• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.232-236
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• 2006

The Y1.99-xMxCe0.01SiO5(M=Li, La, Nd, and Gd) phosphors were synthesized by solid-state reaction at 1350oC for 10h under reducing atmosphere in order to improve properties of blue emitting phosphors. Compared with commercial blue phosphors, the Y2SiO5:Ce blue phosphors substituted with various elements showed significant enhancement of the emission intensity. Particularly, 1 mol% Li doped Y2SiO5:Ce phosphors indicated the maximum emission intensity in the photoluminescence spectra. Thanks to SEM analyses revealed that the morphology of Y2SiO5:(Ce,Li) blue phosphors was a pseudo-spherical with particle size of 3m.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.794-798
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• 2001

$Y_{2-x}SiO_5:Ce_x^{3+}$(x=0.002∼0.04) phosphors were prepared by sol-gel process, amorphous crystal phase was observed in calcining dry gel at 800$^{\circ}$C, but pure $X_2$ type of type $Y_2SiO_5$ phase appeared from heat treatment above 1000$^{\circ}$C. Light absorption of tye $Y_2SiO_5$ host lattice occurred at 230∼360nm, and light absorption of the $Y_{2-x}SiO_5:Ce_x^{3+}$ phosphors was observed at 300∼400nm in adding $Ce^{3+}$. $Y_{2-x}SiO_5:Ce_x^{3+}$ phosphors showed maximum emission shoulder at 436nm. Maximum CL intensities of $Y_{2-x}SiO_5:Ce_x^{3+}$ were observed in adding 0.025 $Ce^{3+}$ and the phosphor showed x=0.161, y=0.124 in color coordinate of CIE1931.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.590-593
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• 1999

$Y_2SiO_5$:Ce was considered as blue phosphor for field emission display because it had an excellent resistance against brightness saturation. But unfortunately It hadn't a sufficient brightness to be applied to FED. In this experiment It-$In_2O_3$, MgO and $SiO_2$ were coated onto $Y_2SiO_5$:Ce phosphor in order to improve the cathodoluminance(CL properties. The coating structures were identified to be the crystalline phases of $In_2O_3$ and MgO respectively. They had fine particle-like shape and were distributed on the surface of $Y_2SiO_5$:Ce phosphor. It was found that the CL efficiency of $Y_2SiO_5$:Ce phosphors were decreased after coatings with In20:j and MgO in voltage range from 500 V to 5 kV. But the brightness of $Y_2SiO_5$:Ce phosphor was increased after coating of 5 0 2 . And also the aging test showed that $In_2O_3$ coating improved the life time of $Y_2SiO_5$:Ce phosphor.

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.558-563
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• 2000

$Y_2SiO_5:Ce$ phosphor was coated with $In_2O_3$, $Al_2O_3$ and $SiO_2$ and then their cathodoluminance(CL)proper-ties required in field emission display were investigated. It was found that luminance efficiency and aging p개perty of $Y_2SiO_5:Ce$ phosphor was decreased with $In_2O_3$coating. For the case of coating, the luminance intensity was in blue phosphor was dramatically increased with $SiO_2$ coating. And also the aging property of $Y_2SiO_5:Ce$ Phosphor coated with $SiO_2$ was significantly improved compared to non-coated sample.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.67-67
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• 2000

CeO2는 cubic 구조의 일종인 CaR2 구조를 가지고 있으며 격자상수가 Si의 격장상수와 매우 비슷하여 Si 기판위에 에피텍셜하게 성장할 수 있는 가능성이 매우 크다. 따라서 SOI(silicon-on-insulator)구조의 실현을 위하여 Si 기판위에 CeO2 박막을 에피텍셜하게 성장시키려는 많은 노력이 있어왔다. 또한 metal-ferroelectric-semiconductor field effect transistor)에서 ferroelectric 박막과 Si 기판사이의 완충층으로 사용된다. 이러한 CeO2의 응용을 위해서는 Si 기판 위에 성장된 CeO2 박막의 방위성 및 CeO2/Si 구조의 전기적 특성을 알아보는 것이 매우 중요하다. 본 연구에서는 Si(100) 기판위에 CeO2(200)방향으로 성장하는 박막과 EcO2(111) 방향으로 성장하는 박막을 rf magnetron sputtering 방법으로 증착하여 각각의 구조적, 전기적 특성을 분석하였다. RCA 방법으로 세정한 P-type Si(100)기판위에 Ce target과 O2를 사용하여 CeO2(200) 및 CeO2(111)박막을 증착하였다. 증착후 RTA(rapid thermal annealing)방법으로 95$0^{\circ}C$, O2 분위기에서 5분간 열처리를 하였다 이렇게 제작된 CeO2 박막의 구조적 특성을 XRD(x-ray diffraction)방법으로 분석하였고, Al/CeO2/Si의 MIS(metal-insulator-semiconductor)구조를 제작하여 C-V (capacitance-voltage), I-V (current-voltage) 특성을 분석하였으며 TEM(transmission electron microscopy)으로 증착된 CeO2막과 Si 기판과의 계면 특성을 연구하였다. C-V특성에 있어서 CeO2(111)/Si은 CeO2(111)의 두께가 증가함에 따라 hysteresis windows가 증가한 방면 CeO2(200)/Si은 hysteresis windows가 아주 작을뿐만 아니라 CeO2(200)의 두께가 증가하더라도 hysteresis windos가 증가하지 않았다. CeO2(111)/Si과 CeO2(200)/Si의 C-V 특성의 차이는 CeO2(111)과 CeO2(200)이 Si 기판에 의해 받은 stress의 차이와 이에 따른 defect형성의 차이에 의한 것으로 사료된다.

