José Figueroa; Yunqi Cao; Tongyu Wang; David Torres; Nelson Sepúlveda
Abstract
The programmability of emissivity states in a monolithically integrated micro window based on vanadium dioxide (VO2) thin film is demonstrated. The 400 window features a VO2 thin film with integrated electrodes for actuation and sensing. The phase transition was induced by resistive heating, while ...
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The programmability of emissivity states in a monolithically integrated micro window based on vanadium dioxide (VO2) thin film is demonstrated. The 400 window features a VO2 thin film with integrated electrodes for actuation and sensing. The phase transition was induced by resistive heating, while the electrical resistivity and optical transmittance (for near IR wavelength of 1550 nm) of the VO2 thin film were monitored simultaneously. Abrupt drops in electrical resistance and optical transmittance confirmed the quality of the VO2 thin film. Electronic pulses were used to program emissivity states in the VO2 window. The emissivity programmed state was shown for a specific DC current over imposed with the programming pulse; but any emissivity state that belongs to the minor hysteretic curves can be obtained by choosing different electronic inputs. The fully monolithically integrated device presented here can be used for IR cloaking applications, where different emissivity values can be programmed with electronic pulses.
Dimitra Vernardou; Dimitris Louloudakis; Emmanouil Spanakis; Nikolaos Katsarakis; Emmanouil Koudoumas
Abstract
Vanadium dioxide coatings were grown on SnO2-precoated glass substrates by atmospheric pressure chemical vapor deposition using vanadyl (V) triisopropoxide at temperatures ≤ 450 o C. X-ray diffraction indicated the presence of metastable phase for the as-grown samples at 350 and 400 o C, while well-defined ...
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Vanadium dioxide coatings were grown on SnO2-precoated glass substrates by atmospheric pressure chemical vapor deposition using vanadyl (V) triisopropoxide at temperatures ≤ 450 o C. X-ray diffraction indicated the presence of metastable phase for the as-grown samples at 350 and 400 o C, while well-defined monoclinic vanadium dioxide phase was shown at 450 o C as derived by Raman spectroscopy. The different phases of vanadium dioxide affected the coating’s morphology presenting long grains with irregular size and shape turning to flattened structures composed with grains of uniform dimensions as the temperature increased from 350 to 450 o C. The best reversible behavior was at 64 o C with hysteresis width of 15 o C and a change in transmittance of 21 % for the as-grown coating at 450 o C. The significance of achieving thermochromic vanadium dioxide at temperatures ≤ 450 o C by a chemical procedure without post-treatment reduction and oxidant source is highlighted.