References 787
ten supplying acids or bases to interfaces between polymers and thin films. These
limitations of polymers tend to speed corrosion and decrease adhesion, resulting
in possible product failure.
An amorphous layer generated by exposure of some polymers to flashlamps
may be used to toughen the polymer surface. On deposition of a thin film, the
amorphous layer improves cohesive strength in the polymer near the interface.
Plasma priming at low pressure can improve adhesion and reduce corrosion
rates of metal films deposited on polymer substrates. Prior to thin-film deposition,
a plasma of an appropriate gas may be generated adjacent to a polymer surface.
This process may create coordination or covalent bonds between polymer sub-
strate and vacuum-deposited thin films. Oxidizing plasmas also remove surface
layers and weakly bound contaminants, typically a thickness of 10 to 20 nm; plas-
mas often smooth polymer surfaces. The effects of plasma treatment are very
stable, because plasma exposure produces a significant chemical change at the
surface. Surface modification and adhesion enhancement by plasma chemistry is
a process confined to surface layers. Vacuum ultraviolet light generated by such
plasma affects deeper layers of polymers.
Reduced oxidation and improved stability may be achieved at interfaces be-
tween polymer surfaces and metal films by forming an appropriate barrier film
at such interfaces. The barrier should coordinate well with the plasma-treated
substrate. Barrier films should be thin, insoluble, and not electrically conducting;
the last item helps decrease electrochemical interactions. Once the substrate is
in vacuum, one wants to provide as many coatings as possible in one pass, such
as plasma priming, barrier and nucleation films, functional films, overcoats, and
lubricants.
REFERENCES
1.
L. I. Maissel and R. Glang, Handbook of
Thin
Film Technology (McGraw-Hill, New York, 1983)
originally published 1970.
2.
J. L. Vossen and W. Kern, Thin Film Technology (Academic Press, New York, 1978).
3.
Don Griffin, "The new
C-MAGT"^*
dual rotatable sputtering cathode," Proc. Third Int.
Conf.
on
Vacuum Web Coating, San Antonio, Texas (1989), pp. 62-74.
4.
R. F. Bunshah, Deposition
Technologies
for Films and Coatings —Developments and Applica-
tions (Noyes Publications, Westwood, NJ, 1982), pp. 231-235.
5.
R. M. Bozorth, Ferromagnetism (Van Nostrand, New York, 1951).
6. J. Kieser, W. Schwarz, and W. Wagner, "On the Design of Vacuum Web Coaters," Thin Solid
Films, 119 (1984) pp. 217-222.
7.
W. M. Rohsenow and J. R Hartnett, eds.. Handbook of Heat Transfer (McGraw-Hill, New York,
1973),
pp. 3-14 to 3-18.
8. H. Fenech and W. M. Rohsenow, "Prediction of thermal conductance of metallic surfaces in
contact," J. Heat
Transfer,
Trans. The American Society of
Mechanical
Engineers, 85 (1963)
pp.
15-24.