• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.762-765
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• 2014

We fabricated a periodically poled lithium niobate (PPLN) by direct laser-writing of a quasi-phase-matching (QPM) structure in photolithographic process. Because we do not need to prepare a photomask by electron-beam writing, the "maskless" process shortens the fabrication time and significantly reduces the cost. We evaluated the poling quality of the direct laser-written PPLN by measuring the diffraction noise from the surface relief pattern of the fabricated QPM grating and comparing the results to those from a conventional PPLN made with a photomask. The quality of the PPLN fabricated by direct laser-writing was shown to be equivalent to that fabricated by the conventional method.

• 대한전자공학회논문지
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• 제27권4호
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• pp.527-533
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• 1990

Zone-melting recrystallization (ZMR) system using two graphite heaters(a stationary sheet and a narrow movable bar) was constructed and implemented in recrystallization op Si films on insulating layers. The recystallized Si films were examined by Nomarski contrast optical microscopy after Dash etching, transmission electron diffraction pattern, and x-ray diffraction. With optimum conditions of process parameters(input powers of the bottom and upper heater, scanning speed of the upper heater, and the gap between sample and upper heater), the recrystallized Si layer has a (100) texture, but contains many subboundaries. The subgrains are misoriented by < 0.5\ulcorner and the average spacing between subboundaries is about 25\ulcorner.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1127-1134
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• 2002

Fine ceramic particles of zirconia toughened alumina (ZTA), titania toughened alumina (TTA), and zirconia-titania toughened alumina (ZTTA) have been synthesized by ultrasonic spray pyrolysis (USP) at various temperatures from starting salt solutio ns of various compositions aiming for the development of catalytic material. These particles were characterized for properties such as shape, size and size distribution, diffraction pattern, and chemical and phase composition of elements by scanning electron microscopy (SEM), particle size analyzer (PSA), x-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Chemical compositions and sizes of ceramic composites have been controled by the stoichiometry of salt solutions and the flow rate of spraying solutions. The optimum experimental conditions for the various composite particle syntheses have been proposed.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.403-406
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• 2012

Effect of thickness on ZnO properties including the compositional ratio and crystallinity has been systematically investigated using a variety of characterization tools of x-ray diffraction, field emission scanning electron microscopy, x-ray fluorescence and x-ray photoelectron spectroscopy. Interestingly, it was observed that ZnO films below 80 nm in thickness were in oxygen deficiency, while the oxygen ratio was increased in the films above the thickness, although the compositional ratio of ZnO film was not linearly varied with increasing film thickness. Also, ZnO crystallinity, which is characterized by (002) diffraction pattern, was clearly improved with increasing film thickness. The properties of ZnO film with different sputtering time and the nature of direct current reactive sputtering process were discussed in terms of compositional ratio, especially oxygen ratio in ZnO film.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.533-536
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• 2001

Single crystal cubic silicon carbide(3C-SiC) thin film were deposited on Si(100) substrate up to a thickness of $4.3{\mu}m$ by APCVD(atmospheric pressure chemical vapor deposition) method using hexamethyildisilane(HMDS) at $1350^{\circ}C$. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like. The growth rate of the 3C-SiC films was $4.3{\mu}m/hr$. The 3C-SiC epitaxical layers on Si(100) were characterized by XRD(X-ray diffraction), raman scattering and RHEED(reflection high-energy electron diffraction), respectively. The 3C-SiC distinct phonons of TO(transverse optical) near $796cm^{-1}$ and LO(longitudinal optical) near $974{\pm}1cm^{-1}$ were recorded by raman scattering measurement. The deposition films were identified as the single crystal 3C-SiC phase by XRD spectra($2{\theta}=41.5^{\circ}$). Also, with increase of films thickness, RHEED patterns gradually changed from a spot pattern to a streak pattern.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.533-536
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• 2001

Single crystal cubic silicon carbide(3C-SiC) thin film were deposited on Si(100) substrate up to a thickness of 4.3 $\mu\textrm{m}$ by APCVD(atmospheric pressure chemical vapor deposition) method using hexamethyildisilane(HMDS) at 1350$^{\circ}C$. The HMDS flow rate was 0.5 sccm and the carrier gas flow rate was 2.5 slm. The HMDS flow rate was important to get a mirror-like. The growth rate of the 3C-SiC films was 4.3 $\mu\textrm{m}$/hr. The 3C-SiC epitaxical layers on Si(100) were characterized by XRD(X-ray diffraction), raman scattering and RHEED(reflection high-energy electron diffraction), respectively The 3C-SiC distinct phonons of TO(transverse optical) near 796 cm$\^$-1/ and LO(longitudinal optical) near 974${\pm}$1 cm$\^$-1/ were recorded by raman scattering measurement. The deposition films were identified as the single crystal 3C-SiC phase by XRD spectra(2$\theta$=41.5$^{\circ}$). Also, with increase of films thickness, RHEED patterns gradually changed from a spot pattern to a streak pattern

