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열처리 효과에 따른 Zn0.7Mn0.3O 박막의 자기 특성 연구
김영미(Y. M. Kim),김유경(Y. Kim),윤명근(M. Yoon),박찬수(C. S. Park),이연숙(Y. S. Lee),전미선(M. S. Jeon),박일우(I.-W. Park),박용주(Y. J. Park),유종훈(Jong H. Lyou),김상수(S. S. Kim) 한국자기학회 2003 韓國磁氣學會誌 Vol.13 No.4
We report on the annealing effect and ferromagnetic characteristics of Zn_(0.7)Mn_(0.3)O film prepared by sol-gel method on the silicon (100) substrate using field emission-scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and superconducting quantum interference device (SQUID) magnetometry. Magnetic measurements show that Zn_(0.7)Mn_(0.3)O films exhibit ferromagnetism at 5 K revealing the coercive field of ~110 Oe for as grown sample and 360, 1035 Oe for samples annealed at 700, 800 ℃, respectively. Our experimental evidence suggests that ferromagnetic precipitates of a manganese oxide may be responsible for the observed ferromagnetic behaviors of the film.
자발형성 InAs/GaAs 양자점의 구조 및 성장 특성
김형석,서주형,박찬경,이상준,노삼규,송진동,박용주,이정일 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.3
Self-assembled InAs/GaAs quantum dots (QDs) were grown by molecular beam epitaxy and the growth characteristics of QDs were studied using field emission gun-electron transmission microscope. The shapes and optical properties of QDs changed according to spacer layers thickness due to the strain between InAs and GaAs layers. The QDs with 50 nm thick GaAs spacer layers were distributed randomly along the growth direction and changed from dome to flat-pyramidal shape after capping with GaAs. However, QDs with 10 nm thick spacer layers were vertically aligned up to the fifth period and the dome-shape was maintained after capping. The density, distribution and crystalline defects depending on growth conditions were also investigated.
김은규,이창효,김채옥,홍진표,현찬경,박용주 漢陽大學校 自然科學硏究所 2003 自然科學論文集 Vol.22 No.-
본 연구에서는 단전자 소자를 제조하는데 활용될 수 있도록 자발형성된 InGaAs/GaAs, InAs/GaAs 양자점의 선택성장기법에 대해 조사하였다. 먼저 분자선 에피탁시를 이용하여 GaAs 기판위에 InAs/GaAs 변형된 초격자 버퍼층을 성장시킨 후 InGaAs 양자점을 형성시켰으며, 형성된 양자점의 성장이 규칙적으로 나열 되는 메카니즘을 연구하였다. InAs/GaAs초격자는 InGaAs버퍼층에 비해 성장된 결정의 균일성이 좋음에도 In비율 조절이 용이하기 때문에 양자점을 제어하는데 좋은 버퍼층이라 하겠다. 또한 원자력간 현미경의 탐침을 이용한 직접 기록방식을 이용하여 기판 상에 패턴을 형성한 후 자발형성 양자점을 성장하여 위치의 배열화가 가능하도록 하였다. AFM 피에조 스캐너에 인가되는 전압 및 속도 조절을 통해 패턴의 폭과 깊이조절이 가능하였고 후 성장을 통하여 양자점이 패턴에 우선적으로 성장되는 것을 확인하였다. 이 같은 자발형성 양자점의 선택성장 기술은 신기능 나노소자제조를 위하여 응용될 수 있다. 이러한 정렬된 양자점은 단일전자소자등에 응용이 가능할 것이다. We have investigated selective growth method of InGaAs/GaAs, InAs/GaAs self assembled quantum dots for the application on single electron tunneling transistor. The first method uses molecular beam epitaxy to grow modified InAs/GaAs superlattice buffer layer on GaAs substrate. InAs/GaAs superlattice has a better crystalline uniformity than InGaAs buffer layer and has a better controllability of In Content which is suitable for the control of quantum dot growth. In another approach, we used the probe of the atomic force microscopy to directly pattern semiconductor surface allowing the position control in the subsequent quantum dot growth. The modulation voltage applied to the piezo scanner and the patterning speed was changed to obtain the controllability of the width and depth of the fabricated pattern. After quantum dot regrowth, we observed that the quantum dots were selectively grown on the pattern. These novel methods for self-assembled quantum dot selective growth can be applied to new functional nano-scaled devices. These well-aligned quantum dots could be applied for applications such as single electron tunneling devices.