• Title/Summary/Keyword: I-V polarization

Search Result 120, Processing Time 0.034 seconds

Ferroelectric Properties of SBT Thin Films Deposited by RF Magnetron Sputering Method (RF 마그네트론 스퍼터링법에 의한 SBT 박막의 강유전체 특성)

  • 조춘남;김진사;최운식;박용필;김충혁
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.14 no.9
    • /
    • pp.731-735
    • /
    • 2001
  • S $r_{0.89}$B $i_{2.4}$T $a_2$ $O_{9}$ (SBT) thin films are deposited on Pt-coated electrode(Pt/Ti $O_2$/ $SiO_2$/Si) using RF magnetron sputtering method. In the XRD pattern, the SBT thin films had (105) orientation. As annealing temperature was increased from $600^{\circ}C$ to 85$0^{\circ}C$, the intensities of peak were increased. In the SEM images, Bi-layered perovskite phase was crystallized above $650^{\circ}C$ and rod-like grains grew above 75$0^{\circ}C$. The maximum remanent polarization and the coercive electric field at annealing temperature of 75$0^{\circ}C$ are 11.60$\mu$C/$\textrm{cm}^2$ and 48kV/cm respectively. The dielectric constant and leakage current density at annealing temperature of 75$0^{\circ}C$ are 213 and 1.01x10$^{-8}$ A/$\textrm{cm}^2$, respectively. The fatigue characteristics of SBT thin filmsdid not change up to 10$^{10}$ switching cycles.s.s.

  • PDF

Fabrication and Properties of MFISFET using SrBi2Ta2O9SiN/Si Structures (SrBi2Ta2O9SiN/Si 구조를 이용한 MFISFET의 제작 및 특성)

  • 김광호
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.15 no.5
    • /
    • pp.383-387
    • /
    • 2002
  • N-channel metal-ferroelectric-insulator-semiconductor field-effect-transistors (MFISFET's) by using $SrBi_2Ta_2O_9$/Silicon Nitride/Si (100) structure were fabricated. The fabricated devices exhibit comfortable memory windows, fast switching speeds, good fatigue resistances, and long retention times that are suitable for advanced ferroelectric memory applications. The estimated switching time and polarization ($2P_r$) of the fabricated FET measured at applied electric field of 376 kV/cm were less than 50 ns and about 1.5 uC/$\textrm{cm}^2$, respectively. The magnitude of on/off ratio indicating the stored information performance was maintained more than 3 orders until 3 days at room temperature. The $I_DV_G$ characteristics before and after being subjected to $10^11$ cycles of fatigue at a frequency of 1 MHz remained almost the same except a little distortion in off state.

Single Crystalline CoFe/MgO Tunnel Contact on Nondegenerate Ge with a Proper Resistance-Area Product for Efficient Spin Injection and Detection

  • Jeon, Kun-Rok;Min, Byoung-Chul;Lee, Hun-Sung;Shin, Il-Jae;Park, Chang-Yup;Shin, Sung-Chul
    • Proceedings of the Korean Magnestics Society Conference
    • /
    • 2010.06a
    • /
    • pp.96-96
    • /
    • 2010
  • We report the proper resistance-area products in the single crystalline bcc CoFe/MgO tunnel contact on nondegenerate n-Ge desirable for efficient spin injection and detection at room temperature. The electric properties of the crystalline CoFe(5 nm)/MgO(1.5,2.0,2.5 nm)/n-Ge(001) tunnel contacts have been investigated by I-V-T and C-V measurements. Interestingly, the tunnel contact with the 2-nm MgO exhibits the ohmic behavior with low resistance-area products, satisfying the theoretical conditions required for significant spin injection and detection. This result is ascribed to the presence of MgO layer between CoFe and n-Ge, enhancing the Schottky pinning parameter as well as shifting the charge neutrality level.

  • PDF

Comparison to Dielectric and Electrical Characteristics of Fatty Acid Organic Thin Film for Length of Alkyl Group (알킬기의 길이에 따른 지방산계 유기초박막의 유전 및 전기적 특성 비교)

  • 강기호;이준호;김도균;권영수;장정수
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 1999.11a
    • /
    • pp.343-346
    • /
    • 1999
  • We have investigated the dielectric and electrical characteristics of palrnitic acid(PA), stearic acid(SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one(alky1 chain lqngth). The dielectric characteristics such as the capacitance-frequency(C-F) characteristics and the dielectric dispersion and absorption characteristics of PA, SA and AA through-plane were measured. In the result, the relative dielectric constants of PA, SA and AA LB films were about 3.0-4.6, 2.7-4.1 and 2.4-3.8, respectively. The relative dielectric constants were decreased in proportion to the chain length of alkyl group. Also, the dielectric dispersion and absorption of each fatty acid LB films have arisen from the dipole polarization in the range of $10^4~10^5[Hz]. And, the conductivity of PA, SA and AA LB films obtained from I-V characteristics were about $9{\times}10^{-14}, 3{\times}10^{-l4} and 5{\times}10^{-15}[S/cm], respectively. These results have shown the insulating materials and could control the conductivity by changing the length of alkyl group. Also, we have confirmed that the barrier height of fatty acid systems were about 1.32-1.40[eV] and the dielectric constant were about 3.0-4.2. These values were almost the same ones obtained from dielectric characteristics.

