• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.180.1-180.1
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• 2014

이중층 그래핀(graphene)의 한쪽 표면에 전하를 주입하면 반전 대칭(inversion symmetry)이 깨지며 라만-비활성 진동모드가 활성화되면서 라만 G-봉우리 부근에 새로운 봉우리가 나타난다고 알려져 있다. 삼중층 그래핀은 그래핀이 적층되는 방식에 따라 ABA (Bernal), ABC (rhombohedral) 그래핀으로 나뉘며, ABC 그래핀은 ABA와는 달리 반전 대칭성을 가지고 있다. 본 연구에서는 화학적인 방법을 이용하여 ABC 그래핀의 반전 대칭을 제어하고 그에 따른 라만 스펙트럼의 변화를 탐구하였다. ABA 그래핀과는 달리 이중층 그래핀과 ABC 그래핀에서는 저진공 열처리 또는 요오드 흡착반응을 한 후에 G-봉우리 부근에서 새로운 봉우리가 나타나는 것을 관찰하였고, 전하밀도 정도가 증가 할수록 G-봉우리와 새로운 봉우리의 위치 차이는 증가하는 것을 관찰하였다. 물과 메탄올에 의한 세척 반응으로부터 열처리는 복층 그래핀과 기판 계면에 그리고 요오드 흡착은 그래핀의 상단표면에 잉여 전하를 유발하여 반전 대칭을 깨트린다는 사실을 확인하였다. 또한 G-봉우리와 새로운 봉우리의 진동수 차이가 반전 대칭을 유발한 전하밀도의 그래디언트에 대한 척도가 될 가능성을 제시하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.3 s.333
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• pp.9-16
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• 2005

The mobility in strained Si inversion layer on $Si_{1-x}Ge_x$ is calculated considering a quantum effect(subband energy and wavefunction) in inversion layer and relaxation time approximation. The quantum effect in inversion layer is obtained by using self-consistent calculation of $Schr\ddot{o}dinger$ and Poisson equations. For the relaxation time, intravalley and intervalley scatterings are considered. The result shows that the reason for the enhancement in mobility as Ge mole fraction increases is that the electron mobility in 2-폴드 valleys is about 3 times higher than that of 4-폴드 valleys and most electrons are located in 2-폴드 valleys as Ge mole fraction increases. Meanwhile, for the phonon-limited mobility the fitting to experimental data, Coulomb and surface roughness mobilities are included in total mobility, Deformation potentials are selected for the calculated effective field, temperature, and Ge mole fraction dependent mobilities to be fitted to experimental data, and then upgraded data can be obtained by considering nonparabolicity in Si band structure.

• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.414-423
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• 2007

Field Emission Display(FED) has significant advantages over existing display technologies, particularly in the area of small and high quality display. In order to test the feasibility of fabricating the System-on-Chip(SOC) with FED, we conducted the experiment to use the p-n junction as an electron beam source for the flat panel display. A novel structure was constructed to form p-n junctions by generating inversion layer with the electric field from the cantilever style gate. When we applied more than 220V at the cantilever style gate which has a height of $1{\mu}m$, avalanche breakdown onset was successfully achieved. The characteristics was compared with the electron emission from the ultra shallow junction in the avalanche region. The experiment result and the future direction were discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.275.1-275.1
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• 2016

반전형 폴리머 태양전지는 그 구조에 의하여 훌륭한 안정성을 가질 뿐만 아니라 roll-to-roll 공정을 통한 대량생산이 가능하여 각광받고 있는 구조이다. 이런 반전형 구조에서, 금속 산화물 나노파티클에 의해 만들어지는 금속 산화물 층은 전자수송층으로서 사용된다. 이 연구에서는 표면개질 물질인 PEIE (Polyethyleneimine-ethoxylate)와 화학적으로 기능화된 산화아연/그래핀 핵/껍질 양자점을 이용하여 전기수송층의 역할을 하는 기능화된 산화아연/그래핀 단분자층을 가지는 태양전지를 제작하였다. 이는 기능화된 산화아연/그래핀 단분자층이 표면개질, 광센서, 전기수송층의 역할을 동시에 수행하는 효과로 인해 제작된 태양전지는 향상된 전자 수집능력을 보였다. 단분자층이 잘 형성되어 있는지 확인하기 위하여 집속 이온 빔 장비를 이용하여 태양전지의 내부 구조를 확인하였으며, density functional theory (DFT)을 이용한 모델링을 통하여 기능화된 산화아연/그래핀 양자점의 전자상태밀도를 분석하였다. 기능화된 산화아연 단분자층에 의한 효과적인 계면 제어 및 전하수송에 의해 약 10.3%의 높은 효율을 가지는 반전형 폴리머 태양전지를 제작할 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8B
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• pp.1469-1476
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• 2000

We have to consider the drain current as consisting of two components the vertical electric field and the longitudinal electric field because the drain current is almost totally due to the presence of drift in strong inversion of n-MOS FET. Especially the mobility of electrons in the inversion layer is smaller than the bulk mobility because the vertical electric field component that is generated by the effect of the gate voltage is perpendicular to the direction of normal current flow. By the multi-box segmentation technical method that are proposed in this paper we calculated the inversion layer depth and analyzed the vertical electric field component which has an large influence on mobility model.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.256-262
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• 1994

$200{\AA}$ thick Co/Pd multilayered thin films were fabricated by sputtering. Two thicknesses of cobalt sublayer, $2{\AA}$ and $4{\AA}$ were chosen and the effects of sputtering pressure on the perpendicular magnetic anisotropy were investigated. It has been found that the optimum pressure for maximum perpendicular magnetic anisotropy(PMA) existed and the pressure for maximum PMA was lower for the multilayer with $2{\AA}$ cobalt layer than that with $4{\AA}$ cobalt thickness. As the sputtering gas presssure increased, domain wall motion with magnetization became difficult and the predominant mode of magnetization reversal changed from domain wall motion to magnetic moment rotation. It turned out that the perpendicular magnetic anisotropy was higher in case of $2{\AA}$ cobalt thickness than $4{\AA}$ cobait thickness.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.05a
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• pp.233-233
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• 2009

• Proceedings of the Korean Magnestics Society Conference
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• 2002.04a
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• pp.166-167
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• 2002

• The Journal of Engineering Geology
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• v.6 no.2
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• pp.83-93
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• 1996

A method is proposed to estimate aquifer parameters in a heterogeneous and anisotropic aquifer under steady-state groundwater flow conditions on the basis of maximum likelihood concept. Zonation method is adopted for parameterization, and estimation errors are analyzed by examining the estimation error covariance matrix in the eigenspace. This study demonstrates the ability of the proposed model to estimate parameters and helps to understand the characteristics of the inverse problem. This study also explores various features of the inverse methodology by applying it to a set of field data of the Taegu area. In the field example, transmissivities were estimated under three different zonation patterns. Recharge rates in the Taegu area were also estimated using MODINV which is an inverse model compatible with MODFLOW.The estimation results indicate that anisotropy of aquifer parameters should be considered for the crystalline rock aquifer which is the dominant aquifer system in Korea.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.2
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• pp.188-195
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• 1988

The electronic states in implanted n-type silicon inversion layers have been calculated by solving Schrodinger and Poisson's equations self-consistently. The results show that implantation affects seriously energy levels, populations, and electron distribution of n-type silicon inversion layers. The calcualted channel charge is in excellent agreement with the experimental data reported elsewhere. This analysis is expected to provide powerful means to evaluate the performance of implanted n-channel MOSTs.