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Exploring Cage-warped Rotation Isomers of C20 Fullerene: MP2 and Density Functional Calculations
Jangwon Lee,Yongjae Cho,MinJeong Jang,GaYoung Kook,HeeSu Gho,이창훈,Geun C. Hoang,Kee Hag Lee 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.2
Using the density functional methods B3LYP, M06-2X, PBE1PBE, B3LYP D3, M06-2X D3, and PBE1PBE D3, and the ab initio MP2 calculations, the optimized atomic structures and energies of C20 cage rotation isomers without a constraint were obtained. The reaction path between the two rotational isomers was then studied, in which there are three local stable atomic structures. One is the most stable fullerene structure with the D2h point group staggered between the upper and bottom pentagons (ST) and the other is the second lowest energy rotational isomer with the Cs point group eclipsed between the upper and bottom pentagons (EC) with a torn fullerene structure (M1) between ST and EC. The first transition structure T1 between the ST and the M1, and the second transition structure T2 between the M1 and the EC were then obtained along the reaction coordinate between these three structures. Vibration analysis of all optimized structures including the transition structures without a constraint was carried out. For each of the rotational isomers obtained by our calculations, thermodynamic stability was explained with the relative energy difference, and then the kinetic stability was analyzed as the HOMO?LUMO energy difference.
Liu, Yan-Yan,Jin, Hu-Jie,Park, Choon-Bae,Hoang, Geun C. The Korean Institute of Electrical and Electronic 2009 Transactions on Electrical and Electronic Material Vol.10 No.1
N-doped ZnO thin films were deposited on n-type Si(100) and homo-buffer layer, and undoped ZnO thin film was also deposited on homo-buffer layer by RF magnetron sputtering method. After deposition, all films were in-situ annealed at $800^{\circ}C$ for 5 minutes in ambient of $O_2$ with pressure of 10Torr. X -ray diffraction shows that the homo-buffer layer is beneficial to the crystalline of N-doped ZnO thin films and all films have preferable c-axis orientation. Atomic force microscopy shows that undoped ZnO thin film grown on homo-buffer layer has an evident improvement of smoothness compared with N-dope ZnO thin films. Hall-effect measurements show that all ZnO films annealed at $800^{\circ}C$ possess p-type conductivities. The undoped ZnO film has the highest carrier concentration of $1.145{\times}10^{17}cm{-3}$. The photoluminescence spectra show the emissions related to FE, DAP and many defects such as $V_{Zn}$, $Zn_O$, $O_i$ and $O_{Zn}$. The p-type defects ($O_i$, $V_{Zn}$, and $O_{Zn}$) are dominant. The undoped ZnO thin film has a better p-type conductivity compared with N-doped ZnO thin film.
Yan-Yan Liu,박춘배,Hu-Jie Jin,Geun C. Hoang 한국전기전자재료학회 2009 Transactions on Electrical and Electronic Material Vol.10 No.1
N-doped ZnO thin films were deposited on n-type Si(100) and homo-buffer layer, and undoped ZnO thin film was also deposited on homo-buffer layer by RF magnetron sputtering method. After deposition, all films were in-situ annealed at 800 oC for 5 minutes in ambient of O2 with pressure of 10 Torr. X-ray diffraction shows that the homo-buffer layer is beneficial to the crystalline of N-doped ZnO thin films and all films have preferable c-axis orientation. Atomic force microscopy shows that undoped ZnO thin film grown on homo-buffer layer has an evident improvement of smoothness compared with N-dope ZnO thin films. Hall-effect measurements show that all ZnO films annealed at 800 oC possess p-type conductivities. The undoped ZnO film has the highest carrier concentration of 1.145x1017 cm-3. The photoluminescence spectra show the emissions related to FE, DAP and many defects such as VZn, ZnO, Oi and OZn. The p-type defects (Oi, VZn, and OZn) are dominant. The undoped ZnO thin film has a better p-type conductivity compared with N-doped ZnO thin film.
