• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2223-2226
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• 2009

Pristine and sulfur-doped (LiFe$PO_{3.98}S_{0.03}$) lithium iron phosphates were synthesized by a sol-gel method. The XRD pattern of the prepared materials suggested an orthorhombic structure with a Pnma space group and an absence of impurities. The Li/LiFe$PO_4$ or LiFe$PO_{3.98}S_{0.03}$ cells were employed for cycling studies at various temperatures (25, 50 and $60\;{^{\circ}C}$). In all cases, the Li/LiFe$PO_{3.98}S_{0.03}$ cell showed an improved performance with a stable discharge behavior of ~155 mA$hg^{-1}$. Nevertheless, pristine LiFeP$O_4$ cells presented poor discharge behavior at elevated temperatures, especially $60\;{^{\circ}C}$.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.95-99
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• 2011

$CaTi_{1-x}Fe_xO_3(0{\leq}x{\leq}0.4)$ solid solution photocatalysts were synthesized by iron doping during the conventional solid state reaction at $1100^{\circ}C$ for 5 h and characterized by ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction, morphological analysis. We found that $CaTi_{1-x}Fe_xO_3$ samples not only absorb UV but also the visible light photons. This is because the Fe substitution at Ti-site in $CaTi_{1-x}Fe_xO_3$ lattice induces the band transition from Fe3d to the Fe3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $CaTiO_3$ samples for hydrogen production under UV light irradiation decreased with the increase in the Fe concentration. There exists an optimized concentration of iron in $CaTiO_3$, which yields a maximum photocatalytic activity under visible light ($\lambda\geq420nm$) photons.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.25-26
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• 2008

Electrical properties of Pt/Ti/Au/Pt contacts to n-GaAs were characterized as the V/III ratio of GaAs grown by metalorganic chemical vapor deposition were 25, 50, and 100, respectively. The samples have been annealed during 30sec at 350 and $450^{\circ}C$ in rapid thermal annealing, and those specific contact resistance investigated by using transmission line method. According to experimental results, the specific contact resistance between p-metal and GaAs was decreased as the V/III ratio was lower. These results indicate that Si doping concentration of GaAs increased as the vacancy of V-series of GaAs was high.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.785-789
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• 2013

Silicon Carbide (SiC) is the material with the wide band-gap (3.26 eV), high critical electric field (~2.3 MV/cm), and high bulk electron mobility (~900 $cm^2/Vs$). These electronic properties allow attractive features, such as high breakdown voltage, high-speed switching capability, and high temperature operation compared to Si devices. In general, device design has a significant effect on the switching and electrical characteristics. It is known that in this paper, we demonstrated that the switching performance and breakdown voltage of IGBT is dependent with doping concentration of p-base region and drift layer by using 2-D simulations. As a result, electrical characteristics of SiC-IGBT deivce is higher breakdown voltage ($V_B$= 1,600 V), lower on-resistance ($R_{on}$= 0.43 $m{\Omega}{\cdot}cm^2$) than Si-IGBT. Also, we determined that processing time and cost is reduced by the depth of n-drift region of IGBT was reduced.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1791-1793
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• 2000

본 연구에서는 다결정 실리콘 박막 트랜지스터(poly-Si TFTs)에서의 소오스 및 드레인 영역 형성을 위해 PSG (phosphosilicate glass)와 BSG (borosilicate glass) 박막을 도핑 물질(dopant)로 하여 저온에서 엑시머 레이저(eximer laser)로 활성화하는 공정을 제안한다. 이 실험을 통해 소스 가스인 $PH_3$와 $SiH_4$의 유량비, 레이저 에너지 밀도와 레이저 조사 횟수를 변화시키면서 면저항(sheet resistance)과 불순물의 확산 깊이(diffusion depth)를 성공적으로 조절하였다. 불순물의 확산 깊이와 표면 농도는 레이저 에너지 밀도와 조사 횟수를 증가시킴에 따라 증가하였으며 그 결과 최소 면저항 값은 인(P)의 경우 450$\Omega/\square$을 얻었고 붕소(B)의 경우 1100$\Omega/\square$을 얻었다. 이러한 실험결과는 제안된 방법을 통해 poly-Si TFTs 에서 소오스, 드레인 영역의 도핑 공정을 수행할 수 있음을 보여준다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.229-233
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• 2015

