• Korean Journal of Materials Research
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• v.23 no.12
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• pp.714-721
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• 2013

A stoichiometric mixture of evaporating materials for $ZnAl_2Se_4$ single-crystal thin films was prepared in a horizontal electric furnace. These $ZnAl_2Se_4$ polycrystals had a defect chalcopyrite structure, and its lattice constants were $a_0=5.5563{\AA}$ and $c_0=10.8897{\AA}$.To obtain a single-crystal thin film, mixed $ZnAl_2Se_4$ crystal was deposited on the thoroughly etched semi-insulating GaAs(100) substrate by a hot wall epitaxy (HWE) system. The source and the substrate temperatures were $620^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single-crystal thin film was investigated by using a double crystal X-ray rocking curve and X-ray diffraction ${\omega}-2{\theta}$ scans. The carrier density and mobility of the $ZnAl_2Se_4$ single-crystal thin film were $8.23{\times}10^{16}cm^{-3}$ and $287m^2/vs$ at 293 K, respectively. To identify the band gap energy, the optical absorption spectra of the $ZnAl_2Se_4$ single-crystal thin film was investigated in the temperature region of 10-293 K. The temperature dependence of the direct optical energy gap is well presented by Varshni's relation: $E_g(T)=E_g(0)-({\alpha}T^2/T+{\beta})$. The constants of Varshni's equation had the values of $E_g(0)=3.5269eV$, ${\alpha}=2.03{\times}10^{-3}eV/K$ and ${\beta}=501.9K$ for the $ZnAl_2Se_4$ single-crystal thin film. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnAl_2Se_4$ were estimated to be 109.5 meV and 124.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnAl_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-exciton for n = 1 and $C_{21}$-exciton peaks for n = 21.

• Journal of Sensor Science and Technology
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• v.10 no.6
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• pp.328-337
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• 2001

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}cm^{-3}$, $345\;cm^2/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$ single crystal thin film, we have found that the values of spin orbit splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 106.5 meV and 418.9 meV at 10 K, respectively. From the photoluminescence measurement on $CdGa_2Se_4$ single crystal thin film, we observed free excition ($E_x$) existing only high quality crystal and neutral bound exiciton ($D^{\circ}$, X) having very strong peak intensity. Then, the full-width-at -half-maximum(FWHM) and binding energy of neutral donor bound excition were 8 meV and 13.7 meV, respectivity. By Haynes rule, an activation energy of impurity was 137 meV.

• Journal of Sensor Science and Technology
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• v.23 no.2
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• pp.134-141
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• 2014

A stoichiometric mixture of evaporating materials for $BaIn_2Se_4$ epilayers was prepared from horizontal electric furnace. To obtain the single crystal thin films, $BaIn_2Se_4$ 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 $400^{\circ}C$, respectively. The crystalline structure of the epilayers was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $BaIn_2Se_4$ epilayers measured from Hall effect by van der Pauw method are $8.94{\times}10^{17}cm^{-3}$ and 343 $cm^2/vs$ at 293 K, respectively. The temperature dependence of the energy band gap of the $BaIn_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=2.6261 eV-$(4.9825{\times}10^{-3}eV/K)T^2/(T+558 K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $BaIn_2Se_4$ have been estimated to be 116 meV and 175.9 meV, 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 $BaIn_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1-$, $B_1$-exciton for n = 1 and $C_{21}$-exciton peaks for n=21.

• Korean Journal of Agricultural Science
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• v.22 no.2
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• pp.151-155
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• 1995

Two types of modified celluloses which contain trinitrophenyl groups as chromophore were synthesized from carboxymethyl cellulose Whatman CM 70 and CM 32. Diaminoethyl groups were added to the CM 70 and CM 32 to make DAE-CM celluloses and then the DAE-CM groups were substituted by 2,4,6-trinitrophenyl groups to produce TNP-celluloses. Average particle size of the TNP-cellulose from CM 32 was $44.6{\pm}9.6{\mu}m$ in diameter and $127.9{\pm}22.5{\mu}m$ in length, which was much smaller than those from CM 70, however its TNP-moiety per gram determined by using the molar extinction coefficient $1.33{\times}10^4$ of ${\varepsilon}$-TNP-lysine at 345 nm, was 0.68 millimoles, which was 5.6-fold greater than those from CM 70. The absorption spectrum of TNP-oligosaccharides which were the soluble products of TNP-celluloses by a cellulase preparation Onozuka R-10, showed a maximal peak at 344 nm. Increases in the absorbance during hydrolysis were linear with the enzyme concentration, and the differences of slope values between two types of TNP-celluloses that the more semsitive assay could be achieved by using those from CM 32 as substrate at the low range of the enzyme concentration.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.97-101
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• 2016

