introduction to thin film,techniques to deposit thin film, pulse laser deposition, creation and dynamics of plasma, types of thin films, nucleation and growth of film,
9. Target:! (metals, semiconductors…)
Laser: (UV, 10 ns)
Vacuum: Atmospheres to ultrahigh vacuum
or inert gas
Pulsed Laser Deposition
With the pulsed laser deposition (PLD) method, thin films are prepared
by the ablation of one or more targets illuminated by a focused pulsed-
laser beam.
10. Gas and ultra high vacume
Ultra high vacume
In vacuum, the plume does
not expand unidirectionally
The ejected species diffuse
in the plume and collide
with each other, which leads
to a rapid thermalization of
the particle cloud.
Gas
Ambient gas scatters and
attenuates the plume
changing its spatial
distribution
the deposition rate
kinetic energy distribution
of the different species.
11. Process in PLD
The removal of atoms from the bulk
material is done by vaporization of
the bulk at the surface region in a
state of non-equilibrium.
Thus transferring some of their
energy to the lattice of the target.The
surface of the target is then heated up
and vaporized.
14. Dynamic of the plasma
Material expands in a plasma parallel to the normal vector of the
target surface towards the substrate.
The spatial distribution of the plume is dependent on the
background pressure inside the PLD chamber.
The dependency of the plume shape on the pressure can be
described by
The vacuum stage, where the plume is very narrow and forward
directed;
The intermediate region where a splitting of the high and less
energetic species can be observed
15. Deposition of the ablation material
The high energetic species ablated from the target are bombarding the
substrate surface
It may cause damage to the surface by sputtering off atoms from the
surface.
16. Nucleation and growth of the film
The nucleation process and growth kinetics of the film depend
on several growth parameters including:
Laser parameters
Surface temperature
Substrate surface
Background pressure
17. Types of deposited film
three-dimensional island
growth
two-dimensional monolayer
growth of separate islands on top of a full
monolayer
18. Conclusion
Flexible, easy to implement
Exact transfer of complicated materials
Variable growth rate
Atoms arrive in bunches, allowing for much more controlled
deposition
When compared to other thin film techniques (e.g. chemical
vapour deposition, sol-gel, sputtering, etc), PLD does not
need expensive or corrosive precursors,large volume targets.
Neither it need very high temperature and/or pressure