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 inertnessChemical characteristicsdecoration

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 DepositionWith 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

Laser Beam

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