• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.346.2-346.2
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• 2014

To use the GaN based light-emitting diodes (LEDs) as solid state lighting sources, the improvement of light extraction and internal quantum efficiency is essential factors for high brightness LEDs. In this study, we suggested the new materials system of a zinc tin oxide (ZTO) layer formed on blue LED epi-structures to improve the light extraction. ZTO is a representative n-type oxide material consisted of ZnO and SnO system. Moreover, ZTO is one of the promising oxide semiconductor material. Even though ZTO has higher chemical stability than IGZO owing to its SnO2 content this has high mobility and high reliability. After formation of ZTO layer on p-GaN layer by using the spin coating method, structural and optical properties are investigated. The x-ray diffraction (XRD) measurement results show the successful formation of ZTO. The photoluminescence (PL) and absorption spectrum shows that it has 3.6-4.1eV band gap. Finally, the light extraction properties of ZTO/LED chip using electroluminescence (EL) measurement were investigated. The experimental and theoretical analyses were simultaneously conducted.

• Journal of Powder Materials
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• v.6 no.1
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• pp.75-80
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• 1999

The formation of $n-TiO_2$ powder by oxidation of Ti-ethoxied vapor in a flat flame burner reactor maintained under 20 torr has been studied. The produced powder were characterized in terms of crystal structure, chemical composition by XRD and TEM. The results showed that the powder consisted of loose agglomerated anatase and rutile particles and their size were about 10 nm and 20 nm, respectively. In the course of synthesis, changes of the flame color were happened to each condition during heating up the bubbler. The flame color transition phenomena reveled that a critical precursor delivery rate was needed for the powder formation (obtainable powder yield). The critical precursor delivery rate was estimated by a simple function of the bubbler temperature and the carrier gas flow rate. The critical precursor delivery rate was reviewed as an important variable of the nanopowder synthesis.

• Tribology and Lubricants
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• v.11 no.4
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• pp.35-44
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• 1995

Within the practical ranges of speed and load, the formation of transfer films and the consequent effects on the friction and wear behavior of ceramic materials during repeated pass sliding contact were studied. These tests were done using $Al_{2}O_{3}$, SiC and $Si_{3}N_{4}$ with the cylinder-on-flat test configuration. The three pairings behaved differently, even if some wear mechanisms were common to the three systems. The $Al_{2}O_{3}$ pair showed the least wear in overall conditions, followed by the $Si_{3}N_{4}$ pair in harder sliding conditions. The wear of SiC was very high at severe loading. In case of $AL_{2}O_{3}$ and $Si_{3}N_{4}$, the transfer film, whenever formed, is strongly attached, enough to resist being wiped off by the slider. As a consequence, the formation of this f'fim leads to a decrease in the wear rate because of the protecting role of the film. The presence of the film at the contact interface also results in high friction. Also, the wear rate of each ceramics is related to the frictional power provided by load, speed and friction.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2517-2522
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• 2012

New polynuclear poly(hexaaza macrocyclic) copper(II) complexes $[1](ClO_4)_{2n}{\cdot}(H_2O)_{2n}$, $[2](ClO_4)_{2n}{\cdot}(H_2O)_{2n}$, and $[3](ClO_4)_{2n}{\cdot}(H_2O)_{2n}$ have been prepared by the one-pot reaction of formaldehyde with ethylenediamine and 1,2-bis(2-aminoethoxy)ethane, 1,3-diaminopropane, or 1,6-diaminohexane in the presence of the metal ion. The polymer complexes contain fully saturated 14-membered hexaaza macrocyclic units (1,3,6,8,10,13-hexaazacyclotetradecane) that are linked by $N-(CH_2)_2-O-(CH_2)_2-O-(CH_2)_2-N$, $N-(CH_2)_3-N$, or $N-(CH_2)_6-N$ chains. The mononuclear complex $[Cu(H_2L^5)](ClO_4)_4$ ($H_2L^5$ = a protonated form of $L^5$) bearing two $N-(CH_2)_2-O-(CH_2)_2-O-(CH_2)_2-NH_2$ pendant arms has also been prepared by the metal-directed reaction of ethylenediamine, 1,2-bis(2-aminoethoxy)ethane, and formaldehyde. The polymer complexes were characterized employing elemental analyses, FT-IR and electronic absorption spectra, molar conductance, X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron micrograph (SEM). Electronic absorption spectra of the complexes show that each macrocyclic unit of them has square-planar coordination geometry with a 5-6-5-6 chelate ring sequence. The polymer complexes as well as $[Cu(H_2L^5)]^{4+}$ are quite stable even in concentrated $HClO_4$ solutions. Synthesis and characterization of the polynuclear and mononuclear copper(II) complexes are reported.

