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Micro-Structural Properties of YBa2Cu3O(7-x)/ZnO Nanorods on SrTiO3.
Jin, Zhenlan,Park, Changin,Song, Kyu Jeong,Kang, Sukil,Ko, Kyeong-Eun,Park, Chan,Ko, Rock Kil,Han, S W American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.1
<P>We examined the local structural and the interfacial properties of YBa2Cu3O7-x, (YBCO)/ZnO nanorods on SrTiO3 (STO) substrates using various measurements. Vertically aligned ZnO nanorods were synthesized on STO substrates using a catalyst-free metal-organic chemical vapor deposition. YBCO films were deposited ex-situ on the ZnO nanorods/STO templates using a DC magnetron sputtering deposition. X-ray diffraction revealed that the YBCO films were crystallized along their c-axes on the ZnO nanorods/STO templates. Transmission electron microscopy measurements demonstrated that YBCO filled the space between ZnO nanorods and that both interfaces of YBCO/ZnO nanorods and ZnO nanorods/STO were quite clean with no disorder. Polarization-dependent extended X-ray absorption fine structure measurements at the Cu K edge showed extra disorder in the CuO2 planes of YBCO/ZnO nanorods/STO, compared with that of YBCO/STO. The superconductivity transition temperature (T-c) of YBCO/ZnO nanorods/STO was approximately 50 K whereas that of YBCO/STO was 93 K. The decrease of T-c, of YBCO/ZnO nanorods/STO was ascribed to the structural disorder of CuO2 planes as well as grain boundaries in the YBCO films.</P>
Structural and electrical properties of VO<sub>2</sub>/ZnO nanostructures
Jin, Zhenlan,Hwang, In-Hui,Park, Chang-In,Park, Sun-Hong,Han, Sang-Wook ELSEVIER 2018 Current Applied Physics Vol.18 No.3
<P>We examined the structural and electrical properties of uniformly-oriented VO2/ZnO nanostructures. VO2 was deposited on ZnO templates by using a direct current-sputtering deposition. Scanning electron microscope and transmission electron microscope measurements indicated that b-oriented VO2 were uniformly crystallized on ZnO templates with different lengths. VO2/ZnO formed nanorods on ZnO nanorods with length longer than 250 nm. X-ray absorption fine structure at the V K edge of VO2/ZnO showed M-1 and R phases of VO2 at 30 and 100 degrees C, respectively, suggesting structural-phase transition occurring between the two temperatures. Temperature-dependent resistance measurements of VO2/ZnO nanostructures revealed metal-to-insulator transition at 65 degrees C and 55 degrees C during a heating and a cooling, respectively, regardless of ZnO length. Asymmetry behavior of resistance curves from VO2/ZnO nanostructure during a heating and a cooling was attributed from a strong bond of VO2 and ZnO. (C) 2017 Elsevier B.V. All rights reserved.</P>
Selective Synthesis and Structural Stability of Anatase and Rutile Ti1−xFexO2 Nanoparticles
Zhenlan Jin,박창인,한상욱,Bingzhi Jiang 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.2
Anatase and rutile Ti<sub>1−x</sub>Fe<sub>x</sub>O<sub>2</sub> nanocrystals with x = 0.0 - 0.05 were synthesized selectively in an aqueous solution. X-ray diffraction with refinements showed that TiO<sub>2</sub> crystals calcined at 500 and 800 ℃ were pure anatase and rutile phases, respectively. However, TiO<sub>2</sub> calcined at 550 ≤ T ≤ 600 ℃ showed a mixture of anatase and rutile phases. Ti<sub>1−x</sub>Fe<sub>x</sub>O<sub>2</sub> nanoparticles calcined at 500 C had a high-quality anatase structure with no extra phases while Ti<sub>1−x</sub>Fe<sub>x</sub>O<sub>2</sub> calcined at 800 ℃ showed mainly a rutile structure. More disorder was observed in anatase than rutile Ti<sub>1−x</sub>Fe<sub>x</sub>O<sub>2</sub> nanoparticles. The results suggest that rutile Ti<sub>1−x</sub>Fe<sub>x</sub>O<sub>2</sub> nanoparticles are more stable than anatase Ti<sub>1−x</sub>Fe<sub>x</sub>O<sub>2</sub> nanoparticles. No change was observed from anatase or rutile TiO<sub>2</sub> nanoparticles when annealed at 900 ℃, suggesting that both anatase and rutile TiO<sub>2</sub> nanoparticles are quite stable, once TiO<sub>2</sub> is crystallized.
