Temperature and Frequency Dependencies of Ferroelectric Properties in Rhombohedral Epitaxial Pb(Zr,Ti)O 3 Films with Per
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Temperature and Frequency Dependencies of Ferroelectric Properties in Rhombohedral Epitaxial Pb(Zr,Ti)O3 Films with Perfect (111) Orientations Grown on CaF2 Substrates. Yoshitaka Ehara1, 5, Tomoaki Yamada2, 3, Takashi Iijima4, Nagarajan Valanoor5, and Hiroshi Funakubo1 1
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama, Kanagawa, 226-8502, Japan 2 Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan 3 PRESTO, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0075, Japan 4 Research Center for Hydrogen Industrial Use and Storage, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan. 5 School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
ABSTRACT Perfectly (111)-oriented rhombohedral Pb(Zr, Ti)O3 [PZT] films were successfully grown on (111) CaF2 substrates. These films have the polar-axis perpendicular to the substrate surface without non-180o domains. Well saturated polarization (P) –electric field (E) hysteresis loops were observed at various frequencies and temperatures. Temperature dependence of the saturation polarization (Psat.) was in good agreement with the estimated one by Haun et al. using phenomenological approach but did not strongly depend on the measured frequencies. On the other hand, the coercive field (Ec) increased with decreasing temperature and with increasing the measurement frequency.
INTRODUCTION Ferroelectric and piezoelectric films have attracted attention due to their numerous potential applications, such as ferroelectric random access memories, sensors and micro-electromechanical systems (MEMS) [1-4]. Among various ferroelectrics and piezoelectrics materials, PZT has been intensively investigated not only for the fundamental research, but also for the applications due to its large spontaneous polarization and large piezoelectric response with stable insulation characteristics [1-4]. For the film form of PZT, many fundamental researches were also carried out using epitaxial films with tetragonal structure, Ti-rich composition, grown on the single crystal substrates [5, 6]. This approach thing films form is useful to obtain fundamental information of PZT because of the small information from the single crystal. On the other hand, the number of reports for Zr-rich rhombohedral PZT films is limited compared to that for tetragonal one mainly due to their complexity of the domain structure [7, 8]. For example, {100}-oriented rhombohedral PZT can have 4 different domains comparing with 3 ones of tetragonal PZT having the same orientation. To simplify this complexity and understand the fundamental issues of rhombohedral PZT, the growth of perfectly polar axis-oriented films, i.e. (111)-oriented films, by eliminating non-180o domains, (11-1) orientation, is most
straightforward approach. However, such polar axis-oriented films has been hardly reported because the phase transition from
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