• Proceedings of the Optical Society of Korea Conference
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• 1995.06a
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• pp.75-83
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• 1995

In-situ, 실시간 측정을 위해 상업화 모형의 He-Ne 타원해석기 및 고속 분광 타원해석기(SE, Spectoscopic Ellipsometer)를 제작하였다. 후자의 경우 1024개의 화소를 가진 광학 다채널분석기 (OMA, Optical Multichannel Analyzer)를 이용한 RP형 분광타원해석기로써 1.5∼5.0eV의 측정 파장대역을 가지며, 한 스펙트럼의 측정시간은 약 100msec이다. cos 와 tanΨ의 정확도는 각각 약0.01이하로 측정되었다. 이러한 in-situ 타원해석기들을 사용하여 Au, ZnS 박막들의 성장 초기단계에서의 박막구조의 변화, 성장속도 그리고 HF식각후의 Si 자연산화층(SiO2)의 초기 성장과정을 밝히고 SiO2/c-Si 시료의 온도를 비 접촉적, 비간석적으로 기존의 방법에 의한 결과와 비교하였다.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.208-213
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• 1999

We proposed a new technique to precisely calibrate the angle of incidence in spectroscopic ellipsometer. The proposed technique can be useful to the thickness measurement of semiconductor thin films and optical thin films. The usefulness has been confirmed experimentally. We cut a block of optical glass into two pieces and made a prism as well as a slab using each piece. The apex angle and the angle of the minimum deviation of prism were measured. From these angles, the refractive index of glass material was calculated. From the analysis of the spectro-ellipsometric data collected near Brewster's angle, we could not only determine the error in the angle of incidence in the spectroscopic ellipsometer, but also calibrated the angle of incidence to the accuracy of 0.01 degree.

• Journal of the Korean Vacuum Society
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• v.2 no.1
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• pp.92-98
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• 1993

Si 기판 위에 증착된 Al 박막을 질소 ECR 플라즈마에 노출시켜 시료를 제작하고 분광타원해석법으로 분석한 결과 Al박막에 질화층이 형성되었음을 확인하였다. 사용한 질소 ECR 플라즈마의 전자온도와 전자밀도는 챔버내의 위치에 따라 각각 10~20eV, 0.9~1.2$\times$1011/㎤의 값을 보였다. 질소 ECR 플라즈마에 노출된 기판은 급격한 온도상승을 보였으며 노출시킨 뒤 5~6분이 지나면 $500^{\circ}C$ 근처에서 포화상태를 이루었다. 분광타원해석상수인 $\Delta$와 Ψ를 분석한 결과 증착된 Al의 두께는 시료에 따라 $140~160AA$이었고 표면에 형성된 AIN 층의 두께는 질소 ECR 플라즈마에 노출된 시간이 길수록 그리고 시료의 위치가 공명지점에 가까울수록 증가하였다. AlN층의 두께가 노출시간의 제곱근에 비례하는 것으로부터 AlN층은 Al의 표면에 흡착된 질소가 Al속으로 확산하여 이루어진 것으로 설명하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 1993.07a
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• pp.63-64
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• 1993

• Proceedings of the Korean Vacuum Society Conference
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• 1993.02a
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• pp.55-56
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• 1993

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.277-282
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• 1997

The complex refractive index of Diamond-like Carbon (DLC) thin films, which can be applied to optical devices or electrical devices, have been determined using optical methods. DLC thin films are grown on Si(100) substrates and vitreous silica substrates respectively, using the technique of plasma enhanced chemical vapor deposition (PECVD). The spectroscopic ellipsometry data($\psi$, $\Delta$) and the transmission spectra of these DLC films are obtained. These optical spectra are analyzed with the help of the Sellmeier dipersion relation and a quantum mechanically derived dispersion relation. Using spectroscopic ellipsometry data at their transparent region, the refractive index and the effective thickness of DLC films on vitreous silica are model calculated, Then the transmission spectra are inverted to yield the extinction coefficient spectra k(λ) at absorbing region. These spectra are fit to the quantum mechanical dispersion relation and the best fit dispersion constants are determined. The complex refractive indices are easily calculated with these constants. The spectroscopic ellipsometry data at the absorbing region in model calculated to give the packing densities and the degrees of surface microroughness of DLC films. Discussions are made in correlation with the growth condition of DLC films.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.351-361
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• 2007

