• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.359-360
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• 2013

The effect of electrode and deposition methods on non-linear interfacial resistive switching in HfO2 based $250{\times}250$ nm2 cross-point device was studied. HfO2 based device has the interfacial resistive switching properties of non-linearity and self-compliance current switching. The operating current in HfO2 based device was increased with negatively increasing the heat of formation energy in top electrode. Also, it was investigated that the operating current in HfO2 based device was changed with deposition methods of O3 reactant ALD, H2O reactant ALD and dc reactive sputtering, resulting the magnitude of the operating current and on/off ratio in order of HfO2 films deposited by dc reactive sputtering, H2O reactant ALD, and O3 reactant ALD. To investigate the effect of electrode and deposition methods on operating current of non-linear interfacial resistive switching in the cross-point device, X-ray photoelectron spectroscopy was measured. Through the analysis of O 1s spectra, non-lattice oxygen concentration, which is closely related to oxygen vacancies, was increased in order of Pt, TiN, and Ti top electrodes and in order of O3 reactant ALD, H2O reactant ALD, and O3 reactant ALD, and dc reactive sputtering deposition method. From all results, non-lattice oxygen concentration in ultra-thin HfO2 films play a crucial role in the operating current and memory states (LRS & HRS) in the non-linear interfacial resistive switching.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.665-672
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• 2000

The ferroelectric YMnO3 thin films were prepared by MOD(metal-organic decomposition) method with Y- and Mn-acetylacetonate as starting materials. Thin films were grown on various substrates by spin-coating technique. The crystalline phases of the thin films were identified by X-ray diffractometer as a function of heat-treatment temperature, pH of coating solution and substrate. In addition, the effect of Mn/Y molar ratio(0.8~1.2) on the formation of hexagonal-YMnO3 phase was investigated. In forming highly c-axisoriented hexagonal-YMnO3 single phase, the Pt coated Si substrate was more effective than the bare Si substrate, and the optimum heat-treatment condition was at 82$0^{\circ}C$ for 30 min. Higher Mn/Y molar ratio within 0.8~1.2 and pH of YMnO3 precursor solution within 0.5~2.5 favored formation of ferroelectric hexagonal phase rather than orthorhombic phase. Leakage current density of the hexagonal-YMnO3 thin film formed on Pt(111)/TiO2/SiO2/Si substrate was low enough as 0.4~4.0$\times$10-8(A/$\textrm{cm}^2$) at 5 V and its remanent polarization(Pr), calculated from the P-E hysteresis loop, was 3 nC/$\textrm{cm}^2$.

• Journal of Sensor Science and Technology
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• v.23 no.5
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• pp.337-341
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• 2014

For various additives doped-$VO_2$ critical temperature sensors using the nature of semiconductor to metal transition, the crystallinity, microstructure, and temperature vs. resistance characteristics were systematically investigated. As a starting material of $VO_2$ sensor, vanadium pentoxide ($V_2O_5$) powders were used, and CaO, SrO, $Bi_2O_3$, $TiO_2$, and PbO dopants were used, respectively. The $V_2O_5$ powders with dopants were mixed with a vehicle to form paste. This paste was silk screen-printed on $Al_2O_3$ substrates and then $V_2O_5$-based thick films were heat-treated at $500^{\circ}C$ for 2 hours in $N_2$ gas atmosphere for the reduction to $VO_2$. From X-ray diffraction analysis, $VO_2$ phases for pure $VO_2$, and CaO and SrO-doped $VO_2$ thick films were confirmed and their grain sizes were 0.57 to $0.59{\mu}m$. The on/off resistance ratio of the $VO_2$ sensor in phase transition temperature range was $5.3{\times}10^3$ and that of the 0.5 wt.% CaO-doped $VO_2$ sensor was $5.46{\times}10^3$. The presented critical temperature sensors could be commercialized for fire-protection and control systems.

• Journal of the Speleological Society of Korea
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• no.74
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• pp.23-31
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• 2006

