• Journal of the Korean Vacuum Society
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• v.6 no.2
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• pp.129-135
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• 1997

Undoped and Co-doped $ZnIn_2Se_4$ single crystals crystallized in the tetragonal space group 142m, with lattice constants a=5.748 $\AA$ and c=11.475 $\AA$, and a=5.567 $\AA$ and c=11.401 $\AA$. The optical absorption measured near the fundamental band edge showed that the optical energy band structure of these compounds had an indirect band gap, the direct and the indirect energy gaps of these compounds decreased as temperature changed from 10 to 300 K. The temperature coefficients of the direct energy gaps were found to be $\alpha=3.71\times10^{-4}$eV/K and $\beta$=519 K for $\alpha=3.71\times10^{-4}$eV/K and $\beta$=421K for $ZnIn_2Se_4$: Co. The temperature coefficients of the indirect energy gaps were also found to be $\alpha=2.31\times10^{-4}$ eV/K and $\beta$=285 K for $ZnIn_2Se_4$, and $\alpha=3.71\times10^{-4}$eV/K and $\beta$=609 K for $ZnIn_2Se_4$:Co, respectively. Six impurity optical absorption peaks due to cobalt are observed in $ZnIn_2Se_4$:Co single crystal. These impurity optical absorption peaks can be attibuted to the electronic transitions between the split energy levels of$CO^{2+}$ ions located at Td symmetry site of $ZnIn_2Se_4$ host lattice. The 1st order spin-orbit coupling constant ($\lambda$), Racah parameter (B), and crystal field parameter (Dq) ARE GIVEN AS -$243\textrm{cm}^{-1}, 587\textrm{cm}^{-1}, \;and\;327\textrm{cm}^{-1}$, respectively.

• Corrosion Science and Technology
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• v.2 no.5
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• pp.212-218
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• 2003

Electronic properties of passive films formed on Ti at film formation potentials $(E_f)V_{SCE}$ in pH 8.5 buffer solution and in an artificial seawater were examined through the photocurrent measurement and Mott-Schottky analysis. The passive films formed on Ti in pH 8.5 buffer solution exhibited a n-type semiconductor with a band gap energys $(E_g);E_g^{n=2}=3.4$ eV for nondirect electron transition, and $E_g^{n=0.5}=3.7$ eV for direct electron transition. These band gap values were almost same as those for the passive films formed in artificial seawater, indicating that chloride ion ($Cl^-$ in solution did not affect the electronic structure of the passive film on Ti. $E_g$ for passive films formed on Ti were found to be greater than those ($E_g^{n=0.5}=3.1$ eV, $E_g^{n=2}=3.4$) for a thermal oxide film formed on Ti in air at $400^{\circ}C$. The disorder energy of passive film, determined from the absorption tail of photocurrent spectrum, was much greater than that for the thermal oxide film farmed on Ti in air at $400^{\circ}C$. The greater $E_g$ and the higher disorder energy for the passive film compared with those for the thermal oxide fIlm suggest that the passive film on Ti exhibited more disorded structure than the thermal oxide film. The donor density (about $2.4{\times}10^{20}cm^{-3}$) for the passive film formed in artificial seawater was greater than that (about $20{\times}10^{20}cm^{-3}$) formed in pH 8.5 buffer solution, indicating that $Cl^-$ increased the donor density for the passive film on Ti.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.577-580
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• 2014

Indium hydroxy sulfide ($In(OH)_xS_y$) as a cadmium (Cd)-free buffer layer for $CuInGaSe_2$ (CIGS) solar cells was prepared by the chemical bath deposition (CBD) and the reaction time was optimized. The band gap energy and transmittance data alongside the thickness results from the direct observation with focused ion beam system (FIB) could be a powerful tool for optimizing the conditions. In addition, X-ray diffractometer (XRD), X-ray photoelectron microscopy (XPS), and scanning electron microscope (SEM) were also employed for the layer characterization. The results indicated that the optimum reaction time for $In(OH)_xS_y$ buffer layer deposition by CBD was 20 min at $70^{\circ}C$ under the conditions employed. At the optimum conditions, the buffer layer thickness was near 57 nm and the band gap energy was 2.7 eV. In addition, it was found that there was no XPS peak shift in between the buffer layers deposited on molybdenum (Mo)/glass and that on CIGS layer.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.91-95
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• 1991

In this paper, the characteristics of IPMSM(Interior-type Permanent Magnet Synchronous Motor) are simulated using 2-Dimensional finite element method. This paper deals with the following characteristics: Air gap flux density considering skew. Back E.M.F, Torque and Inductance. Torque is calculated using current angle which is known from the controller. Direct axis inductance and Quadrature axis inductance are also calculated using energy perturbation method. This results can be used for the computation of the saliency of IPMSM. Computed results are found in satisfactory agreement with experimental ones.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.56-59
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• 1991