In this paper, in order to develop outstanding Pb-free piezoelectric composition ceramics, the $(Na_{0.525}K_{0.443}Li_{0.037})(Nb_{0.883}Sb_{0.08}Ta_{0.037})O_3+0.3wt%Bi_2O_3+0.4wt%Fe_2O_3+xwt%CuO$ (x= 0~0.8 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effects of CuO-doping on the structure and electrical properties of the NKL-NST ceramics were systematically studied. The results show that the ceramics exhibit a pure perovskite structure with orthorhombic phase at room temperature, and secondary phase was found in the ceramics. The 0.4 wt%CuO added ceramics sintered at $950^{\circ}C$ showed the optimum properties of piezoelectric constant($d_{33}$), planar piezoelectric coupling coefficient(kp) and mechanical quality factor(Qm) : $d_{33}=213$[pC/N], kp= 0.43, Qm= 423,respectively.

• Proceedings of the Ginseng society Conference
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• 1980.09a
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• pp.143-150
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• 1980

The purpose of this double-blind study was to study the standardized ginseng-extract (marketed form, GINSANA), in regard to its efficacy on the reaction time, pulmonary function and general health in subjects of various age-groups. The trial was conducted as a double-blind study in a total of 120 subjectsm allocated to different groups, according to age (30 to 39 and 40 to 60 year age-groups), sex and preparation administered (ginseng/placebo). The study lasted 12 weeks and the dosage was fixed at 2 capsules per day. The rusults regarding reaction time and pulmonary function showed significant differences in favour of the GINSANA group, over the placebo group, in the 40 to 60-year-old men and women. In the self-evaluation (performance, mood, concentration) we observed a clear improvement (p < 0.001) in the subjects treated with GINSANA, with the exception of the men age 30-39 years. The results botained, which are specially related to reaction, pulmonary function, self evaluation and tolerability, have shown that GINSANA, as standardized ginseng extract, has a favourable effect on the psychic and physical functions studied. 3. Performance test in top sportsmen before and after 9 weeks' treatment with GINSANA To what extent can GINSANA influence physical performance? It is precisely we the physicians whose task it is to find drugs which in physiological amounts do not have any special pharmacodynamic effects. We were therefore interested in the preparation, GINSANA which was made available to us, since it contains a qualitatively and quantitatively standardized GINSENG EXTRACT and is not doping agent.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.351-354
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• 2006

[ $Co_{1-x}Fe_xSb_3$ ] skutterudites were synthesized by encapsulated induction melting and their thermoelectric properties were investigated. Single phase ${\delta}-CoSb_3$ was successfully obtained by the subsequent heat treatment at 773 K for 24 hours in vacuum. However, ${\delta}-CoSb_3$ was decomposed to FeSb2 and Sb when $x{\leq}0.3$, which means that the solubility limit of Fe to Co is x<0.3. The positive signs of Seebeck coefficients for all Fe-doped specimens revealed that Fe atoms acted as p-type dopants by substituting Co atoms. Thermoelectric properties were remarkably enhanced by Fe doping and optimum composition was found to be $Co_{0.7}Fe_{0.3}Sb_3$ in this study.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.274-277
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• 2016

Effects of interlayer insertion between multi-quantum well and electron blocking layer of green light emitting diode on diode performances were studied by device simulation. Dependence of Mg doping depth on characteristics of current-voltage, emitting wavelength, leakage current, and external quantum efficiency was investigated, and the optimum diode structure was presented. Device structures with interlayers doped in entire region and up to 30 nm showed remarkable reduced leakage current and effectively relieved efficiency droop which is one of the biggest challenges in green light emitting diode. Furthermore, the most improved characteristics in current-voltage and electroluminescence was obtained by the latter structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.18-26
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• 1999

In this study, the undoped amorphous layers and phosphorus doped amorphous layers are fabricated using LPCVD at 531$^{\circ}C$ with SiH$_4$ gas or at same temperature with PH$_3$ gas during deposition, respectively. The thickness of deposited amorphous layer from this experiments was 5000 ${\AA}$. In this experiments, undoped amorphous layers are deposited with SiH$_4$and Si$_2$H$\_$6/ gas in a low pressure reactor using LPCVD. These amorphous layers can be doped for poly-silicon by phosphorus ion implantation. The experiments of this study are carried out by phosphorus ion implantation with energy 40 keV into P doped and undoped amorphous silicon layers. The distribution of phosphorus profiles are measured by SIMS(Cameca 6f). Recoiling effects and two dimensional profiles are also explained by comparisions of experimental and simulated data. Finally range moments of SIMS profiles are calculated and compared with simulation results.