Determination Factors of Strain-relaxed Complex Domain Structure Observed in Thick Epitaxial Pb (Zr, Ti)O 3 Films
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1199-F08-08
Determination Factors of Strain-relaxed Complex Domain Structure Observed in Thick Epitaxial Pb(Zr, Ti)O3 Films Hiroshi Nakaki1, Satoru Utsugi1, Takashi Fujisawa1, Mitsumasa Nakajima1, Yoshitaka Ehara1, Tomoaki Yamada1, Hitoshi Morioka1, 2, Toshihiro Ifuku 3, and Hiroshi Funakubo 1 1
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan. 2 Application Laboratory, Bruker AXS, Yokohama, Kanagawa, Japan. 3 Nano materials Technology Development Center, Corporate R&D Headquarters, Canon Inc.,
ABSTRACT Crystal structure change with the temperature was investigated for 3 m-thick (100)/(001)-oriented epitaxial PbTiO3 films grown on SrTiO3 substrates. Complex strain-relaxed domain structure labeled as Type III was observed and directly transformed to the cubic phase at about 490 oC. This transition temperature and the lattice parameter (a and c- axes) change with the temperature well agreed with the reported data for the PbTiO3 powders. The volume fraction of the (001) orientations, Vc, was almost independent of the temperature up to the phase transition temperature. The tilting angles of the spots in XRD plan view were almost the same with the estimated ones from the lattice parameters and the Vc. This suggests that the angle of the domains identified by the domain structure in Type III. This structure is mainly determined by the tetragonality, (c/a ratio) and the Vc.
INTRODUCTION PZT has been widely investigated due to its large piezoresponse [1]. Film form of this PZT has also been investigated due to it potential application in micro electro mechanical system [MEMS], but its longitudinal piezoresponse was reported to be smaller than that of bulk PZT, mainly due to the clamping effects from the substrates[2, 3]. To enhance the piezoelectric property of the films, controlled concept of domain structure, such as so called “domain engineering” proposed for Pb(Mg1/3Nb 2/3)O3-PbTiO3[4], must be take into account. To apply this idea to PZT films, the understanding of the domain structure of the PZT films above 1 m in thickness is the most fundamental and also critical issues. We found the novel strain-relaxed domain structure, which was obtained in thick tetragonal PZT films [5-9]. In the present study, we investigated the change of the domain structure with the temperature and tried to understand the determination factors of this domain structure.
EXPERIMENT 3 m-thick epitaxial PbTiO3 films with the mixture orientations of (100)/(001) were grown on (100) SrTiO3 substrates by pulsed metal organic chemical vapor deposition. Details of the film growth are already reported elsewhere[10].
RESULTS AND DISCUSSIONS
PbTiO3 002 4
Omega (deg.)
PbTiO3 200 4
(a)
2
2
0
0
-2
-2
-4
-4 4
4
(c)
2
2
0
0
-2
-2
-4
-4
4
4
(e)
2
[010]SrTiO3
Composition of the film was ascertained to be Pb/(Pb+Ti)=0.5 by X-ray fluorescence spectroscopy (XRF). The crystal structure as a function of temperature was measured by high-resolution X-ray diffraction (XRD) usi
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