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DOE OSTI · 2586397

Ferroelectricity of wurtzite Al 1−x Hf x N heterovalent alloys

Bernstein, Nate S. P. [Colorado School of Mines, Golden, CO (United States)] (ORCID:0009000914041157)·Drury, Daniel [Army Research Lab., Adelphi, MD (United States)] (ORCID:0000000284135927)·Lee, Cheng-Wei [Colorado School of Mines, Golden, CO (United States)] (ORCID:000000028317588X)·Shimada, Tatau [TAIYO YUDEN Co., Ltd., Tokyo (Japan)] (ORCID:0009000904995600)·Sakai, Yuki [TAIYO YUDEN Co., Ltd., Tokyo (Japan)] (ORCID:000900018426610X)·Rehm, Oliver [Universität Konstanz (Germany)] (ORCID:0000000232510799)·Baumgarten, Lutz [Forschungszentrum Jülich GmbH (Germany)] (ORCID:0000000172997581)·Müller, Martina [Universität Konstanz (Germany)] (ORCID:0000000160829038)·Gorai, Prashun [Colorado School of Mines, Golden, CO (United States); Rensselaer Polytechnic Inst., Troy, NY (United States)] (ORCID:0000000178660672)·Iwazaki, Yoshiki [TAIYO YUDEN Co., Ltd., Tokyo (Japan)] (ORCID:000900035189733X)·Fox, Glen R. [Fox Materials Consulting, LLC, Colorado Springs, CO (United States)] (ORCID:0009000499332490)·Yazawa, Keisuke [Colorado School of Mines, Golden, CO (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000253041696)·Hanrahan, Brendan [Army Research Lab., Adelphi, MD (United States)] (ORCID:0000000266664390)·Brennecka, Geoff L. [Colorado School of Mines, Golden, CO (United States)] (ORCID:0000000244767655)
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Abstract

Thin films of aluminum hafnium nitride (Al1−xHfxN) were synthesized via reactive magnetron sputtering for Hf contents up to x = 0.13. X-ray diffraction showed a single c-axis oriented wurtzite phase for all films. Hard x-ray photoelectron spectroscopy demonstrated homogeneous Al:Hf distribution through the thin films and confirmed their insulating character. A collection of complementary tests showed unambiguous polarization inversion, and thus ferroelectricity in multiple samples. Current density vs electric field hysteresis measurements showed distinct ferroelectric switching current peaks, the piezoelectric coefficient d 33,f,meas measured using a double beam laser interferometer (DBLI) showed a reversal in sign with similar magnitude, and anisotropic wet etching confirmed field-induced polarization inversion. This demonstrates the possibility of using tetravalent–and not just trivalent–alloying elements to enable ferroelectricity in AlN-based thin films, highlighting the compositional flexibility of ferroelectricity in wurtzites and greatly expanding the chemistries that can be considered for future devices.

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36 MATERIALS SCIENCEcrystal structurecrystallographic defectsferroelectricheterovalent alloymagnetron sputteringnitridenitridespiezoelectricitysputteringthin filmswurtzitex-ray photoelectron spectroscopy

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Bernstein, Nate S. P. [Colorado School of Mines, Golden, CO (United States)] (ORCID:0009000914041157), Drury, Daniel [Army Research Lab., Adelphi, MD (United States)] (ORCID:0000000284135927), Lee, Cheng-Wei [Colorado School of Mines, Golden, CO (United States)] (ORCID:000000028317588X), Shimada, Tatau [TAIYO YUDEN Co., Ltd., Tokyo (Japan)] (ORCID:0009000904995600), Sakai, Yuki [TAIYO YUDEN Co., Ltd., Tokyo (Japan)] (ORCID:000900018426610X), Rehm, Oliver [Universität Konstanz (Germany)] (ORCID:0000000232510799), Baumgarten, Lutz [Forschungszentrum Jülich GmbH (Germany)] (ORCID:0000000172997581), Müller, Martina [Universität Konstanz (Germany)] (ORCID:0000000160829038), Gorai, Prashun [Colorado School of Mines, Golden, CO (United States); Rensselaer Polytechnic Inst., Troy, NY (United States)] (ORCID:0000000178660672), Iwazaki, Yoshiki [TAIYO YUDEN Co., Ltd., Tokyo (Japan)] (ORCID:000900035189733X), Fox, Glen R. [Fox Materials Consulting, LLC, Colorado Springs, CO (United States)] (ORCID:0009000499332490), Yazawa, Keisuke [Colorado School of Mines, Golden, CO (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000253041696), Hanrahan, Brendan [Army Research Lab., Adelphi, MD (United States)] (ORCID:0000000266664390), Brennecka, Geoff L. [Colorado School of Mines, Golden, CO (United States)] (ORCID:0000000244767655). 2025-08-11. Ferroelectricity of wurtzite Al 1−x Hf x N heterovalent alloys. https://doi.org/10.1063/5.0271563

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