• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.159-163
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• 2003

ln this work, we studied electrical characteristics and leakage current mechanism of $Ta_2O_{5}$ MOS(Metal-Oxide-Semiconductor) devices. $Ta_2O_{5}$ thin film (63 nm) was deposited by ALD(Atomic Layer Deposition) method at temperature of 235 $^{\circ}C$. The structures of the $Ta_2O_{5}$ thin films were examined by XRD(X-Ray Diffraction). From XRD, it is found that the structure of $Ta_2O_{5}$ is single phase and orthorhombic. From capacitance-voltage (C-V) anaysis, the dielectric constant was 19.4. The temperature dependence of current density-electric field (J-E) characteristics of $Ta_2O_{5}$ thin film was studied at temperature range of 300 - 423 K. In ohmic region (<0.5 MV/cm), the resistivity was 2.456${\times}10^{14}$ ($\omega{\cdot}cm$ at 348 K. The Schottky emission is dominant at lower temperature range from 300 to 323 K and Poole-Frenkel emission is dominant at higher temperature range from 348 to 423 K.

• Journal of Korean Vacuum Science & Technology
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• v.4 no.1
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• pp.6-10
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• 2000

Ferroelectric YMnO$_3$ thin films were deposited on $Y_2$O$_3$/si(100) substrates by metalorganic chemical vapor deposition. The YMnO$_3$ thin films annealed in vacuum ambient (100 mTorr) above 75$0^{\circ}C$ show hexagonal structured YMnO$_3$. However, the film annealed in oxygen ambient shows poor crystallinity, and the second phase as $Y_2$O$_3$ and orthorhombic-YMnO$_3$ were shown. The annealing ambient and pressure on the crystallinity of YMnO$_3$ thin films is very important. The C-V characteristics have a hysteresis curve with a clockwise rotation, which indicates ferroelectric polarization switching behavior. When the gate voltage sweeps from +5 to 5 V, the memory window of the Pt/YMnO$_3$/Y$_2$O$_3$/Si gate capacitor annealed at 85$0^{\circ}C$ is 1.8 V. The typical leakage current densities of the films annealed in oxygen and vacuum ambient are about 10$^{-3}$ and 10$^{-7}$ A/cm$^2$ at applied voltage of 5 V.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1794-1798
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• 2014

Graphitic g-$C_3N_4-WO_3$ composite was synthesized simply by decomposing melamine in the presence of $WO_3$ at $500^{\circ}C$. The obtained material was characterized by XRD, SEM, IR and XPS. The results showed that the as-prepared composite exhibits orthorhombic $WO_3$ phase coated by g-$C_3N_4$ and the g-$C_3N_4$ decomposed completely with N-doped $WO_3$ remaining at elevated calcination temperatures. The photocatalytic activity of the composite was evaluated by the photodegradation of methylene blue under visible light. An enhancement in photocatalytic activity for the graphitic g-$C_3N_4-WO_3$ composite compared to the conventional nitrogen-doped $WO_3$ was observed, which can be attributed to the presence of g-$C_3N_4$ in the material.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.35-39
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• 2003

This paper is contents on the orthorhombic crystalline calcined by the solid phase method with LiMnO$_2$ thin film structured as the result which an average pore diameter of power was 132.3${\AA}$ in porosity analysis. Voltage ranges are able to get the properties of charge and discharge for experimental results of LiMnO$_2$ thin film were 2.2V 4.3V. The current density and scan speed were 0. 1㎃/$\textrm{cm}^2$ and 0.2㎷/sec respectively. Properties of the charge and discharge are obtained by optimum experiment condition parameters. Li dense ratio of the LiMnO$_2$ thin film that discharged capacities were 87㎃h/g have been 96.9［ppm］ at 670.784［nm］ wavelength. The dense ratio of Mn analyzed to 837［ppm］ at 257.610［nm］ wavelength. It can be estimated the quality of the LiMnO$_2$ thin film as that the wrong LiMnO$_2$ thin film pulled up from cell of electrolyte and became dry it at 800$^{\circ}C$. The results of SEM and XRD were the same as that of original researchers.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.21-26
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• 2000

Nanosized powders of trimetallic orthoferrites containing La and Sm in different ratios were synthesised by the thermal decomposition at low temperatures of the corresponding hexacyanocomplexes. The precursors and their decomposition products were analyzed by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), x-ray diffraction (XRD) and Raman spectroscopy. Single phase trimetallic precursors and oxides were obtained. The crystal structure of the perovskitic oxides was orthorhombic, and the lattice parameters were affected by the ionic size of the rare earth elements present in the oxides. Raman spectroscopy showed a disorder effect in the vibrational bands with increasing the La content.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.537-541
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• 2007

