Pulse laser deposition of thin film

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Transcript of Pulse laser deposition of thin film

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

optics electricity computer magnetics Solar cells

Applications of thin films

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.

Creation of plasma

e-

e-

e-

e-e-

e-

e-

solid

Cont…

Melting (tens of ns), Evaporation, Plasma

Formation (microseconds), Resolidification

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