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박기철,남기홍,김기완,Park, Ki-Cheol,Nam, Ki-Hong,Kim, Ki-Wan 대한전자공학회 1989 전자공학회논문지 Vol. No.
The image sensitive PbO photoconductive films were fabricated ar several deposition conditions such as $O_2$ gas pressure, deposition rate, and substrate temperature. And the effects of these deposition condition on the structural and electrical properties of them were investigated with the aid of scanning electron photomicrographs. X-ray diffraction patterns, and current-valtage chatacteristics. The results show that when PbO film has red tetragonal structure and its dominant orientations are <110> and <010> direction, photocurrent-darkcurrent ratio and light transfer ratio are increase. 영상감지막으로 사용되는 PbO광도전막을 산소압, 증착속도 및 기판온도 등의 조건을 변화시켜 가면서 유도성가열증착법으로 제조하였다. 이 때 증착조건이 PbO막의 구조적 및 전기적 특성에 미치는 영향을 SEM사진, X선회절도 및 전류-전압특성 등을 통해 조사 하였다. 이 결과로 부터 정방정계의 구조의 적색PbO가 <110> 및 <101> 방향으로 우세하게 성장할 때 광전류대 암전류의 비와 광전변환률이 증가함을 알 수 있었다.
인듐량에 따른 In<sub>x</sub>GaN<sub>1-x</sub> 박막의 에너지밴드갭 변화
박기철,마대영,Park, Ki-Cheol,Ma, Tae-Young 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8
$In_xGa_{1-x}N$ alloys with 20-nm-thickness were deposited onto Mg:GaN/AlN/SiC substrates by MOCVD at $800\;^{\circ}C$. TMGa, TMIn and $NH_3$ were used as the precursor of gallium, indium and nitrogen, respectively. The mole ratio of indium in $In_xGa_{1-x}N$ films varied between 0 and 0.2. The energy-band-gaps of the films were obtained from the photoluminescence and cathodoluminescence peaks. The mole ratios of $In_xGa_{1-x}N$ films were calculated by applying Vegard's law to XRD results. The energy-band-gap versus indium composition plot for $In_xGa_{1-x}N$ alloys were well fit with a bowing parameter of 2.27.
rf 마그네트론 스퍼터링으로 증착한 Mg-doped Zinc Tin Oxide막의 특성에 미치는 산소의 영향
박기철,마대영,Park, Ki Cheol,Ma, Tae Young 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.5
Mg-doped zinc tin oxide (ZTO:Mg) thin films were prepared on glasses by rf magnetron sputtering. $O_2$ was introduced into the chamber during the sputtering. The optical properties of the films as a function of oxygen flow rate were studied. The crystal structure, elementary properties, and depth profiles of the films were investigated by X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS), respectively. Bottom-gate transparent thin film transistors were fabricated on $N^+$ Si wafers, and the variation of mobility, threshold voltage etc. with the oxygen flow rate were observed.
박기철,마대영,Park, Ki-Cheol,Ma, Tae-Young 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.10
CdSe films were deposited on glass substrates (CdSe/glass) by thermal evaporation. Substrate temperature was lowered by cooling substrate holder with liquid nitrogen. Substrate temperatures were $200^{\circ}C$, $0^{\circ}C$ and $-40^{\circ}C$. The crystallographic properties and surface morphologies of the CdSe/glass films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical and electrical properties of the films were investigated by dependence of energy gap, photosensitivity and resistivity on the substrate temperature. CdSe/glass showed energy gap of ~1.72 eV regardless of substrate temperature. The resistivity of the films decreased to $0.5{\Omega}cm$ by lowering the substrate temperature to $-40^{\circ}C$. The CdSe/glass films prepared at $0^{\circ}C$ showed the highest photosensitivity among the films in this study.
Ga이 첨가된 ZnO-SnO<sub>2</sub>막의 구조적 및 전기적 특성
박기철,마대영,Park, Ki-Cheol,Ma, Tae-Young 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.8
Ga-doped ZnO-$SnO_2$ (ZSGO) films were deposited by rf magnetron sputtering and their structural and electrical properties were investigated. In order to fabricate the target for sputtering, the mixture of ZnO, $SnO_2$ (1:1 weight ratio) and $Ga_2O_3$ (3.0 wt%) powder was calcined at $800^{\circ}C$ for 1 h. The substrate temperature was varied from room temperature to $300^{\circ}C$. The crystallographic properties and the surface morphologies of the films were studied by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The optical transmittances of the films were measured and the optical energy band gaps were obtained from the absorption coefficients. The resistivity variation with substrate temperature was measured. Auger electron spectroscopy was employed to find the atomic ratio of Zn, Sn, Ga and O in the film deposited at room temperature. ZSGO films exhibited the optical transmittance in the visible region of more than 80% and resistivity higher than $10\;{\Omega}cm$.
