MOCVD 방법에 의한 Si 기판위 GaN 나노선의 성장

우시관,신대근,오병성,이형규,Woo, Shi-Gwan,Shin, Dae-Keun,O, Byung-Sung,Lee, Hyung-Gyoo 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.11

We have grown GaN nanowires by the low pressure MOCVD method on Ni deposited oxidized Si surface and have established optimum conditions by observing surface microstructure and its photoluminescence. Optimum growth temperature of $880^{\circ}C$, growth time of 30 min, TMG source flow rate of 10 sccm have resulted in dense nanowires on the surface, however further increase of growth time or TMG flow rate has not increased the length of nanowire but has formed nanocrystals. On the contrary, the increase of ammonia flow has increased the length of nanowires and the coverage of nanowire over the surface. The shape of nanowire is needle-like with a Ni droplet at its tip; the length is tens of micron with more than 40 nm in diameter. Low temperature photoluminescence obtained from the sample at optimum growth condition has revealed several peaks related to exciton decay near band-edge, but does not show any characteristic originated from one dimensional quantum confinement. Strong and broad luminescence at 2.2 eV is observed from dense nanowire samples and this suggests that the broad band is related to e-h recombination at the surface state in a nanowire. The current result is implemented to the nanowire device fabrication by nanowire bridging between micro-patterned neighboring Ni catalysis islands.

AlGaN 단결정 박막의 구조 및 광학적 특성

우시관,유선향,오병성 충남대학교 기초과학연구소 2005 忠南科學硏究誌 Vol.32 No.1

The Al_(x)Ga_(1-x)N epitaxial layers were grown on sapphire substrates by metalorganic chemical vapor deposition with various Al composition(x = 0.1 ~ 1.0). The Al composition was determined by a X-ray diffraction and photoluminescence spcetra as a function of Al composition were investigated. The bowing parameter of AlGaN energy band gap was found to be 0.85 eV with near edge emission peaks.

기체 분위기에 따른 GaN 에피층의 열처리 효과

우시관,박성은,오병성 충남대학교 기초과학연구소 2001 忠南科學硏究誌 Vol.28 No.2

The changes due to the annealing in the electrical and optical characteristics of GaN epilayers have been investigated. The annealing was performed in hydrogen, nitrogen and ammonia gas environment. X-ray diffraction, Hall effect and photoluminescence measurement showed that the characteritics were unproved after the annealing ammonia gas. It is attributed to the reduction of N vacancy in the epilayer by the thermal dissociation of ammonia gas.

GaN 나노선의 성장 및 특성

신대근, 우시관, 오병성, 김태규, 이형규 충북대학교 컴퓨터 정보통신 연구소 2009 컴퓨터정보통신연구 Vol.17 No.1

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벡터연산에 대한 일반물리실험 수업안

이호연,우시관,박병윤 한국물리학회 2010 새물리 Vol.60 No.7

We designed a basic physics laboratory syllabus that encourages students to pursue an understanding of vector operations. The students are guided to design a geodesic dome and then to construct it using XL pipes and specially manufactured connecting pins. By doing this, the students learn the basic concepts of vector operations, and they learn how to handle data by using EXCEL program. As a results of this syllabus, students became interested in vector operations and apply those operations to their future physics classes. 학생들이 벡터의 기본 연산을 익히도록 하는 일반물리 실험 수업안을개발하였다. 이 실험에서는 XL파이프와 특수 제작한 연결핀을 이용하여지오데식 돔의 골조를 제작하는 것으로 설계과정에서 학생들이 벡터의기본 개념을 익히게 할 뿐 아니라 EXCEL 프로그램을 사용하여 데이터를처리하는 방법을 함께 교육할 수 있다. 실험이후 학생들의 벡터에 대한흥미가 증가하여 벡터 이용에 대한 관심이 높아진 것을 알 수 있었다.

전자 밀도에 따른 AZO 박막의 전기광학적 특성

김재석,오병성,우시관 한국물리학회 2017 새물리 Vol.67 No.6

Al-doped ZnO thin films were grown by co-sputtering. As the deposition temperature was increased, the resistivity decreased, and the electron density ($n_e$) increased, which can be explained in term of the increase in the Al content, as determined by using energy dispersive X-ray spectroscopy. The mean free path of the free electrons was found not to be influenced by the grain boundary scattering, but was influenced by the grain size. The energy gap was found to increase as $n_e^{2/3}$, and the effective mass of the electrons was calculated. The intensity of the low-temperature photoluminescence (PL) spectra was proportional to the free electron density, which shows that the transition of conduction electrons to the valence band is the most important factor for PL emission. 동시 스퍼터링 방법으로 Al을 도핑한 ZnO (AZO) 박막을 증착온도를 바꾸어 성장하였다. 증착온도가 높을수록 비저항이 작아지고 전자 밀도는 증가하였다. 증착온도가 높을수록 Al의 함량이 증가함을 에너지 분산 X-선 분광으로 확인하였다. 따라서 더 많은 Al이 Zn와 치환하여 도펀트 역할을 함으로 전자 밀도가 증가하고 저항은 감소하는 것을 설명하였다. 전자의 평균 자유행로를 결정입자의 크기와 비교하여 입자경계면 산란의 영향이 크지 않음을 보였다. 또 에너지 갭이 자유 전자밀도 ($n_e$)의 2/3 제곱에 비례하여 증가함에 확인하고 이로부터 전자의 유효 질량을 살펴보았다. 저온 광발광 스펙트럼의 세기가 자유 전자밀도에 비례함을 확인하고 이로부터 전도대의 전자가 가전대로의 전이에 의한 발광이 가장 큰 요인임을 알 수 있었다.

