• Journal of Korean Vacuum Science & Technology
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• v.4 no.3
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• pp.73-77
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• 2000

Single crystal and polycrystalline Si thin films were doped with phosphorus by a 2-zone diffusion method to develop the low-resistivity polycrystalline Si electrode for a hemispherical grain. Solid phosphorus source was used in order to achieve uniformly and highly doped surface region of polycrystalline Si films having rough surface morphology. In case of 2-zone diffusion method, it is proved that the heavy doping near the surface area can be achieved even at a relatively low temperature. SIMS analysis revealed that phosphorus doping concentration in case of using solid P as a doping source was about 50 times as that of phosphine source at 750$^{\circ}C$. Also, ASR analysis revealed that the carrier concentration was about 50 times as that of phosphine. In order to evaluate the electrical characteristics of doped polycrystalline Si films for semiconductor devices, MOS capacitors were fabricated to measure capacitance of polycrystalline Si films. In ${\pm}$2 V measuring condition, Si films, doped with solid source, have 8% higher $C_{min}$ than that of unadditional doped Si films and 3% higher $C_{min}$ than that of Si films doped with $PH_3$ source. The leakage current of these films was a few fA/${\mu}m^2$. As a result, a 2-zone diffusion method is suggested as an effective method to achieve highly doped polycrystalline Si films even at low temperature.

• Korean Journal of Materials Research
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• v.22 no.4
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• pp.207-210
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• 2012

The preparation of $Sm_2O_3$ doped $CeO_2$ in Igepal CO-520/cyclohexane reverse micelle solutions has been studied. In the present work, we synthesized nanosized $Sm_2O_3$ doped $CeO_2$ powders by reverse micelle process using aqueous ammonia as the precipitant; hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase, and poly (xoyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by Thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), and Transmission electron microscopy (TEM). The crystallite size was found to increase with increase in water to surfactant (R) molar ratio. Average particle size and distribution of the synthesized $Sm_2O_3$ doped $CeO_2$ were below 10 nm and narrow, respectively. TG-DTA analysis shows that phase of $Sm_2O_3$ doped $CeO_2$ nanoparticles changed from monoclinic to tetragonal at approximately $560^{\circ}C$. The phase of the synthesized $Sm_2O_3$ doped $CeO_2$ with heating to $600^{\circ}C$ for 30 min was tetragonal $CeO_2$. This study revealed that the particle formation process in reverse micelles is based on a two step model. The rapid first step is the complete reduction of the metal to the zero valence state. The second step is growth, via reagent exchanges between micelles through the inter-micellar exchange.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.47-48
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• 2006

Carbon nanotubes (CNTs)-doped homogeneously aligned nematic liquid crystal (LC) cells driven by in-plane field were fabricated and their electro-optic characteristics were investigated. Effective cell retardation values in an absence of an electric field between doped and undoped LC were the same each other. In the presence of an electric field, however, measured effective cell retardation value was smaller in the CNT-doped cell than in the undoped cell so that the transmittance was slightly smaller in the CNT-doped cell than in the undoped cell. In addition, the CNT-doped cell exhibited slight increase in driving voltage and decrease in response time compared to the undoped cell. The CNT effects on electro-optic characteristics of the cell were discussed.

• Korean Journal of Materials Research
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• v.24 no.10
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• pp.565-571
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• 2014

Nitrogen-doped ZnO nanoparticle-carbon nanofiber composites were prepared using electrospinning. As the relative amounts of N-doped ZnO nanoparticles in the composites were controlled to levels of 3.4, 9.6, and 13.8 wt%, the morphological, structural, and chemical properties of the composites were characterized by means of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, the carbon nanofiber composites containing 13.8 wt% N-doped ZnO nanoparticles exhibited superior catalytic properties, making them suitable for use as counter electrodes in dye-sensitized solar cells (DSSCs). This result can be attributed to the enhanced surface roughness of the composites, which offers sites for $I_3{^-}$ ion reductions and the formation of Zn3N2 phases that facilitate electron transfer. Therefore, DSSCs fabricated with 13.8 wt% N-doped ZnO nanoparticle-carbon nanofiber composites showed high current density ($16.3mA/cm^2$), high fill factor (57.8%), and excellent power-conversion efficiency (6.69%); at the same time, these DSSCs displayed power-conversion efficiency almost identical to that of DSSCs fabricated with a pure Pt counter electrode (6.57%).

