열 필라멘트 CVD법에 의해서 제작한 다이아몬드 막의 잔류응력제어

최시경,정대영,최한메 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.7

The relaxation of the intrinsic stresses in the diamond films fabricated by the hot filament CVD was studied, and it was confirmed that the tensile intrinsic stresses in the films could be controlled without any degradation in the quality of the diamond films. The tensile intrinsic stresses in the films decreased from 2.97 to 1.42 GPa when the substrate thickness increased from 1 to 10mm. This result showed that the residual stress was affected by the substrate thickness as well as by the interaction between grains. Applying of +50 V between the W filament and the Si substrate during deposition, the tensile intrinsic stress in the film deposited at 0 V was decreased from 2.40 GPa to 0.71 GPa. Such large decrease in the tensile intrinsic stress was due to $\beta$-SiC which acted as a buffer layer for the stress relaxation. However, the application of the large voltage above +200V resulted in the change of quality of the diamond film, and nearly had no effect on relaxation in the tensile intrinsic stress.

알루미나의 Ag-33.5Cu-1.5Ti 브레이징 합금 계면에서 생성되는 반응층의 미세조직 관찰과 상 동정

최시경,권순용 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.9

Pressureless-sintered polycrystalline alumina and carbon steel were joined with Ag-33.5Cu-1.5Ti (wt%) brazing alloy. SEM observation revealed that two reaction layers with different thicknesses were continuously formed between the alumina and the brazing alloy. A thick layer formed on the brazing alloy side was identified as Ti3(Cu0.93Al0.07)3O phase with diamond cubic structure. Another thin layer adjacent to the alumina was revealed as $\delta$-TiO phase of which the crystal structure was HCP with a lattice parameter of a0=0.419 nm and c0=0.284 nm. It was confirmed using XPS analysis that $\delta$-TiO was formed directly by a redox reaction of alumina with titanium ir, molten brazing alloy.

2-Pass DInSAR를 활용한 강원도 산사태 탐측

최시경(Choi Si Kyong),손홍규(Sohn Hong Kyu),유수홍(You Su Hong),정재훈(Jung Jae Hoon) 대한공간정보학회 2009 한국지형공간정보학회 학술대회 Vol.2009 No.4

대부분이 지형이 산악 지형으로 되어있는 강원도지역은 여름철의 집중호우와 산사태 피해가 심각한 상황이다. 최근 주목받고 있는 인공위성을 이용한 원격탐측은 기존의 직접측량 방식보다 효율적으로 산사태를 감지할 수 있다. 특히 고해상도 영상레이다(SAR: Synthetic Aperture Radar)는 빛의 유ㆍ무나 기상상태에 제한 없이 탐측이 가능하다. 본 연구에서는 L-Band JERS-1 위성 영상을 이용한 DInSAR 방법을 적용하여 1998년 2월부터 8월까지의 강원도 지역의 시계열 지형변위를 관측하였다. 관측 결과 강우가 집중되는 5월에서 8월 사이의 지표변위가 컸고, 강원도 양양군 지역에서 지속적인 미세지형변위가 있어 산사태 발생의 위험이 큰 것으로 추정되었다.