The polyervstalline $Cu_{0.28}Ag_{0.72}InSe_{4.4}S_{0.6}$ thin films are prepared by vacuum heat treatment of laver, which is deposited by direct resisting vacuum evaporation. From optical absorption spetra, the optical hand gap energy is determined to be 1.5[eV] at room temerature. From electrical method. hole concentration, resistivity and mobility are 9.3*$10^{18}$[$cm^{-3}$], 6*$10^{-2}$[$\Omega$$.$cm], 11.2[$\textrm{cm}^2$/V$.$sec] respectively at room temperature.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1500-1502
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• 2001

Plate-type ${\beta}-FeSi_2$ single crystals were grown using $FeSi_2$, Fe, and Si as starting materials by the chemical transport reaction method. The ${\beta}-FeSi_2$ single crystal was an orthorhombic structure. The direct optical energy gap was found to be 0.87eV at 300K. Hall effect shows a n-type conductivity in the ${\beta}-FeSi_2$ single crystal. The electrical resistivity values was 1.608$\Omega$cm and electron mobility was $3{\times}10^{-1}cm^2/V{\cdot}sec$ at room temperature.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.367-370
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• 2015

Monolayer transition metal dicalcogenide (TMDC) materials are currently attracting extensive attention due to their distinctive electronic, transport, and optical properties. For example, monolayer $MoS_2$ exhibits a direct band gap in the visible frequency range, which makes it an attractive candidate for the photocatalytic water splitting. For the photoelectrochemical water splitting, the appropriate band edge positions that overlap with the water redox potential are necessary. Similarly, appropriate band level alignments will be crucial for the light emitting diode and photovoltaic applications utlizing heterojunctions between two TMDC materials. Carrying out first-principles calculations, we here investigate how the band edges of $MoS_2$ can be adjusted by surface ligand functionalization. This study will provide useful information for the realization of ligand-based band engineering of monolayer $MoS_2$ for various electronic, energy, and bio device applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.618-621
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• 2001

Plate-type $\beta$-FeSi$_2$single crystals were grown using FeSi$_2$, Fe, and Si as starting materials by the chemical transport reaction method. The $\beta$-FeSi$_2$single crystal was an orthorhombic structure. The direct optical energy gap was found to be 0.87eV at 300K. Hall effect shows a n-type conductivity in the $\beta$-FeSi$_2$ single crystal. The electrical resistivity values was 1.608Ωcm and electron mobility was 3x10$^{-1}$ $\textrm{cm}^2$/V.sec at room temperature.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.7
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• pp.723-734
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• 1992

In this paper, the characteristics of IPMSM(Interior-type Permanent Magnet Synchronous Motor) are simulated using 2-D. finite element method. This paper deals with the following characteristics : air gap flux density considering skew, back e.m.f., torque and inductance. Back e.m.f. is calculated using the flux obtained from the vector potential of FEM solution. Torque is calculated using improved Maxwell stress tensor method and current angle which is obtained from the controller. Direct axis inductance and quadrature axis inductance are also calculated using energy perturbation method. Computed results are found in satisfactory agreement with experimental ones. This method also can be applied for the computation and analysis of the characteristics of SPMSM, current-excited synchronous motor and reluctance motor.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.347-352
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• 2016

ZnO with wurtzite structure has a wide band gap of 3.37 eV. Because ZnO has a direct band gap and a large exciton binding energy, it has higher optical efficiency and thermal stability than the GaN material of blue light emitting devices. To fabricate ZnO devices with optical and thermal advantages, n-type and p-type doping are needed. Many research groups have devoted themselves to fabricating stable p-type ZnO. In this study, $As^+$ ion was implanted using an ion implanter to fabricate p-type ZnO. After the ion implant, rapid thermal annealing (RTA) was conducted to activate the arsenic dopants. First, the structural and optical properties of the ZnO thin films were investigated for as-grown, as-implanted, and annealed ZnO using FE-SEM, XRD, and PL, respectively. Then, the structural, optical, and electrical properties of the ZnO thin films, depending on the As ion dose variation and the RTA temperatures, were analyzed using the same methods. In our experiment, p-type ZnO thin films with a hole concentration of $1.263{\times}10^{18}cm^{-3}$ were obtained when the dose of $5{\times}10^{14}$ As $ions/cm^2$ was implanted and the RTA was conducted at $850^{\circ}C$ for 1 min.