Influence of metal plasma ion implantation on photo-sensitivity of anatase TiO2 thin films |
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Authors: | Da-Yung Wang Hsiao-Cheng Lin Chung-Chih Yen |
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Affiliation: | Department of Materials Science and Engineering, Mingdao University, Taiwan, ROC |
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Abstract: | Nano-scale TiO2 thin films were synthesized by using sol-gel and spin-coating techniques on glass substrates for photo-catalytic applications. The Ti(IV) butoxide-based TiO2 thin films were optimized for transforming into the high-purity crystalline anatase phase when calcined at 500 °C. To further enhance the photo-catalysis sensitivity of TiO2 thin films for use in visible light environments, a metal plasma ion implantation process was implemented to modify the band gap electron configuration of Ti. Various transition metal atoms such as Ni, Cu, V, and Fe were ionized and accelerated at 20 keV to impinge on the surface of TiO2 substrates at a dosage of 5 × 1015 ions/cm2. ESCA analysis confirmed the binding energy shift of Ti by 0.8-1.2 eV, which accounted for the increased effective positive charge of Ti, resulting in more effective electron trapping capability and, thus, the electron-hole pair separation. In addition, the absorption spectroscopy demonstrated that optical absorption in the visible light regime occurred in specimens implanted with transition metal ions, likely due to the formation of extra impurity energy levels within the original TiO2 band gap energy structure. Among all tested implant materials, the band gap energy of TiO2 was effectively reduced by Cu and Fe ion implantation by 0.9-1.0 eV, which was sufficient enough to excite valence electrons over the band gap in visible light environments. The feasibility of the metal-doped TiO2 thin films for effective applications under visible light irradiation was further confirmed by using super-hydrophilicity contact-angle measurement. |
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Keywords: | Photo-catalysis TiO2 Ion implantation Sol-gel |
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