• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.869-873
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• 2002

$Cu_2ZnSnS_4$ (CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. In annealing process of thin films deposited with mixture target, the thin films were appeared the peeling. The resistivity was decreased. Thin films were deposited on ITO glass substrates using a compound target which were made by $CU_2S$, ZnS, $SnS_2$ powder were sintered in the atmosphere of Al at room temperature by rf magnetron sputtering We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2ZnSnS_4$ composition A (112) preferred orientation was appeared without annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.4 to 1.7eV as the composition ratio of Zn/Sn.. The optical absorption coefficient of the thin film was above $10^4cm^{-1}$.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.331-337
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• 2012

Electrical properties as a function of composition in silicon nitride ($SiN_x$) films grown at low temperatures ($<200^{\circ}C$) were studied for applications to photonic devices and thin film transistors. Both silicon-rich and nitrogen-rich compositions were successfully produced in final films by controlling the source gas mixing ratio, $R=[(N_2\;or\;NH_3)/SiH_4]$, and the RF plasma power. Depending on the film composition, the dielectric and optical properties of $SiN_x$ films varied substantially. Both the resistivity and breakdown field strength showed the maximum value at the stoichiometric composition (N/Si = 1.33), and degraded as the composition deviated to either side. The electrical properties degraded more rapidly when the composition shifted toward the silicon-rich side than toward the nitrogen-rich side. The composition shift from the silicon-rich side to the nitrogen-rich side accompanied the shift in the photoluminescence characteristic peak to a shorter wavelength, indicating an increase in the band gap. As long as the film composition is close to the stoichiometry, the breakdown field strength and the bulk resistivity showed adequate values for use as a gate dielectric layer down to $150^{\circ}C$ of the process temperature.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.783-790
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• 2017

The energy band gaps and the bowing parameters of zincblende GaP1-xNx on the variation of temperature and composition are determined by using an empirical pseudopotential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter calculated is 13.1eV and the energy band gaps are decreased rapidly for GaP1-xNx ($0{\leq}x{\leq}0.05$, 300K). A refractive index n and a function of real dielectric constant ${\varepsilon}$ are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.320-320
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• 2014

Amorphous silicon alloy (a-Si) solar cells and modules have been receiving a great deal of attention as a low-cost alternate energy source for large-scale terrestrial applications. Key to the achievement of high-efficiency solar cells using the multi-junction approach is the development of high quality, low band-gap materials which can capture the low-energy photons of the solar spectrum. Several cell designs have been reported in the past where grading or buffer layers have been incorporated at the junction interface to reduce carrier recombination near the junction. We have investigated profiling the composition of the a-SiGe alloy throughout the bulk of the intrinsic material so as to have a built-in electrical field in a substantial portion of the intrinsic material. As a result, the band gap mismatch between a-Si:H and $a-Si_{1-x}Ge_x:H$ creates a barrier for carrier transport. Previous reports have proposed a graded band gap structure in the absorber layer not only effectively increases the short wavelength absorption near the p/i interface, but also enhances the hole transport near the i-n interface. Here, we modulated the GeH4 flow rate to control the band gap to be graded from 1.75 eV (a-Si:H) to 1.55 eV ($a-Si_{1-x}Ge_x:H$). The band structure in the absorber layer thus became like a U-shape in which the lowest band gap was located in the middle of the i-layer. Incorporation of this structure in the middle and top cell of the triple-cell configuration is expected to increase the conversion efficiency further.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.304-309
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• 2001

With the development of electromagnetic communication technology and increased use of electromagnetic wave, the countermeasure of EMI(Electromagnetic Interference) becomes more important socially, and interest for the electromagnetic wave absorber has also increased. In this paper, we have studied characteristics of frequency dependency on complex permittivity and complex permeability according to the changes of composition rate and sintering temperature of NiCuZn ferrite also known as electromagnetic wave absorber and further looked into effect of electromagnetic wave absorption properties. From the measurement where the composition of Fe$_2$O$_3$ and ZnO of NiCuZn ferrite was fixed at 49 and 34 mol% respectively while composition of NiO and CuO has been varied at each test, we found out that initial permeability and permittivity were high and the absorbing ability of electromagnetic wave recorded best with loss tangent(${\mu}$r"/${\mu}$r′) displays more than 1 within the frequency band of 2MHz～9.5MHz when the composition ratio of NiO was ranged around 8.5～9.5 mol% and the sintering temperature was 1,080$^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.19 no.6
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• pp.203-208
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• 2009

Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.6
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• pp.225-231
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• 2016

The valence band maximum (VBM) and conduction band minimum (CBM) of Al-doped GaInAsSb alloys substrated on GaSb are calculated by using an analytic approximation based on the tight binding method. The relative positions of the VBM and CBM between Al-GaInASSb and GaSb determine band alignement type, valence band offset (VBO) and conductin band offset (CBO) for the heterojunctions. In this study, aluminium doping is assumed to be substituted in the cation site and limited up to 20 % because it can easily oxidize and degrade materials. It is found that the Al-doped alloys exhibit type-II band alignments over the entire composition range and make the band gaps increase, whereas the VBO and CBO decrease. The decreasing rate of VBO is higher than that of CBO, which implies the Al components play a decisive role in controlling electrons at the interface. The Al-dopled GaInAsSb alloy has a direct band gap induced by $E({\Gamma})$ with a considerable distance from the E(L) and E(X), however, $E({\Gamma})$ approaches to E(L) and E(X) in the high Sb concentration (Sb > 0.7-0.8) which might affect the electron mobility and degrade the optical quality.

