Thermochromic characteristic of Ti-doped VO2 thin film
Thermochromic characteristic of Ti-doped VO2 thin film
- 주제(키워드) thin film , VO2 , sputter
- 발행기관 아주대학교
- 지도교수 고경현
- 발행년도 2014
- 학위수여년월 2014. 2
- 학위명 석사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000015931
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
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.
more목차
1.Introduction 1
2.Background 3
2.1 Vanadium system 3
2.2 Doping of VO2 films 7
2.3 Synthesis of VO2 thin films 8
2.3.1 Sputtering 10
2.3.2 Sol-gel 11
3.Experimental design 12
3.1 Fabrication of VO2 film 12
3.1.1 Sputtering 12
3.1.2 Sol-gel 14
3.2 Characterization of thin film 16
3.2.1 Measurement of thickness 16
3.2.2 Characterization of X-ray Diffraction(XRD) 16
3.2.3 Characterization of Scanning Electron Microscopy(SEM) 16
3.2.4 Metal to Insulator (MIT) character analysis 16
3.2.4.1 Measurement of resistivity 16
3.2.4.2 Measurement of transmittance 17
3.2.5 Characterization of the thin film composition 17
4.Results and discussion 18
4.1 Manufacture and characterization of VO2 film 18
4.1.1 Sputter deposition of VO2 film 18
4.1.1.1 Influence of sputtering parameter on deposition rate 18
4.1.1.2 Phase characterization of the deposited films 20
4.1.1.3 Effect of sputtering parameter on morphology 25
4.1.1.4 MIT characteristic of deposited VO2 film 31
4.1.2 Sol-gel coating of VO2 film 36
4.1.2.1 Optimal condition for synthesis of dip-coated V2O5 xerogel 36
4.1.2.2 Phase characterization of the post-treated films 39
4.1.2.3 MIT characteristic of deposited VO2 film 48
4.1.3 Conclusions 51
4.2 Deposition from Ti oxide-V2O5 double target co-sputtering system 52
4.2.1 Influence of sputtering parameter on deposition rate and Ti concentration 53
4.2.2 Phase characterization of the deposited films 57
4.2.3 MIT characteristic of Ti doped vanadium oxide films 66
4.2.4 Conclusions 74
5.Conclusions 75
Reference 76
