Browse > Article
http://dx.doi.org/10.4191/KCERS.2006.43.11.688

Effects of Lanthanides-Substitution on the Ferroelectric Properties of Bismuth Titanate Thin Films Prepared by MOCVD Process  

Kim, Byong-Ho (Department of Materials Science and Engineering, Korea University)
Kang, Dong-Kyun (Department of Materials Science and Engineering, Korea University)
Publication Information
Abstract
Ferroelectric lanthanides-substituted $Bi_4Ti_3O_{12}$ $(Bi_{4-x}Ln_xTi_3O_{12}, BLnT)$ thin films approximately 200 nm in thickness were deposited by metal organic chemical vapor deposition onto Pt(111)/Ti/SiO$_2$/Si(100) substrates. Many researchers reported that the lanthanides substitution for Bi in the pseudo-perovskite layer caused the distortion of TiO$_6$ octahedron in the a-b plane accompanied with a shift of the octahedron along the a-axis. In this study, the effect of lanthanides (Ln=Pr, Eu, Gd, Dy)-substitution and crystallization temperature on their ferroelectric properties of bismuth titanate $(Bi_4Ti_3O_{12}, BIT)$ thin films were investigated. As BLnT thin films were substituted to lanthanide elements (Pr, Eu, Gd, Dy) with a smaller ionic radius, the remnant polarization (2P$_r$) values had a tendency to increase and made an exception of the Eu-substituted case because $Bi_{4-x}Eu_xTi_3O_{12}$ (BET) thin films had the smaller grain sizes than the others. In this study, we confirmed that better ferroelectric properties can be expected for films composed of larger grains in bismuth layered peroskite materials. The crystallinity of the thin films was improved and the average grain size increased as the crystallization temperature,increased from 600 to 720$^{\circ}C$. Moreover, the BLnT thin film capacitor is characterized by well-saturated polarization-electric field (P-E) curves with an increase in annealing temperature. The BLnT thin films exhibited no significant degradation of switching charge for at least up to $1.0\times10^{11}$ switching cycles at a frequency of 1 MHz. From these results, we can suggest that the BLnT thin films are the suitable dielectric materials for ferroelectric random access memory applications.
Keywords
Ferroelectric; Lanthanides-substituted; Randomly-oriented; Fatigue-free;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Y. Noguchi, I. Miwa, Y. Goshima, and M. Miyayama, 'Defect Control for Large Remnant Polarization in Bismuth Titanate Ferroelectrics -Doping Effect of Higher- Valent Cations-,' Jpn. J. Appl. Phys., 39 1259-62 (2000)   DOI   ScienceOn
2 M. Yamada, N. Iizawa, T. Yamaguchi, W. Sakamoto, K. Kikuta, T. Yogo, T. Hayashi, and S. Hirano, 'Processing and Properties of Rare Earth Ion-Doped Bismuth Titanate Thin Films by Chemical Solution Deposition Method,' Jpn. J. Appl. Phys., 42 5222-26 (2003)   DOI
3 S. K. Kim, M. Miyayama, and H. Yanagida, 'Electrical Anisotropy and a Plausible Explanation for Dielectric Anomaly of $Bi_4Ti_3O_{12}$ Single Crystal,' Mater. Res. Bull., 31 121-31 (1996)   DOI   ScienceOn
4 Y. Shimakawa, Y. Kubo, Y. Tauchi, H. Asano, T. Kamiyama, F. Izumi, and Z. Hiroi, 'Structural and Ferroelectric Studies of $Bi_{3.44}La_{0.56}Ti_3O_{12}$ Films,' Appl. Phys. Lett., 83 341-43 (2003)   DOI   ScienceOn
