• Journal of Magnetics
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• 제16권4호
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• pp.427-430
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• 2011

The rolled steels for welded structure applied tensile stress have been examined by means of magnetic Barkhausen noise (MBN) method and of a physical parameter obtained from a hysteresis loop. The behaviors of MBN parameters and coercive force with tensile stress were discussed in relation to microstructure changes. There is no change in MBN parameters and coercive force below yield strength. The coercive force rises rapidly with tensile stress above yield strength. On the other hand, the rms voltage and the peak in averaged rms voltage take a maximum around yield strength and then decreases. The magnetomotive force at peak in the averaged rms voltage shows a minimum around yield strength. These phenomena are attributed to the combined effects of cell texture and dislocation density. In addition, the behaviors of MBN parameters around yield strength may be reflected by the localized changes in strain field due to the formation of dislocation tangles.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.48-55
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• 2024

The changes in threshold voltage and DIBL were investigated for changes in remanent polarization P_r and coercive field E_c, which determine the characteristics of the P-E hysteresis curve of ferroelectric in NCFET (negative capacitance FET). The threshold voltage and DIBL (drain-induced barrier lowering) were observed for a junctionless double gate MOSFET using a gate oxide structure of MFMIS (metal-ferroelectric-metal-insulator-semiconductor). To obtain the threshold voltage, series-type potential distribution and second derivative method were used. As a result, it can be seen that the threshold voltage increases when P_r decreases and E_c increases, and the threshold voltage is also maintained constant when the P_r/E_c is constant. However, as the drain voltage increases, the threshold voltage changes significantly according to P_r/E_c, so the DIBL greatly changes for P_r/E_c. In other words, when P_r/E_c=15 pF/cm, DIBL showed a negative value regardless of the channel length under the conditions of ferroelectric thickness of 10 nm and SiO₂ thickness of 1 nm. The DIBL value was in the negative or positive range for the channel length when the P_r/E_c is 25 pF/cm or more under the same conditions, so the condition of DIBL=0 could be obtained. As such, the optimal condition to reduce short channel effects can be obtained since the threshold voltage and DIBL can be adjusted according to the device dimension of NCFET and the P_r and E_c of ferroelectric.

• 전기학회논문지
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• 제60권6호
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• pp.1175-1177
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• 2011

The SBN thin films were deposited on Pt/Ti/$SiO_2$/Si and p-type Si(100) substrate by rf magnetron sputtering method using $Sr_{0.7}Bi_{2.3}Nb_2O_9$ ceramic target. SBN thin films deposited were annealed at 600~800[$^{\circ}C$] by furnace in oxygen atmosphere during 40min. The polarization characteristics have been investigated to confirm the possibility of the SBN thin films for the application to destructive read out ferroelectric random access memory. The maximum remanent polarization and the coercive voltage are 0.6[${\mu}C/cm^2$], 1.2[V] respectively at annealing temperature of 800[$^{\circ}C$]. The leakage current density was the $2.57{\times}10^{-6}[A/cm^2]$ at an applied voltage of 5[V] at annealing temperature of 650[$^{\circ}C$]. Also, the fatigue characteristics of SBN thin films did not change up to $10^8$ switching cycles.

• 한국결정성장학회지
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• 제12권3호
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• pp.157-160
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• 2002

The ferroelectric domain variation and electrical performance of $Pb(Zr,Ti)O_{3}$ (PZT) based capacitors through La additions were systematically studied. La substitution up to 10 % was performed to lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a (Ti_{0.9}Al_{0.1})N/Pt$ conducting barrier composite. Ferroelectric capacitors substituted with 10 % La show significantly lower coercive voltage compared to capacitors with 0 % and 3 % La. This is attributed to a systematic microstructure change into $180^{\circ}C$ domain and decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. These capacitors show promise as storage elements in low power memory architectures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.309-312
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• 2002

Ferroelectric $Sr_{0.3}Ba_{0.7}Nb_{2}O_{6}$ (SBN30) thin films were deposited on Pt/Ti/$SiO_{2}$/Si(100) substrates by ion beam sputtering. During annealing treatment at $750^{\circ}C$, poling was attempted by applying dc voltage bias across polished surfaces. Phase relation, microstructure and crystallization behavior were examined using XRD and FE-SEM. Ferroelectric hysteresis characteristics were also determined where both remanent polarization and coercive values decreased with the increase of bias voltage. The measured remanent polarization and coercive field values at 5 V and 10 V bias were $36{\mu}C/cm^2$, $10{\mu}C/cm^2$ and 100kV /cm, 80kV /cm, respectively.

• 한국응용과학기술학회지
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• 제35권4호
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• pp.1206-1212
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• 2018

본 연구에서는 강유전성 고분자를 이용하여 제작된 100 nm 이하 두께를 가지는 박막형 커페시터의 측정 주파수에 따른 분극 반전 특성을 측정, 분석하였다. 고정된 박막 두께에 대해, 인가되는 최고 전기장의 세기가 증가할수록 더 높은 항전계에서 분극 반전이 발생되었다. 고정된 최고 전기장에 대해, 박막의 두께에 무관하게 같은 항전계에서 분극 반전이 발생되었다. 모든 측정에서 로그스케일 전기장 및 로그스케일 주파수의 관계에서 약 $0.12{\pm}0.01$의 비례 상수를 보였다. 결과적으로, 강유전체 고분자 커페시터가 40 nm 두께까지는 size effect 없이 일정한 분극 반전 특성을 보였다. 본 연구는 저전압 동작 고분자 메모리 소자의 동작 예측에 유용할 것이므로 저전압에서 동작 가능한 고분자 메모리 소자의 가능성을 보여준다.

