• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.85-90
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• 2010

In the present work, peak relative efficiency for the energy was obtained and response function was worked out. This study was carried out using the high resolution high efficiency HPGe detector(diameter 78.7 mm, length 86.5 mm) and NaI(Tl) detector for anti-compton. The anti-coincidence of the signals from the two detectors could be used to lessen the Compton effect signal; thus, the $\gamma$-ray energy resolution could be improved. The $\gamma$-ray spectrum was measured at $55^{\circ}$ to the direction of the incident proton beam. Reaction spectrum was obtained from the $^{23}Na$(p, $\gamma$)$^{24}Mg$ reaction at $E_p$ = 1424 keV and $^{27}Al$(p, $\gamma$)$^{28}Si$ reaction at $E_p$ = 992 keV. To accelerate the incident proton which creates the (p, $\gamma$) capture reaction, the 3 MeV Pelletron accelerator at the Tokyo Institute of Technology was used. Response function was worked out by a noble technique. We worked out a response function from 1.2 to 9.4 MeV at intervals of 0.75 MeV.

• Journal of the Korean Vacuum Society
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• v.2 no.1
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• pp.65-72
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• 1993

MgGa2-xInxSe4 single crystal을 bridgman technique로 성장시켰다. 성장된 단결정은 rhombohedral 구조를 가지고 있었으며, lattice constant는 a=3.950~4.070$\AA$, c=38.89~39.50$\AA$으로 주어졌고, 높은 photoconductivity를 가지고 있었다. 이 단결정의 energy gap은 2.20~1.90eV이었고, photoconductivity spectrum에 peak의 energy는 2.31~2.01eV로 주어졌으며, photoconductivity의 time constant는 0.24~0.34sec로 주어졌다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.5
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• pp.1-4
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• 1982

Single crystals of InSe were obtained by the Bridgman method. The crystal structure was hombohedral(R3m) with lattice paramete. a=4.02A, c=24.96A. At 300$^{\circ}$K the electrical conductivity was about ~10-2($\Omega$.cm)-1, reslpectively. The electrical conductivity type was n- type. The donor level located at 0.072eV below the conduction band. The Photosensitivity was observed in range from 840nm to 1120nm. The energy gap of InSe single crystal measured from the photoconductivity and the optical transmittance spectrum was 1.20eV, 1.21eV, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.992-995
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• 2011

The optical properties of ZnO thin film, being treated by O-plasma, have been studied using Photoluminescence(PL) spectroscopy with the change of temperature from 10 K to 290 K. Two characteristic peaks were identified at 10 K : 3.357 eV($D^{\circ}X$) and 3.324 eV(TES). The peak of $D^{\circ}X$ is believed to be due to neutral donor bound excitons where the donor is in the ground state. However, the TES(Two Electron Satellite) peak indicates the excited state of the donor(excitation energy was ~30 meV). The donor binding energy was estimated to be 44 meV, which indicates the possible presence of the neutral donor bound excitons at RT. The thermal effect including thermal broadening was identified from temperature evolution of the spectrum. Both the peak intensity and the peak energy have decreased as the temperature increases. As the temperature approaches to RT, the two peak merges into one broad peak, which is considered a combination of multiple peaks having different physical origins.

• Journal of Korean Vacuum Science & Technology
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• v.4 no.1
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• pp.1-5
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• 2000

The C 1s photoelectron energy loss spectra of tris (8-hydroxy-quinoline) aluminum (Alq$_3$) and N,N'-diphenyl-N,N'-bis (3-methyl phenyl)-1,1'-bi-phenyl-4,4'-diamine (TPD) thin films have been investigated. Two major loss structures, namely the plasmon dominated loss lines and shake-up satellites, have been observed. The shake-up spectrum of the C 1s photoelectron line is directly related to the $\pi$-$\pi$$\^$*/ energy gap of the molecule which plays an important role in organic electroluminescent materials. The molecular orbitals of Alq$_3$ and TPD and their major components, quinolime and benzene, have been calculated with the AMI semi-empirical method. The amount of the plasma-dominated loss of Alq$_3$ and TPD, which has to do with the delocalization of electrons through the molecule, was about 24 eV, alike in both cases. The main peak of the C 1s shake-up spectrum of Alq$_3$ and TPD, however, was 5.2 eV and 6.8 eV respectively. It was found that the main shake-up peak reflects more the local $\pi$\longrightarrow$\pi$$\^$*/ transition of quinoline and benzene component rather than the excitation of the whole molecule of Alq$_3$ and TPD. The C 1s shake-up spectra, however, revealed some correlation with the optical energy gap of the organic eletroluminescent materials.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.457-464
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• 2000

