complete basic description of thin film

2. Pulsed laser
deposition of thin
films
HASNAIN JAVED
BS HONS.
DEPARTMENT OF PHYSICS
UNIVERSITY OF GUJRAT, GUJRAT

3. 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.

4. Thin film is used to modify
Physical characteristics
Electrical conductivity
Chemical inertness
Chemical characteristics
decoration

5. 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

6. optics electricity computer magnetics Solar cells
Applications of thin films

7. 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

8. target
substrate
Evaporation
target
substrate
Chemical
vapor
deposition
Ar+
substrate
gas
Sputtering

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.

12. Creation of plasma
e-
e-
e-
e-
e-
e-
e-
solid

13. Cont…
Melting (tens of ns), Evaporation, Plasma
Formation (microseconds), Resolidification

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