• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.133-133
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• 2003

최근에 강유전체 매체와 원자력 현미경 (Atomic Force Microscopy, AFM)을 이용한 초고밀도 정보 저장 장치에 대한 연구가 활발히 진행되고 있다. 이와 아울러 나도 크기의 도메인에 대하 연구에 있어서 PZT 박막의 분극 방향에 따른 SrRuO$_3$의 저항 변화를 AFM 탐침을 이용하여 감지하는 방법을 제안하였다. 본 연구에서는 Metal tip/semiconductor/barrier oxide/ferroelectric 구조에서 강유전체 분극에 의한 저항 변화의 가능성을 실험하고자, 이와 등가 구조인 Pt tip/n-Si/SiO$_2$ 구조에서 Pt 탐침과 반도체 층 사이의 I-V 특성을 측정함으로써, 게이트 전압에 따른 반도체 층의 저항변화에 대해서 분석해 보았다. 그 결과 게이트 전압에 따라서 과밀 지역 (accumulation layer)과 공핍 지역 (depletion layer)이 형성됨에 따라서 반도체 층의 정항이 변하여 I-V 특성이 변하게 됨을 관찰하였으며, 이 결과로부터 분극 방향에 따라서도 반도체 층의 저항이 변할 수 있음을 알 수 있었다.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.142-149
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• 2003

Domain switching effect on crack growth in ferroelectric ceramics under combined electric and mechanical loading is investigated. The shape and size of the switching zone is shown to depend strongly on the relative magnitude between the applied electric field and stress field as well as on the ratio of the coercive electric field to the yield electric field. The toughening mechanism is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. Crack-tip stress intensity factor induced by domain switching for the steady state crack growth is numerically obtained.

• Electrical & Electronic Materials
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• v.7 no.2
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• pp.152-156
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• 1994

The rapid thermal annealing effects of Sol-Gel derived ferroelectric PZT thin films were investigated. It was found that rapid thermal annealing(RTA) of spin coated thin films on silicon typically >$800^{\circ}C$ for about 1 min. was changed to the perovskite phase. Rapid thermally annealed films recorded maximum remanent polarization of about 5 .mu.C/cm$^{2}$, coercive field of around 30kV/cm. The switching time for polarization reversal was about 220ns. The films of RTA process showed smooth surface, and high breakdown voltages of over 1 MV/cm and resistivity of $1{\times}{10^12}$ .ohm.cm at 1 MV/cm. It was verified that the polarization reversal of the PZT film was varied partially with applying the multiple short pulse.

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.157-161
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• 2001

The observe relaxation phenomena and freezing behavior in Pb(Mg/sub ⅓/Nb/sub ⅔/O₃, relaxor ferroelectrics, weak electric-field properties as well as strong electric-field properties were investigated. The temperature dependence of the dielectric properties obtained using the low electric-field of 1 V/w was investigated. The dielectric properties obtained from the slope of the dielectric hysteresis loop and the temperature dependence of the pyroelectric properties were also investigated. When fitting all the experimental data with the Vogel-Filcher relation, a close agreement between the experimental data and equation was observed. The freezing temperature could be consistently calculated by the various methods.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.138-144
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• 2003

A crack in a ferroelectric ceramic subjected to an electric field is analyzed. The boundary of the electrical saturation zone is estimated based on the finite-width saturation zone model, which is analogous to a finite-width Dugdale zone model for mode III. It is shown that the shape and size of the switching zone depends strongly on the boundary of the electrical saturation zone and the ratio of the coercive electric field to the yield electric field. The crack tip stress intensity factor under small scale conditions is evaluated by employing the model of electric nonlinear domain switching. It is found that fracture toughness of the ferroelectric material may be increased or decreased depending on the material property of electrical nonlinearity.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1206-1210
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• 2003

Effect of transverse electric field on crack kinking in ferroelectric ceramics subjected to purely electric loading is investigated. It is shown that the shape and size of the domain switching zone depends strongly on the direction of the applied electric field as well as the ratio of the transverse electric field to the coercive electric field. Under small-scale conditions, mode I and II stress intensity factors induced by ferroelectric domain switching are numerically obtained. The crack kinking in ferroelectrics is also discussed.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.921-923
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• 1999

비휘발성 메모리의 고집적화와 적응학습형 뉴럴 소자의 실현을 위하여 1-트랜지스터 구조 강유전체 비휘발성 메모리(MFS-FET)를 SOI 기판위에 제작하고 평가하였다. 먼저 SBT($Sr_{0.8}Bi_{2.2}Ta_{2}O_{9}$)를 직접 Si위에 증착하고 C-V를 측정하여 1V의 메모리 윈도우를 얻음으로써 비휘발성 메모리로써의 동작가능성을 확인하였다. 또한 다양하게 게이트의 W/L 비를 바꾸어서 MFS-FET를 제작하여 다양한 드레인 전압-드레인 전류 특성을 얻었고 실제로 쓰기와 읽기 동작을 수행하여 MFS-FET가 비휘발성 메모리로써 제대로 동작하고 있음을 확인하였다.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.113-119
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• 2005

A crack emanating from an internal electrode or a conducting damage path in ferroelectric ceramic actuators is analyzed. The boundary of the domain switching zone near the edge of the internal electrode in a ceramic multilayer actuator is determined based on the nonlinear electric theory. The stress intensity factor induced by a ferroelectric domain switching under small scale conditions is numerically obtained for flaws of various sizes near the electrode edge. It is found that stress intensity factor near the crack tip depends on the material property of the electrical nonlinearity.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.120-125
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• 2005

Effect of transverse electric fields on fracture behavior in ferroelectric ceramics under purely electrical loading is investigated. It is shown that the shape and size of the domain switching zone depend strongly on the ratio of the transverse electric field to the coercive electric field as well as the direction of the applied electric field. Under small-scale conditions, the crack-tip mode I and II stress intensity factors induced by ferroelectric domain switching are numerically obtained. The crack kinking in ferroelectric ceramics is also discussed.