ZnO has nanostructured material because of unique properties suitable for various applications. Amongst all chemical and physics methods of synthesis of ZnO nanostructure, the hydrothermal method is attractive for its simplicity and environment friendly condition. Nanostructure ZnO thin films have been successfully synthesized on fluorine doped tin oxide (FTO) substrate using hydrothermal method. A possible growth mechanism of the various nanostructures ZnO is discussed in schematics. The prepared materials were characterized by standard analytical techniques, i.e., X-ray diffraction (XRD) and Field-emission scanning electron microscopy (SEM). The XRD study showed that the obtained ZnO nanostructure thin films are in crystalline nature with hexagonal wurtzite phase. The SEM image shows substrate surface covered with nanostructure ZnO nanrod. The UV-vis absorption spectrum of the synthesized nanostructure ZnO shows a strong excitonic absorption band at 365 nm which indicate formation nanostructure ZnO thin film. Photoluminescence spectra illustrated two emission peaks, with the first one at 424 nm due to the band edge emission of ZnO and the second broad peak centered around 500 nm possibly due to oxygen vacancies in nanostructure ZnO. The Raman measurements peaks observed at $325cm^{-1}$, $418cm^{-1}$, $518cm^{-1}$ and $584cm^{-1}$ indicated that nanostrusture ZnO thin film is high crystalline quality. We trust that nanostructure ZnO material can be effectively will be used as a highly active and stable phtocatalysis application.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.39-42
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• 1999

Nitrogen-doped SiC(3C) (N-SiC(3C)) epliayers were grown on Si(111) substrate at $1250^{\circ}C$ using chemical vapor deposition (CVD) technique by pyrolyzing tetramethylsilane(TMS) in $H_{2}$ carrier gas. SiC(3C) layer was doped using $NH_{3}$ during the CVD growth to be n-type conduction. Physical properties of N-SiC(3C) were investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) patterns, Raman spectroscopy, cross-sectional transmission electron microscopy (XTEM), Hall measurement, and current-voltage(I-V) characteristcs of the N-SiC(3C)/Si(p) diode. N-SiC(3C) layers exhibited n-type conductivity. The n-type doping of SiC(3C) could be controlled by nitrogen dopant using $NH_{3}$ at low temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.553-557
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• 1999

In order to investigate the optical properties of the $Al_XGa_{1-X}N/GaN$ thin film grown by metalorganic chemical vapor deposition (MOCVD) method, the photoluminescene (PL), photocurrent (PC) and persistent photoconductivity (PPC) measurements were carried out at room temperature. The band gap of the $A1_x$$Ga_{1-x}$N/GaN was determined to 3.70 eV by the PL and PC measurements. The PC measurement on the light illumination from the top of the $A1_x$$Ga_{1-x}$N/GaN thin film provides peaks at 3.70, 3.43, and around 2.2 eV. The PC spectrum by the illumination passing through from the substrate of the sample can be shown at 3.43 eV together with a broad tail band from the GaN band edge to around 2.23 eV. The photocurrent quenching and anomalous PPC decay observed in PPC measurements indicate that metastable electron states are fomed in the band gap of GaN layer to trap electrons which can be tunneled the potential barrier for long recovery time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.144-145
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• 2009

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the poly crystal source of $CdGa_2Se_4$ 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 $CdGa_2Se_4$ thin films measured with Hall effect by van der Pauw method are $8.27\;\times\;10^{17}\;cm^{-3}$, $345\;cm^2/V{\cdot}s$ at 293 K, respectively. The photocurrent and the absorption spectra of $CdGa_2Se_4$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10K. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) = 2.6400 eV - ($7.721\;{\times}\;10^{-4}\;eV/K)T^2$/(T + 399 K). Using the photocurrent spectra and the Hopfield quasi cubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) for the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-, and $C_{11}$-exciton peaks.

• Journal of Life Science
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• v.16 no.3 s.76
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• pp.420-426
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• 2006

Bacillus sp. KMU-991 was isolated from Oslo city soils at Norway and shown a strong antifungal activity on red-pepper anthracnose, Colletotrichum gloeosporioides. Bacillus sp. KMU-991 produced a maximum level of antifungal substrate under aerobic incubation at $30^{\circ}C$, 180 rpm for 48 hours in TSB medium(initial pH 7.0) containing 1.0% mannitol and 1.0% ammonium chloride. Precipitate of culture broth by $30{\sim}60%$ ammonium sulfate precipitation exhibited strong antifungal activity against C. gloeosporioides KACC 40804. Butanol extract of cultured broth also shown fungal growth inhibitory activity against Fusarium oxysporum f. sp. radicus-lycopersici KACC 40537, Rhizoctonia solani AG-4 KACC 40142, Botrytis cinerea KACC 40573, Colletotrichum orbiculare KACC 40808, and Phytophthora cambivora KACC 40160 by agar diffusion method.

• BMB Reports
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• v.31 no.3
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• pp.274-280
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• 1998

An inositol monophosphatase (IMPase) was purified to homogeneity from rat duodenal mucosa for the first time and its enzymatic properties were investigated. Rat duodenal mucosa peculiarly exhibited the highest IMPase activity among various rat tissues examined. By means of ammonium sulfate precipitation, followed by Q-Sepharose, polylysine agarose, reactive-red agarose column chromatography, Uno-Q FPLC, and Bio-Silect FPLC, duodenal IMPase was purified 223-fold to a specific activity of 13.6 U/mg protein. The molecular mass of the native enzyme was estimated to be 48,000 Da on gel filtration. The subunit molecular mass was determined by SDS-PAGE to be 24,000 Da. These results indicate that duodenal IMPase is a dime ric protein made up of identical subunits. Rat duodenal IMPase has distinct properties from brain IMPase. It has a broad spectrum of substrate specificity and is insensitive to $Li^+$. Duodenal IMPase does not absolutely require $Mg^{2+}$ for its catalytic activity. Furthermore, duodenal IMPase is less stable to heat than brain enzyme. It is suggested that the rat duodenal mucosa needs a large amount of IMPase whose properties are quite different from that of the brain enzyme.