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Understanding the formation of the metastable ferroelectric phase in hafnia-zirconia solid solution thin films

Abstract

Hf1-xZrxO2 (x ~ 0.5 ~ 0.7) has been the leading candidate of ferroelectric material with a fluorite crystal structure showing highly promising compatibility with the complementary metal oxide semiconductor devices. Despite the notable improvement in the device performance and processing techniques, the origin of its ferroelectric crystalline phase (space group: Pca21) formation has not been clearly elucidated. Several recent experimental and theoretical works evidently showed that the interface and grain boundary energies of the higher symmetry phases (orthorhombic and tetragonal) contribute to the stabilization of the metastable non-centrosymmetric orthorhombic phase or tetragonal phase. However, there was a clear quantitative discrepancy between the theoretical expectation and experiment results, suggesting that the thermodynamic model may not provide the full explanation. This work, therefore, focuses on the phase transition kinetics during the cooling step after the crystallization annealing. It was found that the large activation barrier for the transition from the tetragonal/orthorhombic to monoclinic phase, which is the stable phase at room temperature, suppresses the phase transition, and thus, plays the critical role in the emergence of the ferroelectricity.

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Publication details

The article was received on 25 Aug 2017, accepted on 29 Nov 2017 and first published on 30 Nov 2017


Article type: Paper
DOI: 10.1039/C7NR06342C
Citation: Nanoscale, 2017, Accepted Manuscript
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    Understanding the formation of the metastable ferroelectric phase in hafnia-zirconia solid solution thin films

    M. H. Park, Y. H. Lee, H. J. Kim, Y. J. Kim, T. Moon, K. D. Kim, S. D. Hyun, T. Mikolajick, U. Schroeder and C. S. Hwang, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR06342C

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