Local Structural Properties and Growth Mechanism of ZnO Nanorods on Hetero-Interfaces.
Jin, Zhenlan,Park, Chang-In,Hwang, In-Hui,Han, Sang-Wook American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.7
<P>We investigated the growth mechanism of ZnO(001) nanorods on SrTiO3(001) substrates. In the beginning of ZnO growth, a ZnO(110) film was developed on SrTiO3 substrates and then (001)-oriented ZnO nanorods grew on the ZnO(110) film. The strain energy of ZnO(110) growth on SrTiO3(001) planes was approximately 2.7 x 10(8) J/m3 whereas it was estimated to be ~1.61 x 10(9) J/m3 for ZnO(001) directly grown on SrTiO3(001) planes using Young's modulus of elasticity. Stress due to the lattice mismatch between ZnO and SrTiO3 was mostly relaxed in several monolayers and then ZnO(001) nanorods were finally formed along their easy growth directions. Keywords: ZnO Nanorod, Hetero-Interface, Local Structural, Growth Mechanism.</P>
Structural and electrical properties of VO2/ZnO nanostructures
Zhenlan Jin,황인희,박창인,박선홍,한상욱 한국물리학회 2018 Current Applied Physics Vol.18 No.3
We examined the structural and electrical properties of uniformly-oriented VO2/ZnO nanostructures. VO2 was deposited on ZnO templates by using a direct current-sputtering deposition. Scanning electron microscope and transmission electron microscope measurements indicated that b-oriented VO2 were uniformly crystallized on ZnO templates with different lengths. VO2/ZnO formed nanorods on ZnO nanorods with length longer than 250 nm. X-ray absorption fine structure at the V K edge of VO2/ZnO showed M1 and R phases of VO2 at 30 and 100 °C, respectively, suggesting structural-phase transition occurring between the two temperatures. Temperature-dependent resistance measurements of VO2/ZnO nanostructures revealed metal-to-insulator transition at 65 °C and 55 °C during a heating and a cooling, respectively, regardless of ZnO length. Asymmetry behavior of resistance curves from VO2/ZnO nanostructure during a heating and a cooling was attributed from a strong bond of VO2 and ZnO.
Synthesis and temperature-dependent local structural and electrical properties of VO2 films
Zhenlan Jin,황인희,박창인,Jae-Kuan Son,Sang-Wook Han 한국물리학회 2016 Current Applied Physics Vol.16 No.2
We examine the local structural and electrical properties of VO2 films showing metal-to-insulator transition (MIT) by using in-situ x-ray absorption fine structure (XAFS) measurements at the V K edge and resistance measurements in the temperature range 20e120 C. VO2 films are synthesized on Al2O3 (0001) substrates by DC magnetron sputtering deposition. X-ray diffraction measurements show that the films have b-oriented monoclinic-phase crystals at room temperature. XAFS measurements reveal a local structural transition in the films from the monoclinic (M1) to the rutile (R) phase at ~70 C during their heating; further, temperature-dependent resistance (ReT) measurements showed a sharp MIT in the films at ~75 C. Extended XAFS (EXAFS) measurements reveal non-rigid changes of VeO and VeV bond lengths from the M1 to the R phase via the M2 phase. In-situ EXAFS and ReT measurements show that the synthesized VO2 films act as Mott insulators and that their electrical property change is not proportional to their structural property change at their MIT temperature.