

Al-rich YxAl1-xN thin films were synthesized and reported for the first time. Formation of solid solution was observed up to x=0.22 and an increase in growth temperature up to 900°C improved the crystalline quality of the YxAl1-xN films. The band gap of YxAl1-xN decreased from 6.2 eV for AlN down to 4.5 eV (x=0.22) and was shown to follow Vegard’s rule. Refractive indices and extinction coefficients were also determined. Lattice constants of wurtzite YxAl1-xN measured experimentally are in good agreement with theoretical predictions obtained through ab initio calculations. The mixing enthalpy

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 64 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1564
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-103832 (URN)10.3384/diss.diva-103832 (DOI)978-91-7519-434-9 (ISBN)
Public defence
2014-02-21, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2014-01-29 Created: 2014-01-29 Last updated: 2016-08-31Bibliographically approved

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