Internal electrochromism in vanadium pentoxide xerogel films

Modification of the Properties of Vanadium Oxide Thin Films by Plasma-Immersion Ion Implantation

“…In our experiment, the interlayer distance, as a result of heating by hydrogenation, decreases by about 1.5Å, down to 10.04Å (Table 2), that is, for the time of hydrogenation, monomolecular layer of water is only partly extracted from the film. At the electrochromic coloration of an initial (nonhydrogenated) film, analogous changes occur [13]. Here, partial dehydration is caused by the heating due to the current flow.…”

“…Film samples of 200 nm thick polycrystalline vanadium dioxide VO 2 on glass-ceramic substrates were fabricated using an AJA ORION 5 setup by reactive magnetron sputtering in a mixture of argon and oxygen (the partial pressures of Ar and O 2 were 4.3 and 0.7 Torr, and the DC generator power was 200 W) with subsequent annealing at a temperature of 500 ∘ C. The V 2 O 5 ⋅nH 2 O films were obtained by the sol-gel method [8,13,15]: the vanadium pentoxide powder was placed in an alundum crucible and kept in a muffle furnace for 1 hour at a temperature of 900 ∘ C. After that, the V 2 O 5 Figure 2: : Mass spectrum of gas in the experimental chamber when the crucible with W(CO) 6 is heated.…”

“…For the manifestation of the IECE in V 2 O 5 ⋅nH 2 O films, a constant DC voltage of about 30 V was applied to the film using point spring-loaded electrodes located at a distance of 3 mm from each other. The red spot (similar to that shown in Figure 1 of our previous work [13]) growing around the negative electrode was photographed at regular intervals, and the spot area was then calculated from the photographs.…”

“…In the hydrated vanadium pentoxide V 2 O 5 ⋅nH 2 O ( = 1.6-1.8), the internal electrochromic effect (IECE) is observed without the use of an external electrolyte [13].…”

“…At the flowing current, a bright red spot appears and gradually grows under the negative electrode. This phenomenon is associated with the migration of protons, which are present in the xerogel water phase, toward the cathode and formation of red-colored highest polyvanadic acids, particularly, hexavanadic X 4 V 6 O 7 or decavanadic H 6 V 10 O 28 acid inclusions, inside the vanadium pentoxide layers [13]. Accordingly, one can suppose that the effect might be enhanced by means of an additional saturation of the V 2 O 5 ⋅nH 2 O film by hydrogen.…”