• Title/Summary/Keyword: ferroelectricity

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Phase Evolution Behavior of Multiferroic (Bi,Nd)(Fe,Ti)$O_3$ Ceramics and Thin Films ((Bi,Nd)(Fe,Ti)$O_3$ 다강체 세라믹 및 박막의 상변화 거동)

  • Kim, Kyung-Man;Yang, Pan;Lee, Jai-Yeoul;Lee, Hee-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.11a
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    • pp.231-232
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    • 2008
  • The coupling between electric, magnetic, and structural order parameters results in the so-called multiferroics, which possess ferroelectricity, ferromagnetism, and/or ferroelasticity. The simultaneous ferroelectricity and ferromagnetism (magnetoelectricity) allow potential applications in information storage, spintronics, and in magnetic or electric field sensors. Perovskite compound $BiFeO_3$ (BFO) is antiferromagnetic below Neel temperature of 647K and ferroelectric with a high Curie temperature of 1043K. It exhibits weak magnetism at room temperature(RT) due to the residual moment from a canted spin structure. It is likely that non-stoichiometry and second-phase formation are the factors which cause leakage in BFO. It has been suggested that oxygen non-stoichiometry leads to valence fluctuations of Fe ions in BFO, resulting in high conductivity. To reduce the large leakage current of BFO, one attempt is fabricating donor doped BFO compounds and thin films. We report here the successful fabrication of the Nd, Ti co-doped $BiFeO_3$ ceramics and thin films by pulsed laser deposition technique.

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In-situ Growth of Epitaxial PbVO3 Thin Films under Reduction Atmosphere

  • Oh, Seol Hee;Jin, Hye-Jin;Shin, Hye-Young;Shin, Ran Hee;Yoon, Seokhyun;Jo, William;Seo, Yu-Seong;Ahn, Jai-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.361.1-361.1
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    • 2014
  • PbVO3 (PVO), a polar magnetic material considered as a candidate of multiferroic, has ferroelectricity along the c-axis and 2-dimensional antiferromagnetism lying in the in-plane through epitaxial growth [1,2]. PVO thin films were grown on LaAlO3 (001) substrates under reduction atmosphere from a stable Pb2V2O7 sintered target using pulsed laser deposition method. Epitaxial growth of the PVO films is possible only under Ar atmospheren with no oxygen partial pressure. X-ray diffraction was used to investigate the phase formation and texture of the films. We confirmed epitaxial growth of the PVO films with crystalline relationship of PbVO3[001]//LaAlO3[001] and PbVO3[100]//LaAlO3[100]. In addition, surface morphology of the films displays drastic changes in accordance with the growth conditions. Elongated PVO grains are related to the Pb2V2O7 pyrochlore structure. The relation between structural deformation and ferroelectricity in the PVO films was examined by local measurement of piezoresponse force microscopy.

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A study on measurement apparatus for ferroelectricity in ferroelectrics (강유전특성 측정장치의 연구개발)

  • Lee, Chang-Hun;Kang, Dae-Ha
    • Proceedings of the KIEE Conference
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    • 1997.07d
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    • pp.1317-1319
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    • 1997
  • This paper is to study and develope a measurement apparatus for ferroelectricity. The apparatus consists of wave generation part, high voltage amplifier part, measurement part, data acquisition part and the related controll circuits. Single or double excitation wave is digitalized and sent to the external RAM of wave generation part by personal computer. These datas saved in the RAM are converted to analog excitation wave through D/A converter. The frequency of excitation wave is depend on the read-out speed of the RAM by clock pulse. Such generated wave is applied to high voltage amplifier as a input voltage. The output of high voltage amplifier is applied to ferroelectrics and the response is obtained from the charge amplifier of measurement part. The response is sampled and converted to digital datas through AID converter. These digital datas are automatically saved in the external RAM of acquisition part. The computer takes the digital datas and calculates the electric displacement D, the electric field and the dielectric constant $\varepsilon$. We tested for PZT ceramic sample and could observed the D-E hysteresis lops and ${\varepsilon}_s$-E hysteresis loops with good forms.

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Review on Atomic Layer Deposition of HfO2-based Ferroelectrics for Semiconductor Devices (반도체 소자용 산화하프늄 기반 강유전체의 원자층 증착법 리뷰)

  • Lee, Younghwan;Kwon, Taegyu;Park, Min Hyuk
    • Journal of the Korean institute of surface engineering
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    • v.55 no.5
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    • pp.247-260
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    • 2022
  • Since the first report on ferroelectricity in Si-doped hafnia (HfO2), this emerging ferroelectrics have been considered promising for the next-generation semiconductor devices with their characteristic nonvolatile data storage. The robust ferroelectricity in the sub-10-nm thickness regime has been proven by numerous research groups. However, extending their scalability below the 5 nm thickness with low temperature processes compatible with the back-end-of-line technology. In this review, therefore, the current status, technical issues, and their potential solutions of atomic layer deposition (ALD) of HfO2-based ferroelectrics are comprehensively reviewed. Several technical issues in the physical scaling of the ferroelectric thin films and potential solutions including advanced ALD techniques including discrete feeding ALD, atomic layer etching, and area selective ALD are introduced.

Angle-resolved photoemission spectrscopy for chalcogenide and oxide heterostructures (칼코겐화물과 산화물 이종구조의 각도분해능 광전자분광 연구)

  • Chang, Young Jun
    • Vacuum Magazine
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    • v.5 no.2
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    • pp.10-17
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    • 2018
  • Chalcogenide and oxide heterostructures have been studied as a next-generation electronic materials, due to their interesting electronic properties, such as direct bandgap semiconductor, ferroelectricity, ferromagnetism, superconductivity, charge-density waves, and metal-insulator transition, and their modification near heterointerfaces, so called, electronic reconstruction. An angle-resolved photoemission spectroscopy (ARPES) is a powerful technique to unveil such novel electronic phases in detail, especially combined with high quality thin film preparation methods, such as, molecular beam epitaxy and pulsed laser deposition. In this article, the recent ARPES results in chalcogenide and oxide thin films will be introduced.

