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Thermochromic characteristic of Ti-doped VO2 thin film
- Alternative Title
- Thermochromic characteristic of Ti-doped VO2 thin film
- Author(s)
- Lee, Hwa Soo
- Alternative Author(s)
- Hwasoo Lee
- Advisor
- 고경현
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2014-02
- Language
- eng
- Alternative Abstract
- Utilizing metal-to-insulator transition (MIT) properties of V-oxide thin film, stable VO2 phase is necessary. In this study, development of a sol-gel method and sputtering for the deposition of VO2 films was focused because it had one identical advantage which was the low cost. Sol-gel method for the deposition of VO2 films usually requires specific raw materials or post-treatments, which greatly limit their practical application. Therefore, a simple and effective method for the deposition of VO2 films is urgently needed. For this, melt-quench method was used to create V2O5 xerogel and was dip-coated for post-treatment. Under treatment temperature as high as 600oC, pure VO2 was crystallized with fair Thermochromic property. In sputtering deposition of VO2, simple target preparation and high deposition rate are recommendable. For this, VO2 thin film was deposited on quartz substrate by RF magnetron sputter system under low working pressure using V2O5 target. Due to the lower sputtering yield of oxygen compared to vanadium, oxygen ion contents is usually deficient from that of target. So, the reduction of V ions was a result of charge compensation with the oxygen ions. Under lower working pressure, deposition rate become higher so that this deficiency is getting larger to cause further reduction to destabilize VO2. Preventing this under very low working pressure (high deposition rate), titanium oxide co-sputtering was suggested to enrich oxygen source. When TiO2 was used, Ti ion has stable +4 charge state so that extra oxygen sputtered prevents V ion reduction below +4 state, but that was not the case for TiO. For latter, Ti ions were oxidized from +2 to +3 and +4 state and V ions with less oxidation potential should be reduced to +3 or so. Pure VO2 thin film had MIT at 66oC and large resistivity ratio of 4 orders of magnitude from 30oC to 90oC. Under working pressure as low as 5 mtorr, (V2O5 + TiO2) system yield fairly good films comparable to pure VO2, while films with poor or absence of MIT were produced with TiO case.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 3. Theses(Master)
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