• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.59-59
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• 2003

ZnO는 상온에서 3.37 eV의 넓은 밴드갭을 가지는 직접천이형 반도체이다. 상온에서 60 meV의 큰 엑시톤 결합에너지를 가짐으로 인해 엑시톤 재결합에 의한 강한 UV 레이저 발진효과를 기대할 수 있다. 이러한 장점을 갖는 ZnO 박막을 이용하여 광소자 등에 응용하기 위하여 양질의 ZnO 박막성장이 필수적이며, 이를 위해 MBE, MOCVD, PLD, rf magnetron sputtering 등 다양한 증착방법을 통한 연구결과가 보고되고 있다. 또한 p형 불순물인 As과 N 도핑 및 Ga과 N의 co-doping 방법 등을 통하여 p형 ZnO 박막을 제조하였음이 보고되고 있으나 재현성 문제 등으로 인해 계속적인 연구가 진행되고 있다. 본 연구에서는 MOCVD를 이용하여 A1$_2$O$_3$(0001) 기판 위에 ZnO 박막을 성장시켰다. Zn 전구체로 DEZn을 사용하였으며, 산소 source로 $O_2$를 사용하였다. 증착온도, Ⅵ/II 비율, 반응기 압력 등 MOCVD의 중요한 공정변수들의 체계적인 변화에 따른 박막성장 양상을 조사하였다. 증착 조건에 따라 ZnO 입자의 모양이 주상(column), nano-rod, nano-needle, nano-wire 등으로 급격하게 변화됨을 확인하였으며, 이러한 입자의 모양과 결정성장 방향 및 광학적 특성과의 상관관계의 해석을 시도하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.329-332
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• 2004

ZnO thin films were grown with different plume-substrate angles by pulsed laser deposition (PLD) to control the amount of ablated species arriving on a substrate per laser shot. The angles between plume propagation direction and substrate plane (P-S angle) were 0$^{\circ}$, 45$^{\circ}$ and 90$^{\circ}$. The growth time was changed in order to adjust film thickness. From the XRD pattern exhibiting a dominant (002) and a minor (101) XRD peak of ZnO, all films were found to be well oriented along c-axis. From the AFM image, it was found that the grain size of ZnO thin film was increased, as P-S angle decreased. UV intensity investigated by PL (Photoluminescence) increased as P-S angle decreased.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.642-646
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• 1989

We have developed analysis program of discharge chracteristics of KrF laser system with charge transfer type, that studied about deposited energy, nonlinear discharge, and electron number density in the laser tube. With this program, voltagr, current, and deposited energy was calculated 27 KV,32.6 KA,200 MW at total pressure 2 atm and charging voltage 33 KV, respectively. At this condition, circuit parameters are L1=150nH, R1=$0.3{\Omega}$, L2=15nH, R2= $0.3{\Omega}$. In addition, nonlinear discharge resistance and electron number density was calculated ${\infty}{\sim}0.17{\Omega}.1{\times}10^{16}cm^{-3}$, respectively.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.268-271
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• 1993

Discharge pumped high power excimer laser is a very useful light source of ultraviolet region. In this paper. the design and operation characteristics of UV pre-ionized discharge pumped XeCl laser are discussed. Maximum output power of 890mJ at the efficiency of 1.4% was achieved with 35kV charging voltage, 3.4atm of total pressure and 10pps of pulse repetition rate. Optimum HCl pressure is considered to be between 2.5 and 3.5torr.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.616-619
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• 2003

Photochemical and photothermal effects have correlation with each other and depend on laser wavelength. Multi-scanning laser ablation process of polymer with DPSS(Diode Pumped Solid State) 3rd harmonic Nd:YVO$_4$ laser with wavelength of 355nm is applied to fabricate three-dimensional micro shape. The DPSSL photomachining system can rapidly and cheaply fabricate 2D pattern or 3D shape with high efficiency because we only use CAD/CAM software and precision stages instead of complex projection mask. Photomachinability of polymer is highly influenced by laser wavelength and its own chemical structure. So the optical characteristics of polymers for 355nm laser source is investigated by experimentally and theoretically.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.65-69
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• 2003