Microwave dielectric properties of $0.95 Ca_{0.85}Nd_{0.1}TiO_3-0.05LnAlO_3$ (Ln=Sm, DH, Er) were investigated as a function of sintering temperature and lanthanide ion type. A single perovskite phase with an orthorhombic structure was obtained throughout the entire range of composition. The dielectric constant (K) was dependent upon the dielectric polarizabilities and the B-site bond valence in the $ABO_3$ perovskite structure. The quality factor (Qf) of the specimens with $ErAlO_3$ was smaller than those with $SmAlO_3\;and/or\;DyAlO_3$ due to the smaller grain size. The temperature coefficient of resonant frequency (TCF) could be controlled from $107.28ppm/^{\circ}C$ at Ln=Sm to $87.23ppm/^{\circ}C$ at Ln=Er due to the changes of B-site bond valence in the $ABO_3$ perovskite structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.637-640
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• 2017

In this study, $(1-x)(Na_{0.52}K_{0.443}Li_{0.037})(Nb_{0.883}Sb_{0.08}Ta_{0.037})O_3-x(Bi_{0.5}(Na_{0.7}K_{0.3})_{0.5}ZrO_3$ ceramics were fabricated by BNKZ substitution using a conventional solid-state method to develop excellent lead-free piezoelectric ceramics for piezoelectric actuators; their dielectric and piezoelectric properties were then investigated. All specimens were in the orthorhombic phase. $NKL-NSTO_3$ ceramics with x=0.01 showed excellent piezoelectric properties. The density (${\rho}$), piezoelectric charge constant ($d_{33}$), planar piezoelectric coupling coefficient ($k_p$), mechanical quality factor ($Q_m$), and dielectric constant (${\varepsilon}_r$) had optimized values of $4.56g/cm^3$, 208 pC/N, 0.43, 96, and 975, respectively.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.195-198
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• 1999

A Bi$_4$Ti$_3$O$_{12}$ (BIT) thin film is prepared by sol-gel method using acetate precursors and evaluated whether it could be applied to NVFRAM. The drying and the annealing temperature are 40$0^{\circ}C$ and $650^{\circ}C$, respectively and they are determined from the DT-TG analysis. The BIT thin film deposited on Pt/Ta/SiO$_2$/Si substrate shows orthorhombic perovskite phase. The grain size and the surface roughness are about 100 nm and 70.2$\AA$, respectively. The dielectric constant and the loss tangent at 10 KHz are 176 and 0.038, respectively, and the leakage current density at 100㎸/cm is 4.71$mutextrm{A}$/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$250㎸/cm, the remanent polarization (Pr) and the coercive field (Ec) are 5.92$mutextrm{A}$/$\textrm{cm}^2$ and 86.3㎸/cm, respectively. After applying 10$^{9}$ square pulses of $\pm$5V, the remanent polarization of the BIT thin film decreases as much as about 33% from 5.92 $\mu$C/$\textrm{cm}^2$ of initial state to 3.95 $\mu$C/$\textrm{cm}^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.41-46
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• 2002

In this work, we studied electrical characteristics and leakage current mechanism of Au/$Ta_2O_5$/Si metal-oxide-semiconductor (MOS) devices. $Ta_2O_5$ thin film (63nm) was deposited by atomic layer deposition (ALD) method at temperature of $235^{\circ}C$. The structures of the $Ta_2O_5$ thin films were examined by X-Ray Diffraction (XRD). From XRD, the structure of $Ta_2O_5$ was single phase and orthorhombic. From capacitance-voltage (C-V) analysis, the dielectric constant was 19.4. The temperature dependence of current-voltage (I-V) characteristics of $Ta_2O_5$ thin film was studied from 300 to 423 K. In ohmic region (<0.5 MVcm${-1}$), the resistivity was $2.4056{\times}10^{14}({\Omega}cm)$ at 348 K. The Schottky emission is dominant in lower temperature range from 300 to 323 K and Poole-Frenkel emission dominant in higher temperature range from 348 to 423 K.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.822-826
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• 2008

We report the cathodoluminescence and aging properties of a series of green phosphors of formula $Sr_{1-x}M_xGa_2S_4$:Eu (x = 0.0-1.0, M = Ba or Ca) that have potential applications in field emission displays (FEDs). The series of phosphors was synthesized via NaBr-aided solid-state reactions in a flowing $H_2S$ stream. A low level ($\sim$20%) of Ba or Ca substitution for Sr in $SrGa_2S_4$:Eu maintains the orthorhombic phase of pure $SrGa_2S_4$:Eu phosphors. Further, a low level ($\sim$20%) of Ba or Ca substitution for Sr in $SrGa_2S_4$:Eu provides various green colors and sufficient brightness for FED applications. Substitution of Ba or Ca for Sr in $SrGa_2S_4$:Eu also improved the stability of the phosphor when it was operated under electron-beam irradiation of 5 kV.