Contact potential barriers and characterization of Ag-doped composite TiO2 nanotubes |
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| Affiliation: | 1. College of Ero-environment & Urban-construction, Fujian University of Technology, Fuzhou 350108, China;2. College of Material Science and Engineering, Fuzhou University, Fuzhou 350108, China;3. Department of Physics and Electronic, Minjiang University, Fuzhou 350108, China;4. Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510641, China;5. Fujian Key Laboratory of Microelectronics & Integrated Circuits, Fuzhou 350108, China;1. School of Science, Henan Institute of Engineering, Zhengzhou 451191, China;2. School of Science, Jiaozuo Teacher’s College, Jiaozuo 454001, China;1. Physical and Life Sciences, Lawrence Livermore National Laboratory, PO Box 808, L-372, Livermore, CA 94551, United States;2. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6493, United States;3. Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States;4. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States;1. School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47906, USA;2. Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA |
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| Abstract: | Ag-doping TiO2 composite nanotubes (Ag-TNTs) were synthesized by alkaline fusion followed by hydrothermal treatment. The microstructure and morphology of the materials were characterized by XRD, TEM, XPS, SPS (surface photovoltage spectroscopy), FISPS (electric field-induced surface photovoltage spectroscopy) and Raman spectroscopy. First-principles calculations based on density-functional theory (DFT) showed the formation of several impurity levels near the top of the valence band in the band gap (Eg) of rutile TiO2 due to Ag doping. A “double junction” is proposed, involving a Schottky junction and p–n junction (denoted as “Ag-p–n junction”) occurring between the Ag particles and the nanotube surface, as well as forming inside TiO2 nanotubes, respectively. The strongly built-in electric field of the junctions promotes the separation of photo-holes and photoelectrons, enhancing the photocatalytic efficiency. XRD results indicated that the composite Ag-TNTs exist as a mixture of anatase and rutile phases. XPS results showed that Ti4+ is the primary state of Ti. Raman spectral analysis of Ag-TNTs revealed the presence of a new peak at 271 cm−1. The red-shift of the absorption light wavelength of Ag-TNTs was 0.16 eV (20 nm) due to a considerable narrowing of Eg by the existing impurity levels. |
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| Keywords: | A. Nanostructures C. Ab initio calculations D. Microstructure D. Surface properties D. Transport properties |
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