In this paper, we describe the results of various calculations performed for a design of the thickness gauges that use the gamma-ray backscattering method. The radiation source is assumed to be the $_{24}$1Am(60keV gamma-ray) and the detector is a single crystal scintillator in a cylindrical form. The source is located at the center of the detector with the collimator of a cylindrical shape. First, when gamma-rays are incident on a material with a constant angle, we compute the variations of the spectrum for the photons scattered into different angular intervals. Next, we compute for an optimal size for the collimator cylinder for a fixed detector size and an optimal distance from the detector to the material. Finally, we compute the number of observed photons for different thickness of two different materials, a plastic film and an Al foil.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.282-285
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• 2003

Single crystal $CuAlSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $410\;^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $CuAlSe_2$ source at $680\;^{\circ}C$. 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 $CuAlSe_2$ thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}\;and\;295\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuAlSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;2.8382\;eV\;-\;(8.68\;{\times}\;10^{-4}eV/K)T^2/(T\;+\;155\;K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CuAlSe_2$ have been estimated to be 0.2026 eV and 0.2165 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 $CuAlSe_2$. 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.226-229
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• 2004

A stoichiometric mixture of evaporating materials for $CuAlSe_2$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $CuAlSe_2$ 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 $680^{\circ}C$ 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 $CuAlSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}$ and $295\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuAlSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;2.8382\;eV\;-\;(8.68{\times}10^{-4}\;eV/K)T^2/(T+155K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CuAlSe_2$ have been estimated to be 0.2026 eV and 0.2165 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 ${\Gamma}_5$ states of the valence band of the $CuAlSe_2$. 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 Vacuum Society Conference
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• 2013.02a
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• pp.398-398
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• 2013

The electronic properties and the local structure of tantalum oxide thin film with variation of oxygen flow rate ranging from 9.5 to 16 sccm (standard cubic centimeters per minute) have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results show that the Ta4f spectrum for all films consist of the strong spin-orbit doublet $Ta4f_{7/2}$ and $Ta4f_{5/2}$ with splitting of 1.9 eV. The oxygen flow rate of the film results in the appearance of new features in the Ta4f at binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV, these peaks attribute to $Ta^{1+}$, $Ta^{2+}$, $Ta^{4+}$/$Ta^{2+}$, and $Ta^{5+}$, respectively. Thus, the presence of non-stoichiometric state from tantalum oxide ($TaO_x$) thin films could be generated by the oxygen vacancies. The REELS spectra suggest the decrease of band gap for tantalum oxide thin films with increasing the oxygen flow rate. The absorption coefficient ${\mu}$ and its fine structure were extracted from the fluorescence mode of extended X-ray absorption fine structure (EXAFS) spectra. In addition, bond distances (r), coordination numbers (N) and Debye-Waller factors (${\sigma}^2$) each film were determined by a detailed of EXAFS data analysis. EXAFS spectrapresent both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the increase of oxygen flow rate.

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.419-427
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• 2007

Single crystal $ZnIn_{2}S_{4}$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $450^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the polycrystal source of $ZnIn_{2}S_{4}$ at $610^{\circ}C$ prepared from horizontal electric furnace. 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 $ZnIn_{2}S_{4}$ thin films measured with Hall effect by van der Pauw method are $8.51{\times}10^{17}\;electron/cm^{-3}$, $291{\;}cm^{2}/v-s$ at 293 K, respectively. The photocurrent and the absorption spectra of $ZnIn_{2}S_{4}$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10 K. The temperature dependence of the energy band gap of the $ZnIn_{2}S_{4}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=2.9514 eV. ($7.24{\times}10^{-4}\;eV/K$)$T^{2}$/(T+489 K). Using the photocurrent spectra and the Hopfield quasicubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) for the valence band of the $ZnIn_{2}S_{4}$ have been estimated to be 167.8 meV and 14.8 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1}$-, $B_{1}$-, and $C_{41}$-exciton peaks.