• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.47-47
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• 2009

The formation of variable one-dimensional structures including core/shell structure is of particular significance with respect to potential applications for thermoelectric devices with the enhanced figure of merit ($ZT=S2{\sigma}T/{\kappa}$). We report the fabrication of Bi-Te core/shell nanowire based on a novel stress induced method. Fig. 1 schematically shows the nanowire fabrication process. Bi nanowires are grown on the Si substrate by the stress-induced method, and then Te is evaporated on the Bi nanowires. Fig. 2 is a transmission electron microscopy image clearly showing a core/shell structure for which effective phonon scattering and quantum confinement effect are expected. Electrical conductivity of the core/shell nanowire was measured at the temperatures from 4K to 300K, respectively. Our results demonstrate that Bi-Te core/shell nanowire can be grown successfully by the stress-induced method. Based on the result of electrical transport measurement and characteristic morphology of rough surface, Seebeck coefficient and thermal conductivity of Bi-Te core/shell nanowires are presented.

• 한국분말재료학회지
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• 제21권5호
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• pp.360-365
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• 2014

$SnO_2-CoO$/carbon-coated CoO core/shell nanowire composites were synthesized by using electrospinning and hydrothermal methods. In order to obtain $SnO_2-CoO$/carbon-coated CoO core/shell nanowire composites, $SnO_2-Co_3O_4$ nanowire composites and $SnO_2-Co_3O_4$/polygonal $Co_3O_4$ core/shell nanowire composites are also synthesized. To demonstrate their structural, chemical bonding, and morphological properties, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were carried out. These results indicated that the morphologies and structures of the samples were changed from $SnO_2-Co_3O_4$ nanowires having cylindrical structures to $SnO_2-Co_3O_4/Co_3O_4$ core/shell nanowires having polygonal structures after a hydrothermal process. At last, $SnO_2-CoO$/carbon-coated CoO core/shell nanowire composites having irregular and high surface area are formed after carbon coating using a polypyrrole (PPy). Also, there occur phases transformation of cobalt phases from $Co_3O_4$ to CoO during carbon coating using a PPy under a argon atmosphere.

• 한국재료학회지
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• 제20권1호
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• pp.25-30
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• 2010

Si nanowire/multiwalled carbon nanotube nanocomposite arrays were synthesized. Vertically aligned Si nanowire arrays were fabricated by Ag nanodendrite-assisted wet chemical etching of n-type wafers using $HF/AgNO_3$ solution. The composite structure was synthesized by formation of a sheath of carbon multilayers on a Si nanowire template surface through a thermal CVD process under various conditions. The results of Raman spectroscopy, scanning electron microscopy, and high resolution transmission electron microcopy demonstrate that the obtained nanocomposite has a Si nanowire core/carbon nanotube shell structure. The remarkable feature of the proposed method is that the vertically aligned Si nanowire was encapsulated with a multiwalled carbon nanotube without metal catalysts, which is important for nanodevice fabrication. It can be expected that the introduction of Si nanowires into multiwalled carbon nanotubes may significantly alter their electronic and mechanical properties, and may even result in some unexpected material properties. The proposed method possesses great potential for fabricating other semiconductor/CNT nanocomposites.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.430.1-430.1
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• 2016

We present the concept of reducible fugitive material that conformally surrounds core Cu nanowire (NW) to fabricate transparent conducting electrode (TCE). Reducing atmosphere can corrodes/erodes the underlying/surrounding layers and might cause undesirable reactions such impurity doing and contamination, so that hydrogen-/forming gas based annealing is impractical to make device. In this regards, we introduce novel reducible shell conformally surrounding indivial CuNW to provide a protection against the oxidation when exposed to both air and solvent. Uniform copper lactate shell formation is readily achievable by injecting lactic acid to the CuNW dispersion as the acid reacts with the surface oxide/hydroxide or pure copper. Cu lactate shell prevents the core CuNW from the oxidation during the storage and/or film formation, so that the core-shell CuNW maintains without signficant oxidation for long time. Upon simple thermal annealing under vacuum or in nitrogen atmosphere, the Cu lactate shell is easily decomposed to pure Cu, providing an effective way to produce pure CuNW network TCE with typically sheet resistance of $19.8{\Omega}/sq$ and optical transmittance of 85.5% at 550 nm. Our reducible copper lactate core-shell Cu nanowires have the great advantage in fabrication of device such as composite transparent electrodes or solar cells.

• ETRI Journal
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• 제41권6호
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• pp.829-837
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• 2019

The p-type nanowire field-effect transistor (FET) with a SiGe shell channel on a Si core is optimally designed and characterized using in-depth technology computer-aided design (TCAD) with quantum models for sub-10-nm advanced logic technology. SiGe is adopted as the material for the ultrathin shell channel owing to its two primary merits of high hole mobility and strong Si compatibility. The SiGe shell can effectively confine the hole because of the large valence-band offset (VBO) between the Si core and the SiGe channel arranged in the radial direction. The proposed device is optimized in terms of the Ge shell channel thickness, Ge fraction in the SiGe channel, and the channel length (L_g) by examining a set of primary DC and AC parameters. The cutoff frequency (f_T) and maximum oscillation frequency (f_max) of the proposed device were determined to be 440.0 and 753.9 GHz when L_g is 5 nm, respectively, with an intrinsic delay time (τ) of 3.14 ps. The proposed SiGe-shell channel p-type nanowire FET has demonstrated a strong potential for low-power and high-speed applications in 10-nm-and-beyond complementary metal-oxide-semiconductor (CMOS) technology.

• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.94-98
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• 2020

The core/shell of nanowires (NWs) with Cu-doped CdSe quantum dots were fabricated as an electron transport layer (ETL) for perovskite solar cells, based on ZnO/TiO2 arrays. We presented CdSe with Cu2+ dopants that were synthesized by a colloidal process. An improvement of the recombination barrier, due to shell supplementation with Cu-doped CdSe quantum dots. The enhanced cell steady state was attributable to TiO2 with Cu-doped CdSe QD supplementation. The mechanism of the recombination and electron transport in the perovskite solar cells becoming the basis of ZnO/TiO2 arrays was investigated to represent the merit of core/shell as an electron transport layer in effective devices.

• 대한기계학회논문집B
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• 제39권10호
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• pp.825-829
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• 2015

나노선에서 코어-셸 헤테로 구조를 도입함으로써 열 전도율을 낮출 수 있으며, 이로 인해 열전 효율(ZT)을 향상시킬 수 있다는 것이 이론 연구를 통해 제안되었다. 본 논문에서는 코어-셸 나노선의 열전도율 감소를 실험적인 방법을 통해 확인하였다. 화학증기 증착법을 통해 만든 게르마늄-규소 $_x$ 게르마늄 $_{1-x}(Ge-Si_xGe_{1-x})$ 코어-셸 나노선의 열전도율을 마이크로 크기의 뜬 디바이스를 이용하여 측정하였다. 셸에서 측정된 실리콘의 함유율(x)는 0.65 로 확인하였으며, 게르마늄은 코어와 셸 사이에서, 격자 불일치(lattice mismatch)에서 비롯된 결점(defect)와 같은 역할을 한다. 또한, 4-point I-V 측정실험에, 휘트스톤 브릿지 실험을 추가 진행함으로써 측정 민감도를 강화하였다. 측정된 열전도율은 상온에서 9~13 W/mK 으로써, 비슷한 지름을 가지는 게르마늄 나노선과 비교하였을 때, 열전도율이 약 30 % 낮아졌음을 확인하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.183.1-183.1
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• 2016

Due to the latest research trend toward wearable energy devices, transparent and stretchable supercapacitors which can sustain their performance even under physical deformation have steadily attracted huge attention. Despite the Ag NW is the most promising candidate for fabrication of transparent and stretchable electronics, the electrochemical instability interrupts its application to development of the energy device. Here, we introduce a transparent and highly stretchable supercapacitor made by Au-Ag core shell NW network percolation electrode. The Au-Ag core shell NW synthesized by a simple solution process not only shows excellent electrical conductivity but also greatly enhanced chemical and electrochemical stability compare to pristine Ag NW. These outstanding properties of the Au-Ag core shell NW are attributed both to the core Ag NW and the Au protecting sheath layer. The proposed Au-Ag core shell NW based supercapacitor exhibits optical transmittance with outstanding mechanical stability withstanding 60% strain without any decrease of the performance. The supercapacitors connected in series are charged and discharged stable in 30% strain turning on a red LED. These notable results demonstrate the potential of the Au-Ag core shell NW as a strong candidate for development of wearable energy devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.37-40
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• 2003

Amorphous $Al_2O_3$ nanotubes have been fabricated by utilizing the ZnO nanowires as template with wet etching method. ZnO nanowires synthesized by thermal evaporation are conformally coated with $Al_2O_3$ by atomic-layer deposition(ALD) method. The $Al_2O_3$-coated ZnO nanowires are of core-shell structure; ZnO core nanowires and $Al_2O_3$ shells. When the $ZnO/Al_2O_3$ core-shell structure is dipped in $H_3PO_4$ solution at $25^{\circ}C$ for a 6 min, the core ZnO materials are completely etched, and only $Al_2O_3$ nanotubes are remained. This nanotube fabrication is technically easier than others, and simply approachable. Transmission electron microscopy shows that the $Al_2O_3$ nanotubes have various thicknesses that can be controlled.

• 한국재료학회지
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• 제29권5호
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• pp.311-316
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• 2019

Transparent conducting electrodes are essential components in various optoelectrical devices. Although indium tin oxide thin films have been widely used for transparent conducting electrodes, silver nanowire network is a promising alternative to indium tin oxide thin films owing to its lower processing cost and greater suitability for flexible device application. In order to widen the application of silver nanowire network, the electrical conductance has to be improved while maintaining high optical transparency. In this study, we report the enhancement of the electrical conductance of silver nanowire network transparent electrodes by copper electrodeposition on the silver nanowire networks. The electrodeposited copper lowered the sheet resistance of the silver nanowire networks from $21.9{\Omega}{\square}$ to $12.6{\Omega}{\square}$. We perform detailed X-ray diffraction analysis revealing the effect of the amount of electrodeposited copper-shell on the sheet resistance of the core-shell(silver/copper) nanowire network transparent electrodes. From the relationship between the cross-sectional area of the copper-shell and the sheet resistance of the transparent electrodes, we deduce the electrical resistivity of electrodeposited copper to be approximately 4.5 times that of copper bulk.