• Electrical & Electronic Materials
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• v.8 no.3
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• pp.261-266
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• 1995

In this study, PZT solutions added impurities of Yttrium acetate were prepared by sol-gel processing and were deposited on Pt/ $SiO_{2}$/Si substrates at 5000 rpm for 20 sec. using spin-coating method. Coated films were annealed at 700-750.deg. C for 30 min. using conventional furnace method. Variations of the crystallographic structure and microstructure of PZT thin films with adding impurities were observed using XRD and SEM, and the electrical properties, such as relative permittivity, tan .delta., hysteresis curves and leakage currents, were measured. As the yttrium contents were increased, the remanent polarization and coercive field were decreased. Variations of remanent polarizations and coercive fields of pure and yttrium doped specimens according to polarization reversal cycles were observed using hysteresis measurement. PZT thin films added $Y^{3+}$ ions were completely crystallized at 750.deg. C. $Y^{3+}$ ions, as donor impurity, substituted Pb.sup 2+/ ions located at A-site of perovskite structure. By substitution of $Y^{3+}$ ions, leakage currents became less by decreasing the space charges. Degradation of remanent polarizations of Yttrium added specimens after fatigue was not observed and coercive fields increased more than those of pure PZT thin films.

• Journal of the Korean Ceramic Society
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• v.37 no.10
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• pp.975-980
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• 2000

스테인레스 스틸 기판 위에 Pb($Zr_{0.45}$ $Ti_{0.55}$) $O_3$후막을 졸-겔 스핀 코팅법으로 제조하였다. 스테인레스 스틸은 그 자체로 좋은 도체이지만 PZT 후막의 강유전 특성을 개선하고자 Ru $O_2$박막을 중간층 겸 하부전극으로 사용하였다. PZT 전구체 용액을 코팅하고 급속 열처리하였을 때 5$50^{\circ}C$ 이하에서 pyrochlore 상이 먼저 나타났고 이 transient 상은 61$0^{\circ}C$에서 모두 perovskite 상으로 변화하였다. $600^{\circ}C$에서 열처리된 PZT 후막은 잔존하는 pyrochlore로 인해 걸어준 전기장에 무관하게 5-7$\mu$C/$ extrm{cm}^2$의 낮은 $P_{r}$값을 나타내었으나 61$0^{\circ}C$ 이상에서 열처리된 시편들은 모두 25$\mu$C/$\textrm{cm}^2$ 이상의 잔류분극을 가지고 있었다. 또한 Ru $O_2$중간층이 PZT의 강유전성에 미치는 영향을 조사하였을 때 잔류분극 값은 거의 영향을 받지 않았으나 항전계 값은 상당한 영향을 받았다. 즉 100nm 두께의 Ru $O_2$박막을 중간층으로 사용할 경우 중간층 없이 직접 스테인레스 스틸 위에 코팅할 때에 비해 항전계 값을 45% 가량 줄일 수 있었다.

• Electrical & Electronic Materials
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• v.8 no.5
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• pp.606-610
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• 1995

In this study, Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_{3}$ ceramic thin films were fabricated from an alkoxide-based by Sol-Gel method. Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_{3}$ stock solution was made and spin-coated on the Pt/ $SiO_{2}$/Si substrate at 4000[rpm] for 30[sec.]. Coated specimens were chied at 400[.deg. C] for 10[min]. The coating process was repeated 6 times and then heat-treated at 500-800[.deg. C] and 1 hour. The final thickness of the thin films were about 4800[.angs.]. The ferroelectric perovskite phases precipitated under the sintering of 700[.deg. C] for 1 hour. Pb(Z $r_{0.52}$ $Ti_{0.48}$) $O_{3}$ thin films sintered at 700[.deg. C] for 1 hour showed good dielectric and ferroelectric properties.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.91-97
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• 2004

PBT thin films were formed by rf-magnetron sputtering on $Pt/Ti/SiO_2/Si$ substrate. Bulk-PZT target containing $5\%$-excess PbO was used. After PZT thin films had been deposited at room temperature, remaining portion of the thin film was formed by in-situ process. The ferroelectric perovskite phase was formed at $650^{\circ}C$. The leakage current property was improved dramatically by 2-step sputtering, and in the sample containing optimum thickness of room temp.-layer very low leakage current of $2{\times}10^{-7}A/cm^2$ was shown. As a result of the investigation on the leakage current mechanism, the electrical conduction mechanism in all PZT thin films formed by several conditions was confirmed as bulk-limited mechanism.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.191-194
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• 1999

Switching behaviour of the ferroelectric thin film and device characteristics of the MFSFET (Metal-Ferroelectric-Semiconductor FET) are simulated with taking into account the accumulation of oxygen vacancies near interface between the ferroelectric thin film and the bottom electrode caused by the progress of fatigue. We show net switching current decreases due fatigue in the switching model. It indicates that oxygen vacancy strongly suppresses polarization reversal. The difference of saturation drain current of the device before fatigue is shown by the dual threshold voltages in I$_{D}$-V$_{D}$ curve as 6㎃/$\textrm{cm}^2$ and decreases as much as 50% after fatigue. Our simulation model is expected to play an important role in estimation of the behavior of MFSFET device with various ferroelectric thin films.lms.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.141-146
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• 2009

