• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2002년도 제22회 학술발표회 초록집
• /
• pp.207-207
• /
• 2002

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2005년도 제29회 학술발표회 초록집
• /
• pp.49-49
• /
• 2005

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2004년도 제26회 학술발표회 초록집
• /
• pp.53-53
• /
• 2004

• 한국진공학회지
• /
• 제22권6호
• /
• pp.306-312
• /
• 2013

화학적 증기증착(Chemical Vapor Deposition, CVD) 방법을 이용하여 단결정 Indium antimonide (InSb) 나노와이어를 $SiO_2$ wafer 위에 성장시켰으며, 성장된 InSb 나노와이어의 결정성과 조성비를 X-Ray Diffraction (XRD)과 Energy Dispersive x-ray Spectroscopy (EDS)의 측정을 통하여 확인하였다. 또한, 반응 source로 사용된 InSb 분말의 기상화(vaporization) 정도를 source container의 모형, 즉 open 및 close 시스템으로 변형하여 조절하였고 이렇게 성장된 InSb 나노와이어들의 구조적 특성을 주사전자현미경(Scaning Electron Microscopy, SEM)을 통하여 자세히 분석함으로써, 그들의 성장과정을 Vapor-Liquid-Solid (VLS) 및 Vapor-Solid (VS) 메커니즘으로 설명하였다. Open-boat를 사용하여 나노와이어를 성장시켰을 경우, close-boat 의 경우와 비교하여 합성된 나노와이어의 yield가 높았으며 나노와이어의 길이와 두께도 증가하는 현상이 관측되었다. 이러한 결과는, InSb source 의 기상화 정도가 close-boat에서 보다 open-boat에서 더욱 가속화되면서 공통적으로 일어나는 VLS 성장 이외에 VS 성장이 추가적으로 진행되어지기 때문으로 추측되어진다. 또한, 반응시간을 증가시켰을 때, 나노와이어의 두께가 증가하는 결과를 통하여 InSb 나노와이어의 성장에서 VS 메커니즘이 우세하게 작용하고 있음을 확인할 수 있었다.

• 한국전기전자재료학회논문지
• /
• 제23권11호
• /
• pp.848-853
• /
• 2010

We have grown GaN nanowires by the low pressure MOCVD method on Ni deposited oxidized Si surface and have established optimum conditions by observing surface microstructure and its photoluminescence. Optimum growth temperature of $880^{\circ}C$, growth time of 30 min, TMG source flow rate of 10 sccm have resulted in dense nanowires on the surface, however further increase of growth time or TMG flow rate has not increased the length of nanowire but has formed nanocrystals. On the contrary, the increase of ammonia flow has increased the length of nanowires and the coverage of nanowire over the surface. The shape of nanowire is needle-like with a Ni droplet at its tip; the length is tens of micron with more than 40 nm in diameter. Low temperature photoluminescence obtained from the sample at optimum growth condition has revealed several peaks related to exciton decay near band-edge, but does not show any characteristic originated from one dimensional quantum confinement. Strong and broad luminescence at 2.2 eV is observed from dense nanowire samples and this suggests that the broad band is related to e-h recombination at the surface state in a nanowire. The current result is implemented to the nanowire device fabrication by nanowire bridging between micro-patterned neighboring Ni catalysis islands.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2012년도 춘계학술발표대회
• /
• pp.88.1-88.1
• /
• 2012

Silicon nanowires (SiNWs), due to their unusual quantum-confinement effects that lead to superior electrical and optical properties compared to those of the bulk silicon, have been widely researched as a potential building block in a variety of novel electronic devices. The conventional means for the synthesis of SiNWs has been the vapor-liquid-solid method using chemical vapor deposition; however, this method is time consuming, environmentally unfriendly, and do not support vertical growth. As an alternate, the electroless etching method has been proposed, which uses metal catalysts contained in aqueous hydrofluoric acids (HF) for vertically etching the bulk silicon substrate. This new method can support large-area growth in a short time, and vertically aligned SiNWs with high aspect ratio can be readily synthesized with excellent reproducibility. Nonetheless, there still are rooms for improvement such as the poor surface characteristics that lead to degradation in electrical performance, and non-uniformity of the diameter and shapes of the synthesized SiNWs. Here, we report a facile method of SiNWs synthesis having uniform sizes, diameters, and shapes, which may be other than just cylindrical shapes using a modified nanosphere lithography technique. The diameters of the polystyrene nanospheres can be adjustable through varying the time of O2 plasma treatment, which serve as a mask template for metal deposition on a silicon substrate. After the removal of the nanospheres, SiNWs having the exact same shape as the mask are synthesized using wet etching technique in a solution of HF, hydrogen peroxide, and deionized water. Different electrical and optical characteristics were obtained according to the shapes and sizes of the SiNWs, which implies that they can serve specific purposes according to their types.