Hoang, Geun C. 圓光大學校 基礎自然科學硏究所 1993 基礎科學硏究誌 Vol.12 No.1
고압 라만 분광법을 이용하여 TEOS (Si(OC_2H_5)_4)의 가수분해 현상을 연구하였다. TEOS는 자발적으로 고분자화 되지 못 하기 때문에 알코올을 용매로 물과 반응하여 (가수분해 반응) 중간물질이 되며 (Si(OH)_4) 이들이 상호결합하여 고분자가 된다. 이 가수분해 반응에서, 압력, pH가 다른 물, 그리고 pH는 같으나 촉매가 다른 물을 사용하는 경우, 이들이 반응 속도에 미치는 영향에 관하여 고찰하였다. 압력과 반응 상수의 상관 관계에서 volume of activation을 도출하여 TEOS가 가수분해될 때의 반응 mechanism에 대하여 고찰하였다. TEOS가 가수분해 될 때 Si원자가 intermeditate state에서 penta-valent state를 가진다는 것을 알았으며, 이 반응 mechanism은 TEOS와 알코올 그리고 촉매가 다른 물을 사용하여도 변하지 않는 다는 것을 고찰하였다.
황근창(Geun C. Hoang) 한국정신과학학회 2014 한국정신과학회 학술대회 논문집 Vol.2014 No.4
자연 현상에 대한 물리학적 이해는 역학, 전자기학, 광학, 핵 물리학, 고체 물리학, 응집물리학, 반도체 물리학등이 있으나 크게 보면, 고전 물리학과 현대 물리학으로 대별할 수 있고, 그 중에서 역학은 물체의 위치변화 (변위), 속도, 가속도 등의 물체의 운동과 힘, 에너지에 관한 이론이다. 역학은 크게 고전 역학과 양자 역학이라는 학문의 체계가 대표적이라고 할 수 있다. 이 두 개의 역학은 인간의 사고에 영향을 미쳤으며, 패러다임 쉬프트에 기여 하였다. 두 학문의 체계는 각각의 범주가 있으며, 범주 안에서 그 역학의 체계가 성립한다. 본 논문은 두 역학의 체계를 살펴보고 각 이론을 우리 현실생활과 결부시켜 고찰하며 서로 다른 범주가 어떤 경우에 상관성(접접)을 가지는가를 고찰 해본다.
Influence of Hydrogen on Al-doped ZnO Thin Films in the Process of Deposition and Annealing
Chen, Hao,Jin, Hu-Jie,Park, Choon-Bae,Hoang, Geun-C. The Korean Institute of Electrical and Electronic 2009 Transactions on Electrical and Electronic Material Vol.10 No.3
The Al-doped ZnO (AZO) films were deposited on a glass substrate by RF magnetron sputtering in pure Ar and $Ar+H_2$ gas ambient at temperature of $100^{\circ}C$ and annealed in hydrogen ambient at the temperature range from 100 to 300 $^{\circ}C$, respectively. It was found that either the addition of hydrogen to the sputtering gas or the annealing treatment effectively reduced the resistivity of the AZO films. When the AZO films were annealed at the temperature of 300 $^{\circ}C$ for lhr in a hydrogen atmosphere, the resistivity decreased from $2.60{\times}10^{-3}\;{\Omega}cm$ to $8.42{\times}l0^{-4}\;{\Omega}cm$ for the film deposited in pure Ar gas ambient. Under the same annealing conditions of temperature and hydrogen ambient, the resistivity of AZO films deposited in the $Ar+H_2$ gas mixture decreased from $8.22{\times}l0^{-4}\;{\Omega}cm$ to $4.25{\times}l0^{-4}\;{\Omega}cm$. The lowest resistivity of $4.25{\times}l0^{-4}\;{\Omega}cm$ was obtained by adding hydrogen gas to the deposition and annealing process. X-ray diffraction (XRD) pattern of all films showed preferable growth orientation of (002) plane. The average transmittance is above 85 % and in the range of 400-1000 nm for all films.
