• Proceedings of the Korean Magnestics Society Conference
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• 2005.12a
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• pp.208-208
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• 2005

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.55-55
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• 2010

We use ab initio density functional theory to determine the effect of bundling on the equilibrium structure, electronic and magnetic properties of $Mo_6S_{9-x}I_x$nanowires with x = 0, 3, 4.5, 6. Each unit cell of these systems contains two $Mo_6S_{6-x}I_x$ clusters connected by S3 linkages to form an ordered linear array. Due to the bi-stability of the sulfur linkages, the total energy of the nanowires exhibits typically many minima as a function of the wire length. We find that nanowires can switch over from metallic to semiconducting by applying axial stress. Structural order is expected in bundles with x=0 and x=6, since there is no disorder in the decoration of the Mo clusters. In bundles with other stoichiometries, we expect structural disorder to occur. We find the optimum inter-wire distance to depend sensitively on the orientation of the wires, but only weakly on x. It is also found that the electronic properties of nanowires are affected strongly due to bundling of nanowires exhibiting very unusual Fermi surfaces. Furthermore, ferromagnetic behaviors are observed in selected stable and many more unstable atomic arrangements in nanowire bundles.

• Proceedings of the Korean Vacuum Society Conference
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• 2004.08a
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• pp.52-52
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• 2004

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.590-594
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• 2013

Semiconductor CdSe nanowires (NWs) can serve as model systems for investigating the physical properties of one-dimensional (1D) nanostructures and have great potential for applications in electronics and photonic nanodevices. With numerous attractions arisen from their physical properties, CdSe NWs have been synthesized by vapor-liquid-solid (VLS) methods, but they have some limitations of high reaction temperature and low production. Here, we synthesized CdSe NWs via the solution-liquid-solid (SLS) mechanisms using bismuth (Bi) covered substrates as a low-melting point catalyst and compared the products after injecting identical amount of Se and different amount of tributylphosphine (TBP). CdSe NWs have similar diameters but longer lengths with decreasing TBP, so we proposed the role of TBP as a solvent and capping agent of Se.

• Journal of the Korean Magnetics Society
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• v.17 no.4
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• pp.166-171
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• 2007

We report the magneto-transport properties of an individual single crystalline Bi nanowire grown by a spontaneous growth method. We have successfully fabricated a four-terminal device based on an individual 400-nm-diameter nanowire using plasma etching technique to remove an oxide layer forming on the outer surface of the nanowire. The transverse MR (2496% at 110 K) and longitudinal MR ratios (38% at 2 K) for the Bi nanowire were found to be the largest known values in Bi nanowires. This result demonstrates that the Bi nanowires grown by the spontaneous growth method are the highest-quality single crystalline in the literatures ever reported. We find that temperature dependence of Fermi energy ($E_F$) and band overlap (${\triangle}_0$) leads to the imbalance between electron concentration ($n_e$) and hole concentration ($n_h$) in the Bi nanowire, which is good agreement with the calculated $n_e\;and\;n_h$ from the respective density of states, N(E), for electrons and holes. We also find that the imbalance of $n_e\;and\;n_h$ plays a crucial role in determining magnetoresistance (MR) at T<75 K for $R_T$ and at T<205 K for $R_L$, while mean-free path is responsible for MR at T>75 K for $R_T$ and T>205 K for $R_L$.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.12a
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• pp.86-87
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.307-307
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• 2008

• Proceedings of the Korean Magnestics Society Conference
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• 2010.06a
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• pp.80-81
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• 2010

We observed period of SdH oscillation in an individual Bi nanowire with the transverse and longitudinal magnetic fields along the axis of the nanowire grown by OFF-ON. Our results provide good qualitative description of the cyclotron behavior of the single-crystalline Bi nanowire in the ballistic regime.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3368-3372
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• 2012

The $Bi_2O_3$ nanowires are highly sensitive to low concentrations of $NO_2$ in ambient air and are almost insensitive to most other common gases. However, it still remains a challenge to enhance their sensing performance and detection limit. This study examined the influence of the encapsulation of ${\beta}-Bi_2O_3$ nanorods with $In_2O_3$ on the $NO_2$ gas sensing properties. ${\beta}-Bi_2O_3-core/In_2O_3-shell$ nanorods were fabricated by a two-step process comprising the thermal evaporation of $Bi_2O_3$ powders and sputter-deposition of $In_2O_3$. Multiple networked ${\beta}-Bi_2O_3-core/In_2O_3-shell$ nanorod sensors showed the responses of 12-156% at 1-5 ppm $NO_2$ at $300^{\circ}C$. These response values were 1.3-2.7 times larger than those of bare ${\beta}-Bi_2O_3$ nanorod sensors at 1-5 ppm $NO_2$. The enhancement in the response of ${\beta}-Bi_2O_3$ nanorods to $NO_2$ gas by the encapsulation by $In_2O_3$ can be accounted for based on the space-charge model.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.59-60
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• 2007

열전재료는 냉각과 발전 분야에서 매우 매력적인 친환경 에너지 소재이다. 열전 재료의 효율을 나타내는 성능 지수는 ZT로 나타내는데, 기존의 bulk 재 열전소재의 경우 그 값이 1 내외이다. 그러나 기존의 타 기술과의 경쟁에서 우위를 점하기 위해서는 ZT 값이 3이 되어야 한다. 이론적인 계산에 의하면 나노 박막이나 나노와이어 형태로 열전재료를 제어를 함으로써 ZT 값의 현저한 향상이 예상되어 ZT값이 3이상의 값도 얻을 수 있을 것으로 기대된다. 전기도금법은 나노와이어 형태의 열전재료를 경제적으로 대량 생산할 수 있는 가장 유력한 방법이다. 본 발표에서는 전기도금법을 이용하여 n-형 BiTe 계와 p-형 BiSbTe계 열전반도체 나노와이어를 제조하고 그 특성을 측정한 연구결과를 소개한다.