  • PDF

Study on Low Temperature Formation of Ferroelectric $Sr_{0.9}4$Bi_{2.1}$$Ta_2$$O_9$ Thin Films by Sol-Gel Process and Rapid Thermal Annealing (솔-젤법 및 급속열처리에 의한 $Sr_{0.9}4$Bi_{2.1}$$Ta_2$$O_9$ 박막의 저온형성에 관한 연구)

  • 장현호;송석표;김병호
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.13 no.4
    • /
    • pp.312-317
    • /
    • 2000
  • Ferroelectric S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ solutions were synthesized using sol-gel process in which strontinum ethoxide bismuth ethoxide trantalum ethoxide were used a s startring materials. SBT thin films were coated on Pt/Ti/ $SiO_2$/Si substrates by spin-coating. rapid thermal annealing (RTA) was used to promote crystallization. Thin films were annealed at $700^{\circ}C$ for 1 hr in an oxygen atmosphere. This temperature is about 10$0^{\circ}C$ lower than the usual annealing temperature for SBT thin films. Pt top-electrode was deposited by sputtering and thin films were post-annealed at $700^{\circ}C$ for 30 min. to enhance electrical properties. As the RTA temperature increased the higher 2 $P_{r}$ values were obtained. At RTA temperature being 78$0^{\circ}C$ remanent polarization of S $r_{0.9}$/B $i_{2.1}$/T $a_{2}$/ $O_{9}$ thin film was 7.73 $\mu$C/cm $_2$ and the leakage current density was 1.14$\times$10$^{-7}$ A/c $m^2$ at 3 V. As RTA temperature increased the breakdown voltage was decreased. It is considered that the low-field breadown is caused by the rough surface of SBT films and forming bismuth metal in SBT thin films.films.lms.

  • PDF

Electrical Properties of Sol-gel Derived Ferroelectric Bi3.35Sm0.65Ti3O12 Thin Films by Rapid Thermal Annealing

  • Cho, Tae-Jin;Kang, Dong-Kyun;Kim, Byong-Ho
    • Transactions on Electrical and Electronic Materials
    • /
    • v.6 no.2
    • /
    • pp.51-56
    • /
    • 2005
  • Ferroelectric Bi$_{3.35}$Sm$_{0.65}$Ti$_{3}$O$_{12}$(BSmT) thin films were synthesized using a sol-gel process. Bi(TMHD)$_{3}$, Sm$_{5}$(O$^{i}$Pr)13, Ti(O$^{i}$Pr)4 were used as the precursors, which were dissolved in 2­methoxyethanol. The BSmT thin films were deposited on Pt/TiO$_{x}$/SiO$_{2}$/Si substrates by spin­coating. The electrical properties of the thin films were enhanced using rapid thermal annealing process (RTA) at 600 $^{circ}$C for 1 min in O$_{2}$. Thereafter, the thin films were annealed from 600 to 720 $^{circ}$C in oxygen ambient for 1 hr, which was followed by post-annealed for 1 hr after depositing a Pt electrode to enhance the electrical properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystallinity and surface morphology of layered perovskite phase, respectively. The remanent polarization value of the BSmT thin films annealed at 720 $^{circ}$C after the RTA treatment was 35.31 $\mu$C/cmz at an applied voltage of 5 V.

Study on the Degradation of MEA Using Sulfonated Poly(ether ether ketone) Membrane in Proton Exchange Membrane Fuel Cells (고분자 전해질 연료전지에서 sPEEK 막을 이용한 전극과 막 합체(MEA)의 열화에 관한 연구)

  • Lee, Hye-Ri;Lee, Se-Hoon;Hwang, Byung-Chan;Na, Il-Chai;Lee, Jung-Hun;Oh, Sung-June;Park, Kwon-Pil
    • Korean Chemical Engineering Research
    • /
    • v.54 no.3
    • /
    • pp.305-309
    • /
    • 2016
  • Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, to test the durability of sPEEK MEA (Membrane and Electrode Assembly), ADT (Accelerated Degradation Test) of MEA degradation was done at the condition that membrane and electrode were degraded simultaneously. Before and after degradation, I-V polarization curve, hydrogen crossover, electrochemical surface area, membrane resistance and charge transfer resistance were measured. Although the permeability of hydrogen through sPEEK membrane was low, sPEEK membrane was weaker to radical evolved at low humidity and OCV condition than fluorinated membrane such as Nafion. Performance after MEA degradation for 144 hours and 271 hours were reduced by 15% and 65%, respectively. It was showed that the main cause of rapid decrease of performance after 144 hours was shorting due to Pt/C particles in the pinholes.

