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  4. On the exceptional temperature stability of ferroelectric Al1-xScxN thin films
 
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2021
Journal Article
Title

On the exceptional temperature stability of ferroelectric Al1-xScxN thin films

Abstract
Through its dependence on low symmetry crystal phases, ferroelectricity is inherently a property tied to the lower temperature ranges of the phase diagram for a given material. This paper presents conclusive evidence that in the case of ferroelectric Al1−xScxN, low temperature has to be seen as a purely relative term, since its ferroelectric-to-paraelectric transition temperature is confirmed to surpass 1100 °C and thus the transition temperature of virtually any other thin film ferroelectric. We arrived at this conclusion through investigating the structural stability of 0.4-2 mm thick Al0.73Sc0.27N films grown on Mo bottom electrodes via in situ high-temperature x-ray diffraction and permittivity measurements. Our studies reveal that the wurtzite-type structure of Al0.73Sc0.27N is conserved during the entire 1100 °C annealing cycle, apparent through a constant c/a lattice parameter ratio. In situ permittivity measurements performed up to 1000 °C strongly support this conclusion and include what could be the onset of a diverging permittivity only at the very upper end of the measurement interval. Our in situ measurements are well-supported by ex situ (scanning) transmission electron microscopy and polarization and capacity hysteresis measurements. These results confirm the structural stability on the sub-mm scale next to the stability of the inscribed polarization during the complete 1100 °C annealing treatment. Thus, Al1−xScxN, there is the first readily available thin film ferroelectric with a temperature stability that surpasses virtually all thermal budgets occurring in microtechnology, be it during fabrication or the lifetime of a device-even in harshest environments.
Author(s)
Islam, M.R.
Institute for Material Science, Kiel University
Wolff, N.
Synthesis and Real Structure, Institute for Material Science, Kiel University
Yassine, M.
Power Electronics, Institute for Sustainable Systems Engineering, Freiburg University
Schönweger, G.
Institute of Electrical Engineering and Information Engineering, Kiel University
Christian, B.
Institute for Sustainable Systems Engineering, Freiburg University
Kohlstedt, H.
Institute of Electrical Engineering and Information Engineering, Kiel University
Ambacher, O.
Fraunhofer-Institut für Angewandte Festkörperphysik IAF  
Lofink, F.
Fraunhofer-Institut für Siliziumtechnologie ISIT  
Kienle, L.
Institute for Material Science, Kiel University
Fichtner, S.
Fraunhofer-Institut für Siliziumtechnologie ISIT  
Journal
Applied Physics Letters  
Open Access
DOI
10.1063/5.0053649
Language
English
Fraunhofer-Institut für Angewandte Festkörperphysik IAF  
Fraunhofer-Institut für Siliziumtechnologie ISIT  
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