• Journal of Korean Vacuum Science & Technology
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• v.2 no.1
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• pp.13-19
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• 1998

We have calculated the electronic structure of impurity atoms in metal host by using the tight binding model in the recursion method. For a self-consistent calculation, we assumed that the effect of impurity introduction was localized only at the impurity site and its neighbours. We calculated the Madelung term by limiting the contribution to Vm of the charge perturbations to the first shell around the impurity with Evjen technique. The calculated local density of states and charge transfer values have been compared with the experimental values for a single impurity in metal host. We fund that d-reso-nance state came from the repulsive interaction between impurity d-state and host band, and the position of d-resonance state depended on the difference of valence electrons between the host and the impurity. the results also showed that the charge transfer value between an impurity and host metal was comparable to the ionicity difference between them.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.374-374
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• 2010

Charge transfer mechanism of poly(4,4'-aminotriphenylene hexafluoroisopropylidenediphthalimide) (TP6F PI) which exhibits bistable ON and OFF switching has been studied using photoemission electron spectroscopy (PES) and near-edge x-ray absorption fine structure (NEXAFS). Here, we demonstrate novel set-up in which holes are injected by photoemission process instead of direct charge carrier injection via metal electrode. The accumulated charges on the PI surface in the OFF state abruptly flow across the PI film when the bias voltage of a back electrode reaches a specific value, indicating that the film is changed to the ON state. Core level and x-ray absorption spectra probed at charge injection region via photoemission process do not show any evidences implying structural modification of TP6F PI during the phase change. Whereas, in valence band spectra, the highest occupied molecular orbital (HOMO) is shifted toward Fermi level, responsible for improved hole-mobility of TP6F PI of ON state.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09b
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• pp.173-176
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• 2003

본 논문은 기존의 다치오토마타 모델을 적용하여 개성과 감성상태 모델을 제안한다. 기존 다치오토마타 모델을 2개의 오토마타로 분리하여 하나는 감성상태, 다른 하나는 개성을 모델링하는데 이용하였다. 사용자의 내부 감성과 개성은 Valence-Arousal 공간으로 정의된 감성상태를 바탕으로 구성하였고, 2개로 분리된 다치오토마타의 관계를 정의에 따라 구성하여 감성상태와 개성이 동시에 한 개의 오토마타 모델로 모델링 될 수 있는 가능성을 제시하였다.

• Bulletin of the Korean Chemical Society
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• v.20 no.2
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• pp.147-149
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• 1999

The electronic structures of α- and β-gold selenides are studied. α- and β-AuSe are known as mixed valence compounds having linear (AuSe2, Au+) and square-planar (AuSe4, Au3+) units in their structure simultaneously. Our EHTB calculations, however, show that the oxidation states of Au in α- and β-AuSe are both close to +1. This is because the frontier orbitals are largely made up of Se p-orbitals and Au d-orbitals that lie well below the Fermi level. Our results are consistent with the recent X-ray absorption spectroscopy study on AuSe which show that all Au in the compound exhibit a monovalent state independent of their chemical environments.

• Bulletin of the Korean Chemical Society
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• v.11 no.2
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• pp.115-118
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• 1990

Solution and frozen solution EPR spectra of $\alpha-1,2,3-[HPV(IV)V_2W_9O_{40}]^{6-}$ have been analyzed. The isotropic hyperfine coupling constants remain constant at 350-77 K, indicating that the unpaired electron is delocalized over three vanadium atoms probably even in the ground state.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.259-262
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• 2003

The surface electronic state of rutile $TiO_2$, which is an oxide semiconductor and has a wide band gap of 3.1 $\sim$ 3.5 eV, was calculated by DV-$X_{\alpha}$ method, which is a sort of the first principle molecular orbital method and uses Hartre-Fock-Slater approximation. The $[Ti_{15}O_{56}]^{-52}$ cluster model was used for the calculation of bulk state and the $[OTi_{11}O_{34}]^{-24}$ model for the surface state calculation. After calculations, the energy level diagrams and the deformation electron density distribution map were compared in both models. As results, it was identified that the surface energy levels are found between the valence and conduction band of bulk $TiO_2$ on the surface area. The energy values of these surface-induced levels are lower than conduction band of bulk $TiO_2$ by 0.1 $\sim$ 1 eV. From this fact, it is expected that the surface energy levels act as donar levels in n-type semiconductor.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.134-134
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• 2010

