• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1217-1223
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• 2008

A series of Zr,S co-doped $TiO_2$ were synthesized by a modified sol-gel method and characterized by various spectroscopic and analytical techniques. The presence of sulfur caused a red-shift in the absorption band of $TiO_2$. Co-doping of sulfur and zirconium (Zr-$TiO_2$-S) improves the surface properties such as surface area, pore volume, and pore diameter and also enhances the thermal stability of the anatase phase. The Zr-$TiO_2$-S systems are very effective visible-light active catalysts for the degradation of toluene. All reactions follow pseudo firstorder kinetics with the decomposition rate reaching as high as 77% within 4 h. The catalytic activity decreases in the following order: Zr-$TiO_2$-S >$TiO_2$-S >Zr-$TiO_2$>$TiO_2$$\approx$ P-25, demonstrating the synergic effect of codoping with zirconium and sulfur. When the comparison is made within the series of Zr-$TiO_2$-S, the catalytic performance is found to be a function of Zr-contents as follows: 3 wt % Zr-TiO2-S >0.5 wt % Zr-$TiO_2$-S> 5 wt % Zr-$TiO_2$-S >1 wt % Zr-$TiO_2$-S. Higher calcination temperature decreases the reactivity of Zr-$TiO_2$-S.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.238-239
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• 2010

Dimethyl sulphoxide (DMSO) is one of the widely-used secondary dopants in order to enhance the conductivity of poly(3, 4-ethylenedioxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS) film. In this work, we investigated the effect of DMSO doping in to PEDOT:PSS on the electrical performance of the bulk heterojunction photovoltaics consisting of poly(3-hexylthiophene-2, 5-diyl) and phenyl-C61-butyric acid methyl ester. Correlation between the power conversion efficiency and the mechanism of improving conductivity, surface morphology, and contact properties was examined. The PEDOT:PSS films, which contain different concentration of DMSO, have been prepared and annealed at different annealing temperatures. The mixture of DMSO and PEDOT:PSS was prepared with a ratio of 1%, 5%, 15%, 25%, 35%, 45%, 55% by volume of DMSO, respectively. The DMSO-contained PEDOT:PSS solutions were stirred for 1hr at $40^{\circ}C$, then spin-coated on the ultra-sonicated glass. The spin-coated films were baked for 10min at $65^{\circ}C$, $85^{\circ}C$, and $120^{\circ}C$ in air. In order to investigate the electrical performance, P3HT:PCBM blended film was deposited with thickness of 150nm on DMSO-doped PEDOT:PSS layer. After depositing 100nm of Al, the device was post-annealed for 30min at $120^{\circ}C$ in vacuum. The fabricated cells, in this study, have been characterized by using several techniques such as UV-Visible spectrum, 4-point probe, J-V characteristics, and atomic force microscopy (AFM). The power conversion efficiency (AM 1.5G conditions) was increased from 0.91% to 2.35% by tuning DMSO doping ratio and annealing temperature. It is believed that the improved power conversion efficiency of the photovoltaics is attributed to the increased conductivity, leading to increasing short-circuit current in DMSO-doped PEDOT:PSS layer.

• Journal of Powder Materials
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• v.30 no.6
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• pp.516-520
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• 2023

Highly safe lithium-ion batteries (LIBs) are required for large-scale applications such as electrical vehicles and energy storage systems. A highly stable cathode is essential for the development of safe LIBs. LiFePO₄ is one of the most stable cathodes because of its stable structure and strong bonding between P and O. However, it has a lower energy density than lithium transition metal oxides. To investigate the high energy density of phosphate materials, vanadium phosphates were investigated. Vanadium enables multiple redox reactions as well as high redox potentials. LiVPO₄O has two redox reactions (V⁵⁺/V⁴⁺/V³⁺) but low electrochemical activity. In this study, LiVPO₄O is doped with fluorine to improve its electrochemical activity and increase its operational redox potential. With increasing fluorine content in LiVPO₄O_1-xF_x, the local vanadium structure changed as the vanadium oxidation state changed. In addition, the operating potential increased with increasing fluorine content. Thus, it was confirmed that fluorine doping leads to a strong inductive effect and high operating voltage, which helps improve the energy density of the cathode materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.11
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• pp.690-693
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• 2015

In this paper, in order to develop excellent Pb-free composition ceramics for ultrasonic sensor. The $SnO_2$-doped ($Na_{0.525}K_{0.443}Li_{0.037})(Nb_{0.883}Sb_{0.08}Ta_{0.037})O_3$)(abbreviated as NKL-NST) ceramics have been synthesized using the ordinary solid state reaction method. The effect of $SnO_2$-doping on their dielectric and piezoelectric properties was investigated. The ceramics doped with 0 wt% $SnO_2$ have the optimum values of piezoelectric constant($d_{33}$), piezoelectric figure of merit($d_{33}.g_{33}$), planar piezoelectric coupling coefficient($k_p$) and density : $d_{33}=195[pC/N]$, $d_{33}.g_{33}=5.62pm^2/N.kp=0.40$, $density=4.436[g/cm^3]$. suitable for duplex ultrasonic sensor application.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.833-837
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• 2012

