Switchable glazing technology for eco-efficient construction - Nanotechnology in Eco-efficient Construction - page 255

absorption and hence is inherent in the material. This problem with vana-
dium dioxide has been known for decades, and much effort has gone into
fi nding ways to diminish its infl uence. The problem received an at least
partial solution in recent work on sputter deposited fi lms (Mlyuka et al. ,
2009c), where it was shown that Mg doping could produce band gap widen-
ing, i.e., an enhancement of T ( m. The upper panel of

Fig. 11.10 shows spectral data for a VO 2 -based fi lm containing 7.2 at% Mg
at

λ ) for λ < 0.6 μ

τ < τ c and τ > τ c and compares these results with corresponding ones for

22 °C

80

60

40

20

Undoped
7.2% Mg

100 °C

0

500 1000 1500 2000 2500

Wavelength (nm)

50

￿ ￿ ￿ ￿ ￿ ￿

45

40

0 2 4 6 8

Doping level (%)

c
and lower panel shows the luminous transmittance vs. doping level at
τ

11.10 Upper panel shows the spectral transmittance at τ < τ c and τ > τ

m-thick Mg-containing VO 2 fi lms. The line in the lower
panel was drawn for convenience. From Mlyuka et al. (2009c).

< τ c for 0.05- μ