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Organic SOL -GEL prepared doped vanadium oxide thin films and Electrical Properties

Author: ZhangZuoLin
Tutor: JiangYaDong
School: University of Electronic Science and Technology
Course: Optical Engineering
Keywords: Organic sol-gel VOx thin film doping sheet resistance TCR
CLC: O484.1
Type: Master's thesis
Year: 2010
Downloads: 61
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Abstract


Vanadium dioxide is a kind of heat sensitive functional material. With the increase of temperature, the semiconductor-to-metal phase transition will occur at 68°C, with a abrupt change of VO2 crystal structure. The electrical resistance and infrared transmittance will change, which results in great application potentials in many fields such as information storage, photoelectric switch and intelligent window materials. The doping of other elements can change the phase transition temperature effectively. In particular, the doping of higher valence ion can lower the phase transition temperature.Aiming at the development trend and practical need of VOx thin film, The properties of VOx film doping with two metal ions such as Mo6+ and W6+ have been systematically investigated in this work.Firstly, VOx thin films doped with Mo6+ and W6+ ion were prepared by organic sol-gel method respectively. Sheet resistance and film thickness were characterized by ellipsometry and four-point probe measurement respectively. By varying the doping concentrations, corresponding resistance-temperature curves were measured. The effects of doping concentration and film thickness on the electrical properties of vanadium oxide thin film and film uniformity have been studied. Results show that the TCR of VOx films was increased, and the sheet resistance was reduced effectively both by Mo-doping and W-doping. But the doping of W improved the electrical property better than the doping of Mo. It’s also found that when the doping concentrations of Mo and W raised to 10% and 5% respectively, sheet resistance increased while TCR reduced, which showed heavy doped problem. Additionally, compared with the film resistance uniformity of pure VOx films, the film resistance uniformity of Mo-doped and W-doped VOx thin films is better, which shows the doping can improve film resistance uniformity to some extent.Secondly, two kinds of doped vanadium oxide thin film compositions were characterized by X-ray photoelectron spectroscopy （XPS）. The results show that the existing forms of impurity elements are Mo6+ and W6+, either of them didn’t participate in the chemical reaction during film preparation. The analysis shows, Mo6+ or W6+ replaced the portion of V4+, the conversion rate from V5+ to V4+ was improved by doping, making the average valence of vanadium reduced. Based on the results of XPS, the effect of doping with different ions on vanadium oxide films was studied from the microscopic point of view.The results show that doping is an effective way to improve electrical properties of vanadium oxide thin film.

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Thin Film Physics > Film growth,structure and epitaxy
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