Experimental evidence of ferroelectricity in calcium doped hafnium oxide thin films

Ferroelectricity in calcium doped hafnium oxide (Ca:HfO2) thin films has been experimentally proved for the first time in this work. All films prepared by chemical solution deposition exhibited smooth and crack-free surfaces, which were observed using an atomic force microscope. After 104 field cycl...

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Bibliographic Details
Published in:Journal of applied physics 2019-10, Vol.126 (15)
Main Authors: Yao, Yifan, Zhou, Dayu, Li, Shuaidong, Wang, Jingjing, Sun, Nana, Liu, Feng, Zhao, Xiuming
Format: Article
Language:English
Subjects:
Applied physics
Atomic force microscopes
Atomic force microscopy
Calcium
Ferroelectricity
Free surfaces
Hafnium oxide
Lime
Organic chemistry
Phase transitions
Photoelectrons
Thin films
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Summary:Ferroelectricity in calcium doped hafnium oxide (Ca:HfO2) thin films has been experimentally proved for the first time in this work. All films prepared by chemical solution deposition exhibited smooth and crack-free surfaces, which were observed using an atomic force microscope. After 104 field cycling, a maximum remanent polarization of 10.5 μC/cm2 was achieved in HfO2 films with 4.8 mol. % Ca content. Meanwhile, the breakdown of the film occurred after 7 × 106 electric cycles. A phase transition from the monoclinic phase to cubic/orthorhombic phases was observed with increasing Ca concentration. We suggest the change in oxygen vacancy concentration as the origin of phase evolution, which was confirmed by X-ray photoelectron spectroscopy analysis. These results open a new pathway for realizing ferroelectricity in HfO2-based films.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5117358