Thin films and nanostructured coatings for eco-efficient buildings - Nanotechnology in Eco-efficient Construction - page 178

Magnetron

Oxygen nozzle

Direction of band
movement

Spools

8.18 Schematic diagram of a roll-to-roll coating unit for continuous
production of magnetron sputter-deposited fi lms with graded cross-
sectional composition. From Zhao (2007).

fi lms with somewhat inclined columnar structures, which are formed by the
processes outlined in Section 8.2.2.
It is even possible to use large-scale sputter deposition to make fi lms
whose composition varies in a highly controlled manner over the cross
section. This latter possibility can be accomplished as illustrated in Fig. 8.18,
showing continuous deposition onto a long metallic band. As the band
moves past the sputter cathode, the initial deposition is in argon so that the
fi lm is metallic. Closer to the asymmetrically positioned oxygen inlet, the
fi lms get increasingly oxidized and - with properly adjusted parameters -
the top layer can be almost purely comprised of oxide implying that it serves
to anti-refl ect the underlying material. This innovative technology has been
used to make sputter-deposited surfaces for effi cient conversion of solar
energy into heat, i.e., conforming to the second example mentioned in
Section 8.1 (Zhao, 2007). Large-scale deposition of fi lms with inclined
columnar structures, employing the GLAD technique discussed in Section
8.2.2, is another possibility (Motohiro et al. , 1989).
Cost issues are often misunderstood in scientifi c papers. Thus it is common
to read statements implying that sol-gel deposition is 'cheap' because inher-
ently expensive vacuum equipment is not needed. However, the necessary
thermal post-deposition treatments of the sol-gel coatings lead to slow
manufacturing, which may be disastrous for mass fabrication.

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8.4 Conclusion and future trends
This chapter has given a survey over the manufacturing of thin fi lms and
nanostructured coatings for eco-effi cient constructions. It has been demon-
strated that there are a great many techniques with distinctive features and