This paper proposes a DRAM data retention time enhancement method that minimizes silicon loss and undercut at STI sidewall by reducing the SC1 (Standard Cleaning) time. SC1 time optimization debilitates the parasitic electric field in STI's top corner, which reduces an inverse narrow width effect to result in reduction of channel doping density without increasing the subthreshold leakage of cell Tr. Moreover, it minimizes the electric field in depletion area from cell junction to P-well, increasing yield or data retention time.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.2
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• pp.106-113
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• 2006

Electrical properties of $Si_{0.88}Ge_{0.12}(C)$ p-MOSFETs have been exploited in an effort to investigate $Si_{0.88}Ge_{0.12}(C)$ channel structures designed especially to suppress diffusion of dopants during epitaxial growth and subsequent fabrication processes. The incorporation of 0.1 percent of carbon in $Si_{0.88}Ge_{0.12}$ channel layer could accomodate stress due to lattice mismatch and adjust bandgap energy slightly, but resulted in deteriorated current-voltage properties in a broad range of operation conditions with depressed gain, high subthreshold current level and many weak breakdown electric field in gateoxide. $Si_{0.88}Ge_{0.12}(C)$ channel structures with boron delta-doping represented increased conductance and feasible use of modulation doped device of $Si_{0.88}Ge_{0.12}(C)$ heterostructures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.216-217
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• 2008

Zinc-oxide films were deposited by pulsed laser deposition (PLD) technique using doped ZnO target (mixed $In_2O_3$ 0.1, 0.3, 0.6 at. % - atomic percentage) on the p-type Si(111) substrate. A little Indium has added at the n-ZnO films for the electron concentration control and enhanced the electrical properties. Also, post thermal annealed ZnO films are shown an enhanced structural and controled electron concentration by the annealing condition for the hetero junction diode of a better emitting characteristics. The electrical and the diode characteristics of the ZnO films were investigated by using Hall effect measurement and current-voltage measurement.

• Journal of Magnetics
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• v.8 no.4
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• pp.129-132
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• 2003

We investigated the crystallographic and magnetic properties of double perovskite $Sr_2Fe_{l-x}Cr_{x}MoO_{6}$ (x=0.0, 0.01, 0.03, 0.05, and 0.10). Mossbauer spectra of the $Sr_2Fe_{l-x}Cr_{x}MoO_{6}$ have been taken at various temperatures ranging from 15 to 415 K. As the temperature increased towards $T_{c}$(415 K), the Mossbauer spectra showed line broadening and 1, 6 and 3, 4 line-width differences because of anisotropic hyperfine field fluctuation. The Mossbauer spectra indicated that an anisotropic field fluctuation of +H ( $P_{+}$=0.85) was greater than that of -H ($P_{-}$=0.15). We also calculated the field fluctuation frequency factors and the temperature dependence of anisotropy energies from its relaxation rate. We interpreted the effect of Cr ($t^3$$_{2g}$) doping as a decrease in the anisotropy energy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.442-443
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• 2007

Al-N co-doped ZnO films were fabricated on n-Si (100) and homo-buffer layers in the mixture of oxygen and nitrogen at $450^{\circ}C$ by magnetron sputtering. Target was ZnO ceramic mixed with $2wt%Al_2O_3$. XRD spectra show that as-grown and $600^{\circ}C$ annealed films are prolonged along crystal c-axis. However they are not prolonged in (001) plane vertical to c-axix. The films annealed at $800^{\circ}C$ are not prolonged in any directions. Codoping makes ZnO films unidirectional variation. XPS show that Al content hardly varies and N escapes with increasing annealing temperature from $600^{\circ}C\;to\;800^{\circ}C$. The electric properties of as-grown films were tested by Hall Effect with Van der Pauw configuration show some of them to be p-type conduction.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.226-226
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• 2012

The electronic and electrical properties of nickel oxide (NiO) thin films were investigated by reflection electron energy loss spectroscopy (REELS), x-ray photoelectron spectroscopy (XPS), and Hall Effect measurements. REELS spectra revealed that the band gap of the NiO thin film was increased from 3.50 eV to 4.02 eV after annealing the sample at $800^{\circ}C$. Our XPS spectra showed that the amount of Ni2O3 decreased after annealing. The Hall Effect results showed that the doping type of the sample changed from n type to p type after annealing. The resistivity decreased drastically from $4.6{\times}10^3$ to $3.5{\times}10^{-2}$ ${\Omega}{\cdot}cm$. The mobility of NiO thin films was changed form $3.29{\times}10^3$ to $3.09{\times}10^5cm^2/V{\cdot}s$. Our results showed that the annealing temperature plays a crucial role in increasing the carrier concentration and the mobility which leads to lowering resistivity of NiO thin films.