• 한국세라믹학회지
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• 제35권9호
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• pp.1002-1005
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• 1998

Bismuth titanate thin films were prepared on {{{{ { SrTiO}_{3 } }}(100) and Si(100) substrates by dipping-pyrolysis pro-cess using metal naphthenates as starting materials. crystallinity and in-phase alignment of the films were analyzed by X-ray diffraction $\theta$-2$\theta$ scans and $\beta$ scans (pole-figures) respectively. Highly c-axis-oriented {{{{ { { {Bi }_{4 }Ti }_{3 }O }_{12 } }} thin films with smooth surfaces were obtained after heat treatment at 75$0^{\circ}C$ on {{{{ { SrTiO}_{3 } }}(100) sub-strate while the films grown of Si(100) exhibited polycrstalline characteristics. C-axis oriented film show-ed an epitaxial relationship with the {{{{ { SrTiO}_{3 } }} substrate.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2006년도 추계학술대회 발표 논문집
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• pp.170-173
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• 2006

Ferroelectric $Bi_{3.35}Sm_{0.65}Ti_3O_{12}(BST)$ thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by a sol-gel spin-coating process. In this experiments, $Bi(TMHD)_3$, $Sm_5(O^iPr)_{13}$, $Ti(O^iPr)_4$ were used as precursors, which were dissolved in 2-methoxyethanol. Thereafter, the thin films with the thickness, of 240nm were annealed from 600 to $720^{\circ}C$ in oxygen atmosphere for 1 hr, and post-annealed in oxygen atmosphere for 1 hr after deposition of Pt electrode to enhance the electrical properties. The remanent polarization and coercive voltage of the BST thin films annealed at $720^{\circ}C$ were $19.48\;{\mu}C/cm^2$ and 3.40 V, respectively, and a fatigue-free characteristics. As a result, Sm-substituted bismuth titanate films with good ferroelectric properties and excellent fatigue resistance are useful candidates for ferroelectric memory applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.371-374
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• 2002

Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/$SiO_2$/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10 % excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of n9 and dielectric loss of 1.85[%]. The BLT thin films showed little polarization fatigue test up to 3.5 x $10^{9}$ bipolar switching cycling.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.287-287
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• 2007

The ferroelectric and electric properties of UV-irradiated bismuth lanthanum titanate (BLT) films prepared using photosensitive starting precursors were characterized. The effects of lanthanum doping on ferroelectric and electric properties were investigated by polarization-electric field hysteresis loops and leakage current-voltage measurements. X-ray diffractometer and ellipsometry were served to provide the information about the crystalline structure and thickness of the films after annealing. The images of the surface microstructure and direct-patterned BLT films were observed by using scanning electron microscopy. The effects of lanthanum doping on the electric properties of direct-pattern able BLT films and their direct-patterning were studied.

• 한국결정성장학회지
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• 제13권2호
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• pp.56-62
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• 2003

졸-겔법을 이용하고 금속 나프테네이트를 출발원료로 사용하여 $SrTiO_3$(100), $LaA1O_3$(100) 및 MgO(100) 기판 위에 에피탁샬 $Bi_4Ti_3O_{12}$ 박막을 제조하였다. 코팅된 전구막은 $500^{\circ}C$에서 10분간 전열처리 하였고, $750^{\circ}C$에서 30분간 최종 열처리를 행하였다. 박막의 결정화도는 X-선회절 분석법 ($\theta$-2$\theta$ 스캔과 $\beta$ 스캔)으로 조사하였고, 표면 미세구조와 거칠기를 field emission-scanning electron microscope와 atomic force microscope를 이용하여 각각 분석하였다. MgO(100) 기판 위에 제조한 박막은 모든 기판 중에서 가장 낮은 결정화도와 면내 배향성을 보였다. 가장 낮은 결정화도와 배향성을 보인 MgO(100) 기판위의 박막은 침상 형태로 성장한 반면, 결정성과 배향성이 좋은 $LaA1O_3$(100)과 $SrTiO_3$(100) 기판위의 박막들은 원형의 입자 성장 형태를 보이고 있었다.

