• Proceedings of the Korean Vacuum Society Conference
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• 2004.08a
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• pp.52-52
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• 2004

• Journal of the Korean Ceramic Society
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• v.35 no.9
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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.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1440-1441
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• 2011

Apatite-lanthanum silicate has attracted considerable interest in recent years due to its high oxide ion conductivity, In this paper, Bi-doped samples $La_8Bi_2(SiO_4)_6O_3$ were prepared by conventional solid-state method and the influences of Bi-dopant content on calcining temperature were reported. The Samples were characterized by X-ray diffraction (XRD) and scanning electron micrograph (SEM) and impedance analysis.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.37-37
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• 2003

Ferroelectric random acess memories (FeRAMs) 재료로 주목받고 있는 강유전 물질은 이미 여러 해 전부터 많은 물질들에 대해 연구가 진행되어 왔다. 그 중 낮은 공정 온도를 가지며 큰 remanent polarization 값을 갖는 lead zirconium titanate (PZT) 박막에 대해 많은 연구가 진행되고 있다. 하지만 Pt 기판위에 증착된 PZT 박막은 높은 피로 현상을 보이는 문제가 있다. 최근 Pulsed laser deposition이나 metal-organic vapor phase epitaxy (MOVPE) 등의 방법에 의해 epitaxial substituted-$Bi_4Ti_3O_{12}$ (La, Nd) 박막에 대해 보고가 되고 있다. 본 연구에서는 높은 remanent polarization 값을 갖는 $(Bi,Ce)_4Ti_3O_{12}$ (BCT) 박막을 pulsed laser deposition 방법을 사용하여 증착하였다. 또한 Bismuth의 양을 변화시켜 Bismuth의 양에 따른 remanent polarization의 변화를 확인하여 보았다. 사용된 기판은 Pt/$TiO_2$/$SiO_2$/Si 기판을 사용하였다.

• Proceedings of the KAIS Fall Conference
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• 2002.05a
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• pp.121-123
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• 2002

졸-겔법(Sol-Gel Method)으로 강유전체 Bi/sub 3.3/La/sub 0.7/Ti/sub 3/O/sub 12/(BLT) 박막을 Pt/Ti/SiO₂/Si 기판위에 스핀 코팅하여 Metal-Ferroelectric-Metal(MFM 구조를 형성하였다. As-coated BLT 박막은 650℃ 이상에서 결정화되었으며, 전형적인 Bi층상의 페롭스카이트 결정구조를 나타내었다. 또한 열처리 온도를 증가시킴에 따라 결정성이 향상되었다. 3V 전압에서 650℃로 열처리된 박막의 경우 누설전류가 약 2.25×10/sup -8/A/㎠ 정도를 보였다. 650℃에서 열처리된 BLT박막은 5V의 인가 전압에서 잔류분극 2Pr(±(P/sup */-P/sup A/)) 값은 약 29.5μC/㎠을 나타내었으며, 1.5×10/sup 10/ 스위칭 cycles까지 분극 스위칭을 반복한 후에도 거의 잔류 분극의 변화가 없었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.39-40
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• 2005

Ferroelectric Eu-substituted $Bi_4Ti_3O_{12}$ (BET) thin films with a thickness of 200 nm were deposited on Pt(111)/Ti/SiO$_2$/Si(100) substrate by means of the liquid delivery MOCVD system and annealed at several temperatures in an oxygen atmosphere. At annealing temperature above $600^{\circ}C$, the microstructure of layered perovskite phase was observed. The remanent polarization of these films increased with increase in annealing temperature. The remanent polarization values ($2P_r$) of the BET thin films annealed at $720^{\circ}C$ were $37.71{\mu}C/cm^2$ at an applied voltage of 5 V.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.68-72
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• 2005

