A very promising piezoelectric property of Ta₂O₅ thin films. I: Monoclinic–trigonal phase transition

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• 作者：M. Audier^a ; ^{Marc.Audier@grenoble-inp.fr"" rel=""nofollow} ; B. Chenevier^a ; H. Roussel^a ; L. Vincent^b ; A. Peñ ; a^c ; A. Lintanf Salaü ; n^d
• 关键词：Tantalum oxide ; Ceramic thin film ; Phase transition ; Transmission electron microscopy ; X-ray diffraction ; X-ray photoelectron spectroscopy
• 刊名：Journal of Solid State Chemistry
• 出版年：2011
• 出版时间：August 2011
• 年：2011
• 卷：184
• 期：8
• 页码：2023-2032
• 全文大小：2417 K

文摘

Ceramic thin films of tantalum oxide of a new trigonal structure (a=12.713(7) Å, α=28.201(0)°, space-group R3) were produced by thermal treatments of amorphous deposits on (001)Si wafers, either by electrostatic spray deposition or by injection metal-organic chemical vapor decomposition. This trigonal phase comes from the transformation of a monoclinic phase 11L- or 25L-Ta₂O₅. The transformation is reversible under oxygen atmosphere and, from results of TEM investigations, occurs mainly via atomic motions along the z unique axis of the monoclinic structure parallel to the polar three-fold axis of the trigonal structure. The non-centrosymmetry and direction of polar axis of the trigonal phase, identified by high resolution TEM imaging, indicate a possibility of very high electric dipole moments linked to a strong piezoelectricity. From results of XPS analyses of both monoclinic and trigonal structures, the binding energies remain similar to those of Ta₂O₅. As the formation of the trigonal structure gives rise to an important volume expansion, stresses induced in ceramic thin films are likely influencing both properties of birefringence and piezoelectricity which are presented in a separated article (part II). It is mentioned that the formation of trigonal phase does not occur in bulk Ta₂O₅ samples, for which an incommensurate phase transition has been observed in a previous work.