(1) Kaeusetgul Cave in Kimnyong-Ri, Jeju-Do, Korea. Kaeuset-gul Cave (KC) is situated in NNE area of the Manjang-gul cave (125m a.s.l.). Kaeuset-gul Cave lies at $126^{\circ}45'22"$ E in longitude and $33^{\circ}33'09"$ N in latitude. The coast belong Kimnyeong-Ri, Kujwa-eup, Jeju-Do. Altitude of the cave-entrance is 10m and length of the cave is 90m. Lava hand-specimens of KC are studied by X-ray fluorescence analysis (XRF). Average major chemical components of specimens from KC is as follows (wt.%); $SiO_2=47.03$, $TiO_2=3.16$, $Al_2O_3=18.41$, FeO*=13.53, MnO=0.14, MgO=5.05, CaO=8.66, $Na_2O=2.81$, $K_2O=0.67$, $P_2O_5=0.55$ in KC. Polarizing microscopic studyindicates that these specimens are described of alkali-basalt. (2) Tachibori Fuketsu (Cave) in Shizuoka Prefecture, Fuji Volcano, Japan Tachibori Fuketsu lies attoward the south in skirt of the Fuji volcano, $138^{\circ}42'04"$ east longitude and $35^{\circ}18'00"$ north latitude. The location of cave entrance is 2745, Awakura, Fujinomiya-shi, Shizuoka Prefecture. The above sea level and length of Tachibori Fuketsu are 1,170m and 82m. Average major chemical components of specimens from cave areas follows (Total 100 wt.%) ; ($SiO_2$=50.52, $TiO_2$=1.69, $Al_2O_3$=15.47, FeO*=13.13, MnO=0.20, MgO=5.97, CaO=9.17, $Na_2O$=2.52, $K_2O$=0.94 and $P_2O_5=0.40).$ Polarizing microscopic study indicates that these specimens may belong to tholeiite-basalt series. According to polarizing microscopic study, Au (Augite), P1 (Plagioclase), and O1 (Olivine) are contained as phenocryst minerals. (3) Gorely Cave in Kamchatka Peninsula, Russia Gorely caldera is located at the southeastern part of Kamchatka Peninsula, about 75km southwest of Petropavlovsk-Kamchatskiy.. Gorely lava caves are situated in NHE area of Mt. Gorely volcano (1829m a.s.1.). One of lava cave (Go-9612=K-1) lies at $158^{\circ}00'22"$ east longitude and $52^{\circ}36'18"$ north latitude. The elevation of cave entrance is about 990m a.s.1. and the main cave extends in the NNW direction for about 50m by 15m wide and 5m in depth. The cave of K-3is near the K-1 cave. "@Lava hand-specimens K-1 and K-3 caves are studied by X-ray fluorescence analysis and polarizing microscopic observation. Average major chemical components of specimens from these caves are as follows (wt.%) ;($SiO_2$=55.12, $TiO_2$=1.25, $Al_2O_3$=16.07, T-FeO* =9.41, MnO=0.16, MgO=5.01, CaO=7.21, $Na_2O$=3.39, $K_2O$=1.92, $P_2O_5$=0.45) and these values indicate that the Gorely basaltic andesite belong to high alumina basalt. Polarizing microscopic study indicates that these specimens are described of Augite andesite.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1146-1151
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• 1998

The crystallization behaviour of perovskite $PbTiO_3$ for the samples heat- treated at various temperatures for various times in the $PbO-TiO_2-A1_2O_3-SiO_2$, glass system has been investigated by the means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Higher crystallinity obtained in the sample heat-treated at higher temperature for longer time. With increasing heat-treatment time, dielectric constant of the samples heat-treated at $610^{\circ}C$ and $650^{\circ}C$ increased, but that of the sample heat- treated at $800^{\circ}C$ decreased. Loss tangent of the heat-treated samples was not much influenced by heat-treatment conditions. Piezodielectric charge constant was approximately $1.0\times10^{-12}~8.0$\times$10^{-12}C/N$ in the samples heat-treated at $800^{\circ}C$ for 1h, 2h, and 8h.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.104-104
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• 2009

Critical dimensions has rapidly shrunk to increase the degree of integration and to reduce the power consumption. However, it is accompanied with several problems like direct tunneling through the gate insulator layer and the low conductivity characteristic of poly-silicon. To cover these faults, the study of new materials is urgently needed. Recently, high dielectric materials like $Al_2O_3$, $ZrO_2$ and $HfO_2$ are being studied for equivalent oxide thickness (EOT). However, poly-silicon gate is not compatible with high-k materials for gate-insulator. To integrate high-k gate dielectric materials in nano-scale devices, metal gate electrodes are expected to be used in the future. Currently, metal gate electrode materials like TiN, TaN, and WN are being widely studied for next-generation nano-scale devices. The TaN gate electrode for metal/high-k gate stack is compatible with high-k materials. According to this trend, the study about dry etching technology of the TaN film is needed. In this study, we investigated the etch mechanism of the TaN thin film in an inductively coupled plasma (ICP) system with $O_2/BCl_3/Ar$ gas chemistry. The etch rates and selectivities of TaN thin films were investigated in terms of the gas mixing ratio, the RF power, the DC-bias voltage, and the process pressure. The characteristics of the plasma were estimated using optical emission spectroscopy (OES). The surface reactions after etching were investigated using X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04b
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• pp.3-5
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• 2008

