Biomedical Engineering Reference
In-Depth Information
Fig. 5.20
Formation stages
of the continuous thin film:
(
a
) arrival of the first atom on
the substrate; (
b
) migration
and re-evaporation; (
c
)
collision and recombination
of atoms; (
d
) nucleation; (
e
)
growth; (
f
)formof
cross-sectional islets; (
g
)
coalescence; and (
h
)film
continuity
Several parameters are involved in particle size:
(A) The nature of chemical elements used as sources
(B) The different particle-production methods
1. Evaporation by the Joule effect
2. Evaporation using an electron gun
3. Pulverization using an ion gun
4. Cathodic pulverization
(C) The quality of the vacuum acting on the transport of particles during their
deposit
(D) The nature, surface state, and temperature of the substrate during the coating
process
7.2.1 Nature of Chemical Elements Used as Sources
Coatings are generally composed of atoms of carbon, carbon-metal, metal, or poly-
mer molecules. The atoms produce finer grains than the molecules. The metals most
commonly used are platinum, chrome, tungsten, and osmium, as the grains obtained
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