• Journal of the Korean Chemical Society
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• v.19 no.2
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• pp.116-122
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• 1975

Determination has been made of the kinetics of the reaction of benzyl arenesulfonates with pyridine in acetone. The substituent effects of the leaving groups in benzyl arenesulfonates are correlated by Hammett equations, with the exception of p-MeO and $p-NO_2$ groups, where the electron attracting substituents in the benzyl arenesulfonate increase the rate. The substituent effects of the leaving groups are as expected due to the nucleophilic attack of amine on the benzyl carbon atom. This can be understood in terms of changes in bond formation (C-N) and bond breaking (C-O) in the transition state with charges in electron-attracting ability of the substituents. The predicted substituent effects may indicate a small increase in bond formation and thus a tighter transition state, in benzyl p-bromobenzene sulfonate than in benzyl p-nitrobenzenesulfonate. Predicting made by Thornton concerning the substituent effects on $S_N2$ transition state structures agrees with the changes in bond formation and bond breaking.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.453-460
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• 1997

Sr-ferrite having magnetoplumbite structure is similar to Ba-ferrite in magnetic characteristics, but better magnetic characteristics for using motor application. To improve remanence magnetic flux density(Br) and coercive force(iHc), it is necessary that sintered ferrites must have high density and grain size less than 1 $\mu$m. By varying n values in SrO.nFe2O3 basic composition, calcination temperature, and BaO addition, Sr-ferrite powder and sintered specimen was prepared. The n values, calcination temperature, and BaO addition affected secondary phase formation, particle size, and particle shape. BaO addition enhanced Fe2O3 secondary phase and hexagonal shape particle. Fe2O3 phase reduced sintered density which greatly decreased Br.

• Journal of Powder Materials
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• v.24 no.6
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• pp.431-436
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• 2017

SiAlON-based ceramics are some of the most typical oxynitride ceramic materials, which can be used as cutting tools for heat-resistant super-alloys (HRSA). SiAlON can be fabricated by using gas-pressure reactive sintering from the raw materials, nitrides and oxides such as $Si_3N_4$, AlN, $Al_2O_3$, and $Yb_2O_3$. In this study, we fabricate $Yb_{m/3}Si_{12-(m+n)}Al_{m+n}O_nN_{16-n}$ (m=0.3, n=1.9, 2.3, 2.7) ceramics by using gas-pressure sintering at different sintering temperatures. Then, the densification behavior, phase formation, microstructure, and hardness of the sintered specimens are characterized. We obtain a fully densified specimen with ${\beta}$-SiAlON after gas-pressure sintering at $1820^{\circ}C$ for 90 min. under 10 atm $N_2$ pressure. These SiAlON ceramic materials exhibited hardness values of ~92.9 HRA. The potential of these SiAlON ceramics for cutting tool application is also discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.3
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• pp.139-143
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• 2017

N-type crystalline silicon solar cells have high metal impurity tolerance and higher minority carrier lifetime that increases conversion efficiency. However, junction quality between the boron diffused layer and the n-type substrate is more important for increased efficiency. In this paper, the current status and prospects for boron diffused layers in N-type crystalline silicon solar cell applications are described. Boron diffused layer formation methods (thermal diffusion and co-diffusion using $a-SiO_X:B$), boron rich layer (BRL) and boron silicate glass (BSG) reactions, and analysis of the effects to improve junction characteristics are discussed. In-situ oxidation is performed to remove the boron rich layer. The oxidation process after diffusion shows a lower B-O peak than before the Oxidation process was changed into $SiO_2$ phase by FTIR and BRL. The $a-SiO_X:B$ layer is deposited by PECVD using $SiH_4$, $B_2H_6$, $H_2$, $CO_2$ gases in N-type wafer and annealed by thermal tube furnace for performing the P+ layer. MCLT (minority carrier lifetime) is improved by increasing $SiH_4$ and $B_2H_6$. When $a-SiO_X:B$ is removed, the Si-O peak decreases and the B-H peak declines a little, but MCLT is improved by hydrogen passivated inactive boron atoms. In this paper, we focused on the boron emitter for N-type crystalline solar cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.10
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• pp.642-647
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• 2014

For feasible study of opto-electrical application regarding to oxide semiconductor, we implemented the N doped ZnO growth using a atomic layer deposition technique. The p-type ZnO deposition, necessary for ZnO-based optoelectronics, has considered to be very difficulty due to sufficiently deep acceptor location and self-compensating process on doping. Various sources of N such as $N_2$, $NH_3$, NO, and $NO_2$ and deposition techniques have been used to fabricate p-type ZnO. Hall measurement showed that p-type ZnO was prepared in condition with low deposition temperature and dopant concentration. From the evaluation of photoluminescence spectroscopy, we could observe defect formation formed by N dopant. In this paper, we exhibited the electrical and optical properties of N-doped ZnO thin films grown by atomic layer deposition with $NH_3OH$ doping source.

• Corrosion Science and Technology
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• v.10 no.1
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• pp.6-12
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• 2011

The selective surface oxidation of a transformation-induced-plasticity (TRIP) steel containing 1.6 wt.% Mn and 1.5 wt.% Si during annealing at $800^{\circ}C$ was investigated for its influence on the formation of an inhibition layer during hot-dip galvanizing. The selective oxidation of the alloying elements and the oxide morphology were significantly influenced by the annealing atmosphere. The pure $N_{2}$ atmosphere with a dew point $-40^{\circ}C$ promoted the selective oxidation of Mn as a crystalline $Mn_{2}SiO_{4}$ phase, whereas the $N_{2}$ + 10% $H_{2}$ atmosphere with the same dew point $-40^{\circ}C$ promoted the selective oxidation of Si as an amorphous Si-rich oxide phase. During hot-dip galvanizing, the $Mn_{2}SiO_{4}$ phase was reduced more readily by Al in the Zn bath than the Si-rich oxide phase. Consequently, the pure $N_{2}$ atmosphere resulted in a higher formation rate of $Fe_{2}Al_{5}$ particles at the Zn/steel interface and better galvanizability than the $N_{2}$ + 10% $H_{2}$ atmosphere.