Ga-In-Zn-O 물질은 비정질상태에서 높은 전하 운동성을 가지고 있으며 차세대 투명전극 thin film transistor 대안 소재로 각광받고 있다. 그런데 이 물질은 ion sputtering에 따라 전기적인 특성에 큰 변화가 관찰되고 있으며, 이는 표면에서의 화학적 상태가 전기적 특성을 좌우할 것이라는 것을 의미한다. 또한 보다 안정적이고 신뢰적인 소자를 구현하기 위해서는 ion sputtering에 의한 표면에서의 화학적 특성 변화를 이해하는 것이 매우 중요하다는 것을 의미한다. 본 연구에서는 $Ga_2O_3:In_2O_3$:ZnO의 비율이 각각 1:1:1, 2:2:1, 3:2:1 그리고 4:2:1인 시료를 $Ne^+$이온을 이용하여 sputtering하면서 표면에 민감한 분광분석 기법인 x-ray photoelectron spectroscopy와 x-ray absorption spectroscopy를 이용하여 분광정보의 변화들을 연구하였다. 실험에 의하면, Ga 3d의 양에 비해서 In 4d, Zn 3d의 양은 sputtering 시간에 따라서 각 각 양이 줄어들었으며, 전체적으로 보다 산화가가 높은 경향을 보였으며, valence band maximum 근처에 subgap state를 형성하는 것을 관찰하였다. 또한 sputtering을 계속하는 경우 In 3d, In 4d, 및 Fermi energy 근처에 metallic state가 형성되는 것을 관찰하였다. 이러한 subgap state와 metallic state의 관측은 각기 sputtering에 따라서, 아직 명확하지는 않지만, surface state의 형성 및/혹은 oxygen interstitial의 형성 그리고 metallic In의 형성 및/혹은 oxygen defect의 형성이 이루어지는 것을 의미한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.84-85
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• 2009

The single crystals of p-$CdIn_2Te_4$ were grown by the Bridgman method without the seed crystal. From photocurrent measurements, it was found that three peaks, A, B, and C, correspond to the intrinsic transition from the valence band states of $\Gamma_7(A)$, $\Gamma_6(B)$, and $\Gamma_7(C)$ to the conduction band state of $\Gamma_6$, respectively. The crystal field splitting and the spin orbit splitting were found to be 0.2360 and 0.1119 eV, respectively, from the photocurrent spectroscopy. The temperature dependence of the $CdIn_2Te_4$ band gap energy was given by the equation of $E_g(T)=E_g(0)$ - $(9.43\times10^{-3})T^2$/(2676+T). $E_g(0)$ was estimated to be 1.4750, 1.7110, and 1.8229 eV at the valence band states of A, B, and C, respectively. The band gap energy of $p-CdIn_2Te_4$ at room temperature was determined to be 1.2023 eV.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.269-275
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• 1999

The phase transition on the surface which several adsorbates (K, Mg, etc.) are deposited was observed by Low Energy Electron Diffraction (LEED) and Reflection High Energy Electron Diffraction (RGEED). We took the photoelectron spectra from the valence and core level at several oxygen exposure. For oxygen adsorption, the surface state in valence spectra diminished concurrently with S1, S2 peaks in core level spectra and surface periodicity turned to 3$\times$2 by post-annealing. These results suggest that the phase transition from 3$\times$2 to 3$\times$ on the Si(113) at initial stage is induced by a rearrangement of atoms on the substrate, not by the formation of overlayer.

• Journal of Korea Multimedia Society
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• v.20 no.10
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• pp.1646-1654
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• 2017

Pupil size variation can not be controlled intentionally by the user and includes various features such as the blinking frequency and the duration of a blink, so it is suitable for understanding the user's emotional state. In addition, an ocular feature based emotion classification method should be studied for virtual and augmented reality, which is expected to be applied to various fields. In this paper, we propose a novel emotion classification based on CNN with pupil size variation signals which include not only various ocular feature information but also time information. As a result, compared to previous studies using the same database, the proposed method showed improved results of 5.99% and 12.98% respectively from arousal and valence emotion classification.