• Korean Journal of Materials Research
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• v.7 no.8
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• pp.646-649
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• 1997

(111)과 (100)우선방위의 정방정계의 Pb(Zr$_{0.2}$, Ti$_{0.8}$)O$_{3}$박막의 강유전체 특성과 신뢰성특성을 상부 전극의 두께를 변화시키면서 연구하였다. (111)우선방위의 박막이 (100)우선방위의 박막보다 큰 잔류분극과 항전계 값을 갖고 있어 정방형의 이력곡선 특성을 보여주었다. 스위칭전하의 상부전극의 두께 의존성은 상부전극을 열처리 할 때 유도되는 압축응력에 의한 stress효과로 설명할 수 있었다. 상부전극의 두께가 얇은 박막은 초기에는 작은 스위칭 전하를 갖고 있으나 스위칭 횟수가 증대됨에 따라 기계적인 응력의 감소로 인하여 부분 수위칭 영역이 확대되어 내구성이 향상되었다.

• Journal of the Korean Vacuum Society
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• v.13 no.4
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• pp.145-149
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• 2004

We have grown piezoelectric oxide films by RF magnetron sputtering using miscut substrates. Films were Brown on(001) $SrTiO_3$ substrates with miscut angles from 0 to 8 degrees toward the (100) direction. Films on high miscut substrates (>$4^{\circ}$) showed almost the pure perovskite phase in x-ray diffraction and were nearly stoichiometric. In contrast, films on exact (001) $SrTiO_3$ contained a high volume fraction of pyrochlore phases. A film on an $8^{\circ}$ miscut substrate exhibits a polarization hysteresis loop with a remnent polarization of 20$\mu$C/$\textrm{cm}^2$ at room temperature.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.159-165
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• 2005

Shot peening can be defined as the process of work hardening of the surface of components by means of propelled stream of spherical shot. Benefits due to shot peening are increase in resistance to fatigue, stress corrosion cracking, fretting, galling, erosion and closing of pores. In this study, the influence of shot peening on the corrosion was investigated on spring steel immersed in $3.5\%\;NaCl$. The immersion test was performed on the two kinds of specimens. Corrosion potential, polarization curve, residual stress and etc. were investigated from experimental results. From test results, the effect of shot peening on the corrosion was evaluated. The important results of the experimental study on the effects of shot peened spring steels on the environment corrosion are as follows; In case of corrosion potential, shot peened specimen shows more activated negative direction as compared with parent metal. Surface of specimen, which is treated with the shot peened, is placed as more activated state against inner base metal. It can cause the anti-corrosion effect on the base metal.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.983-988
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• 1997

We investigated the structural and dielectric properties of PZT(20/80)/PZT(80/20) heterolayered thin films that fabricated by the alkoxide-based Sol-Gel method. PZT(20/80)/PZT(80/20) heterolayered thin films were spin-coated on the Pt/Ti/SiO$_2$/Si substrate with PZT(20/80) film of tetragonal structure and PZT(80/20) film of rhombohedral structure by turns. Each layers were dried to remove the organic materials at 30$0^{\circ}C$ for 30min and sintered at $650^{\circ}C$ for 1hr. This procedure was repeated several times to form PZT(20/80)/PZT(80/20) heterolayered films and thickness of the film obtained by one-times of drying/sintering process was approximately 80-90nm. PZt-1, 3, 5 films with top layer of PZT(20/80) film of tetragonal structure showed fine grain structure and PZT-2, 4, 6 films with top layer of PZT(80/20) film of rhombohedral structure showed the dense grain microstructure without rosette-type. Dielectric constant and dielectric loss of the PZT-6 film were approximaterly 1385 and 3.3% respectively. Increasing the number of coatings remanent polarization was increased and coercive field was decreased and the values of the PZT-6 film were 8.13$\mu$C/cm$^2$and 12.5kV/cm respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.1-8
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• 2000

Fatigue and data retention characteristics of the Pt/PZT/Pt structure using single grain PZT thin films by PZT seeding method were investigated. In case of fatigue, there is no loss in switched polarization up to 2$\times$10$^{11}$ cycles using 1MHz square wave form at $\pm$10V and no data loss after 30000sec of memory retention at room temperature. From the activation energy measured at high temperatures, the time required 20% loss in remanent polarization is estimated to be 6.6$\times$10$^{7}$ years at room temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.2
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• pp.143-150
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• 2000

