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Enhancement of Remanent Polarization of BIT-based Thin Films by Ti-site Substitution using Ions with Higher Charge Valences

Published online by Cambridge University Press:  11 February 2011

Hiroshi Uchida ,
Isao Okada ,
Hirofumi Matsuda ,
Takashi Iijima ,
Takayuki Watanabe  and
Hiroshi Funakubo
Hiroshi Uchida
Affiliation:
Department of Chemistry, Faculty of Science and Engineering, Sophia University, 7–1 Kioi-cho, Chiyoda-ku, Tokyo, 102–8554, Japan
Isao Okada
Affiliation:
Department of Chemistry, Faculty of Science and Engineering, Sophia University, 7–1 Kioi-cho, Chiyoda-ku, Tokyo, 102–8554, Japan
Hirofumi Matsuda
Affiliation:
Smart Structure Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1–1–1 Umezono, Tsukuba, 305–8568, Japan
Takashi Iijima
Affiliation:
Smart Structure Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1–1–1 Umezono, Tsukuba, 305–8568, Japan
Takayuki Watanabe
Affiliation:
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226–8502, Japan
Hiroshi Funakubo
Affiliation:
Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, 226–8502, Japan
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Abstract

Bismuth titanate (Bi4Ti3O12; BIT) -based ferroelectric thin films fabricated from a view point of “the site-engineering technique” have been expected to improve the fatal disadvantage of a ferroelectric BIT film, i.e., its low spontaneous polarization; here, Bi- and Ti-site ions in the BIT crystal are cosubstituted by lanthanoid ions and cations with a higher charge valence, respectively, In the present study, we have mainly focused on Ti-site substitution of bismuth titanate (Bi4Ti3O12; BIT)-based thin films using some ions with higher charge valences (V5+, Nb5+, Ta 5+ and W6+; in this study) to enhance the ferroelectric properties of those materials. The BIT-based films with various chemical compositions were fabricated on a (111)Pt/Ti/SiO2/(100)Si substrate by a chemical solution deposition method.

Ti-site substitution of BIT films by the higher-valent ions, Bi3.99(Ti2.97V0.03)O12, Bi3.99(Ti2.97Nb0.03)O12, Bi3.99(Ti2.97Ta0.03)O12 and Bi3.98(Ti2.97W0.03)O12, reduced the leakage current density of BIT films from ∼ 10-6 down to ∼ 10-7 A/cm2 at an applied field of 50 kV/cm, while the substitution by the same-valent cation, e.g., Bi4.00(Ti2.97Zr0.03)O12, did not affect the behavior of leakage current. Whereas polarization (P) - electrical field (E) hysteresis loops of non-substituted and Zr-substituted BIT films were distorted due to the leakage current, non-distorted P-E loops were obtained at V5+-, Nb5+-, Ta5+- and W6+-substituted BIT films.

Also, Ti-site substitution was effective for improving the ferroelectric properties in lanthanoid-substituted BIT films. In the case of La3+-substituted BIT film (BLT), remanent polarization (Pr) of V5+- and W6+-substituted BLT films, (Bi3.24La0.75)(Ti2.97V0.03)O12 and (Bi3.23La0.75)(Ti2.97W0.03)O12 (13 and 12 μC/cm2, respectively), were larger than those of Zr4+- and non-substituted BLT films, (Bi3.25La0.75)(Ti2.97Zr0.03)O12 and (Bi3.25La0.75)(Ti3.00)O12 (8 and 9 μC/cm2, respectively), while those films had similar coercive field (Ec) of approximately 120 kV/cm. Also in the case of Nd3+-substituted BIT film (BNT), Pr and Ec values of V5+-substituted BNT film, (Bi3.24Nd0.75)(Ti2.98V0.02)O12, were 37 μC/cm2 and 119 kV/cm, respectively, which were comparable with those of conventional Pb-based ferroelectrics such as lead zirconate titanate, Pb(Zr,Ti)O3. We concluded that enhancement of the Pr value was achieved by the charge compensation of oxygen vacancies in BIT-based ferroelectrics using higher-valent cations than Ti4+ ion whereas no obvious differences were found in the crystal orientation and or microstructure of these films.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 748: Symposium U – Ferroelectric Thin Films XI , 2002 , U12.1
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCES

1. Celinska, J., Joshi, V., Narayan, S., Macmillian, L. D., and Paz, C. A. de Araujo, Integr. Ferroelectr. 30, 1 (2001).Google Scholar
2. Cummins, S. E., and Cross, L. E., J. Appl. Phys. 39, 2268 (1968).Google Scholar
3. Wu, D., Li, A., Zhu, T., Li, Z., Liu, Z., and Ming, N., J. Mater. Res. 16. 1325 (2001).Google Scholar
4. Watanabe, T., Sakai, A., and Funakubo, H., J. Appl. Phys. 89, 3934 (2001).Google Scholar
5. Shannon, R. D., Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. A32, 751(1976).Google Scholar
6. Park, B. H., Kang, B. S., Bu, S. D., Noh, T. W., Lee, J., and Jo, W., Nature (London) 401, 682 (1999).Google Scholar
7. Uchida, H., Yoshikawa, H., Okada, I., Matsuda, H., Iijima, T., Watanabe, T., and Funakubo, H., Jpn. J. Appl. Phys. in press (2002).Google Scholar
8. Uchida, H., Yoshikawa, H., Okada, I., Matsuda, H., Iijima, T., Watanabe, T., Kojima, T., and Funakubo, H., Appl. Phys. Lett. 81, 2229 (2002).Google Scholar
9. Kelman, M. B., Schloss, L. F., McIntyre, P. C., Hendrix, B. C., Bilodeau, S. M., and Roeder, J. F., Appl. Phys. Lett. 80, 1258, (2002).Google Scholar
10. Aratani, M., Oikawa, T., Ozeki, T., and Funakubo, H., Appl. Phys. Lett. 79, 1000 (2001).Google Scholar
11. Noguchi, Y., and Miyayama, M., Appl. Phys. Lett. 78, 1903 (2001).Google Scholar
12. Watanabe, T., Funakubo, H., Osada, M., Noguchi, Y., and Miyayama, M., Appl. Phys. Lett. 80, 100 (2002).Google Scholar
13. Noguchi, Y., Miwa, I., Goshima, Y., and Miyayama, M., Jpn. J. Appl. Phys. 39, L1259 (2000).Google Scholar
14. Uchida, H., Yoshikawa, H., Okada, I., Matsuda, H., Iijima, T., Watanabe, T., and Funakubo, H., Mat. Res. Soc. Symp. Proc. 688, C2.3 (2002).Google Scholar