5 M. S. Tomar, R. E. Melgarejo, A. Hidalgo, S. B. Mazumder, and R. S. Katiyar, 'Large Ferroelectric Response in $Bi_{4-x}Nd_xTi_3O_{12}$ Films Prepared by Sol-Gel Process,' Appl. Phys. Lett., 81 2611-13 (2002)   DOI   ScienceOn
6 M. Yamaguchi and T. Nagamoto, 'Preparation and Properties of $Bi_4Ti_3O_{12}$ Thin Films Grown at Low Substrate Temperatures,' Thin Solid Films, 348 294-98 (1999)   DOI   ScienceOn
7 S. S. Kim and W. J. Kim, 'Ferroelectric Properties of Randomly Oriented $Bi_{1-x}Pr_xTi_3O_{12}$ Thin Films Fabricated by a Sol-Gel Method,' Thin Solid Films, 484 303-09 (2005)   DOI   ScienceOn
8 D. Wu, A. Li, Z. Liu, and N. Ming, 'Structrural and Electrical Properties of $Bi_{3.25}La_{0.75}Ti_3O_{12}$ and $Bi_{3.25}Pr_{0.75}Ti_3O_{12}$ Thin Films for Memory Applications,' Integ. Ferroelectr., 45 177- 82 (2002)   DOI
9 M. Toyada, Y. Hamaji, K. Tomono, and D. A. Payne, 'Ferroelectric Properties and Fatigue Characteristics of $Bi_4Ti_3O_{12}$ Thin Films by Sol-Gel Crystal,' Jpn. J. Appl. Phys., 33 5543-48 (1994)   DOI
10 W. C. Shin, K. J. Choi, N. J. Seong, E. S. Choi, B. H. Kim, and S. G. Yoon, 'Liquid-Delivery Metal Organic CVD of Strontium Bismuth Tantalite Thin Films Using Sr[Ta $(OC_2H_5)_5(OC_2H_4OCH_3)]_2\;and\;Bi(C_6H_5)_3 $Precursors,' Chem. Vap. Deposition, 8 [5] 221-25 (2002)   DOI   ScienceOn
11 M. Yamaguchi, T. Nagamoto, and O. Omoto, 'Preparation of Highly c-Axis-Oriented $Bi_4Ti_3O_{12} $Thin Films and their Crystallographic, Dielectric, and Optical Properties,' Thin Solid Films, 300 299-304 (1997)   DOI   ScienceOn
12 A. R. Chaudhuri, A. Laha, and S. B. Krupanidhi, 'Enhanced Ferroelectric Properties of Vanadium Doped Bismuth Titanate (BTV) Thin Films Grown by Pulsed Laser Ablation Technique,' Solid State Commun., 133 611-14 (2005)   DOI   ScienceOn
13 J. F. Scott, 'Ferroelectric Memories'; Springer Press, New York, 2001
14 Y. Shimakawa, Y. Kubo, Y. Nakagawa, and T. Kamiyama, 'Crystal Structure and Ferroelectric Properties of $ABi_2Ta_2O_9$ (A=Ca, Sr, and Ba),' H. Asano, F. Izumi, Phys. Rev. B, 61 6559-64 (2000)   DOI   ScienceOn
15 T. Watanabe et al., 'Lager Remnant Polarization of $Bi_4Ti_3O_{12}$-Based Thin Films Modified by the Site Engineering Technique,' J. Appl. Phys., 92 1518-21 (2002)   DOI   ScienceOn
16 T. Kojima, T. Sakai, T. Watanabe, and H. Funakubo, 'Large Remnant Polarization of $(Bi,Nd)_4Ti_3O_{12}$ Epitaxial Thin Films Grown by Metalorganic Chemical Vapor Deposition,' Appl. Phys. Lett., 80 2746-48 (2002)   DOI   ScienceOn
17 B. H. Park et al., 'Lanthanide-Substituted Bismuth Titanate for Use in Non-Volatile Memories,' Nature(London), 401 682-84 (1999)   DOI
18 B. H. Kim and D. K. Kang, 'Characteristics of Ferroelectric $Sr_{0.9}Bi_{2.1}Ta_2O_9$ Thin Films Grown by Liquid Delivery Metal Organic Chemical Vapor Deposition Process,' Thin Solid Films, 492 [1-2] 140-45 (2005)   DOI   ScienceOn
19 K. T. Kim, C. I. Kim, D. H. Kang, and I. W. Shin, 'The Effect of Eu Substitution on the Ferroelectric Properties of $Bi_4Ti_3O_{12}$ Thin Films Prepared by Metal-Organic Decomposition,' Thin Solid Films, 422 230-34 (2002)   DOI   ScienceOn