고주파 마그네트론 스퍼터링법에 의해 제조된 TO:F 투명도전막의 제조 및 특성 ( 1 )
박기철,김정규 ( Ki Cheol Park,Jeong Gyoo Kim ) 한국센서학회 1994 센서학회지 Vol.3 No.2
TO:F(SnO₂:F) thin films were prepared by RF magnetron sputtering system. The dependence of their structural, electrical, and optical properties on deposition conditions such as substrate temperature, working pressure and power was studied. The optimum conditions of TO:F thin film are SnF₂ content of 15wt.% in target, RF power of 150W, substrate temperature of 150℃ and working pressure of 2mmTr. The resistivity and transmittance at 550nm in visible spectrum of the TO:F film deposlt . d at optimum condition are 9 X 10^(-4)Ω·cm and above 85%, respectively. For the films deposited from the target without SnF₂ and with 15wt.% SnF₂, the optical bandgaps calculated from the transmittance curves are 3.f34 and 3.9eV, respectively. X-ray diffraction patterns showed that TO and TO:F films had tetragonal ruble structure with (101), (200) direction.
기판온도 및 열처리온도에 대한 CdS 박막의 전기적 및 광학적 특성
박기철,심호섭,김정규 ( Ki Cheol Park,Ho Seob Shim,Jeong Gyoo Kim ) 한국센서학회 1997 센서학회지 Vol.6 No.2
CdS thin films for window material of solar cell were prepared by close spaced vapor transport deposition system and annealed at different temperatures. The structural, electrical, and optical properties of as-deposited and annealed CdS films were investigated as functions of substrate and annealing temperatures. The CdS thin films were grown perpendicularly to the substrate along the (002)plane with hexagonal structure regardless of the preparation conditions The resistivity of the CdS film deposited was increased gradually from 60Ω·cm for 25℃ to 2X10⁴Ωcm for 300℃. The optical transmittance at the substrate temperature of 25℃ was about 80% in the visible spectrum. The resistivity increased monotonically, and the optical transmittance was decreased substantially with annealing temperature due to the increased defect density in the CdS film.
구속된 환경에서의 여유자유도 로봇의 기구학적 제어와 원자력 발전소 노즐댐 장 /탈착작업에의 적용
박기철,장평훈,김승호,Park, Ki-Cheol,Chang, Pyung-Hun,Kim, Seung-Ho 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.12
In this paper, a closed-form formulation for inverse kinematics of robot manipulators with kinematic redundancy under the constrained environment has been derived using the Kuhn-Tucker condition, the extended Lagrange multiplier method and the working set method. The proposed algorithm satisfies the necessaryand sufficient conditions for optimization subject to equality and inequality constraints. In addition, computationally efficient kinematic control methods have been proposed using differential kinemetics and gradient projection mehtod. The effectiveness of the proposed methods has been demonstrated with a 4-dof planar robot, and then a 7-dof spatial robot as a practical application to the nozzle dam task in the Nuclear Power Plant.
CSVT 법으로 제조된 CdS ㅊ 전기적 및 광학적 특성
박기철 ( Ki Cheol Park ),심호섭 ( Ho Seob Shim ) 한국센서학회 1997 센서학회지 Vol.6 No.5
CdS thin films with low resistivity and adeduate transmittance in the visible region for the window of CdS/CdTe hetero junction solar cell were prepared by close-spaced vapor transport(CSVT) method. The electrical and optical properties of the CdS thin films were investigated in terms of the deposition conditions, such as the substrate temperature, the working pressure, and the source temperature. The substrate temperature, the working pressure, and the source temperature for the optimum deposition of the CdS thin films were 300℃, 100mTorr, and 730℃, respectively. The resistivity and the transmittance of the CdS thin films deposited under this condition were about 7.21 X l0^(-3)Ωcm and over 65%, respectively. The crystallinity, the resistivity, and optical band gap were improved greatly compared to the CdS thin films deposited by general high vacuum evaporation.