• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.76-77
• /
• 2005

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(PL) and double crystal X-ray diffraction (DCXO). The temperature dependence of the energy band gap of the $CuAlSe_2$ obtained from the absorpt ion spectra was wel1 described by the Varshni's relation, $E_g$(T) = 2.8382 eV - ($8.86\times10^{-4}$ eV/H)$T_2$/(T + 155K). After the as-grown single crystal $CuAlSe_2$ thin films were annealed in Cu-, Se-, and Al-atmospheres, the origin of point defects of single crystal $CuAlSe_2$ thin films has been investigated by PL at 10 K. The native defects of $V_{cd}$, $V_{se}$, $Cd_{int}$, and $Se_{int}$ obtained by PL measurements were classified as donors or acceptors. And we concluded that the heat-treatment in the Cu-atmosphere converted single crystal $CuAlSe_2$ thin films to an optical n-type. Also. we confirmed that hi in $CuAlSe_2$/GaAs did not form the native defects because Al in single crystal $CuAlSe_2$ thin films existed in the form of stable bonds.

• Korean Journal of Materials Research
• /
• v.18 no.6
• /
• pp.318-325
• /
• 2008

Single crystal $ZnIn_2S_4$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $450^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $ZnIn_2S_4$ source at $610^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray rocking curve (DCRC). The temperature dependence of the energy band gap of the $ZnIn_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.9514\;eV-(7.24{\times}10^{-4}\;eV/K)T^2/(T＋489\;K)$. After the as-grown $ZnIn_2S_4$ single crystal thin films were annealed in Zn-, S-, and In-atmospheres, the origin of point defects of $ZnIn_2S_4$ single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_S$, $Zn_{int}$, and $S_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted $ZnIn_2S_4$ single crystal thin films to an optical p-type. Also, we confirmed that In in $ZnIn_2S_4$/GaAs did not form the native defects because In in $ZnIn_2S_4$ single crystal thin films existed in the form of stable bonds.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.11 no.6
• /
• pp.274-284
• /
• 2001

A stoichimetric mixture of evaporating materials for $AgInS_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films. $AgInS_2$mixed crystal was deposited on thorughly 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 thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of $AgInS_2$ single crystal the films measured from Hall effect by van der Pauw method are $9.35\times 10^{16}/\terxtm{cm}^3$ and $294\terxtm{cm}^2$/V.s at 293 K, respectively. From the optical absorption measurement the temperature dependence of the energy band gap on AgInS$_2$ single crystal thin film was found to be $E_g$(T)= 2.1365eV-($9.89\times 10^{-3}eV/T^2$/(2930+T). After the as-grown $AgInS_2$ single crystal thin films was annealed in $Ag^-S^-$ and In-atmospheres, the origin of point defects of AgInS$_2$ single crystal the films has been investigated by using the photoluminescence(PL) at 10K. The native defects of $V_{Ag},V_s, Ag_{int}$ and $S_{int}$ int/ obtained from PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted $AgInS_2$ single crystal thin films to an optical p-type. Also, we confirmed that In in $AgInS_2$ /GaAs did not form the native defects because In is $AgInS_2$ single crystal thin films did exist in the form of stable bonds.

• Journal of Sensor Science and Technology
• /
• v.17 no.6
• /
• pp.437-446
• /
• 2008

Single crystalline ${ZnIn_2}{Se_4}$ layers were grown on thoroughly etched semi-insulating GaAs (100) substrate at $400^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating ${ZnIn_2}{Se_4}$ source at $630^{\circ}C$. The crystalline structure of the single crystalline thick films was investigated by the photoluminescence (PL) and Double crystalline X-ray rocking curve (DCRC). The carrier density and mobility of ${ZnIn_2}{Se_4}$ single crystalline thick films measured from Hall effect by van der Pauw method are $9.41{\times}10^{16}cm^{-3}$ and $292cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the ${ZnIn_2}{Se_4}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=1.8622 eV-$(5.23{\times}10^{-4}eV/K)T^2$/(T+775.5 K). After the as-grown ${ZnIn_2}{Se_4}$ single crystalline thick films was annealed in Zn-, Se-, and In-atmospheres, the origin of point defects of ${ZnIn_2}{Se_4}$ single crystalline thick films has been investigated by the photoluminescence (PL) at 10 K. The native defects of $V_{Zn}$, $V_{Se}$, $Zn_{int}$, and $Se_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Se-atmosphere converted ${ZnIn_2}{Se_4}$ single crystalline thick films to an optical p-type. Also, we confirmed that In in ${ZnIn_2}{Se_4}$/GaAs did not form the native defects because In in ${ZnIn_2}{Se_4}$ single crystalline thick films existed in the form of stable bonds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.79-80
• /
• 2007

To obtain the single crystal thin films, $AgGaSe_2$ 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 $630^{\circ}C\;and\;420^{\circ}C$, 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). After the as-grown $AgGaSe_2$ single crystal thin films was annealed in Ag-, Se-, and Ga-atmospheres, the origin of point defects of $AgGaSe_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{Ag},\;V_{Se},\;Ag_{int},\;and\;Se_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted $AgGaSe_2$ single crystal thin films to an optical p-type. Also, we confirmed that Ga in $AgGaSe_2$/GaAs did not form the native defects because Ga in $AgGaSe_2$ single crystal thin films existed in the form of stable bonds.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.115-115
• /
• 2015