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.740-744
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• 2001

The $Y_2SiO_5:Ce$ phosphors were synthesized by sol-gel technique in order to improve the performance of blue emitting phosphors for field emission display(FED). The resulted$Y_2SiO_5:Ce$ phosphors enhanced the emission intensity. In addition, calcination temperature of sol-gel technique(1300~140$0^{\circ}C$) was lower than that of the solid state reaction(>1$600^{\circ}C$). Under 365 nm and low voltage electron excitations. $Ce^{3+}$ -activated $Y_2SiO_5$phosphors showed blue emission band with a range of 400~ 430nm. Especially, 2mol% $Ce^{3+}$ doped $Y_2SiO_5:Ce$phosphors showed the maximum emission intensity. We have also controlled drying temperature of wet gel, pH, and $H_2O$/TEOS molar ratio for the optimum condition of TEOS hydrolysis.

• Journal of the Korean Vacuum Society
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• v.7 no.3
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• pp.195-200
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• 1998

We have investigated the crystal structure and electrical properties of Pt/SBT/$CeO_2$/Si(MFIS) and Pt/SBT/Si(MFS) structures for the gate oxide of ferroelectric memory. XRD spectra and SEM showed that the SBT film of SBT/$CeO_2$/Si structure had larger grain than that of SBT/Si structure. Furthermore HRTEM showed that SBT/$CeO_2$/Si had 5 nm thick $SiO_2$layer and very smooth interface but SBT/Si had 6nm thick $SiO_2$layer and 7nm thick amorphous intermediate interface. Therefore, $CeO_2$film between SBT film and Si substrate is confirmed as a good candidate for a diffusion barrier. The remanent polarization decreased and coercive voltage increased in Pt/SBT/$CeO_2/Pt/SiO_2$/Si structure. This effect may increase memory window of MFIS structure directly related to the coercive voltage. From the capacitance-voltage characteristics, the memory of Pt/SBT(140 nm)/$CeO_2$(25 nm)/Si structure were in the range of 1~2 V at the applied voltage of 4~6 V. The memory window increased with the thickness of SBT film. These results may be due to voltage applied at SBT films. The leakage currents of Pt/SBT/$CeO_2$/Si and Pt/SBT/Si were $ 10^8A/\textrm{cm}^2$ and $ 10^6 A/\textrm{cm}^2$, respectively.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.322-326
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• 1999

We have investigated the growing process of a silicon film on the $CeO_2/Si$ surface. The silicon was deposited by using electron beam deposition method. The $CeO_2$(111) film was grown on a (111)-oriented silicon substrate at $700^{\circ}C$ at oxygen [partial pressure of $5\times10^{-5}$ Torr. To investigate the condition of epitaxial growth of si films on the $CeO_2/Si$ substrate, we deposited Si at various temperature니 The overlayer silicon was characterized by using x-ray diffraction(XRD). double crystal x-ray diffraction (DCXRD), and transmission electron microscopy (TEM). At temperature higher than $690^{\circ}C$, $CeO_2$ layer was observed at the $CeO_2/Si$ interface, which was formed by chemical reaction with silicon and oxygen dissociated from $CeO_2$. When silicon was deposited on the $CeO_2/Si$ at $620^{\circ}C$, silicon grew epitaxially along the (111)-direction.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.104-104
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• 1999

Cerium dioxide 박막의 포토루미네슨에 관해서는 Cerium 4f band에서 oxygen 2p band로의 transition에 의한 발광(400nm) 현상이 보고되었다. 또한 Indium Oxide 박막의 발광(637nm0 현상이 보고되었다. 본 연구에서는 3족인 Indium을 Si/In/CeO2/Si 구조와 CeO2/Si 구조에 도핑하여 포토루미네슨스 현상을 관찰하였다. E-beam evaporator를 사용하여 Silicon(111) 기판에 Cerium dioxcide 박막을 성장시킨 경우의 두가지 시료를 분석하였다. 포토루미네슨스 관찰을 위해서 Ge-Cd laser (325nm)가 사용되었으며 Indium의 도핑양과 분포 상태를 알기 위해 SIMS와 ADP를 이용하여 분석하였다. Indium양에 대한 포토루미네슨스 변화와 열처리 후의 indium의 분포의 변화에 의한 포토루미네슨스 변화를 관찰하였다. 상온에서 In/CeO2/Si 시료와 Si/In/CeO2/Si 시료에 대한 포토루미네슨스 현상을 관찰한 결과 Si/In/CeO2/Si 시료에서만 500nm(2.5eV)에서 발광 현상이 관찰되었다. 도핑된 indium은 ADP에서는 검출되지 않고 SIMS에서만 검출되어 ADP의 detection range(1-0.1%) 이하의 양이 도핑된 것으로 추측된다. 도핑된 Indium의 양이 증가할수록 포토루미네슨스의 Intensity가 증가하였다. 또한 열처리(110$0^{\circ}C$, 1min) 후 포토루미네슨스의 peak위치가 390nm(3.18eV)로 변화하였다. Si/In/CeO2/Si에서 포토루미네슨스 현상이 관측되고 Intensity가 indium의 양에 의존하므로 완전하지 못한 Cerium dioxide의 CeOx 구조와 indium과의 결합이 포토루미네슨스의 원인으로 추측된다. 열처리 후 SIMS의 분석결과 indium의 분포가 변화하였으며 이는 포토루미네슨스의 변화의 원인으로 판단된다.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.148.2-148
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• 2002