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딥코팅 방법으로 성장한 CdxZn1-xO 박막의 Cd 농도 변화에 따른 구조적 및 광학적 특성
지익수 ( Ii Ksoo Ji ),박형길 ( Hyung Gil Park ),김영규 ( Young Gyu Kim ),김소아람 ( Soaram Kim ),남기웅 ( Gi Woong Nam ),김양수 ( Yang Soo Kim ),임재영 ( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.4
Ternary CdxZn1-xO thin films are deposited by a sol-gel dip-coating method onto quartz substrates with various amounts of Cd content (x = 0, 0.05, 0.15, and 0.25). The structural and optical properties of the CdxZn1-xO thin films are investigated using x-ray diffraction (XRD), photoluminescence (PL), and (ultravioletvisible) (UV-Vis) spectroscopy. In the XRD patterns, the intensity of the diffraction peaks for ZnO decreases, while the intensity of the diffraction peaks for CdO increases with increases in the Cd content. Above x = 0.15, both diffraction peaks for ZnO and CdO are observed in the XRD pattern, and this indicates that the wurtzite structure for ZnO and the rock-salt structure for CdO coexist in CdZnO thin films. The PL spectra of the films results demonstrate that the near band edge emission peaks in the ultraviolet region shift to lower energy range (red-shift) and the deep level emission peaks at the visible region decreases with increases in the Cd content. The optical properties such as transmittance, optical band gap, and Urbach energy are calculated using the optical data. Using linear fitting of the absorption edge, the band gap energies of the thin films are derived as 3.27, 3.19, 3.12, and 3.03 eV for x = 0, 0.05, 0.15 and 0.25, respectively. In addition, the bowing parameter for the energy band gap of CdxZn1-xO is estimated to be Eg( x) = 3.3 . 1.2 x + x2.
졸겔 스핀코팅 방법으로 제작된 ZnO 박막에서 Li 원자들이 물성에 미치는 영향
김영규 ( Young Gyu Kim ),박형길 ( Hyung Gil Park ),지익수 ( Ik Soo Ji ),김소아람 ( So A Ram Kim ),김종수 ( Jong Su Kim ),김진수 ( Jin Soo Kim ),김양수 ( Yang Soo Kim ),임재영 ( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.5
Undoped and Li-doped ZnO(LZO) thin films were grown on quartz substrates by a sol-gel spin- coating method. The effects of Li contents on the structural and optical properties of the ZnO thin flims were investigated by X-ray diffraction (XRD), photoluminescence (PL), and ultraviolet-visible spectrophotometer. In the XRD investigation, undoped and LZO thin films had a wurtzite structure and high c-axis orientation. The intensity and the full width at half maximum (FWHM) of the (002) peak for LZO was the largest and smallest at 2.5 at%, which indicate that the LZO thin film is the most crystalline at 2.5 at%. In the PL investigation, the near band edge emissions of the LZO thin films were blue-shifted and the FWHM of the LZO thin films decreased with increasing Li doping concentrations.
분자선에피택시에 의해 성장한 ZnO 나노결정 박막에 완충층 두께와 활성층 성장 온도가 미치는 효과
김병구 ( Byung Gu Kim ),남기웅 ( Gi Woong Nam ),박영빈 ( Young Bin Park ),박형길 ( Hyung Gil Park ),임재영 ( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.9
ZnO thin films were deposited on a Si (100) substrate by plasma-assisted molecular beam epitaxy (PA-MBE). Growth of ZnO thin films on a Si substrate is limited due to the large difference between the lattice constants of ZnO and Si. In this research, we studied the effects of the buffer-layer thickness and active-layer growth temperature on the structural and optical properties of ZnO thin films. Scanning electron microscopy, X-ray diffraction, and photoluminescence were carried out to investigate the structural and optical properties of the ZnO thin films. The structural and optical properties of the ZnO thin films were improved when the buffer layers were grown for 20 min and the active layers were grown at 800 ℃.(Received September 9, 2013)
변분 원리를 응용한 타에 부착된 Post-Swirl Fin의 최적 설계에 관한 연구
이경준(Kyung-Jun Lee),호시노(Tetsuji Hoshino),이진석(Jin-Suk Lee),오세면(Se-Myun Oh),박형길(Hyung-Gil Park) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.11
This study treats an application of variational principle to the design of post swirl fins which develop additional thrust from propeller slip stream. The design problem is formulated with the vortex lattice lifting line representation of the components so that the power absorbed by a propeller is minimized with the thrust generated by the propeller and fin given by a prescribed value. The optimum circulation distribution of each component is determined by solving a resulting discrete variational problem. The interactions between the two components are considered in circumferentially averaged velocity field calculation at one component location induced by the other one. The procedure is first applied to the determination of the optimum single propeller loading distribution and compared with the Lerbs solution in open water configuration. The developed method is then applied to the design of the propeller and post-swirl fins attached to rudder for a VLCC. To verify the velocity field calculations, flow measurement is conducted behind a propeller. Finally self propulsion tests are carried out to estimate the efficiency increase by the fins. The result proves the validity of the design procedure.