The samples composed of a GST thin film and the protective layers of $ZnS-SiO_2$ or $Al_2O_3$ coated on c-Si substrate were prepared by using the magnetron sputtering method. Samples of three different structures were prepared, that is, i) the GST single film on c-Si substrate, ii) the GST film sandwiched by the protective $ZnS-SiO_2$ layers on c-Si substrate, and iii) the GST film sandwiched by $Al_2O_3$ protective layers on c-Si substrate. The ellipsometric constants in the temperature range from room temperature to $700^{\circ}C$ were obtained by using the in-situ ellipsometer equipped with a conventional heating chamber. The measured ellipsometric constants show strong variations versus temperature. The variation of ellipsometric constants at the temperature region higher than $300^{\circ}C$ shows different behaviors as the ambient medium is changed from in air to in vacuum or the protective layers are changed from $ZnS-SiO_2$ to $Al_2O_3$. Since the long heating time of 1-2 hours is believed to be the origin of the high temperature variation of ellipsometric constants upon the heating environment and the protective layers, a PRAM (Phase-Change Random Access Memory) recorder is introduced to reduce the heating time drastically. By using the PRAM recorder, the GST samples are heated up to $700^{\circ}C$ decomposed preventing its partial evaporation or chemical reactions with adjacent protective layers. The surface image obtained by SEM and the surface micro-roughness verified by AFM also confirmed that samples prepared by the PRAM recorder have smoother surface than the samples prepared by using the conventional heater.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.4
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• pp.496-501
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• 1995

The N $O_{2}$ gas-detection characteristics were investigated using the functional organic Langmuir-Blodgett (LB) films of Copper-tetra-tert-butylphthalocyanine (CuTBP), Dilithium phthalocyanine (Li$_{2}$Pc), N-docosylpyridinium TCNQ(C$_{22}$Py(TCNQ)), Polyamic acid alkylamine salts (PAAS). The optimum conditions for a film deposition were obtained through a study of .pi.-.ALPHA. isotherms and the deposited film status was confirmed by electrical and optical methods such as UV/visible absortion spectra, thickness measurements by ellipsometry, and electrical capacitances. A response of the LB films to the N $O_{2}$ gas was measured by a change of the electrical conductivities when the film is exposed to the gases. The CuTBP LB film shows the biggest change of the electrical conductivities when it is exposed to the N $O_{2}$ gases. And the order of gas-detection performance is the following;Li$_{2}$Pc, $C_{22}$Py(TCNQ), and PAAS LB films. Especially, the CuTBP and Li$_{2}$Pc LB films not only show the bigger change in the electircal conductivities when exposed to the gas, but return to the original state when the gas is desorbed.d.

• Journal of the Korean Geotechnical Society
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• v.23 no.9
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• pp.5-16
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• 2007

The simple linear elastic-perfectly plastic model with soil parameters $s_u,\;E_u$ and n of undrained condition is usually applied to predict the displacement of a constructed diaphragm wall(DW) on soft soils during excavation. However, the application of this soil model for finite element analysis could not interpret the continued increment of the lateral displacement of the DW for the large and deep excavation area both during the elapsed time without activity of excavation and after finishing excavation. To study the characteristic behaviors of soil behind the DW during the periods without excavation, a series of tests on soft Bangkok clay samples are simulated in the same manner as stress condition of soil elements happening behind diaphragm wall by triaxial tests. Three kinds of triaxial tests are carried out in this research: $K_0$ consolidated undrained compression($CK_0U_C$) and $K_0$ consolidated drained/undrained unloading compression with periodic decrement of horizontal pressure($CK_0DUC$ and $CK_0UUC$). The study shows that the shear strength of series $CK_0DUC$ tests is equal to the residual strength of $CK_0UC$ tests. The Young's modulus determined at each decrement step of the horizontal pressure of soil specimen on $CK_0DUC$ tests decreases with increase in the deviator stress. In addition, the slope of Critical State Line of both $CK_0UC$ and $CK_0DUC$ tests is equal. Moreover, the axial and radial strain rates of each decrement of horizontal pressure step of $CK_0DUC$ tests are established with the function of time, a slope of critical state line and a ratio of deviator and mean effective stress. This study shows that the results of the unloading compression triaxial tests can be used to predict the diaphragm wall deflection during excavation.