| Vanadium dioxide (VO2) is a typical thermochromic functional material. It exhibits a metalinsulator transition (MIT) abrupt transition at about68℃and accompanies with a crystallographictransition from a low temperature monoclinic phase to a high temperature tetragonal rutilestructure. Since F.J.Morin found out the phase transition properties of VO2in the Bell Labs in1959, it had attracted the attention of many researchers. At the same time, due to its hightemperature coefficient of resistance (TCR), it considered as a thermistor material in research. It iswidely used in uncooled infrared detectors, smart window, photonic crystals, information storage,energy-saving coating and so on.In this article, we prepared high quality VO2thin films in different oxidation temperatures byDC sputtering and oxidation coupling (SOC) method. It was found that particle size keptincreasing when the oxidation temperature increased in the experiment. As the particle sizereached76.30nm, TCR value reached a very high rate at-5.11%/℃. After analyzing it showedthat TCR absolute values increased along with particle size at room temperature and had a linearrelationship. This result can give a basic theory to fabricate VO2thin films with higher TCR andset a foundation to produce uncooled infrared detectors with more outstanding property.However, the phase transition temperature of VO2is about68℃, which is higher for manyapplications. In order to satisfy the applications, the main researches recently concentrate inreducing phase transition temperature of VO2to nearly ambient temperature. We preparedMo-doped VO2thin films by a sandwich structure of V/Mo/V metal thin films Oxidized anddecreased the phase change temperature from65.03℃to51.36℃successfully. For the more, itwas found that Mo doping can keep TCR on a high rate and decrease the sheet resistance of the thin film at the same time which provides a new path in researching VO2thin films of uncooledinfrared detectors. |
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