14.7: Summary

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Thin films can be constructed by the deposition of vapourised atoms onto a substrate surface. There are 2 principle methods of generating the flux for Physical Vapour Deposition (PVD) – Evaporation and Sputtering. Both of these involve the use of a vacuum chamber.

Evaporation

Thermal Process
High Vacuum
Low energy vapour flux
Line of sight deposition

Sputtering

Physical Process
Background of Inert Gas
High energy vapour flux
Scattering of atoms

If the incoming vapour flux has low energy, then the resultant film will have shadowed regions. However, if there is enough energy for surface diffusion to occur then the film will rearrange into one of 3 possible structures – depending on the relative bonding energies between the film and substrate atoms.

Deposition of films made from alloys or compounds are more difficult, as the different elements will not necessarily react to the environment in the same way. One way around this issue is a process known as Pulsed Laser Deposition (PLD). This involves heating the source material instantaneously using a focussed laser in order to avoid fractioning.

Going further

Books

M. Ohring, The Materials Science of Thin Films, Academic Press, 1992, ISBN: 0-12-524990-X

Going further

Books

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