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저압 MOCVD 방법으로 성장된 lnAlAs 에피층에서 상분리와 규칙 현상의 관찰
조형균(Hyung Koun Cho),이번(Bun Lee),백종협(Jong-Hyeob Baek),한원석(Won Seok Han),이정용(Jeong Yong Lee),권명석(Myoung Seok Kwon) 한국진공학회(ASCT) 1999 Applied Science and Convergence Technology Vol.8 No.3(2)
LP-MOCVD 방법에 의해 InP 기판 위에 성장된 InAlAs 에피층의 상분리와 규칙 현상을 DCXRD, PL, TEM을 이용하여 분석하였다. DCXRD와 PL의 반측폭과 강도로부터 InAlAs 에피층의 구조적, 광학적 품질이 성장 온도가 증가함에 따라 향상되었다. 상분리와 규칙 현상으로 인한 밴드갭의 감소량은 565℃, 615℃, 700℃의 성장 온도에서 각각 291, 246, 28 meV이고 구조적, 광학적 품질과 같은 경향성을 보여주었다. TEM으로부터 상분리 현상은 565℃의 성장 온도에서 가장 강하게 관찰되었고, HRTEM 이미지 사진에서 InAs가 풍부한 영역과 AlAs가 풍부한 영역 사이에 조성 차이로 인하여 약 2˚의 격자 줄무늬의 회전이 발생하였다. 565℃에서 성장된 시편에 대한 RTA 열처리 실험은 880℃에서 3분간의 열처리로 약 78 meV 정도의 밴드갭 증가를 보여주고, TEM을 통해 밴드갭의 증가는 규칙 현상의 완전한 사라짐이라는 것이 관찰되었다. 이 결과는 열처리 전에 발생한 밴드갭 감소량의 3/4가 상분리 현상으로 발생하였다는 결론을 얻을 수 있다. We have studied the phase separation and ordering phenomenon of lnAlAs epilayers grown on InP substrate by LP-MOCVD with DCXRD, PL, and TEM. From the intensity and FWHM of DCXRD and PL, we observed that the structural and optical quality of lnAlAs epilayers were improved as growth temperature increased. The band-gap reduction due to phase separation and ordering is 291, 246, and 28 meV in the InAlAs epilayers grown at 565℃, 615℃, and 700℃, respectively, and shows the same trends as structural and optical quality. The maximum degree of phase separation was obtained by TEM from the lnAlAs epilayer grown at 565℃ in which the HRTEM micrograph showed the lattice fringe between lnAs-rich and AlAs-rich regions was tilted by 2˚ due to composition difference. However, the maximum degree of ordering by intensity of extra spots was obtained at the medium growth temperature. The annealing experiment by RTA of sample grown at 565℃ shows a maximum band-gap shift of 78 meV at 880℃ for 3 min, and TEM shows that the origin of the blue shift of band-gap is the complete disappearance of ordering. Through annealing we can conclude that short time annealing affects only ordering and that most of the total band-gap reduction (~3/4) occurs by phase separation.
저압 MOCVD 방법으로 성장된 InAlAs 에피층에서 상분리와 규칙 현상의 관찰
조형균,이번,백종협,한원석,이정용,권명석,Cho, Hyung-Koun,Lee, Bun,Baek, Jong-hyeob,Han, Won-Seok,Lee, Jeong-Yong,Kwon, Myoung-Seok 한국진공학회 1999 Applied Science and Convergence Technology Vol.8 No.3(2)
We have studied the phase separation and ordering phenomeon of InAlAs epilayers grown on InP substrate by LP-MOCVD with DCXRD, PL, and TEM. From the intensity and FWHM of DCXRD and PL, we observed that the structural and optical quality of InAlAs epilayers were improved as growth temperature increased. The band-gap reduction due to phase separation and ordering is 291, 246, and 28 meV in the InAlAs epilayers grown at $565^{\circ}C$, $615^{\circ}C$, and $700^{\circ}C$, respectively, and shows the same from the InAlAs epilayer town at 5$65^{\circ}C$ in which the HRTEM micrograph showed the lattice fringe between InAs-rich and AlAs-rich regions was tilted by $2^{\circ}$ due to composition difference. However the maximum degree of ordering by intensity of extra spots was obtained at medium growth temperature. The annealing experiment by RTA of sample grown at $565^{\circ}$ shows a maximum band-gap shift of 78eV at $880^{\circ}$ for 3 min, and TEM shows that the origin of the blue shift of band-gap is the complete disappearance of ordering. Through annealing we can conclude that short time annealing affects only ordering and that most of the total band-gap reduction (~3/4) occurs by phase separation.