본 논문에서는 $Bi_{3}Ti_{4}O_{12}$에 Nd를 치환했을 때 향상되는 강유전체 특성을 sol-gel 방법을 이용하여 분석하였다. 이를 위해 $10\;wt\%$의 $12\%$과량의 Bi가 첨가된 $Bi_{3.15}Nd_{0.85}Ti_{13}O_{12}$ sol-gel 용액을 제작하였다. BNT 박막은 $Pt/TiO_2/SiO_2/Si$ 기판 위에 스핀 코팅 방법을 이용하여 증착하였으며, 최종 증착된 박막의 조성은 Rutherford backscattering spectroscopy 분석을 이용하여 $Bi_{3.15}Nd_{0.85}Ti_{13}O_{12}$임을 확인하였다. 200 nm 두께의 BNT 박막은 XRD 분석을 통해 (117)방향에서 강한 피크가 나오며, (001) 방향에서 Nd 치환에 따른 효과로 억제된 피크가 나오는 것을 확인하였다. Pt/BNT/Pt 구조를 이용하여 잔류분극을 측정한 결과 7 V에서 $48\;{\mu}\;C/cm^2$ 이 나왔다. 이것은 다른 강유전체 물질인 PZT, SBT, BLT보다 월등히 큰 값이다.

• Korean Journal of Materials Research
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• v.12 no.6
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• pp.464-469
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• 2002

$SrBi_2Nb_2O_9(SBN)$ thin films were grown on Pt/Ti/Si and p-type Si(100) substrates by rf-magnetron co-sputtering method using two ceramic targets, $SrNb_2O_6\; and \;Bi_2O_3$. The structural and electrical characteristics have been investigated to confirm the possibility of the SBN thin films for the applications to destructive and nondestructive read out ferroelectric random access memory(FRAM). For the optimum growth condition X-ray diffraction patterns showed that SBN films had well crystallized Bi-layered perovskite structure after $700^{\circ}C$ heat-treatment in furnace. From this specimen we got remnant polarization $(2P_r)$ of about 6 uC/$\textrm{cm}^2$ and coercive voltage $(V_c)$ of about 1.5 V at an applied voltage of 5 V. The leakage current density was $7.6{\times}10^{-7}$/A/$\textrm{cm}^2$ at an applied voltage of 5V. And for the NDRO-FRAM application, properties of SBN films on Si substrate has been investigated. From transmission electron microscopy (TEM) analysis, we found the furnace treated sample had a native oxide about 2 times thicker than the RTA treated sample and this thick native oxide layer had a bad effect on C-V characteristics of SBN/Si thin film. After $650^{\circ}C$ RTA process, we got the improved memory window of 1.3 V at an applied voltage of 5 V.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.116-119
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• 2000

The a-axis and c-axis prefer oriented SBT thin films could be deposited on Pt(111)/Ti/$SiO_2$$650^{\circ}C$). The c-axis preferred orientation of SBT film can be obtained by Sr deficiency and high compressive stress. However, the a-axis-oriented grains can be formed under stoichiometric Sr content and nearly stress-free state.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.98-101
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• 2007

Yttrium(Y)-substituted bismuth titanate $(Bi_{4-x},Y_x)Ti_3O_{12}$ [x=0, 0.25, 0.5, 0.75, 1](BYT) thin films were deposited using an RF sputtering method on the $Pt/TiO_2/SiO_2/Si$ substrates. The structural properties and electrical properties of yttrium-substituted $(Bi_4-xYx)Ti_3O_{12}$ thin films were analyzed. The remanent polarization of $(Bi_4-xYx)Ti_3O_{12}$ films increased with increasing Y-content. The $(Bi_{3.25}Y_{0.75})Ti_3O_{12}$ films fabricated using a top Au electrode showed saturated polarization-electric field(P-E) switching curves with a remanent polarization(Pr) of $8{\mu}C/cm^2$ and coercive field (Ec) of 53 kV/cm at an applied voltage of 7 V. The $(Bi_{3.25}Y_{0.75})Ti_3O_{12}$ films exhibited fatigue-free behavior up to $4.5{\times}10^{11}$ read/write switching cycles at a frequency of 1MHz.