Mukherjee, Dipta and Dey, Arjun and Esther, A Carmel Mary and Sridhara, N and Kumar, D Raghavendra and Rajendra, A and Sharma, Anand Kumar and Mukhopadhyay, Anoop Kumar
(2018)
Reversible and repeatable phase transition at a negative temperature regime for doped and co-doped spin coated mixed valence vanadium oxide thin films.
RSC Advances, 8 (54).
pp. 30966-30977.
ISSN 2046-2069
Abstract
Smooth, uniform mixed valance vanadium oxide (VO) thin films are grown on flexible, transparent Kapton and opaque Al6061 substrates by the spin coating technique at a constant rpm of 3000. Various elements e.g., F, Ti, Mo and W are utilized for doping and co-doping of VO. All the spin coated films are heat treated in a vacuum. Other than the doping elements the existence of only V4+ and V5+ species is noticed in the present films. Transmittance as a function of wavelength and the optical band gap are also investigated for doped and co-doped VO thin films grown on a Kapton substrate. The highest transparency (approximate to 75%) is observed for the Ti, Mo and F (i.e., Ti-Mo-FVO) co-doped VO system while the lowest transparency (approximate to 35%) is observed for the F (i.e., FVO) doped VO system. Thus, the highest optical band gap is estimated as 2.73 eV for Ti-Mo-FVO and the lowest optical band gap (i.e., 2.59 eV) is found for the FVO system. The temperature dependent phase transition characteristics of doped and co-doped VO films on both Kapton and Al6061 are studied by the differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition is noticed in the range of -24 to -26.3 degrees C.
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