$MnO_2$가 테잎캐스팅법에 의해 제조된 $Pb_{0.9}La_{0.1}TiO_3$ 세라믹스의 초전 특성에 미치는 영향

강병성,최시경 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.8

동일 증착 조건의 스퍼터링에 의해서 제작된 Indium Tin 산화물 박막의 증착위치에 따른 전기적 특성의 불균질성

유동주,최시경 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.11

Sn을 도핑한 In$_2$O$_3$(ITO) 박막을 R.F. 마그네트론 반응성 스퍼터링법에 의해서 증착하였다. 동일한 마그네트론 스퍼터링 조건에서 증착위치에 따른 ITO 박막의 저항, 자유 전하 농도 및 이동도 전기적 특성을 조사하였다. 동일한 마그네트론 스퍼터링 조건임에도 불구하고, ITO 박막의 전기적 특성은 증착위치에 따라 불균질성을 나타내었다. 타겟의 중심에 위치한 기판위에 증착된 ITO 박막의 저항은 최소 값인 2~4$\times$$10^{-4}$ $\Omega$.cm인 반면, 중심에서 멀어질수록 박막의 전기 저항은 대칭적으로 증가하였다. ITO 박막의 밀도 측정 결과도 중심에서 이론 밀도 값의 97%에 해당하는 7.0g/$cm^3$를 나타내나, 위치가 중심에서 멀어질수록 박막의 밀도가 대칭적으로 감소하였다. ITO 박막에서 이동도와 전도도는 밀도에 직접적으로 영향을 받는 것이 실험적으로 확인되었다. ITO 박막의 밀도가 7.0g/$cm^3$(이론 밀도의 97%)인 경우, 자유행정거리와 입자크기(=주상의 직경)가 동일한 값을 가지나, 밀도가 이 보다 감소하면 자유행정거리와 입자크기의 차이는 더욱 증가하였다. 이 결과는 ITO 박막의 밀도가 7.0g/$cm^3$인 경우는 입계가 자유 전자의 전도에 중요한 산란 원으로 작용하는 반면, 그 외의 경우는 결정 내의 공격자점, 공공, 기공 등이 다른 산란 원으로 작용하고 있다는 것을 나타낸다. Tin-doped indium oxide (ITO) thin films were deposited using r.f. magnetron reactive sputtering and the electrical properties, such as the resistivity, carrier concentration and mobility, were investigated as a function of the sample position under a given magnetron sputtering condition. The nonhomogeneity of the electrical properties with the sample position was observed under a given magnetron sputtering condition. The resistivity of ITO thin film on the substrate which corresponded to the center of the target had a minimum value, 2∼4$\times$10$\^$-4/$\Omega$$.$cm, and it increased symmetrically when the substrate deviated from the center. The density measurement result also showed that ITO thin film deposited at the center has a maximum density of 7.0g/cm$^3$, which was a relative density of about 97%, and the density decreased symmetrically as the substrate deviated from the center. The nonhomogeneity of electrical properties with the deposition position could be explained with the incidence angle of the source beam alpha, which is related with an atomic self-shadowing effect. It was confirmed experimentally that the density in film affect both the carrier mobility and the conductivity. In the case where the density of ITO thin film is 7.0g/cm$^3$, the magnitude of the mean free path was identical with that of the grain size(the diameter of column). However, in the other cases, the mean free path was smaller than the grain size. These results showed that the scattering of the free electrons at the grain boundary is the major factor for the electrical conduction in ITO thin films having a high density, and there exists other scattering sources such as vacancies, holes, or pores in ITO thin films having a low density.ing a low density.

$(Pb, La)TiO_3$ 세라믹스의 소결 거동 및 유전.초전 특성

최동구,최시경 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.8

The sintering behavior of La-modified PbTiO3 ceramics was investigated in order to improve the poor sinterability of PbTiO3. Addition of La improved the sinterability. It was confirmed that this improvement was due to the decrease in tetragonality ratio c/a of crystal lattice. The variations of dielectric constant and pyroelectric coefficient were measured with temperature. It was observed that with the increase of La content, Curie temperature decreased and dielectric constant at room temperature increased. La-modified PbTiO3 ceramics had smaller pyroelectric figure of merits than those of pyroelectric materials in use. The effects of grain size on dielectric and pyroelectric properties were also investigated. The change of grain size had effect on maximum dielectric constant and pyroelectric coefficient, but is had little effect on pyroelectric figure of merit at room temperature. The closer examination near ferro-paraelectric phase transition temperature revealed that the behavior of phase transition approached a more relaxor character with the increase of La content and the decrease of grain size.

활성금속법에 의한 Alumina / Ag - Cu - Ti 합금의 계면 미세조직

박세양,최시경 대한금속재료학회 1991 대한금속재료학회 학술대회 개요집 Vol.1991 No.0

반응 스퍼터링법으로 제조한 $Y_2O_3$ 박막의 잔류응력과 성장 방향성

최한메,최시경 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.8

Y2O3 thin films were deposited by reactive sputtering of Y target in Ar and O2 gas mixture. Residual stress was measrued by sin2$\psi$ method of x-ray diffraction (XRD) and growth orientation was examined by measuring the relative intensity of (400) plane and (222) plane of Y2O3 films. In the case that Y2O3 films were deposited at 40$0^{\circ}C$ and at low working pressure below 0.05 torr the film had large compressive stress and (111) plane orientation. At working pressure of about 0.10 torr the film had small compressive stress and (100) orientation. Above working pressure of 0.20 torr, the films had nearly zero stress and random orientation. In the case that the (111) oriented film deposited at low working pressure below 0.05 torr, as substrate temperature decreased, (111) orientation increased. In the case the film, with (100) orientation, deposited at working pressure of about 0.10 torr, (100) orientation increased with decresing substrate temperature. These relationship of residual stress and growth orientation can be explained by the relationship of surface energy and strain energy.

Cr-Ni 오스테나이트강의 Cr2N 불연속 석출거동

위당문,최시경 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.2

A 25Cr-20Ni austenitic steel containing 0.59 wt % nitrogen was aged at 973, 1023, 1073 and 1123K to study the growth features of the cellular precipitation of Cr₂N. Experimentally determined were volume fraction of the cell, averge migration rate of cell boundaries, and averge concentration of nitrogen in the untransformed matrix. The partitioning of nitrogen between the cell and the untransformed matrix was computed on the basis of those data. The average concentration of nitrogen within the cell is higher than initial concentration of nitrogen at the onset of the cellular reaction. It decreases linearly with the increasing volume friction of cell and its gradient increases as the aging temperature decreases. At a given aging temperature, it is determined by the average concentration of nitrogen in the untransformed matrix, irrespective of the initial concentration of nitrogen.

브레이징 방법에 의한 Al₂O₃/탄소강 접합 기술

권순용,최시경 한국추진공학회 1993 한국추진공학회 학술대회논문집 Vol.1993 No.10