ZnO-Si-ZnO multi-layer thin films have been deposited by pulsed laser deposition (PLD). And then, the films have been annealed at 300$^{\circ}C$ in oxygen ambient pressure. Peak positions of ultraviolet (UV) and visible region were changed by addition of Si layer. Mobility of the films was improved slightly than ZnO thin film without Si layer. The structural property changed by inserting intermediate Si layer in ZnO thin film. The optical properties and structural properties of ZnO-Si-ZnO multi-layer thin films were characterized by PL(Photoluminescence) and XRB(X-ray diffraction) method, respectively. Electrical properties were measured by van der Pauw Hall measurements

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.14-15
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• 2001

본 강좌에서는 광통신과 센서 분야에서 최근 실용화되고 있는 중요한 소자인 광섬유 격자(fiber grating)에 대해, 그 원리와 종류, 제작 방법, 시뮬레이션 기법, 광통신용 응용 및 광섬유 격자 센서 시스템의 구현 기법 등에 대해 설명한다. 별도로 제공되는 강의록에서 이에 대해 보다 구체적으로 기술할 것인 바, 그 요약은 아래와 같다. 광섬유에 굴절률 변화 패턴을 만들 수 있다는 사실은 1978년 Hill 등에 의해 발견되었고, 1989년 Meltz 등에 의해, 자외선(UV) 레이저를 광섬유 측면에 조사하여 광섬유 코어(core)의 특정 부위에 광섬유 격자를 만드는 방법이 고안되었다. 광섬유에 격자가 새겨지는 원인에 대한 이론은 여러 가지가 있고 이들이 복합적으로 작용하지만, 중요한 요인은 산소가 빠진 게르마늄과 관련된(oxygen deficient germania related) 결함이다. 따라서, 게르마늄(Ge)이 높게 도우핑(doping)된 광섬유에 격자가 잘 새겨진다. 보통의 단일 모드 광섬유도 수소처리(hydrogenation)를 하면 자외선에 대한 광민감성(photosensitivity)을 증가시킬 수 있어 격자의 제작이 가능하다. (중략)

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.9
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• pp.375-379
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• 1986

The HCP(Hypocycloidal Pinch) device for plasma focus was modified for a pumping source of the dye laser, and the spectral distribution and time behavior of its light pulses were investigated by using a UV spectrometer, 70 MHz CRO and Si-PIN photodiode detector. An array of multiple stages of HCP and narrower electrode gaps were chosen in order to make a more uniform discharge along the HCP axis. The possible spectral range for the pumping of dye laser is 360-620nm, when the HCP is operated at 5-8kv of apllied voltage and 50-150Torr of Ar fill gas pressure. The rise-time and FWHM of light pulses from the HCP are 5us and 30-50us respectively when it is operated under the same conditions as above.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.539-542
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• 2000

ZnO thin films for light emission device have been deposited on sapphire and silicon substrates by pulsed laser deposition technique(PLD). A Nd:YAG laser was used with the wavelength of 355 nm. In order to investigate the emission properties of ZnO thin films, PL measurements with an Ar ion laser as a light source using an excitation wavelength of 351 nm and a power of 100 mW are used. All spectra were taken at room temperature by using a grating spectrometer and a photomultiplier detector. ZnO exhibited PL bands centered around 390, 510 and 640 nm, labeled near ultra-violet (UV), green and orange bands. Structural properties of ZnO thin films are analized with X-ray diffraction (XRD).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.200-202
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• 2004

ZnO thin films were grown at different plume-substrate angles by pulsed laser deposition(PLD). From the X-ray diffraction(XRD) result, all ZnO thin films were found to be well c-axis oriented and c-axis lattice constant approached the value of bulk ZnO as plume-substrate(P-S) angle decreased. The grain size of ZnO thin films measured by atomic force microscopy increased and the UV intensity of ZnO thin films investigated by photoluminescence increased as P-S angle decreased. It is found that the improvement of structural and optical properties mainly comes from the reduction of the flux of ablated species arriving on a substrate per a laser shot by tilting a substrate parallel to the plume propagation direction.