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DC 마그네트론 스퍼터링 방법을 이용하여 증착한 IGZO 박막트랜지스터의 특성
김성연,명재민,Kim, Sung-Yeon,Myoung, Jae-Min 한국재료학회 2009 한국재료학회지 Vol.19 No.1
Indium Gallium Zinc Oxide (IGZO) thin films were deposited onto 300 nm-thick oxidized Si substrates and glass substrates by direct current (DC) magnetron sputtering of IGZO targets at room temperature. FESEM and XRD analyses indicate that non-annealed and annealed IGZO thin films exhibit an amorphous structure. To investigate the effect of an annealing treatment, the films were thermally treated at $300^{\circ}C$ for 1hr in air. The IGZO TFTs structure was a bottom-gate type in which electrodes were deposited by the DC magnetron sputtering of Ti and Au targets at room temperature. The non-annealed and annealed IGZO TFTs exhibit an $I_{on}/I_{off}$ ratio of more than $10^5$. The saturation mobility and threshold voltage of nonannealed IGZO TFTs was $4.92{\times}10^{-1}cm^2/V{\cdot}s$ and 1.46V, respectively, whereas these values for the annealed TFTs were $1.49{\times}10^{-1}cm^2/V{\cdot}$ and 15.43V, respectively. It is believed that an increase in the surface roughness after an annealing treatment degrades the quality of the device. The transmittances of the IGZO thin films were approximately 80%. These results demonstrate that IGZO thin films are suitable for use as transparent thin film transistors (TTFTs).
상온 강자성 (Ga,Mn)N 박막을 이용한 질화물계 스핀 발광소자의 스핀편극된 빛의 발광
함문호,명재민,Ham, Moon-Ho,Myoung, Jae-Min 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.11
We investigated the fabrication and characteristics of the nitride-based spin-polarized LEDs with room-temperature ferromagnetic (Ga,Mn)N layer as a spin injection source. The (Ga,Mn)N thin films having room-temperature ferromagnetic ordering were found to exhibit the negative MR and anomalous Hall resistance up to room temperature, revealing the existence of spin-polarized electrons in (Ga,Mn)N films at room temperature. The electrical characteristics in the spin LEDs did not degraded in spite of the insertion of the (Ga,Mn)N layer into the LED structure. In EL spectra of the spin LEDs, it is confirmed that the devices produce intense EL emission at 7 K as well as room temperature. These results are expected to open up new opportunities to realize room-temperature operating semiconductor spintronic devices.
PLD법에 의해 제조된 ZnO박막의 두께 변화에 따른 특성 연구
윤욱희,명재민,이동희,배상혁,윤일구,이상렬,Yun, Uk-Hui,Myeong, Jae-Min,Lee, Dong-Hui,Bae, Sang-Hyeok,Yun, Il-Gu,Lee, Sang-Ryeol 한국재료학회 2001 한국재료학회지 Vol.11 No.4
펄스레이저 증착법 (PLD)으로 (0001)면 사파이어 기판 위에 성장시킨 ZnO 박막의 두게 변화가 표면형상, 결정성 및 전기/광학적 특성에 미치는 효과에 대하여 조사하였다. SEM 및 XRD 분석을 통해 약 4000 의 두께에서 3차원 island들이 생성되며, 박막의 두께가 증가함에 따라 결정립의 크기가 증가하고, 결정성이 향상되었음을 알 수 있었다 상온에서의 PL 측정을 통해 두께가 증가함에 따라 ultraviolet(UV) 및 deep level emission peak의 강도가 급격히 증가함을 알 수 있었다. Hall측정 결과, 모든 박막들이 H형 전도도를 보였고, 운반자농도가 $10^{19}$ $cm^{-3}$ 이상이었으며, 두께가 증가할수록 운반자농도가 감소하여 약 4000 에서 포화되는 경향을 보였다. 따라서, 사파이어 기판 위에 증착시킨 ZnO 박막은 약 4000 의 두께에서 bulk ZnO의 특성을 나타내었다. In order to investigate the effect of thickness on the properties of ZnO thin films, a series of films having different thickness were deposited on (0001) sapphire by using pulsed laser deposition(PLD). SEM and XRD analyses showed that, as the film thickness increases, the grain size increased and the crystallinity improved. Room-temperature PL spectra also exhibited that the intensities of both ultraviolet and deep level emission Peaks increased as the film thickness increased. Hall measurements at room- temperature revealed that, as the film thickness changes from 400 to 4000 , the carrier concentration of the film showed sharp decrease, which that of thicker film gradually saturated. Therefore, it is concluded that the strain due to the lattice mismatch between substrate and film is fully relaxed around the thickness of 4000 .
Ferromagnetic Properties in Diluted Magnetic Semiconductors (Al,Mn)N grown by PEMBE
함문호,명재민 한국전기전자재료학회 2006 Transactions on Electrical and Electronic Material Vol.7 No.1
We present the structural, magnetic, and electrical properties in the (Al,Mn)N films with various Mn concentrations grown by plasma-enhanced molecular beam epitaxy. X-ray diffraction analyses reveal that the (Al,Mn)N films have the wurtzite structure without secondary phases. All (Al,Mn)N films showed the ferromagnetic ordering. Particularly, (Al1-x Mnx)N film with x = 0.028 exhibited the highest magnetic moment per Mn atom at room temperature. Since all the films exhibit the insulating characteristics, the origin of ferromagnetism in (Al,Mn)N might be attributed to either indirect exchange interaction caused by virtual electron excitations from Mn acceptor level to the valence band within the samples or a percolation of bound magnetic polarons arisen from exchange interaction of localized carriers with magnetic impurities in a low carrier density regime.
Development of Transparent Conductive Oxide for Thin-film Silicon Solar Cells
김태연,명재민,Jeong Woo Lee,Won Seo Park,Seong-Kee Park,Ki Yong Kim,In Byeong Kang 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.2
Gallium-doped zinc oxide (GZO) films were deposited by DC magnetron sputtering using a GZO ceramic target at various substrate temperatures from 298 to 573 K in order to apply the films to amorphous silicon thin film solar cells. A low resistivity (~4.28 × 10−4cm) and a high transmittance (>90%) were obtained from the film deposited at 573 K. From X-ray diffraction, the films had columnar structures oriented along the c-axis, regardless of the substrate temperature. The lattice images and the grains were observed by using a field emission transmission electron microscope. A grain was overlapped by the crystallite of 10-15 nm, and the size of a grain was about 70 nm. Finally, the texturing conditions of the GZO films were optimized as a function of deposition temperature for potential applications to tandem solar cells and single junction amorphous silicon thin film solar cells.