• 한국광물학회지
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• 제16권3호
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• pp.255-263
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• 2003

충청북도 미원지역의 운교리층 내에 산출하는 마가라이트(margarite)를 고분해능 투과전자현미경(HRTEM)을 이용하여 단위포 규모의 미세한 협재조직에 관하여 조사하였다. 편광현미경과 후방산란전자 영상을 이용하여 기존에 확인된 녹니석의 협재조직을 보여주는 마가라이트 결정들을 투과전자현미경으로 관찰한 결과, 마가라이트 결정내에는 녹니석이 흔히 얇은 packet 형태로 매우 불규칙하게 협재되어 있으며, 그 두께는 수백 $\AA$에 달하거나 부분적으로 녹니석 layer가 개별 단위로 나타나기도 한다. HRTEM으로 관찰한 마가라이트는 매우 규칙적인 2M 다형구조를 보여주며, 전자회절 패턴에서 001 (또는 $c^{*}$ ) 방향으로 강한 streaking을 보여주고 있지 않기 때문에 stacking disorder가 심하지 않은 것으로 판단된다. 마가라이트 packet내에는 두께가 $5 \AA$인 부르사이트 layer들이 부분적으로 관찰되는데, 마가라이트 layer사이에 이러한 부르사이트 layer가 단위포 규모로 협재되어 부분적으로 녹니석 구조를 형성한다. 마가라이트의 (001)과 녹니석의 (001)은 서로 평행하지만 두 광물간의 구조적인 연속성이 결여되어 있으므로, 이러한 특징은 마가라이트내에 발견되는 녹니석은 용해와 침전 작용에 의해서 생성되어 협재조직을 이루었음을 지시한다.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.48-53
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• 2001

The crystal structure of ZnS fabricated by gas-liquid phase reaction was refined by the Rietveld program using X-ray diffraction data. The R-weighted pattern (R$\sub$wp/) of ZnS powder was 10.85%. The fraction of HCP phase was closely related with extra amount of H$_2$S gas. The lattice parameters and crystalline size were changed by the relative ratio of multi-phase. The luminescence property of ZnS:Cu, Al green phosphors prepared by conventional methods was good in the range of 91∼94% and 150∼190${\AA}$, respectively. According to the maximum entropy electron density(MEED) methods, any defects in (001) plane of cubic phase were not found. We suggest that both the Rietveld and maximum entropy density methods may be useful tools for studying luminescence mechanism of other phosphors materials.

• 통합자연과학논문집
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• 제1권3호
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• pp.247-249
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• 2008

자성 결정체인 $Fe_3O_4$ 나노 입자를 합성하기위하여 강한 극성 용매인 2-pyrrolidone을 연전도 반응매개체로 하여 용액 내에 $FeCl_3{\cdot}6H_2O$을 용해시켜 2-pyrrolidone의 비등점까지 나노 결정체 고온 열분해 방법을 이용하여 제조되었다. 고온 열분해 후, $Fe_3O_4$ 나노 입자는 methanol/diethyl ether (1:3)에 의해서 침전되어졌다. 합성된 $Fe_3O_4$ 나노 입자는 고결정도, 고자기성을 가지고 있으며, 수용성의 자성 나노 결정체이다. 합성된 $Fe_3O_4$ 나노 입자의 크기와 결정도는 transmission electron microscope (TEM, Tecnai F20)를 이용하여 특성 분석하였으며, area electron diffraction (SAED) pattern과 HRTEM을 이용하여 나노입자의 격자 패턴 (lattice fringes)을 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.455-455
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• 2013

$CeO_2$ nanorings were synthesized by using a surfactant free hydrothermal method. The surface morphology, structural and optical properties of the synthesized $CeO_2$ was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and ultraviolet-visible (UV) spectroscopy measurements. SEM images showed that the surface morphology of the formed $CeO_2$ appeared as nanorings. The XRD pattern of $CeO_2$ nanorings showed the presence of the polycrystalline $CeO_2$ phase readily indexed to the cubic fluorite structure of the $CeO_2$. The mean crystallite size of the $CeO_2$ was calculated using the Scherrer equation from the XRD line broadening of the (111) planes of the cubic $CeO_2$. The UV-Visible spectroscopy spectrum of the $CeO_2$ nanorings exhibited a strong UV absorption band around 350 nm.