Amorphous Thermochromic VO2 Coatings Grown By APCVD At Low Temperatures

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.