Many efforts have been devoted on chemical modification of graphene layer to modulate its electrical properties. In the previous report, laser irradiation on the CYTOP (Amorphous Fluoropolymer) covered graphene layer induces chemical modification wherein carbon fluoride is formed on the graphene surface. This results in the insulating I-V characteristics, which have been attracting much research interests on it. However, the direct analytical evidence of the fluoride formation on graphene surface is not yet studied. In this work we investigated what happened on the CYTOP/graphene interface during photon irradiation using spatially resolved photoemission spectroscopy method. It is found that the soft x-ray (614 eV) induces desorption of fluoride atoms from the CYTOP and change di-fluoride form to mono-fluoride. As the photo-induced fluorine desorption is continue strong dipole field generated by initial di-fluoride forms is gradually decreased, resulting in the overall binding energy shift of the C 1s core levels. Both photo-modified CYTOP and CYTOP starts to desorb above $286^{\circ}C$ (~ 0.047 eV), which means that no strong chemical interaction between CYTOP and graphene is established.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.120-120
• /
• 2003

The metallic oxide nanomaterials including ZnO, Ga$_2$O$_3$, TiO$_2$, and SnO$_2$ have been synthesized by a number of methods including laser ablation, arc discharge, thermal annealing procedure, catalytic growth processes, and vapor transport. We have been interested in preparing the nanomaterials of Ga$_2$O$_3$, which is a wide band gap semiconductor (E$_{g}$ =4.9 eV) and used as insulating oxide layer for all gallium-based semiconductor. Ga$_2$O$_3$ is stable at high temperature and a transparent oxide, which has potential application in optoelectronic devices. The Ga$_2$O$_3$ nanoparticles and nanobelts were produced using GaN single crystals, which were grown by flux method inside SUS$^{TM}$ cell using a Na flux and exhibit plate-like morphologies with 4 ~ 5 mm in size. In these experiments, the conventional electric furnace was used. GaN single crystals were pulverized in form of powder for the growth of Ga$_2$O$_3$ nanomaterials. The structure, morphology and composition of the products were studied mainly by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM).).

• Proceedings of the KIEE Conference
• /
• 2008.09a
• /
• pp.207-210
• /
• 2008

In this paper, we researched the dielectric properties and voltage dependence on slice XLPE sheet from 22[kV] and 154[kV] power cable. We studied effects for impurities and water for semiconductor shield through a dielectric properties experiment to estimate performance of insulating materials in power cable. Capacitance and $tan{\delta}$ of 22[kV], 154[kV] were 53/43[pF] and $7.4{\times}10^{-4}$, $2.1510^{-4}$. In these results, the trend was increased with the increase of temperature. The tan6 of XLPE/semiconductor layer was increased as compared with that of XLPE. Dielectric properties reliability of tan6 was small. Also, To improve mean-life and reliability of power cable in this study, we have investigated chemical properties showing by changing the content of carbon black that is semiconductive additives for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Chemical properties of specimens was measured by FT-ATR (Fourier Transform Attenuated Total Reflectance). The condition of specimens was a solid sheet. We could observe functional group (C=O, carbonyl group) of specimens through FT-ATR. From these experimental result, the concentration of functional group (C=O) was high according to increasing the content of carbon black. We could know EEA was excellent more than other specimens from above experimental results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.318-322
• /
• 1997

The (Sr$_{l-x}$.Ca$_{x}$)TiO$_3$(0.05$\leq$x$\leq$0.2) ceramics were fabricated to form semiconducting ceramics by sintering at about 1350[$^{\circ}C$] in a reducing atmosphere($N_2$gas). After being fired in a reducing atmosphere, metal oxides, CuO, was painted on the both surface of the specimens to diffuse to the grain boundary. They were annealed at 1100[$^{\circ}C$] for 2 hours and cooled to room temperature. The grain boundary was composed of the continuous insulating layers. The capacitance changes slowly and almost linearly in the temperature region of -30~+85[$^{\circ}C$]. The capacitance characteristics appears a stable value within $\pm$10[%]. The conduction mechanism of the specimens observed in the temperature range of 25~125[$^{\circ}C$], and is divined into three regions haying different mechanism as the current increased: the region I below 230[V/cm] shows the ohmic conduction. The region II can be explained by the Poole-Frenkel emission theory, and the region III is dominated by the tunneling effect.ect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.11a
• /
• pp.162-163
• /
• 2006

XLPE is used to insulator for Ultra High Voltage power cable. It is easy to processing also has a good insulating property. The study for diagnosis of lifetime and improvement is proceeding continuously. In this paper, it is investigated partial discharge distribution according to slope of needle electrode 0, 20, $40^{\circ}$. Applied voltage is 0.5 [kV/s] by step form for inception voltage. As the result of study, we conformed that increase of slope led to reduce of discharge number and total discharge quantity.