• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.81.2-81
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• 1998

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.79-80
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• 2006

A stoichiometric mixture of evaporating materials for $CdIn_2S_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $CdIn_2S_4$ mixed crystal was deposited on thoroughly etched semi-Insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The temperature dependence of the energy band gap of the $CdIn_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation. $E_g(T)=2.7116 eV-(7.74{\times}10^{-4} eV)T^2/(T+434)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CdIn_2S_4$ have been estimated to be 0.1291 eV and 0.0248 eV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $AgInS_2$/GaAs epilayer. The three photocurrent peaks observed at 10K are ascribed to the $A_1-$, $B_1-$, and C1-exciton peaks for n = 1.

• Journal of Sensor Science and Technology
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• v.15 no.6
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• pp.397-405
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• 2006

Single crystal $AgGaSe_{2}$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_{2}$ source at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $AgGaSe_{2}$ thin films measured with Hall effect by van der Pauw method are $4.05{\times}10^{16}/cm^{3}$, $139cm^{2}/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $AgGaSe_{2}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_{g}(T)$=1.9501 eV-($8.79{\times}10^{-4}{\;}eV/K)T^{2}$/(T+250 K). The crystal field and the spin-orbit splitting energies for the valence band of the $AgGaSe_{2}$ have been estimated to be 0.3132 eV and 0.3725 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}So$ definitely exists in the ${\Gamma}_{5}$ states of the valence band of the $AgGaSe_{2}$. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-$, and $C_{1}-$exciton peaks for n=1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.234-238
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• 2004

A stoichiometric mixture of evaporating materials for $CuInSe_2$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $CuInSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $620^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuInSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $9.62{\times}10^{l6}\;cm^{-3}$ and $296\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuInSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;1.1851\;eV\;-\;(8.99{\times}10^{-4}\;eV/K)T^2/(T+153K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CuInSe_2$ have been estimated to be 0.0087 eV and 0.2329 eV at 10K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}_{so}$ definitely exists in the $\Gamma_6$ states of the valence band of the $CuInSe_2$. The three photocurrent peaks observed at 10K are ascribed to the $A_1-$, $B_1-$, and $C_1$-exciton peaks for n = 1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.92-96
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• 2002

A silver indium sulfide $(AgInS_{2})$ epilayer was grown by the hot wall epitaxy method, which has not been reported in the literature. The grown $AgInS_{2}$ epilayer has found to be a chalcopyrite structure and evaluated to be high quality crystal. From the photocurrent measurement in the temperature range from 30 K to 300 K, the two peaks of A and B were only observed, whereas the three peaks of A, B, and C were seen in the PC spectrum of 10 K. These peaks are ascribed to the band-ta-band transition. The valence band splitting of $AgInS_{2}$ was investigated by means of the photocurrent measurement. The crystal field splitting, $\Delta_{cr}$, and the spin orbit splitting, $\Delta_{so.}$ have been obtained to be 0.150 eV and 0.009 eV at 10 K, respectively. And, the energy band gap at room temperature has been determined to be 1.868 eV. Also, the temperature dependence of the energy band gap, $E_{g}(T)$, was determined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.380-380
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• 2010

The chalcopyrite $ZnIn_2S_4$ epilayers were grown on the GaAs substrate by using a hot-wall epitaxy (HWE) method. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnIn_2S_4$ have been estimated to be 0.1541 eV and 0.0129 eV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the $\Gamma_5$ states of the valence band of the $ZnIn_2S_4$/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-}$, $B_{1^-}$, and $C_1$-exciton peaks for n = 1. Also, we obtained the $A_{\infty^-}$ and B-exciton peaks from the PC spectrum at 293 K.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.611-617
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• 2001

The non-polar optical phonon scattering in the valence band depends on the masses, ratios, and types of mixtures of constituent atoms. Therefore, the random distribution of atoms in alloy semiconductors should be considered in the analysis of scattering mechanisms. For this purpose, the force equations of n atoms in a unit cell are expressed in a n x n matrix form to obtain the angular frequencies due to the acoustic and non-polar optical phonons. And, n is then assumed to be infinity. When this work is compared with other results published elsewhere, it is concluded that the independence of atomic displacement or amplitude of oscillation as ell as the infinite number of atoms in a unit cell must be taken into account for the random distribution of atoms in alloy semiconductors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.652-660
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• 2004

The cis-hex-3-ene-1,5-diynyl-bridged diiron compound 3, [(η$^{5}$ - $C_{5}$ M $e_{5}$ ) Fe(dppe)］$_2$($\mu$-C≡C-CH=CH-C≡C), have been prepared and characterized by cyclic voltammetry(CV), and electronic spectroscopy (UV-VIS and near-IR, NMR). From the results, compound 3 show two well resolved, single-electron, reversible oxidation waves by CV, and comproportionation constant(Kc) calculated from the CV data for compound 3. The Mixed-valence (MV) radical cation 3$^{+}$ show strong absorptions in the near IR, 1586 nm, and this band is more readily assigned as MV $\pi$-$\pi$ band of delocalized complex (Robin-Day Mixed-valence Class III), and the $H_{ab}$ , effective coupling parameter are most consistent with electronic delocalization.

• Proceedings of the Korean Magnestics Society Conference
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• 2006.06a
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• pp.120-121
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• 2006

• Journal of Biomedical Engineering Research
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• v.39 no.3
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• pp.124-133
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• 2018

We tried to investigate the changes in cortical activities according to emotional valence states during watching video clips. We examined the neural basis of two emotional states (positive and negative) using spectral power analysis and brain functional connectivity analysis of cortical current density time-series reconstructed from high-density electroencephalograms (EEGs). Fifteen healthy participants viewed a series of thirty-two 2 min emotional video clips. Sixty-four channel EEGs were recorded. Distributed cortical sources were reconstructed using weighted minimum norm estimation. The temporal and spatial characteristics of spectral source powers showing significant differences between positive and negative emotion were examined. Also, correlations between gamma-band activities and affective valence ratings were determined. We observed the changes of cortical current density time-series according to emotional states modulated by video clip. Gamma-band activities showed significant difference between emotional states for thirty seconds at the middle and the latter half of the video clip, mainly in prefrontal area. It was also significantly anti-correlated with the self-ratings of emotional valence. In addition, the gamma-band activities in frontal and temporal areas were strongly phase-synchronized, more strongly for negative emotional states. Cortical activities in frontal and temporal areas showed high spectral power and inter-regional phase synchronization in gamma-band during negative emotional states. It is inferred that the higher amygdala activation induced by negative stimuli resulted in strong emotional effects and caused strong local and global synchronization of neural activities in gamma-band in frontal and temporal areas.