Ferroelectric SrxBi2+yTa2O9+$\alpha$ thin films with various compositions(x=0.7, 0.8, 1, y=0.3, 0.4) were prepared by sol-gel method. The film with moled ratio of 0.8:2.3:2.0 in Sr/Bi/Ta, which was deposited on Pt/SiO2/Si (100), showed better ferroelectric properties than other films. To investigate substrate effects, the same compositions were spin coated on Pt/Ti/SiO2/Si (100) substrates. At an applied voltage of 5V, the dielectric constant($\varepsilon$r), remanent polarization (2Pr) and coercive field (Ec) of the Sr0.8Bi2.3Ta2O9+$\alpha$ thin film prepared on Pt/Ti/SiO2/Si (100) were about 296, 24$\mu$C/$\textrm{cm}^2$ and Ec of 49kV/cm respectively. Both SBT films firred at 80$0^{\circ}C$ revealed no fatigue up to 1010 cycles. Retention characteristics of these capacitors showed no degradation up to 104 sec.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.204-205
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• 2007

Self-seed 층을 이용한 PLZT(9/65/35), 강유전체 박막을 Sol-Gel 법을 이용해 Pt/Ti/$SiO_2$/Si 기판 위에 증착한 후, Self-seed 층에 의한 PLZT(9/65/35) 박막의 구조적, 전기적 특성을 고찰하였다. Seed 층을 도입하지 않은 PLZT 박막의 경우 다결정 상으로 형성되는 것을 알 수 있었으며, seed 층을 도입한 PLZT 박막은 (110) 방향으로 우선 배향됨을 알 수 있었다. 증착된 PLZT(9/65/35) 박막의 유전율 및 유전손살은 10kHz에서 유전율 205, 유전손살 0.029 이었으며, Self-seed layer를 도입한 PLZT 박막의 경우 seed layer를 도입하지 않은 PLZT 박막보다 낮은 온도에서 결정화 되는 것을 관찰 할 수 있었다. Self-seed layer가 도입된 PLZT(9/65/35) 박막의 경우 잔류분극 ($P_r$) 값은 $9.1{\mu}C/cm^2$, 항전계($E_c$)는 47 kV/cm을 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.139-140
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• 2006

PZT박막은 비휘발성 재료로 유전율이 높고 항전력이 작으면서 잔류 분극랑이 크기 때문에 적합한 특성을 가지고 FeRAM에 매력적인 물질이다. CMP(chemical mechanical polishing)는 기존의 회생막의 전면 식각 공정과는 달리 특정 부위의 제거 속도를 조절함으로써 평탄화 하는 기술로 wafer 전면을 회전하는 탄성 패드 사이에 액상의 Slurry를 투입하여 연마하는 기술이다. 본 논문에서는 CMP 공정으로 제조한 PZT박막 캐패시터에서 CMP 후처리공정(세척)의 유무 및 종류에 따라 피로특성에 대하여 연구하였다, PZT 박막의 캐패시터의 피로 특성을 연구한 결과 CMP 후처리공정 SC-l용액을 사용하여 세정공정을 하였을때 가장 향상된 PZT 캐패시터의 피로특성이 나타났다.

• Proceedings of the Korean Vacuum Society Conference
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• 1996.06a
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• pp.180-181
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• 1996

적외선 센서의 재료로 활용되고 있는 ppLT 박막(두께:8000~9000$\AA$)을 ppt/MgO(100)의 하부 구조상에 50$0^{\circ}C$ 및 $600^{\circ}C$에서 스퍼터링 증착하여 결정성 및 전기적 특성을 조사하였다. $600^{\circ}C$로 in-situ 성장된 ppLT 박막은 c-축(00l) 방향으로 배향 성장되었 고, 비유전상수(r)와 유전정접(tan)의 값이 10kHz~100kHz의 주파수에서 $\varepsilon$r≒35와 tan$\delta$≒ 0.01로 나타났다. 잔류분극량(2ppr)과 초전계수(${\gamma}$)는 상온부근에서 2ppr≒5$\mu$C/cm2, ${\gamma}$≒4$\times$ 10-8C/cm2.$^{\circ}C$로 비교적 양호한 초전박막의 전기적 특성을 나타내었다.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.39-45
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• 2003

Shot peening is an effective method of improving the fatigue strength of components and structures. The compressive residual stress produced by surface plastic deformation with shot peening is usually regarded as the major factor in increasing fatigue strength. In this study, the influence of shot peening on corrosion was investigated. Spring steel immersed in $3.5\%$ NaCl prior was used to evaluate the effect of shot peening on fatigue properties. The immersion test was performed on the five kinds of specimens with shot peened and unpeened. The distributions of residual stresses of shot peened spring steels were measured in an X-ray diffraction apparatus, using the two-point method. Corrosion potential, polarization curve, residual stress, etc. were investigated, based on the experimental results. From test results, the effect of shot peening on the corrosion was evaluated.