• Journal of the Korean Ceramic Society
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• v.43 no.5 s.288
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• pp.304-308
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• 2006

We have synthesized a $Eu^{2+}-activated\;Sr_3MgSi_2O_8$ blue phosphor and $(Sr,Ba)_2SiO_4$ yellow phosphor and prepared white LEDs by combining these phosphors with a InGaN UV LED chip. Three distinct emission bands from the InGaN-based LED and the two phosphors are clearly observed at 405 nm, 460 nm and at around 560 nm, respectively. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This blue emission was used as an optical transition of the $Sr_3MgSi_2O_8:Eu$ blue phosphor and $(Sr,Ba)_2SiO_4:Eu$ yellow phosphor. The 460 nm and 560 nm emission band is ascribed to a radiative recombination of $Eu^{2+}$ impurity ions in the $Sr_3MgSi_2O_8:Eu$ and $(Sr,Ba)_2SiO_4$ host matrix. As a consequence of a preparation of UV White LED lamp using the $Sr_3MgSi_2O_8:Eu$ blue phosphor and $(Sr,Ba)_2SiO_4:Eu$ yellow phosphor, the highest luminescence efficiency was obtained at the ration of epoxy/two phosphor (1/0.2361). At this time, the CIE chromaticity was CIE x = 0.3140, CIE y = 0.3201 and CCT (6500 K).

• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.530-538
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• 2016

There is a close relationship between the performance and the heat generation of the electronic device. Heat generation causes a significant degradation of the durability and/or efficiency of the device. It is necessary to have an effective method to release the generated heat. Based on demands of the printed circuit board (PCB) manufacturing, it is necessary to develop a robust and reliable plating technique for substrates with high thermal conductivity, such as alumina ($Al_2O_3$), aluminium nitride (AlN), and silicon nitride ($Si_3N_4$). In this study, the plating of metal layers on an insulating silicon nitride ($Si_3N_4$) ceramic substrate was developed. We formed a Pd-$TiO_2$ adhesion layer and used APTES(3-Aminopropyltriethoxysilane) to form OH groups on the surface and adhere the metal layer on the insulating $Si_3N_4$ substrate. We used an electroless Ni plating without sensitization/activation process, as Pd particles were nucleated on the $TiO_2$ layer. The electrical resistivity of Ni and Cu layers is $7.27{\times}10^{-5}$ and $1.32{\times}10^{-6}ohm-cm$ by 4 point prober, respectively. The adhesion strength is 2.506 N by scratch test.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.178-179
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• 2014

In this study, $Ni-W-Si_3N_4$ alloy composite coatings were prepared by pulse electrodeposition method using nickel sulfate bath with different contents of tungsten source, $Na_2WO_4.2H_2O$, and dispersed $Si_3N_4$ nano particles. The structure and microstructure ofcoatings was separately analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicated that nano $Si_3N_4$ and W content in alloy had remarkable effect on microstructure, microhardness and scratch resistant properties. Tungsten content in Ni-W and $Ni-W-Si_3N_4$ alloy ranged from 7 to 14 at.%. Scratch test results suggest that as compared to Ni-W only, $Ni-W-Si_3N_4$ prepared from Ni/W molar ratio of 1:1.5 dispersed with 20 g/L $Si_3N_4$ has shown the best result among different samples.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.171-172
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• 2015

$Ni-W-Si_3N_4$ alloy composite coatings were prepared by pulse electro-deposition method using nickel sulfate bath with different contents of tungsten source, $Na_2WO_4.2H_2O$, and dispersed $Si_3N_4$ nano-particles. The structure and micro-structure of coatings was separately analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicated that nano $Si_3N_4$ and W content in alloy had remarkable effect on micro-structure, micro-hardness and scratch resistant properties. Tungsten content in Ni-W and $Ni-W-Si_3N_4$ alloy ranged from 7 to 14 at.%. Scratch test results suggest that as compared to Ni-W only, $Ni-W-Si_3N_4$ prepared from Ni/W molar ratio of 1:1.5 dispersed with 20 g/L $Si_3N_4$ has shown the best result among different samples.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.2
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• pp.66-69
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• 2003

Various semiconductor nanowires such as GaN, GaP, InP, Si$_3$N$_4$, SiO$_2$/Si, and SiC were coated conformally with aluminum oxide (Al$_2$O$_3$) layers by atomic layer deposition (ALD) using trimethylaluminum (TMA) and distilled water ($H_2O$) at a temperature of 20$0^{\circ}C$. Transmission electron microscopy (TEM) revealed that A1203 cylindrical shells conformally coat the semiconductor nanowires. This study suggests that the ALD of $Al_2$O$_3$ on nanowires is a promising method for preparing cylindrical dielectric shells for coaxially gated nanowire field-effect transistors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.56-56
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• 2009