질화물 반도체의 미세구조 분석을 위한 최적의 TEM 시편 준비법
조형균,김동찬,Cho, Hyung-Koun,Kim, Dong-Chan 한국재료학회 2003 한국재료학회지 Vol.13 No.9
The optimized conditions for the cross-sectional TEM sample preparation using tripod polisher and ion-beam miller was confirmed by AFM and TEM. For the TEM observation of interfaces including InGaN layers like InGaN/GaN MQW structures, the sample preparation by the only tripod polishing was useful due to the reduction of artifacts. On the other hand, in case of the thick nitride films like ELO, PE, and superlattice, both tripod polishing and controlled ion-beam milling were required to improve the reproducibility. As a result, the ion-beam milling with the $60^{\circ}$modulation showed the minimum height difference between film and sapphire interface and the ion-beam milling of the $80^{\circ}$modulation showed the broad observable width.
RF 스퍼터링으로 Si 기판위에 제작된 ZnO 박막에서 ZnO 버퍼층의 가스분위기 영향
박태은,조형균,공보현,홍순구,Park, Tae-Eun,Cho, Hyung-Koun,Kong, Bo-Hyun,Hong, Soon-Ku 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.7
The effects of gas atmosphere and in-situ thermal annealing in buffet layers on the characteristic of the ZnO grown by RF magnetron sputtering have been investigated. It was shown that the introduction of buffer layers grown at the gas atmospheres of the mixed $Ar/O_2$ and the in-situ thermal treatment of the ZnO buffer layer improved the structural and optical properties. In addition, the ZnO films on the buffer layer thermal-annealed at $N_2$ gas ambience showed the strong emission of the near band gap exciton with narrow linewidth by combining the high-temperature growth of the ZnO film.
합성절차에 따른 1차원 ZnO 나노구조의 형태조절과 특성평가
공보현,박태은,조형균,Kong, Bo-Hyun,Park, Tae-Eun,Cho, Hyung-Koun 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.1
The one-dimensional ZnO nanostructures prepared through thermal evaporation under various cooling down procedures by changing the flow rates of the carrier gas and the reactive gas were investigated. The nanorod structures were changed into the nanonail types with a broad head through the reduction of the flow rate of the carrier gas. The decrease of the reactive gas reduced the length of the nail heads due to the limited mass transport of reactive gas. The intensity ratio of the ultraviolet emission/green emission of photoluminescence was proportional to the length of the broad head showing a larger surface area. The vertically aligned nanostructures were grown along the [0001] direction of ZnO regardless of the aligned directions. The crystal direction of the nanostructures was determined by that of the initial ZnO crystal.
다양한 산화물 기판 위에 RF 마그네트론 스퍼터링 방법으로 성장된 ZnO 박막의 특성 비교
이재욱,정철원,한석규,최준호,홍순구,조형균,송정훈,이정용,Lee, Jae-Wook,Jung, Chul-Won,Han, Seok-Kyu,Choi, Jun-Ho,Hong, Soon-Ku,Cho, Hyung-Koun,Song, Jung-Hoon,Lee, Jeong-Yong 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.4
ZnO thn films are grown on five kinds of oxide substrates including $c-Al_2O_3(0001),\;r-Al_2O_3(01-12)$, MgO(100), MgO(111), $NdGaO_3(110)$ by rf magnetron sputtering and effects substrate types on properties of ZnO thin films ate investigated. In order to compare the substrate effects one growth condition is selected and all the films are grown by the same growth condition. Structural and optical properties of the ZnO films ate different depending on the substrates although the films ate not epitaxial but polycrystalline. The ZnO film grown on $NdGaO_3(100)$ substrate shows the best overall properties among the films grown on substrates investigated in this study.
플라즈마분자선에피탁시법으로 성장한 산화비스무스아연 박막의 구조특성
임동석,신은정,임세환,한석규,이효성,홍순구,정명호,이정용,조형균,Lim, Dong-Seok,Shin, Eun-Jung,Lim, Se-Hwan,Han, Seok-Kyu,Lee, Hyo-Sung,Hong, Soon-Ku,Joeng, Myoung-Ho,Lee, Jeong-Yong,Cho, Hyung-Koun,Yao, Takafumi 한국재료학회 2011 한국재료학회지 Vol.21 No.10
We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.
다원자가 금속산화물 기반 박막트랜지스터의 특성 및 안정성 평가
윤명구(Myeong Gu Yun),안철현(Cheol Hyoun Ahn),조성운(Sung Woon Cho),김소희(So Hee Kim),김예균(Ye Kyun Kim),조형균(Hyung Koun Cho) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.6
We demonstrate that depending on the channel structure, the addition of multivalent V atoms into ZTO films can induce a dual electrical performance: semi-insulating and semiconducting. Moreover, in order to catch both high mobility and high stability in zinc tin oxide (ZTO)-based thin film transistor (TFT), we fabricated VZTO/ZTO bi-layer TFT in which V is a doping element that can act as a oxygen vacancy suppressor. The VZTO/ZTO bi-layer TFT showed a field effect mobility of 16.9cm²/(V·s), comparable to that of ZTO TFT (15.3cm²/(V·s)). In addition, it showed much better stability (ΔVth = -0.9 V) under negative bias illumination stress (NBIS) than that of ZTO TFT (ΔVth = -7.3 V).