Dr. Niklas Wolff
Department for Material Science, Kiel University
The New Nitrides – Thin Film Ferroelectrics with Wurtzite-type Structure
In 2009, Akiyama’s report on Sc-alloying of AlN thin films and is enhancement of the piezoelectric response by a factor of four sparked first scientific interest.1 The increased electromechanical coupling properties of AlScN thin films largely benefit piezo-MEMS, such as surface acoustic wave (SAW) devices for high frequency resonators as well as energy harvesting devices.2,3 Ten years later, the discovery of ferroelectricity in AlScN at Kiel University initiated its second blooming phase and the birth of a new family of ferroelectric materials with wurtzite-type structure.4–6 This talk tries to summarize fundamental aspects and showcases recent research highlights on the micro- and nanostructure characterization of AlScN thin films.
(1) Akiyama, M.; Kamohara, T.; Kano, K.; Teshigahara, A.; Takeuchi, Y.; Kawahara, N. Enhancement of Piezoelectric Response in Scandium Aluminum Nitride Alloy Thin Films Prepared by Dual Reactive Cosputtering. Advanced Materials 2009, 21 (5), 593–596. doi.org/10.1002/adma.200802611.
(2) Wang, W.; Mayrhofer, P. M.; He, X.; Gillinger, M.; Ye, Z.; Wang, X.; Bittner, A.; Schmid, U.; Luo, J. K. High Performance AlScN Thin Film Based Surface Acoustic Wave Devices with Large Electromechanical Coupling Coefficient. Appl. Phys. Lett. 2014, 105 (13), 133502. doi.org/10.1063/1.4896853.
(3) Matloub, R.; Hadad, M.; Mazzalai, A.; Chidambaram, N.; Moulard, G.; Sandu, C. S.; . Metzger, T.; Muralt, P. Piezoelectric Al1−xScxN Thin Films: A Semiconductor Compatible Solution for Mechanical Energy Harvesting and Sensors. Appl. Phys. Lett. 2013, 102 (15), 152903. doi.org/10.1063/1.4800231.
(4) Fichtner, S.; Wolff, N.; Lofink, F.; Kienle, L.; Wagner, B. AlScN: A III-V Semiconductor Based Ferroelectric. Journal of Applied Physics 2019, 125 (11), 114103. doi.org/10.1063/1.5084945.
(5) Ferri, K.; Bachu, S.; Zhu, W.; Imperatore, M.; Hayden, J.; Alem, N.; Giebink, N.; Trolier-McKinstry, S.; Maria, J.-P. Ferroelectrics Everywhere: Ferroelectricity in Magnesium Substituted Zinc Oxide Thin Films. Journal of Applied Physics 2021, 130 (4), 044101. doi.org/10.1063/5.0053755.
(6) Hayden, J.; Hossain, M. D.; Xiong, Y.; Ferri, K.; Zhu, W.; Imperatore, M. V.; Giebink, N.; Trolier-McKinstry, S.; Dabo, I.; Maria, J.-P. Ferroelectricity in Boron-Substituted Aluminum Nitride Thin Films. Phys. Rev. Materials 2021, 5 (4), 044412. doi.org/10.1103/PhysRevMaterials.5.044412.