• Journal of Environmental Science International
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• v.18 no.11
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• pp.1215-1224
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• 2009

This study evaluated the applicability of visible-light-driven N- and S-doped titanium dioxide($TiO_2$) for the control of low-level dimethyl sulfide(DMS) and dimethyl disulfide(DMDS). In addition, a photocatalytic unit(PU)-adsorption hybrid was evaluated in order to examine the removal of DMS and DMDS which exited the PU and a gaseous photocatalytic byproduct($SO_2$) which was generated during the photocatalytic processes. Fourier-Tranform-Infrared(FTIR) spectrum exhibited different surface characteristics among the three-types of catalysts. For the N- and S-doped $TiO_2$ powders, a shift of the absorbance spectrum towards the visible-light region was observed. The absorption edge for both the N- and S-doped $TiO_2$ was shifted to $\lambda$ 720 nm. The N-doped $TiO_2$ was superior to the S-doped $TiO_2$ in regards to DMS degradation. Under low input concentration(IC) conditions(0.039 and 0.027 ppm for DMS and DMDS, respectively), the N-doped $TiO_2$ revealed a high DMS removal efficiency(above 95%), but a gradual decreasing removal efficiency under high IC conditions(7.8 and 5.4 ppm for DMS and DMDS, respectively). Although the hybrid system exhibited a superior characteristic to PU alone regarding the removal efficiencies of both DMS and DMDS, this capability decreased during the course of a photocatalytic process under the high IC conditions. The present study identified the generation of sulfate ion on the catalyst surface and sulfur dioxide(maximum concentrations of 0.0019 and 0.0074 ppm for the photocatalytic processes of DMS and DMDS, respectively) in effluent gas of PU. However, this generation of $TiO_2$ would be an insignificant addition to indoor air quality levels.

• 전기의세계
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• v.28 no.5
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• pp.39-43
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• 1979

The aging of permittivity of a barium titanate dielectrics doped with La$_{2}$O$_{3}$ under zero and low DC field has been studied. The aging rate was decreased as the amount of La$_{2}$O$_{3}$ addition is increased to 3 mole%. The zero field aging rate of barium titahate doped with La$_{2}$O$_{3}$. 3TiO$_{2}$ was similar to that doped with La$_{2}$O$_{3}$.5V/mil DC field aging rate of La$_{2}$O$_{3}$.3TiO$_{2}$ doped sample, howeve, was lowered to that of La$_{2}$O$_{3}$ doped sample. When the phase transformation is occured from the paraelectric state to the ferroelectric state, 90.deg. domains are mucleated in order that the system becomes thermodynamically more stable. It is concluded that the aging phenomenon is occured as the dielectric constant is decreasing by the nucleation and growth of 90.deg. domains.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.12
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• pp.1859-1864
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• 1990

The effect of H+ and OH- ion concentrations at doped Si semiconductor/pH buffer solution interfaces were investigated in terms of cyclic current-voltage characteristics. The effects of space charge on oppositely doped Si semiconductors, i.e., p-and n-Si semiconductors, can be effectively applied to study the pH effects and the slow surface states at the interfaces. The adsorptions of H+ and OH- inons on the doped Si semiconductor surfaces are physical adsorption rather than chemical adsorption. Adsorptive processes and charging effects of the slow surface states can be explained as the potential barrier variations and the related current-voltage characteristics at the interfaces. Under forward bias, the charged slow surface states on the p-and n-si semiconductor surface are donor and acceptor slow surface states, respectively. The effects of minority carriers on the slow surface states can be neglected at the doped Si semiconductor interfaces.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.501-502
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• 2008

In this study, P-doped ZnO thin films were prepared on sapphire substrates by pulsed laser deposition and annealing method. The electrical properties were investigated as a function of annealing temperatures at a fixed oxygen pressure. The XRD measurement showed that p-doped ZnO thin films were c-axis oriented. The Hall measurement showed that p-type ZnO thin film was observed. The carrier concentration of $1.18{\times}10^{16}cm^{-3}$ and the mobility of $0.96\;cm^{-3}/Vs$ were obtained for the P-doped ZnO thin film fabricated annealing temperature $850^{\circ}C$.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.215-218
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• 2015

A pyroelctric properties of Ni(x)-doped PMNT systems were analyzed. Modified PMNT samples were prepared using the columbite structure method. Pyroelectric current, polarization, dielectric constant and dissipation factor of Ni-doped PMNT samples were measured as a function of temperature. By adding a small amount of NiO, pyroelectricity of PMNT is increased. Unlike the normal $ABO_3$ ferroelectric, Ni-doped PMNT showed properties for relaxor ferroelectric of causing the successive phase transition over a wide temperature. The optimum conditions for obtaining compositions with improvement ferroelectric properties are a nominal addition of 0.02 mole% Ni. Also, Ni-doped PMNT ferroelectric showed excellent pyroelectric figures of merit in the vicinity of room temperature. The pyroelectric coefficient ($0.00524C/m^2K$ at $25^{\circ}C$) and figures of merit ($F_v{\sim}0.039m^2/C$ and $F_d{\sim}0.664{\times}10^{-4}Pa^{-1/2}$) of composition PMNT with 0.02 mole% Ni are comparable to the earlier reports on lead-type pyroelectrics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.307-308
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• 2008

Zinc oxide is a direct band gap wurtzite-type semiconductor with band gap energy of 3.37eV at room temperature. the n-type doped ZnO oxides, B doped ZnO (BZO) is widely studied in TCOs materials as it shows good electrical, optical, and luminescent properties. we focused on the fabrication of B doped ZnO films with glass substrate using the LSMCD at low temperature. And Novel boron-doped ZnO thin films were deposited and characterized from the structural, optical, electrical point of view. The structure, morphology, and optical properties of the films were studied as a function of by employing the XRD, SEM, Hall system and micro Raman system.