• 한국진공학회지
• /
• 제17권1호
• /
• pp.51-57
• /
• 2008

나노크기의 Au-Si을 촉매로 급속열화학기상증착(rapid thermal chemical vapor deposition)법을 이용하여 Si(111) 기판에 성장한 Si 나노선의 구조적인 형태 변화와 광학적 특성을 연구하였다. 기상-액상-고상(vapor-liquid-solid) 성장법에 의한 Si 나노선 형성 과정에서 액상 입자인 Au-Si 나노점은 나노선 성장온도에서 촉매로 사용되었다. 이 액상 나노점이 형성된 Si 기판에 1.0Torr 압력과 $500-600^{\circ}C$ 기판 온도 하에서 $SiH_4$와 $H_2$의 혼합가스를 공급하여 Si 나노선을 형성하였다. Si 나노선 성장 후 형태를 전계방출 주사전자현미경(Field Emission Scanning Electron Microscope)으로 관찰한 결과, 대부분의 나노선이 균일한 크기로 기판 표면에 수직하게 <111> 방향으로 정렬된 것을 확인하였다. 형성된 나노선의 크기는 평균 직경이 ${\sim}60nm$이고 평균 길이가 ${\sim}5um$임을 확인하였다. 또한 고 분해능 투과전자현미경(High Resolution-Transmission Electron Microscope) 관찰을 통해 Si 나노선은 약 3nm의 비정질 산화층으로 둘러 싸여 있는 Si 단결정임이 분석되었다. 그리고 마이크로 라만 분광(Micro-Raman Scattering)법을 통한 광학적 특성 분석 결과, Si의 광학 포논(Optical Phonon) 신호 위치가 Si 나노선 구조의 영향으로 낮은 에너지 쪽으로 이동하며, Si 포논 신호의 폭이 비대칭적으로 증가함을 확인하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.288-288
• /
• 2013

Lithium-ion battery (LIB) is one of the most important rechargeable battery and portable energy storage for the electric digital devices. In particular, study about the higher energy capacity and longer cycle life is intensively studied because of applications in mobile electronics and electric vehicles. Generally, the LIB's capacity can be improved by replacing anode materials with high capacitance. The graphite, common anode materials, has a good cyclability but shows limitations of capacity (~374 mAh/g). On the contrary, silicon (Si) and germanium(Ge), which is same group elements, are promising candidate for high-performance LIB electrodes because it has a higher theoretical specific capacity. (Si:4200 mAh/g, Ge:1600 mAh/g) However, it is well known that Si volume change by 400% upon full lithiation (lithium insertion into Si), which result in a mechanical pulverization and poor capacity retention during cycling. Therefore, variety of nanostructure group IV elements, including nanoparticles, nanowires, and hollow nanospheres, can be promising solution about the critical issues associated with the large volume change. However, the fundamental research about correlation between the composition and structure for LIB anode is not studied yet. Herein, we successfully synthesized various structure of nanowire such as Si-Ge, Ge-Carbon and Si-graphene core-shell types and analyzed the properties of LIB. Nanowires (NWs) were grown on stainless steel substrates using Au catalyst via VLS (Vapor Liquid Solid) mechanism. And, core-shell NWs were grown by VS (Vapor-Solid) process on the surface of NWs. In order to characterize it, we used FE-SEM, HR-TEM, and Raman spectroscopy. We measured battery property of various nanostructures for checking the capacity and cyclability by cell-tester.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.354-354
• /
• 2012

In this study, we report the vertically aligned ZnO nanowires by using different type of Ga-doped ZnO (GZO) thin films as seed layers to investigate how the underlying GZO film micro structure affects the distribution of ZnO nanowires. Arrays of highly ordered ZnO nanowires have been synthesized on GZO thin film seed layer prepared on p-Si substrates ($7-13{\Omega}cm$) with utilize of a pulsed laser deposition (PLD). With the vapor-liquid-solid (VLS) growth process, the ZnO nanowire synthesis carries out no metal catalyst and is cost-effective; furthermore, The GZO seed layer facilitates the uniform growth of well-aligned ZnO nanowires. The influence of the growth temperature and various thickness of GZO seed layer have been analyzed. Crystallinity of grown seed layer was studied by X-Ray diffraction (XRD); diameter and morphology of ZnO nanowires on seed layer were investigated by field emission scanning electron microscopy (FE-SEM). Our results suggest that the GZO seed layer with high c-axis orientation, good crystallinity, and less lattice mismatch is key parameters to optimize the growth of well-aligned ZnO nanowire arrays.

• 통합자연과학논문집
• /
• 제5권4호
• /
• pp.211-215
• /
• 2012

Single-crystalline silicon nanowire arrays (SiNWAs) using electroless metal-assisted etchings of p-type silicon were successfully fabricated. Ag nanoparticle deposition on silicon wafers in HF solution acted as a localized micro-electrochemical redox reaction process in which both anodic and cathodic process took place simultaneously at the silicon surface to give SiNWAs. The growth effect of SiNWs was investigated by changing of etching times. The morphologies of SiNWAs were obtained by SEM observation. Well-aligned nanowire arrays perpendicular to the surface of the silicon substrate were produced. Optical characteristics of SiNWs were measured by FT-IR spectroscopy and indicated that the surface of SiNWs are terminated with hydrogen. The thicknesses and lengths of SiNWs are typically 150-250 nm and 2 to 5 microns, respectively.