• 한국표면공학회지
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• 제35권3호
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• pp.127-132
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• 2002

High speed performance of ferroelectric Pb(Zr,Ti)$O_3$ (PZT) based capacitors is reported. La substitution up to 10% was performed to systematically lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a ($Ti_{0.9}$ /$Al_{0.1}$ )N/Pt conducting barrier composite. Ferroelectric capacitors substituted with 10% La show significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to a systematic decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. Furthermore, the samples doped with 10% La showed dramatically better retention and pulse width dependent polarization compared to the capacitors with 0% and 3% La. These capacitors show promise as storage elements in low power high density memory architectures.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.35-35
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• 2003

Recent progress in the integration of the ferroelectric random access memories (FRAM) has attracted much interest. Strontium bismuth tantalate(SBT) is one of the most attractive materials for use in nonvolatile-memory applications due to low-voltage operations, low leakage current, and its excellent fatigue-free property. High-density FRAMs operated at a low voltage below 1.5V are applicable to mobile devices operated by battery. SBT films thinner than 0.1 #m can be operated at a low voltage, because the coercive voltage (Vc) decreases as the film thickness is reduced. In addition, the thickness of the SBT film will have to be reduced so it can fit between adjacent storage nodes in a pedestal type capacitor in future FRAMs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.478-480
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• 2001

Fe-base amorphous films exhibit large saturation magnetostriction and soft magnetic Properties, which make them suitable for strain sensor applications. Most important material properties for the performance of these elements are the superior soft magnetic properties, such as high permeability and small coercive force, as well as magnetoelastic properties. It is well known that the strain generated in film deposition and/or post-heat treatment processes is one of important material properties, which effects on the soft magnetic properties of the film via magnetoelastic coupling. In this study, the effect of an isotropic strain in plane of magnetic films have been performed experimently. Amorphous films with the composition of (F $e_{90}$ $Co_{10}$)$_{78}$S $i_{l2}$ $B_{10}$ were employed in this study. The film with 5${\mu}{\textrm}{m}$ thick was deposed onto the polyimide substrate with 50${\mu}{\textrm}{m}$ thick by virtue of RF sputtering. The film was subject to post annealing with a static magnetic field with 500Oe magnetic field intensity at 35$0^{\circ}C$ for 1 hour. The polyimide substrate with the film was bonded with an adhesive on PZT piezoelectric substrate with 600${\mu}{\textrm}{m}$ thick in applying voltage of 500V. The change in MH loops of films due to the isotropic strain was measured by using VSM. The coercive force was evaluated from MH loops. It has shown in the results that M-H loops of films are subject to change considerably with a dc voltage, resulting of the magnetization rotation from normal to plane direction as the applied voltage is changed from 500V to 250V.50V.V.

• 한국진공학회지
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• 제7권3호
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• pp.195-200
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• 1998

본 연구에서는 강유전체 박막의 게이트 산화물로 사용한 $Pt/SrBi_2Ta_2O_9(SBT)/CeO_2/Si(MFS)$와 Pt/SBT/Si(MFS) 구조의 결정 구조 및 전기적 성질 의 차이를 연구하였다. XRD 및 SEM 측정 결과 SBT/$CeO_2$/Si박막은 약5nm정도의 $SiO_2$층 이 형성되었고 비교적 평탄한 계면의 미세구조를 가지는 반면, SBT/Si는 각각 약6nm와 7nm정도의 $SiO_2$층과 비정질 중간상층이 형성되었음을 알 수 있다. 즉 CeO2 박막을 완충층 으로 사용함으로써 SBT박막과 Si기판의 상호 반응을 적절히 억제할 수 있음을 확인하였다. Pt/SBT/$CeO_2/Pt/SiO_2$/와 Pt/SBT/Pt/$SiO_2$/Si구조에서 Polarization-Electric field(P-E) 특 성을 비교해 본 결과 CeO2박막의 첨가에 따라 잔류분극값은 감소하였고 항전계값은 증가하 였다. MFIS구조에서 memory window값은 항전계값과 직접적 관련이 있으므로 이러한 항 전계값의 증가는 MFIS구조에서의 memory window값이 증가할 수 있음을 나타낸다. Pt-SBT(140nm)/$CeO_2$(25nm)/Si구조에서 Capacitance-Voltage(C-V) 측정 결과로부터 동작 전압 4-6V에서 memory wondows가 1-2V정도로 나타났다. SBT박막의 두께가 증가할수록 memory window값은 증가하였는데 memory wondows가 1-2V정도로 나타났다. SBT박막의 두께가 증가할수록 memory window값은 증가하였는데 이는 SBT박막에 걸리는 전압강하가 증가하기 때문인 것으로 생각되어진다. Pt/SBT/$CeO_2$/Si의 누설전류는 10-8A/cm2정도였고 Pt/SBT/Si 구조에서는 약10-6A/cm2정도로 약간 높은 값을 나타내었다.