Influence of Hydrogen on Al-doped ZnO Thin Films in the Process of Deposition and Annealing
진호,박춘배,Hu-Jie Jin,Geun C. Hoang 한국전기전자재료학회 2009 Transactions on Electrical and Electronic Material Vol.10 No.3
The Al-doped ZnO (AZO) films were deposited on a glass substrate by RF magnetron sputtering in pure Ar and Ar+H2 gas ambient at temperature of 100ºC and annealed in hydrogen ambient at the temperature range from 100 to 300 °C, respectively. It was found that either the addition of hydrogen to the sputtering gas or the annealing treatment effectively reduced the resistivity of the AZO films. When the AZO films were annealed at the temperature of 300 °C for 1hr in a hydrogen atmosphere, the resistivity decreased from 2.60×10-3 Ωcm to 8.42×10-4 Ωcm for the film deposited in pure Ar gas ambient. Under the same annealing conditions of temperature and hydrogen ambient, the resistivity of AZO films deposited in the Ar+H2 gas mixture decreased from 8.22×10-4 Ωcm to 4.25×10-4 Ωcm. The lowest resistivity of 4.25×10-4 Ωcm was obtained by adding hydrogen gas to the deposition and annealing process. X-ray diffraction (XRD) pattern of all films showed preferable growth orientation of (002) plane. The average transmittance is above 85 % and in the range of 400-1000 nm for all films.
PL Property of Al-N Codoped p-type ZnO Thin Films Fabricated by DC Magnetron Sputtering
Yan-Yan Liu,박춘배,Hu-Jie Jin,Geun C. Hoang 한국전기전자재료학회 2009 Transactions on Electrical and Electronic Material Vol.10 No.3
High-quality Al-N doped p-type ZnO thin films were deposited on Si and buffer layer/Si by DC magnetron sputtering in a mixture of N2 and O2 gas. The target was ceramic ZnO mixed with Al2O3 (2 wt%). The p-type ZnO thin films showed a carrier concentration in the range of 1.5x1015~2.93x1017 cm-3, resistivity in the range of 131.2~2.864 Ωcm, mobility in the range of 3.99~31.6 cm2V-1s-1, respectively. It was easier to dope p-type ZnO films on Si substrates than on buffer layer/Si. The film grown on Si showed the highest quality of photoluminescence (PL) characteristics. The Al donor energy level depth (Ed) of Al-N codoped ZnO films was reduced to about 50 meV, and the N acceptor energy level depth (Ea) was reduced to 63 meV.
Hwang, Seung-Taek,Park, Choon-Bae,Hoang, Geun-C. The Korean Institute of Electrical and Electronic 2010 Transactions on Electrical and Electronic Material Vol.11 No.6
This study has been carried out to determine the optimal process conditions of $AZO:H_2$ thin films for the maximization of the transmittance of a blue GaN light-emitting diode (LED) with a wavelength of 470 nm. The Al-doped zinc oxide $(AZO):H_2$ thin films were deposited on a sapphire substrate by radio-frequency magnetron sputtering system with varying substrate temperatures, working pressures and annealing temperatures temperature, working pressure and annealing imposed on a AZO (2wt% $Al_2O_3$) ceramic target. The effect of these variables was investigated in order to improve the light extraction efficiency of the LED. As a result, the (002)-oriented peak was found in all the $AZO:H_2$ thin films. The lowest resistivity and the best transmittance at a wavelength of 470 nm was found to be $4.774\;{\times}\;10^{-4}\;{\Omega}cm$ and 92% at a substrate temperature of $500^{\circ}C$, working pressure of 7 mTorr and annealing temperature of $400^{\circ}C$. The transmittance of the $AZO:H_2$ thin film for the Blue GaN LED was improved by approximately 13% relative to that of a ITO thin film (T = 79%).