Electrode characteristics of $AB_2$ type hydrogen storage alloy modified by Cr, La addition and fluorination ($AB_2$계 수소저장합금의 전극특성에 미치는 Cr, La 첨가 효과 및 표면 불화처리 효과)

  • Chang I.;Lee B. H.;Cho W. I.;Jang H.;Cho B. W.;Yun K. S.
    • Journal of the Korean Electrochemical Society
    • /
    • v.1 no.1
    • /
    • pp.45-51
    • /
    • 1998
  • [ $AB_2-type$ ] alloy, one kind of hydrogen storage alloys used as an anode of Ni-MH batteries, has large discharge capacity but has remaining problems regarding initial activation, cycle life and self-discharge. This study investigates the effects of Cr-addition and fluorination after La-addition on $Zr_{0.7}Ti_{0.3}V_{0.4}Mn_{0.4}Ni_{1.2}$, composition $AB_2-type$ alloy. EPMA and SEM surface analysis techniques were used and the crystal structure was characterized by XRD analysis. In addition, electrodes were fabricated out of the alloys and characterized by constant current cycling test, electrochemical impedance spectroscopy and potentiodynamic polarization. Cr-addition was found to be effective to cycle life and self-discharge but ineffective to initial activation due to formation of stable oxide film on surface. Fluorination after La-addition to the alloys improved initial activation remarkably due to formation of highly reactive particles on surface.

Degradation Mechanisms of Organic Light-emitting Devices with a Glass Cap (유리 덮개로 보호된 OLED소자의 발광특성 저하 연구)

  • Yang Yong Suk;Chu Hye Yong;Lee Jeong-Ik;Park Sang-He;Hwang Chi Sun;Chung Sung Mook;Do Lee-Mi;Kim Gi Heon
    • Journal of the Korean Vacuum Society
    • /
    • v.15 no.1
    • /
    • pp.64-72
    • /
    • 2006
  • We demonstrated organic light-emitting devices (OLEDs) based on the organic thin-film materials such as tris-(8-hydroxyquinoline) aluminum $(Alq_3)$. The structure of OLEDs was vacuum deposited upon transparent and thin glass substrates pre-coated with a transparent, conducting indium tin oxide thin film. The luminance characteristics, current, capacitance, and dispersion factor for degraded OLEDs, which were made by various bias currents $(0.5mA\;{\leq}\;I_{Bias}\;{\leq}9mA)$, are studied. The current dependences of lifetime were divided at approximately 2mA, and they represented nearly linear behaviors but had different slopes in a logarithmic plot of lifetime versus bias current. With lighting OLEDs, the anomaly of capacitance, as shown in the CV curve, occurred because of two factors, polarization in the bulk of organic materials and the interface between the metal and organic layers. In decayed OLEDs that had lower bias currents of less than 2mA, it was found that the degradation of luminance was related to both the decrease of polarization and to the lowering of the injection barrier.

Study on Low-Temperature Solid Oxide Fuel Cells Using Y-Doped BaZrO3 (Y-doped BaZrO3을 이용한 저온형 박막 연료전지 연구)

  • Chang, Ik-Whang;Ji, Sang-Hoon;Paek, Jun-Yeol;Lee, Yoon-Ho;Park, Tae-Hyun;Cha, Suk-Won
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.36 no.9
    • /
    • pp.931-935
    • /
    • 2012
  • In this study, we fabricate and investigate low-temperature solid oxide fuel cells with a ceramic substrate/porous metal/ceramic/porous metal structure. To realize low-temperature operation in solid oxide fuel cells, the membrane should be fabricated to have a thickness of the order of a few hundreds nanometers to minimize IR loss. Yttrium-doped barium zirconate (BYZ), a proton conductor, was used as the electrolyte. We deposited a 350-nm-thick Pt (anode) layer on a porous substrate by sputter deposition. We also deposited a 1-${\mu}m$-thick BYZ layer on the Pt anode using pulsed laser deposition (PLD). Finally, we deposited a 200-nm-thick Pt (cathode) layer on the BYZ electrolyte by sputter deposition. The open circuit voltage (OCV) is 0.806 V, and the maximum power density is 11.9 mW/$cm^2$ at $350^{\circ}C$. Even though a fully dense electrolyte is deposited via PLD, a cross-sectional transmission electron microscopy (TEM) image reveals many voids and defects.