A very promising piezoelectric property of Ta{sub 2}O{sub 5} thin films. I: Monoclinic-trigonal phase transition

Journal Article · Mon Aug 15 00:00:00 EDT 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.06.001· OSTI ID:21580179

Audier, M ^[1]; Chenevier, B; Roussel, H ^[1]; Vincent, L ^[2]; Pena, A ^[3]; Lintanf Salauen, A ^[4]

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1. Laboratoire des Materiaux et du Genie Physique, UMR CNRS 5628, Minatec - INP Grenoble, 3 parvis Louis Neel, BP 257, 38016 Grenoble Cedex 1 (France)
2. CIME Nanotech Minatec, Microsystemes et capteurs, F-38016 Grenoble Cedex 1 (France)
3. Institut Neel - CNRS/UJF, Dpt. Matiere Condensee, Materiaux et Fonctions, F-38042 Grenoble (France)
4. L2MA, CEA LETI D2NT, F-38054 Grenoble (France)

Ceramic thin films of tantalum oxide of a new trigonal structure (a=12.713(7) A, {alpha}=28.201(0){sup o}, 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-Ta{sub 2}O{sub 5}. 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 Ta{sub 2}O{sub 5}. 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 Ta{sub 2}O{sub 5} samples, for which an incommensurate phase transition has been observed in a previous work. - Graphical abstract: (a) {theta}/2{theta} X-ray pattern of the tantalum oxide layer prepared by i-MOCVD, cooled down at 5 deg. C min{sup -1} after a thermal treatment at 850 deg. C under N{sub 2} for 1 h. (b) Rhombohedral cell of the Ta{sub 2}O{sub 5} trigonal structure of R3 space-group decorated with its 10 Ta sites. Highlights: > We examine crystallographic properties of a new Ta{sub 2}O{sub 5} trigonal phase. > Its formation occurs only in thin films. > It comes from a reversible transition with a monoclinic phase. > A possibility of strong piezoelectricity is deduced from the present study.

• OSTI ID: 21580179
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 8; Other Information: DOI: 10.1016/j.jssc.2011.06.001; PII: S0022-4596(11)00312-4; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BINDING ENERGY
CERAMICS
CHEMICAL VAPOR DEPOSITION
CRYSTALLOGRAPHY
DECOMPOSITION
DEPOSITS
ELECTRIC DIPOLE MOMENTS
HEAT TREATMENTS
MONOCLINIC LATTICES
ORGANOMETALLIC COMPOUNDS
PHASE TRANSFORMATIONS
PIEZOELECTRICITY
SPACE GROUPS
TANTALUM OXIDES
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY
TRIGONAL LATTICES
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY
CHALCOGENIDES
CHEMICAL COATING
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DEPOSITION
DIFFRACTION
DIPOLE MOMENTS
ELECTRIC MOMENTS
ELECTRICITY
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ENERGY
FILMS
MICROSCOPY
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
REFRACTORY METAL COMPOUNDS
SCATTERING
SPECTROSCOPY
SURFACE COATING
SYMMETRY GROUPS
TANTALUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS