Pulsed laser deposition of thin films
HASNAIN JAVED
BS HONS.
DEPARTMENT OF PHYSICS
UNIVERSITY OF GUJRAT, GUJRAT
What is thin film?
A thin film is a layer of material ranging from fractions of
a nanometer to several micrometer (1 nm - µm) in
thickness.
Thin film is used to modifyPhysical characteristics
Electrical conductivity
Chemical inertness
Chemical characteristics
decoration
Thin Film Deposition
The act of applying thin film on a substrate.
Transfer atoms from target to a vapour and then
deposite on a substrate
Ways to deposit thin films
Chemical deposition
Plating
Chemical solution
deposition
Spin coating
Chemical vapor
deposition
Atomic layer deposition
Physical deposition
Sputtering
Pulse laser deposition
target
substrate
Evaporation
target
substrate
Chemical
vapor
deposition
Ar+
substrate
gas
Sputtering
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.
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.
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.
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
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.
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
Types of deposited film
three-dimensional island
growth
two-dimensional monolayer
growth of separate islands on top of a full
monolayer
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