• 마이크로전자및패키징학회지
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• 제20권4호
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• pp.25-30
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• 2013

Pb-free ferroelectric $(Na_{0.5}Bi_{0.5})TiO_3$ (NBT) thin films were prepared by a modified sol-gel process. Their structural, dielectric and pyroelectric properties were investigated as a function of the excess Na/Bi ratio and the annealing temperature. In the case of thin films containing no excess Na and Bi, only partial amounts of the perovskite NBT were crystallized, where the films consisted mainly of the pyrochlore phase of $Bi_2Ti_2O_7$ for annealing conditions of $600{\sim}800^{\circ}C$. With increasing excess Na/Bi ratio, the proportion of the perovskite phase effectively increased due to the compensation of the volatile Na and Bi components. For a Na/Bi ratio of 2.0, the thin film with single NBT perovskite phase was obtained within XRD detection limit after annealing at $700^{\circ}C$ for 10 min and it showed the excellent dielectric properties, ${\varepsilon}r$ of ~550 and tan ${\delta}$ of 0.03. While these properties were degraded for Na/Bi ratio of 2.5 despite the existence of pure perovskite phase. The NBT thin film with Na/Bi ratio of 2.0 are also promising candidates for applications requiring pyroelectric devices because it was found to have pyroelectric coefficients of $1.3{\sim}7nC/cm^2K$ in the temperature range of $30{\sim}100^{\circ}C$.

• 한국세라믹학회지
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• 제40권4호
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• pp.340-345
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• 2003

B $i_2$ $O_3$-Ti $O_2$ composite dielectric ceramics have been prepared by a conventional solid state ceramic route. The composite ceramics were prepared with starting materials of different origin and the microwave dielectric properties were investigated. The sintered ceramics were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, Raman and microwave methods. Structural and microstructural analyses identified two separate phases: Ti $O_2$(rutile) and B $i_2$ $Ti_4$0$_{11}$. The separate grains of titania and bismuth titanate were distributed uniformly in the ceramic matrix. The composition 0.88Ti $O_2$-0.12B $i_2$ $Ti_4$ $O_{11}$ was found to have a Q$\times$f of 9300 GHz (measured at a frequency of 3.9 GHz), a temperature coefficient of frequency, $\tau$$_{cf}$ near zero and a high relative permittivity, $\varepsilon$r of 83. The microwave dielectric properties were measured down to 20$^{\circ}$K K. The quality factor increased on cooling the ceramic samples.les.

• Transactions on Electrical and Electronic Materials
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• 제12권2호
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• pp.64-67
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• 2011

The effect of Ta substitution on the crystal structure, ferroelectric, and piezoelectric properties of $Bi_{0.5}(Na_{0.82}K_{0.18})_{0.5}Ti_{1-x}Ta_xO_3$ ceramics has been investigated. The Ta doping resulted in a transition from coexistence of ferroelectric tetragonal and rhombohedral phases to an electrostrictive pseudocubic phase, leading to degradations of the remnant polarization, coercive field, and piezoelectric coefficient $d_{33}$. However, the electricfield-induced strain was significantly enhanced by the Ta substitution-induced phase transition and reached a highest value of $S_{max}/E_{max}$ = 566 pm/V under an applied electric field 6 kV/mm when 2% Ta was substituted on Ti sites. The abnormal enhancement in strain was attributed to the pseudocubic phase with high electrostrictive constants.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.894-897
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• 2004

Sodum bismuth titanate $(Na_{0.5}Bi_{0.5}TiO_3$ or NBT) thin films coated on the $LaNiO_3$ (LNO) electrode by sol-gel methode and rapid thermal annealing (RTA) technique. The NBT (NBT/LNO/Si) thin films examined by x-ray diffraction (XRD). The orientation of NBT was observed for films coated at $900^{\circ}C$, 5 min and $600^{\circ}C$, 60 min. Filed emission scanning electron microscopy (FE-SEM) showed uniform surface composed of grains. The grain size of NBT thin films increased with increasing annealing temperature.

• 한국세라믹학회지
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• 제32권10호
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• pp.1178-1188
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• 1995

Bi4Ti3O12 (BIT) and its rare earth (Y, Nd, Sm, Gd)-substituted derivatives were synthesized using a sol-gel method to investigate their microstructures, cystal structures and electrical properties depending on the subsituted elemetns. Nd- or Sm-substitution into BIT appeared to be favorable, while Y- or Gd-substitution occurred with a pyrochlore phase. This suggests that a smaller trivalent rare earth ion may not be favorable in the structure of BIT. The rare earth derivatives showed that their particle sizes and shapes were considerably different depending on the kinds of substituted elements. Y-substitution resulted in developing a relatively even particle size and a dense microstructure. In structure, they may be similar to the pseudo-orthorhombic BIT but close to a paraelectric tetragonal phase. Their a (or b) axes were shortened, compared to the one of BIT. Such a distortion may result a decrease in the tilting of TiO6. BIT and the derivatives showed that their dielectric constants and losses were 40~120 and less than 0.03, respectively in the frequency range of 1~10 MHz. The dielectric loss of Y-substituted derivative was the lowest one and changed a little to frequency. Curie points were observed in all the derivatives like BIT to suggest that they would be ferroelectric. The temperature stability of the delectric properties of the derivatives below the Curie points were relatively better than the one of BIT.