PLZT ferroelectric thin films were deposited on Pt/Ti/$SiO_2$/Si substrate with $TiO_2$ buffer layer in between by rf magnetron sputtering method. In order to investigate the effect of Ar/$O_2$ partial pressure ratio on the ferroelectric properties of PLZT thin films, PLZT thin films were deposited at various Ar/$O_2$ partial pressure ratio ; 27/1.5 seem, 23/5.5 seem, 21/7.5 seem and 19/9.5 seem. The crystallinities of PLZT thin films were analyzed by XRD. The surface morphology was observed using FE-SEM. The P-E hysteresis loops, the remanent polarization characteristics and the leakage current characteristics were obtained using a Precision LC. The crystallinity and elaborateness of PLZT thin films were decreased as increasing the oxygen partial pressure ratio. And preferred orientation of PLZT thin films changed from (110) plane to (111) plane. The oxygen partial pressure ratio affects the thin film surface morphology and the ferroelectric properties.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.211-211
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• 2003

PbTiO$_3$ 씨앗층을 이용하여 완화형 강유전체 Pb(Mg$_{1}$3/Ta$_{2}$3/)O$_3$ (PMT) 박막의 페로브스카이트 상안정화와 열처리 조건에 따른 미세구조변화, 이에 따른 전기적 특성 변화에 관하여 조사하였다. PbTiO$_3$ 박막을 스핀코팅법으로 3000 rpm에서 20초간(111) 방향으로 배향된 Pt / Ti / SiO$_2$/ Si 기판에 증착하여 안정화된 페로브스카이트 박막을 얻었다. 이렇게 제조된 PbTiO$_3$를 Buffer 층으로 사용하고 그 위에 Pb(Mg$_{1}$3/Ta$_{2}$3/)O$_3$를 박막을 Spin coating방법으로 증착한 후, 급속열처리 방법(RTA)으로 550- $650^{\circ}C$ 사이에서 열처리하였다. 제조된 박막의 열처리 온도에 따른 미세구조 변화와 결정성을 XRD, SEM, TEM으로 분석하였고 박막의 저온 강유전 특성을 RT66A를 이용하여 평가하였다. Pb(Mg$_{1}$3/Ta$_{2}$3/)O$_3$ 박막의 경우 씨앗층이 없는 경우에는 pyrochlore상이 주상이었지만 씨앗층을 사용한 경우 페로브스카이트 상이 주상임을 확인하였고 열처리 온도가 증가할수록 페로브스카이트상의 상대적 양이 증가함을 확인하였다. 미세구조와 상의 변화에 따른 전기적 특성 변화에 관하여 자세하게 논의할 것이다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.225-225
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• 2008

PLZT 박막을 Pt/Ti/$SiO_2$/Si 기판 위에 RF-마그네트론 스퍼터링방법으로 형성할 때 기판온도에 따른 PLZT 박막의 결정성과 전기적 특성 및 강유전 특성에 미치는 영향에 관하여 연구하였다. 하부전극 Pt와 PLZT 박막 사이에는 완충층으로 $TiO_2$를 사용하여 계면에서의 상호확산을 제어하면서 우수한 물성의 PLZT 박막을 얻고자 하였으며, 여러 기판온도에서 PLZT 박막을 증착한 후, 박막의 결정화를 위해 급속열처리법으로 $700^{\circ}C$로 후열처리하였다. 그 결과 기판온도 $400^{\circ}C$에서 증착한 PLZT 박막이 가장 우수한 특성을 나타내었으며, 이때의 잔류분극과 누설전류밀도는 각각 15.8 ${\mu}C/cm^2$, $5.4\times10^{-9}A/cm^2$ 이였다. 그러나 $500^{\circ}C$에서는 결정립 조대화현상이 나타나면서 잔류분극과 누설전류밀도는 9 ${\mu}C/cm^2$, $3.09\times10^{-7}A/cm^2$로 특성이 저하되었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.489-493
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• 2004

[ $Ba_2NaNb_5O_{15}$ ]은 orthorhombic tungsten bronze 결정구조를 갖는 강유전체로서, 단결정의 경우 $LiNbO_3$에 비해 우수한 비선형 전광계수 값을 나타내는 것으로 알려져 있으며, 또한 주목할만한 초전, 압전, 강유전특성을 나타내고 있다. 본 연구에서는 다른 강유전체박막에 비하여 상대적으로 연구가 덜 이루어진 BNN 박막을 세라믹 타겟을 사용하여 이온빔 보조 증착법을 사용하여 제조하였으며, $Ar/O_2$ 분위기에서 증착된 BNN 박막에 대한 결정화 및 배향 특성을 고찰하였고, 이에 따른 전기적 특성의 변화를 살펴보았다. 연구에 사용된 기판은 $Pt(100)/TiO_2/SiO_2/Si(100)$이었으며, 이온빔 보조 증착법에서 보조 이온빔의 에너지를 $0{\sim}400eV$로 변화 시키며 BNN 박막을 증착한 후, 열처리하였다. BNN 박막의 전기적 특성은 MFM 박막 커패시터의 형태로 제조하여 강유전 특성에 대해 살펴보았다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.6
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• pp.252-258
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• 2001

($Ba_{0.7}Sr_{0.3})TiO_3$thin films were perpared on ITO-coated glass substrate by spin-coating method. The sol was sonicated in an ultrasonic bath to promote homogenization and the results were compared with untreated case. By application of the sonication process, crystallization temperatures of films were reduced, microstructers of films were more uniform and denser and the surface roughness of the films was lower from 8.4nm to 5.6nm. In addition, optical transmittances and electrical properties of films prepraed from sonicated sol were superior to those of films from untreated.