Phase Evolution Behavior of (Bi,Nd)(Fe,Ti)$O_3$ Ceramics and Thin Films

  • Kim, Kyung-Man;Byun, Seung-Hyun;Yang, Pan;Lee, Yoon-Ho;Lee, Jai-Yeoul;Lee, Hee-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.331-332
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    • 2008
  • Couplings between electric, magnetic, and structural order parameters result in the so-called multiferroic phenomena with two or more ferroic phenomena such as ferroelectricity, ferromagnetism, or ferroelasticity. The simultaneous ferroelectricity and ferromagnetism (magnetoelectricity) permits potential applications in information storage, spintronics, and magnetic or electric field sensors. The perovskite BiFeO3(BFO) is known to be antiferromagnetic below the Neel temperature of 647K and ferroelectric with a high Curie temperature of 1043K. It exhibits weak magnetism at room temperature due to the residual moment from a canted spin structure. It is likely that non-stoichiometry and second-phase formation are the factors responsible for leakage current in BFO. It has been suggested that oxygen non-stoichiometry leads to valence fluctuations of Fe ions in BFO, resulting in high conductivity. To reduce the large leakage current of BFO, one attempt is to make donor-doped BFO compounds and thin films. In this study, (Bi1-x,Ndx)(Fe1-y,Tiy)O3 thin films have been deposited on Pt(111)/TiO2/SiO2/Si substrates by pulsed laser deposition. The effect of dopants on the phase evolution and surface morphology are analyzed. Furthermore, electrical and magnetic properties are measured and their coupling characteristics are discussed.

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Room-Temperature Ferromagnetic Behavior in Ferroelectric BiFeO3-BaTiO3 System Through Engineered Superexchange Path (초교환 상호작용 제어를 통해 강유전 BiFeO3-BaTiO3 시스템에서 유도된 상온 강자성 거동)

  • Ko, Nu-Ri;Cho, Jae-Hyeon;Jang, Jongmoon;Jo, Wook
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.5
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    • pp.386-392
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    • 2021
  • Multiferroics exhibiting the coexistence and a possible coupling of ferromagnetic and ferroelectric order are attracting widespread interest in terms of academic interests and possible applications. However, room-temperature single-phase multiferroics with soft ferromagnetic and displacive ferroelectric properties are still rare owing to the contradiction in the origin of ferromagnetism and ferroelectricity. In this study, we demonstrated that sizable ferromagnetic properties are induced in the ferroelectric bismuth ferrite-barium titanate system simply by introducing Co ions into the A-site. It is noted that all modified compositions exhibit well-saturated magnetic hysteresis loops at room temperature. Especially, 70Bi0.95Co0.05FeO3-30Ba0.95Co0.05TiO3 manifests noticeable ferroelectric and ferromagnetic properties; the spontaneous polarization and the saturation magnetization are 42 µC/cm2 and 3.6 emu/g, respectively. We expect that our methodology will be widely used in the development of perovskite-structured multiferroic oxides.

Electrical Properties SBT capacitor with post-annealing (후속 열처리 온도에 따른 SBT 커패시터의 전기적 특성)

  • 조춘남;김진사;신철기;최운식;박용필;김충혁;이준웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.07a
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    • pp.672-675
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    • 2001
  • The Sr$\sub$0.8/Bi$\sub$2.4/Ta$_2$O$\sub$9/(SBT) thin films are deposited on Pt-coated electrode(Pt/TiO$_2$/SiO$_2$/Si) using RF magnetron sputtering method. With increasing annealing tempera ture from 600[$^{\circ}C$] to 850[$^{\circ}C$], Bi-layered perovskite phase was crystallized above 650[$^{\circ}C$]. The maximum remanent polarization and the coercive electric field is 11.60[${\mu}$C/$\textrm{cm}^2$], 48[kV/cm] respectively. The dielectric constant and leakage current density is 213, 1.01${\times}$10$\^$-8/ A/$\textrm{cm}^2$ respectively at annealing temperature of 750[$^{\circ}C$].

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Degradation of Ferroelectric Properties of Pt/PZT/Pt Capacitors in Hydrogen-containing Environment

  • Kim, Dong-Chun;Lee, Won-Jong
    • Transactions on Electrical and Electronic Materials
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    • v.6 no.5
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    • pp.214-220
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    • 2005
  • The ferroelectric properties of the $Pt/PZT(Pb(Zr,Ti)O_3)/Pt$ capacitors are severely degraded when they are annealed in hydrogen-containing environment. Hydrogen atoms created by the catalytic reaction of Pt top electrode during annealing in hydrogen ambient penetrate into PZT films and generate oxygen vacancies by the reduction of the PZT films, which is likely to cause the degradation. The degree of hydrogen-induced degradation and the direction of voltage shift in P-E curves of the pre-poled PZT capacitors after annealing in hydrogen ambient is dependent on the polarity of the pre-poling voltage. This implies that oxygen vacancies causing hydrogen induced degradation are generated by hydrogen ions having a polarity. The degraded ferroelectricity of the PZT capacitors can be effectively recovered by the shift of oxygen vacancies toward the Pt top electrode interface during post-annealing in oxygen environment with applying negative unipolar stressing.