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Low-Resistivity Sputtered Films of Transparent Conducting Ta-Doped In2O3 Oxide
Joonchul Moon,Honglyoul Ju,Chang-Oh Jeong,Changwoo Park,강광선,Seung-Han Park,Yungsu Shin 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
Low-resistivity Ta-doped In2O3 (InTaO) films were grown on Corning1737 glass substrates from a ceramic target of (In0.95Ta0.05)2O3 by radio-frequency magnetron sputtering. The electrical and the optical properties of these films were investigated by varying the oxygen partial pressure pO2 (0 Torr pO2 1.0 × 10−4 Torr) and the deposition temperature TS (25C TS 350 C) during the deposition. The film grown at 350 C and pO2 = 0 Torr showed a resistivity as low as 0.28 m cm with a carrier density of 7.4 × 1020 cm−3, a Hall mobility of 30.1 cm2V−1s−1, an optical band gap of 4.04 eV, and an average transmittance above 85 % for wavelengths between 400 and 700 nm. These values are comparable to those of optimized Sn-doped In2O3 (ITO).
Kim, Howon,Mun, Bongjin Simon,Park, Changwoo,Ju, Honglyoul Elsevier 2017 CURRENT APPLIED PHYSICS Vol.17 No.2
<P>We have investigated the effect of over oxidized surface layer on the characteristics of metal-insulator transition (MIT) of vanadium dioxide (VO2) films grown by thermal oxidation method. During the oxidation, the over-oxidized V6O13 layer was formed, which increased contact resistance and thus reduced the resistivity ratio before and after MIT. The contact resistivity of the V02 film with over oxidized surface layer was in the range 4.2 x 10(-2) similar to 9.4 x 10(-4) Omega cm(2). Interestingly, the over-oxidized surface layer was removed by simply cooling the film under reduced oxygen pressure. Upon the removal of the over-oxidized layer, the resistivity ratio across MIT increased up to 1.2 x 10(4). The ratio of contact resistance to sample resistance was small (large) at low (high) temperature. (C) 2016 Elsevier B.V. All rights reserved.</P>
Electronic structure of p-type transparent conducting oxide CuAlO2
Salah Mohamed,Yoon Joonseok,El-Desoky Mohamed M.,Hussain Zahid,Ju Honglyoul,Mo Sung-Kwan 한국물리학회 2022 Current Applied Physics Vol.39 No.-
Copper-based delafossite oxides are excellent candidates for the p-type transparent conducting oxide (TCO), which is essential in realizing transparent semiconductor applications. Using angle-resolved photoemission spectroscopy (ARPES), we report the low-energy electronic structure of CuAlO2. We found that the band structure near the valence band top is characterized by hole bands with their maxima along the Brillouin zone boundary. Furthermore, the effective masses along the Γ–M and Γ–K directions were found to be (0.6 ± 0.1) m0 and (0.9 ± 0.1) m0, respectively, which impose an important benchmark against the existing band calculations.
Insulating phases of vanadium dioxide are Mott-Hubbard insulators
Huffman, T. J.,Hendriks, C.,Walter, E. J.,Yoon, Joonseok,Ju, Honglyoul,Smith, R.,Carr, G. L.,Krakauer, H.,Qazilbash, M. M. American Physical Society 2017 Physical Review B Vol.95 No.7
<P>We present comprehensive broadband optical spectroscopy data on two insulating phases of vanadium dioxide (VO2): monoclinic M-2 and triclinic. The main result of our work is that the energy gap and the electronic structure are essentially unaltered by the first-order structural phase transition between the M-2 and triclinic phases. Moreover, the optical interband features in the M-2 and triclinic phases are remarkably similar to those observed in the well-studied monoclinic M-1 insulating phase of VO2. As the energy gap is insensitive to the different lattice structures of the three insulating phases, we rule out vanadium-vanadium pairing (the Peierls component) as the dominant contributor to the opening of the gap. Rather, the energy gap arises primarily from intra-atomic Coulomb correlations.</P>
Nonpercolative metal-insulator transition in VO2single crystals
Mun, Bongjin Simon,Chen, Kai,Yoon, Joonseok,Dejoie, Catherine,Tamura, Nobumichi,Kunz, Martin,Liu, Zhi,Grass, Michael E.,Mo, Sung-Kwan,Park, Changwoo,Lee, Y. Yvette,Ju, Honglyoul American Physical Society 2011 Physical review. B, Condensed matter and materials Vol.84 No.11
Kim, Geonhwa,Yoon, Joonseok,Yang, Hyukjun,Lim, Hojoon,Lee, Hyungcheol,Jeong, Changkil,Yun, Hyungjoong,Jeong, Beomgyun,Crumlin, Ethan,Lee, Jouhahn,Lee, Jaeyoung,Ju, Honglyoul,Mun, Bongjin Simon American Institute of Physics 2016 Journal of Applied Physics Vol.120 No.20
<P>The evolution of oxidation/reduction states of vanadium oxide thin film was monitored in situ as a function of oxygen pressure and temperature via ambient pressure X-ray photoemission spectroscopy. Spectra analysis showed that VO2 can be grown at a relatively low temperature, T similar to 523 K, and that V2O5 oxide develops rapidly at elevated oxygen pressure. Raman spectroscopy was applied to confirm the formation of VO2 oxide inside of the film. In addition, the temperature-dependent resistivity measurement on the grown thin film, e.g., 20 nm exhibited a desirable metal-insulator transition of VO2 with a resistivity change of similar to 1.5 x 10(3) times at 349.3 K, displaying typical characteristics of thick VO2 film, e.g., 100 nm thick. Our results not only provide important spectroscopic information for the fabrication of vanadium oxides, but also show that high quality VO2 films can be formed at relatively low temperature, which is highly critical for engineering oxide film for heat-sensitive electronic devices. Published by AIP Publishing.</P>