In this study, we fabricated the engineered $SiO_2/Si_3N_4/SiO_2$(ONO) tunnel barrier with high-k $HfO_2$ trapping layer for application high performance flash MLC(Multi Level Cell). As a result, memory device show low operation voltage and stable memory characteristics with large memory window. Therefore, the engineered tunnel barrier with ONO stacks were useful structure would be effective method for high-integrated MLC memory applications.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.384-389
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• 2011

Gas pressure sintering (GPS) of reaction bonded silicon nitride (RBSN) was performed using $Lu_2O_3-SiO_2$ additive and the properties were compared with those of specimens prepared using high purity $Si_3N_4$ powder. The relative density of RBSN and compacted $Si_3N_4$ powder were 68.9 and 47.1%, and total linear shrinkage after sintering at $1900^{\circ}C$ were 14.8 and 42.9%, respectively. High nitrogen partial pressure (5MPa) was required during sintering at $1900^{\circ}C$ in order to prevent the decomposition of the nitride and to promote the formation of SiC. The relative density and 4-point bending strength of RBSN and $Si_3N_4$ powder compact were 97.7%, 954MPa and 98.2%, 792MPa, respectively, after sintering at $1900^{\circ}C$. The sintered RBSN also showed high fracture toughness of 9.2MPam$^{1/2}$.

• Journal of the Korean Ceramic Society
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• v.21 no.1
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• pp.11-18
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• 1984

$eta$-Sialon synthesis was investigated via the simultaneous reduction and nitridation of Hadong Pink Kaolin using the graphite as a reducing agent at 135$0^{\circ}C$ under 80% $N_2-20%H_2$ atmosphere. When Hadong Pink Kaolin-graphite-silicon nitride seed(molar ratio ; $SiO_2:C:Si_3N_4$=1;3.5:0.05) mixture was heated at 135$0^{\circ}C$ for as long as 20h in 80%$N_2-20%H_2$ atmosphere a homogeneous $eta$-Sialon$(Si_{3.5}Al_{2.5}O_{2.5}N_{2.5})$ was mainly formed together with a small amount of $\alpha$-$Si_3N_4$.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.322-329
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• 2009

Machinability of LAM(Laser Assisted Machining) has been studied for ceramics such as $Al_2O_3$, $Si_3_N4$ and $ZrO_2$ by $CO_2$ laser. It was possible to remove ceramics by PCBN tool because material became softening and deterioration by local laser beam irradiation. The advantage of LAM is the ability to produce larger material removal rates and tool life. But, for cutting of $Al_2O_3$ and $ZrO_2$, stage of laser power control was needed owing to thermal shock with high temperature of workpiece by laser power. And when $Si_3N_4$ was machined by LAM, $N_2$ gas spouted from surface of one cause of high temperature. Characteristics of LAM were analyzed using pyrometer, dynamometer, SEM and EDS to measure temperature of workpiece surface, cutting force, variation of machining surface and structure of lattice respectively. As the result of this study, it was found that machinability of LAM for ceramics in $CO_2$ laser and mechanism of LAM was different according to the kind of ceramics because of properties of materials.

• Journal of the Korean institute of surface engineering
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• v.37 no.3
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• pp.152-157
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• 2004

Ti-Al-N ($Ti_{75}$ $Al_{25}$ N) and Ti-Al-Si-N ($Ti_{69}$ $Al_{23}$ $Si_{8}$N) coatings synthesized by a DC magnetron sputtering technique were studied comparatively with respect to phase characterization and high-temperature oxidation behavior. $Ti_{69}$ $Al_{23}$ $Si_{ 8}$N coating had a nanocomposite microstructure consisting of nanosized(Ti,Al,Si)N crystallites and amorphous $Si_3$$N_4$, with smooth surface morphology. Ti-Al-N coating of which surface $Al_2$$O_3$ layer formed during oxidation suppressed further oxidation. It was sufficiently stable against oxidation up to about $700^{\circ}C$. Ti-Al-Si-N coating showed better oxidation resistance because both surface Ab03 and near-surface $SiO_2$ layers suppressed further oxidation. XRD, GDOES, XPS, and scratch tests were performed.