Co-sputtering 방법으로 성장한 ZnO:Al의 전기광학적 특성

김재석,오병성,우시관 한국물리학회 2017 새물리 Vol.67 No.3

The crystallographic and the electro-optical characteristics were studied for ZnO:Al transparent conducting thin films grown by using co-sputtering with ZnO and Al targets. The Al content in the films grown at 400 $^{\circ}$C at a constant ZnO target power was found to increase and the electrical resistivity to decrease as the Al target's power was increased to some level. This could be explained by the substitution of Al ions for Zn ions and by an increase in the number of free carriers. However, at target powers above some level, Al ions would be located interstitially in the ZnO lattice, and the quality of the films would deteriorate. With increasing substrate temperature, the electron density increased and the electrical resistivity decreased in the films grown at fixed powers. The transmission in the visible range for all samples was fairly good. Low-temperature photoluminescence showed a strong near-band-edge emission near 3.3 eV compared with the $\sim$2.9 eV green emission, which means a high free-carrier density and a low deep-level-trap density. It shows as the substrate temperature is increased, Al ions are effectively substituted for Zn ions and act as dopants to increase the free-electron density. ZnO와 Al 타겟을 사용하여 동시 스퍼터링 방법으로 유리 기판 위에 ZnO:Al 투명 전도 박막을 성장하여 결정학적 특성 및 전기 광학적 특성을 살펴보았다. 박막 성장시 기판 온도를 400 $^{\circ}$C로 고정하고 ZnO 타겟의 전력을 일정하게 유지한 채 Al 타겟의 전력을 증가시킴에 따라 박막내 Al의 함량이 증가하며 전자의 밀도가 증가하고 전기 비저항이 감소하였다. 그러나 Al 타겟 전력이 어느 정도 이상에서는 박막의 결정학적 품질이 떨어지며 비저항도 증가하였는데 이는 Al의 양이 증가하여 Zn와 치환되던 것이 격자 틈새에 자리잡기 때문으로 설명할 수 있다. 두 타겟의 전력을 일정하게 유지하며 박막 성장시 기판 온도를 증가시킴에 따라 박막의 결정학적 품질이 좋아지며 전자 밀도가 증가하여 비저항이 감소하였다. 모든 경우 가시광 투과는 매우 양호하였다. 저온 광발광 측정에서도 고온 성장 시료의 경우 상온 성장 시료와 비교하여 2.9 eV 근처의 초록색 발광보다 3.3 eV 밴드 가장자리 관련 발광이 크게 나타남으로 깊은 준위 결함이 적고 자유 전자 밀도가 큰 것을 확인할 수 있었다. 이는 기판 온도가 높을수록 Al이 효과적으로 Zn를 치환하여 도펀트 역할을 하여 자유전자 밀도가 증가하는 것으로 설명할 수 있다.

ZnS thermal CVDs solution of phenomenon of roughing exhaust line blockage for increasing continous process time

조용범,김진철,최우성,정원호,우시관 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.2

개선된 진공 배기 성능과 저손상 전처리 장치가 장착된 롤투롤 스퍼터 개발

조용범,홍기성,이철규,정원호,우시관 한국진공학회 2015 한국진공학회 학술발표회초록집 Vol.2015 No.2

PVT공정을 이용한 음향광학 가변 필터용 Hg₂Br₂ 파우더의 고순도 정제

김태현,이희태,권인회,강영민,우시관,장건익,조병진,Kim, Tae Hyeon,Lee, Hee Tae,Kwon, In Hoi,Kang, Young-Min,Woo, Shi-Gwan,Jang, Gun-Eik,Cho, Byungjin 한국재료학회 2018 한국재료학회지 Vol.28 No.12

We develop a purification process of $Hg_2Br_2$ raw powders using a physical vapor transport(PVT) process, which is essential for the fabrication of a high performance acousto-optic tunable filter(AOTF) module. Specifically, we characterize and compare three $Hg_2Br_2$ powders: $Hg_2Br_2$ raw powder, $Hg_2Br_2$ powder purified under pumping conditions, and $Hg_2Br_2$ powder purified under vacuum sealing. Before and after purification, we characterize the powder samples through X-ray diffraction and X-ray photoelectron spectroscopy. The corresponding results indicate that physical properties of the $Hg_2Br_2$ compound are not damaged even after the purification process. The impurities and concentration in the purified $Hg_2Br_2$ powder are evaluated by inductively coupled plasma-mass spectroscopy. Notably, compared to the sample purified under pumping conditions, the purification process under vacuum sealing results in a higher purity $Hg_2Br_2$ (99.999 %). In addition, when the second vacuum sealing purification process is performed, the remaining impurities are almost removed, giving rise to $Hg_2Br_2$ with ultra-high purity. This high purification process might be possible due to independent control of impurities and $Hg_2Br_2$ materials under the optimized vacuum sealing. Preparation of such a highly purified $Hg_2Br_2$ materials will pave a promising way toward a high-quality $Hg_2Br_2$ single crystal and then high performance AOTF modules.