Crystal Structure and Polarization Properties of Ferroelectric Nd-Substituted $Bi_4Ti_3O_{12}$ Thin Films Prepared by MOCVD 강유전체 $(Bi,Nd)_4Ti_3O_{12}$ 박막의 결정 구조와 분극 특성원문보기
Kang, Dong-Kyun
(Department of Materials Science and Engineering, Korea Univ.)
,
Park, Won-Tae
(Department of Materials Science and Engineering, Korea Univ.)
,
Kim, Byong-Ho
(Department of Materials Science and Engineering, Korea Univ.)
Bismuth titanate ($Bi_4Ti_3O_{12}$, BIT) thin film has been studied intensively in the past decade due to its large remanent polarization, low crystallization temperature, and high Curie temperature. Substitution of various trivalent rare-earth cations (such as $La^{3+}$, ...
Bismuth titanate ($Bi_4Ti_3O_{12}$, BIT) thin film has been studied intensively in the past decade due to its large remanent polarization, low crystallization temperature, and high Curie temperature. Substitution of various trivalent rare-earth cations (such as $La^{3+}$, $Nd^{3+}$, $Sm^{3+}$ and $Pr^{3+}$) in the BIT structure is known to improve its ferroelectric properties, such as remanent polarization and fatigue characteristics. Among them, neodymuim-substituted bismuth titanate, ((Bi, Nd)$_4Ti_3O_{12}$, BNT) has been receiving much attention due to its larger ferroelectricity. In this study, Ferroelectric $Bi_{3.3}Nd_{0.7}Ti_3O_{12}$ thin films were successfully fabricated by liquid delivery MOCVD process onto Pt(111)/Ti/$SiO_2$/Si(l00) substrates. Fabricated polycrystailine BNT thin films were found to be random orientations, which were confirmed by X-ray diffraction and scanning electron microscope analyses. The remanent polarization of these films increased with increase in annealing temperature. And the film also demonstrated fatigue-free behavior up to $10^{11}$ read/write switching cycles. These results indicate that the randomly oriented BNT thin film is a promising candidate among ferroelectric materials useful for lead-free nonvolatile ferroelectric random access memory applications.
Bismuth titanate ($Bi_4Ti_3O_{12}$, BIT) thin film has been studied intensively in the past decade due to its large remanent polarization, low crystallization temperature, and high Curie temperature. Substitution of various trivalent rare-earth cations (such as $La^{3+}$, $Nd^{3+}$, $Sm^{3+}$ and $Pr^{3+}$) in the BIT structure is known to improve its ferroelectric properties, such as remanent polarization and fatigue characteristics. Among them, neodymuim-substituted bismuth titanate, ((Bi, Nd)$_4Ti_3O_{12}$, BNT) has been receiving much attention due to its larger ferroelectricity. In this study, Ferroelectric $Bi_{3.3}Nd_{0.7}Ti_3O_{12}$ thin films were successfully fabricated by liquid delivery MOCVD process onto Pt(111)/Ti/$SiO_2$/Si(l00) substrates. Fabricated polycrystailine BNT thin films were found to be random orientations, which were confirmed by X-ray diffraction and scanning electron microscope analyses. The remanent polarization of these films increased with increase in annealing temperature. And the film also demonstrated fatigue-free behavior up to $10^{11}$ read/write switching cycles. These results indicate that the randomly oriented BNT thin film is a promising candidate among ferroelectric materials useful for lead-free nonvolatile ferroelectric random access memory applications.
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제안 방법
Triphenyl bismuth [Bi(ph)a], tri(2, 2, 6, 6-tetramethyl-3, 5-heptanedionate) Neodymium [Nd(TMHD)3] and di(i-propoxide) bis(2, 2, 6, 6-tetramethyl-3, 5-hep tanedionate) titanium [Ti(OlPr)2(TMHD)2] were used as the precursors for Bi, Nd and Ti, respectively; These precursors were dissolved n-butyl acetate to form a single stock solution. In this study, the structural, electric 시 and ferroelectric properties of the deposited films were investigated.
이론/모형
BNT films with a thickness of 150nm were deposited at 600℃ by the LDS-MOCVD method. Triphenyl bismuth [Bi(ph)a], tri(2, 2, 6, 6-tetramethyl-3, 5-heptanedionate) Neodymium [Nd(TMHD)3] and di(i-propoxide) bis(2, 2, 6, 6-tetramethyl-3, 5-hep tanedionate) titanium [Ti(OlPr)2(TMHD)2] were used as the precursors for Bi, Nd and Ti, respectively; These precursors were dissolved n-butyl acetate to form a single stock solution.
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