• Korean Journal of Weed Science
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• v.8 no.3
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• pp.250-257
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• 1988

The study was intended to know any relations between the rice tolerance to bensulfuron and varietal speciation in seed protein composition or any enzymatical allelies with or without chemical treatment. Rice varieties used were UCP-28, Chinsurah Boro II, Fukunohama, Fadehpur-2, IR 14252-13-2-2-5 as the tolerant group, and HP 93(3) FA, HP94(9) FA, Padilabou Alumbis, KH-17854, and IR 1846-2841-1 as the susceptible, respectively. Electrophoretic methods used were SDS-PAGE for seed protein, 7% PAGE for isozymes (acid phosphatase, peroxidase, malate dehydrogenase, and esterase from rice seedling) and variation in isoenzyme profiles (malate dehydrogenase, peroxidase, and esterase) as affected by different concentrations of bensulfuron(0, $10^{-6}$, $10^{-5}$ and $3{\times}10^{-5}M$) was also studied. The results are summarized as follows. -Among 16 bands separated in seed proteins, two different rice groups selected in terms of tolerance to bensulfuron were clustered in dissimilarity, which was based on relatively larger area in whole peaks and higher activities in N, O, P bands for the tolerant group. -Among isozymes obtained from rice seedlings without chemical treatments, the following specificities were obtained. The tolerant varieties had the relatively higher activity in D band out of 4 peroxidase bands. Malate dehydrogenase was separated into 3 bands and only tolerant varieties had A band and higher activities in Band C bands. Esterase was separated into 3-4 bands with higher activities in A and B bands for tolerant varieties. There were one major band accompanied by 2-3 minor bands for acid phosphatase in which only tolerant varieties had the B band. -The effect of Bensulfuron concentration on the isozyme activities showed that the activity of C band in peroxidase was not present in tolerant varieties which was contrary to the increased activities in susceptible varieties. However, D band was gradually disappeared only in susceptible varieties as the concentration of bensulfuron was increased. For malate dehydrogenase in the susceptible varieties, major bands D, E and F kept consistantly higher activities while minor bands A, B and C disappeared sensitively. Among 5 bands of esterase separated, D band was present only in the tolerant varieties while E band only in the susceptible. The activities in A, C, E bands were sharply decreased in the susceptible varieties as the concentration of bensulfuron was increased.

• Korean Journal of Weed Science
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• v.8 no.2
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• pp.199-207
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• 1988

The study was intended to know any relations between the rice tolerance to oxyfluorfen and varietal speciation in seed protein composition or any enzymatical allelies with or without chemical treatment. Rice varieties used were Chokoto, Aichiasahi, Agabyeo, IR 3941 and Tablei as the tolerant group, and Mushakdanti, Weld Pally, HP 1033, HP 857, and HP 907 as the susceptible, respectively. Electrophoretic methods used were SDS-PAGE for seed protein, 7% PAGE for isozymes (acid phosphatase and peroxidase from rice seedling) and changes in isoenzyme activity (malate dehydrogenase, peroxidase and esterase) as affected by oxyfluorfen treatment ($10^{-4}M$) was also studied. The results are summarized as follows. -Among 19 bands separated in seed proteins, two different rice groups selected in terms of tolerance were clustered in dissimilarity. This was based on 2 facts in that G band was not present in susceptible varieties and that less activity of H, N, O, P, Q, Rand S band was shown. -Among 4 bands separated in acid phosphatase, the presence of (band and lower activity of B band was specific for tolerant varieties. For 4 minor bands separated in peroxidase, the tolerant varieties had no activity in B band and higher activity in A, C, D bands. -Time-course study of isozymes as affected by $10^{-4}M$ oxyfluorfen showed that Chokoto, the tolerant varieties, had little activity in A band and consistently higher activities in Band C bands for malate dehydrogenase. For 5 bands separated in peroxidase, B band was not found in Chokoto while A, C, D, and E bands were consistently present. Esterase was separated into about 4 bands in which Chokoto had maintained higher activities in A, C and D bands.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.61.3-62
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• 2015

Remote-sensing observation is one of the observation methods that provide valuable information, such as composition and surface physical conditions of solar system objects. The Hayabusa spacecraft succeeded in the first sample returning from a near-Earth asteroid, (25143) Itokawa. It has established a ground truth technique to connect between ordinary chondrite meteorites and S-type asteroids. One of the scientific observation instruments that Hayabusa carried, Asteroid Multi-band Imaging Camera(AMICA) has seven optical-near infrared filters (ul, b, v, w, x, p, and zs), taking more than 1400 images of Itokawa during the rendezvous phase. The reflectance of planetary body can provide valuable information of the surface properties, such as the optical aspect of asteroid surface at near zero phase angle (i.e. Sun-asteroid-observer's angle is nearly zero), light scattering on the surface, and surface roughness. However, only little information of the phase angle dependences of the reflectance of the asteroid is known so far. In this study, we investigated the phase angle dependences of Itokawa's surface to understand the surface properties in the solar phase angle of $0^{\circ}-40^{\circ}$ using AMICA images. About 700 images at the Hayabusa rendezvous phase were used for this study. In addition, we compared our result with those of several photometry models, Minnaert model, Lommel-Seeliger model, and Hapke model. At this conference, we focus on the AMICA's v-band data to compare with previous ground-based observation researches.