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고밀도 플라즈마를 사용한 Cl₂ / Poly - Si 건식 식각
이휘건(Whi Kun YI) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.1
고밀도 플라즈마 source인 helical resonator의 특성을 알기 위해 Langmuir probe를 사용하여 특성 변수들-플라즈마 밀도, 전자 온도, 이온 전류 밀도-의 값을 측정하였다. 또한 Cl₂/poly-Si 시스템에서의 식각반응 메카니즘을 규명하기 위해 Si와 SiCl의 에미션 시그날을 분석하였다. Cl₂/poly-Si 식각 시스템계에서는 화학 식각에 의한 반응이 물리식각에 의한 반응보다 주됨을 알 수 있다. 또한 폴리 실리콘 내의 불순물 P농도가 증가함에 따라 식각의 화학반응 산출물인 SiCl의 양이 물리식각 산출물인 Si의 양보다 급격히 증가하는 양상을 보였다. 이는 표면 반응중 형성된 Si-Cl 결합을 통해 실리콘 내부의 전자들이 Cl 쪽으후 이동함으로써 Si-Cl은 더욱 유동적이며 이온화된 특성을 갖게 되고, 따라서 Cl₂^+와 같은 에천트들이 표면에 흡착될 확률이 커져 SiCl_x의 형성을 용이하게 하기 때문으로 생각된다. 즉 불순물 P 농도가 증가함에 따라 표면의 Si를 제거하는데는 물리식각보다 화학식각이 더욱 큰 역할을 하는 것으로 밝혀졌다. The characteristic parameters of high density plasma source (Helical Resonator) have been measured with Langmuir probe to get the plasma density, electron temperature, ion current density, etc. Optical emission spectra of Si and SiCl have been analyzed in Cl₂/poly-Si system to elucidate etching mechanism. In this system, the main reaction to remove silicon atoms on the surface is proceeding mostly through chemical reaction, not pure physical reaction. The emission intensity of SiCI (chemical etching product) increases much faster than Si (pure physical etching product) with increasing the concentration of impurities (P). This is due to the electron transfer from substrate to the surface via Si-Cl bond. As a result, Si-Cl bond becomes more ionic and mobile, therefore the Cl-containing etchant forms SiCl_x with surface more easily. Consequently, for the removal of Si atom from poly silicon surface, the chemical etching is more favorable than physical etching with increasing P concentrations.
Conducting Properties of Polypyrrole Coated Imogolite
Yunha Lee,Bumjoong Kim,이휘건,Atsushi Takahara,Daewon Sohn* 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.11
Imogolite which has chemical composition, (HO)3Al2O3SiOH, was synthesized with orthosilicate acid and aluminium chloride at low pH solution. It has extremely large aspect ratio with an external diameter of 2nm and the length of a few micrometers. The high aspect ratio of the imogolite could make the material as the filler for the high strength fiber and as the wire for the electronic applications. Here, Imogolite that derives considerable microporosity from a nanometer-sized tubular structure has been modified with a conducting polymer, polypyrrole. Its bonding and wiring structure were confirmed by IR and TEM. The measured conductivity after modification with polypyrrole increased with polypyrrole thickness at various voltage conditions.
Some Features of CdS/CdSe Quantum Dot-sensitized Solar Cell Incorporating Carbon Nanotubes
이준영,박태희,이종택,양종희,이휘건 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.3
Quantum dot-sensitized solar cells (QDSSCs) were synthesized using CdS and CdSe quantum dots (QDs) incorporated onto one-dimensional ZnO nanorods by successive ionic layer adsorption. In order to get the highest performance of the synthesized cell, the concentration of precursor QD solution and the number of deposition cycles in the QD solution were varied together. The photovoltaic performance of each cell was compared with the ultraviolet/visible absorption spectra and incident photon to current efficiency graphs. QDSSCs incorporating single-walled carbon nanotubes (SWNTs), sprayed onto the substrate before deposition of the next layer, exhibited enhanced or decreased photocell efficiency compared to that of the pristine cell. In particular, a maximum rate increase of 17% was obtained with the solar cell containing SWNTs in CdSe QDs.
Photodissociation of Methane at Lyman Alpha (121.6 nm)
Jaehong Park,한진욱,이휘건,이정우,Kijo Sim 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.1
Laser induced fluorescence studies of hydrogen atom using four wave mixing technique are reported for the photodissociation of CH₄ and its isotopomers at Ly α(121.6 nm). The source of dissociating and probe radiation is one and the same (delay time ≤20 nsec). The average translational energy of ejected hydrogen atoms (50 Kcal/mol) reveals that CH₄+ hv(수식)CH₃ + H(²S) and CH4 + h(수식)CH²(a¹A₁) + H₂(1∑g) are the main dissociation processes. The absolute quantum yield for CH₄and CD₄ are the same, ∮H(CH₄) = ∮D(CD₄) = 0.31 ± 0.05. If one divides the experimental H/D ratios from the isotopomers CH₃D, CH₂D₂, CHD₃ by the isotopic H/D ratios, a value 2 is obtained in all three cases. Overall, the heavier D atoms are more likely than the H atoms to remain attached to the carbon atom
구준모,손대원,김진우,정회일,이영일,이휘건,이호익 한국고분자학회 2012 Macromolecular Research Vol.20 No.2
Organic/inorganic hybrid gels were directly prepared by polymerization on the peroxide surface of silica particles where the particle surface was irradiated by a 60Co γ-ray. These hydrogels have no residues of initiators or cross-linkers, so they can be used in biocompatible gel applications. Wide Raman spectroscopy was used to verify the interaction between the particles and poly(acrylic acid) (PAA). We observed that covalent bonds existing between the peroxide particles and acrylic acid, and the hydrogen bonds between the acrylic acids. For these studies,we prepared hydrogels by varying the particles’ concentration and the size of the silica particles to classify the number of reaction sites, which are the dominant factor for the chemical reaction between the silica particles and PAA.