The $SrBi_2Ta_2O_9$ thin films are deposited on Pt-coated electrode(Pt/$TiO_2/SiO_2$/Si) using RF magnetron sputtering method. The ferroelectric properties of SBT capacitors with annealing temperatures were studied. Through the x-ray diffraction analysis and the scanning electron microscopy (SEM), it could be observed that crystallization of the SBT thin film started around $650^{\circ}C$ and complete crystallization was accomplished around $750^{\circ}C$ and grains grew from a small spheric form to rod-like. For the leakage current density of the SBT capacitor depending upon various annealing atmospheres, capacitor annealed in the oxygen atmosphere showed the most excellent characteristic, and they were respectively about $2.13\times10^{-9}[A/cm^2]$ at 5V and 340.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.19-23
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• 2018

In a Pb-included piezoelectric composition, $Sr_yPb_{1-y}[(Zn_{1/3}Nb_{2/3})_x-(Ni_{1/3}Nb_{2/3})_{0.2}-(Zr_{0.46}Ti_{0.54})_{0.8-x}]O_3$ was selected in order to attain high piezoelectric properties. According to the PZN ratio (x) and the amount of Sr doping (y), the crystal structure, microstructure and piezoelectric properties were measured and evaluated. In the case of Sr 4 mol% doping, the piezoelectric properties were the highest for a PZN ratio of 0.1. In this condition, the grain size was larger and the intensity was higher. With the PZN ratio fixed and varying the Sr doping, the piezoelectric properties increased until 10 mol% doping and then decreased for over 12 mol% doping. In the case of x＝0.1 and y＝10 mol%, the best piezoelectric properties were obtained, i.e., $d_{33}=660pC/N$ and $k_p=68.5%$, and these values seem to be related to the grain size and crystal structure.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.197-203
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• 2002

The TiO$_2$ coating solutions were synthesized with different concentrations (T1-0.7N, T2-2.0N) of hydrochloric acid used as catalyst. and TiO$_2$ thin films were prepared by sol-gel dip coating. Their structural and optical properties were examined as a function of calcination temperature. XRD results showed that T1 thin films calcined at 400~80$0^{\circ}C$ had the anatase phase, while those calcined at 100$0^{\circ}C$ had the rutile phase. T2 thin films calcined at 40$0^{\circ}C$ and $600^{\circ}C$ had the anatase phase, with the rutile phase for calcination at 80$0^{\circ}C$. Crystallinity of T2 thin films was superior to that of T1 thin films. The crystallite size of TiO$_2$ thin films increased with increasing calcination temperature, and the crystallite size of anatase phase in T2 thin films was larger than that in T1 thin films, but the crystallite size of rutile phase in T2 thin films was smaller. The surface morphology of the films showed that the films were formed more densely in the rutile phase than in the anatase phase, this phenomenon appeared conspicuously in T2 thin films. The transmittance of the samples with thin films on quartz glass calcined at 100$0^{\circ}C$ was significantly reduced at wavelength range about 300-700 nm due to the increased absorption originating from the change of crystallite phase and composition of the films and the scattering effect originating from increasing crystallite size. The refractive index of TiO$_2$ thin films increased, and hence the film thickness as well as the porosity of TiO$_2$ thin films decreased with increasing calcination temperature. Furthermore, the refractive index of T2 thin films was higher than T1 thin films, and porosity of T2 films was lower.

• Natural Product Sciences
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• v.26 no.3
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• pp.207-213
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• 2020

Characterization and in vitro inhibition studies of protease inhibitor from the mushroom Pleurotus floridanus (PfTI) towards the pest Papilio demoleus is studied. The addition of 1 mM Mn²⁺, Na²⁺, Ba²⁺ and Ni ²⁺ enhanced the PfTI activity. The ICP-atomic emission spectrum showed the presence of Ca²⁺, Mg²⁺ and Zn²⁺ in the PfTI. Surfactants SDS and CTAB at a concentration of 1% reduced the PfTI activity whereas, the nonionic detergents Triton X and Tween 80 increased the activity. The inhibitory activity gradually decreased with increase in concentration of DMSO and H₂O₂. The activity was increased by dithiothreitol up to a concentration of 80 μM and inactivated at 140 μM. The activity of PMSF modified PfTI was drastically reduced to 0.234 U/mL at 4 mM concentration and similar results were obtained for modification of cysteine by N-Ethylmaleimide at slightly higher concentrations. The complex of trypsin and PfTI showed complete loss in fluorescence intensity at 343 nm compared with control. In vitro inhibition studies of PfTI with midgut proteases isolated from citrus pest P. demoleus with protease activity of 1.236 U was decreased to 0.613 U by 50 μL (0.1 mg/mL) of the inhibitor. Inhibitor was stable up to 0.04 M concentration of HCl.