The laser pulse of high intensity and energy is used to evaporate carbon from graphiteThese carbon atoms are condensed to form nanotubes.

1. PRESENTED BY: ANJANA JAYASHRI
BRANCH:CHE ‘A’

2. PULSE LASER
DEPOSITION
CHEMICAL DEPOSITION
PROPERTIES

4. CCD /PMT
spectromete
r
Target
Substrates
or
Faraday
cup
laser beam

6. LASER PULSE
e-
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e-
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e-
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e-
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LATTICE

7.  Flexible, easy to implement
 Growth in any environment
 Exact transfer of complicated materials (YBCO)
 Variable growth rate
 Epitaxy at low temperature
 Resonant interactions possible (i.e., plasmons in
metals, absorption peaks in dielectrics and
semiconductors)
 Atoms arrive in bunches, allowing for much more
controlled deposition
 Greater control of growth (e.g., by varying laser
parameters)

8. CHEMICAL VAPOUR
DEPOSITION
 INTRODUCTION
 Chemical Vapour Deposition (CVD) is a chemical
process used to produce high purity, high
performance solid materials.
 In a typical CVD process, the substrate is exposed to
one or more volatile precursors which react and
decompose on the substrate surface to produce the
desired deposit.
 During this process, volatile by-products are also
produced, which are removed by gas flow through
the reaction chamber.

9. Transport of
reactants by
forced
convection to
the
deposition
region
Transport of
reactants by
diffusion
from the
main gas
stream to the
substrate
surface.
Adsorption
of reactants
in the wafer
(substrate)
surface.
Chemical
decomposition
and other
surface
reactions take
place.
Desorption
of by-
products
from the
surface
Transport of
by-products
by diffusion
Transport of
by-products
by forced
convection
away from the
deposition
region.
STEPS INVOLVED IN CHEMICAL
VAPOUR DEPOSITION

10. SCHEMATIC DIAGRAM - THE
STEPS INVOLVED IN CVD

11. CVD’s are classified into
two types on the basis of
Operating Pressure.
1. Atmospheric Pressure
CVD
2. Low Pressure CVD
Plasma Enhanced CVD
Photochemical Vapour
Deposition
Thermal CVD
TYPES OF CVD

12. Variable shaped surfaces, given reasonable access
to the coating powders or gases, such as screw
threads, blind holes or channels or recesses, can
be coated evenly without build-up on edges.
Versatile –any element or compound can be
deposited.
High Purity can be obtained.
High Density – nearly 100% of theoretical value.
Material Formation well below the melting point
Economical in production, since many parts can
be coated at the same time.
ADVANTAGES OF CHEMICAL
VAPOUR DEPOSITION

13. APPLICATIONS OF CHEMICAL
VAPOUR DEPOSITION
CVD has applications across a wide range of industries such
as:
Coatings – Coatings for a variety of applications such as
wear resistance, corrosion resistance, high temperature
protection, erosion protection and combinations thereof.
Semiconductors and related devices – Integrated circuits,
sensors and optoelectronic devices
Dense structural parts – CVD can be used to produce
components that are difficult or uneconomical to produce
using conventional fabrication techniques. Dense parts
produced via CVD are generally thin walled and maybe
deposited onto a mandrel or former.

14. Properties of Nano Materials

15. The melting point decreases dramatically
as the particle size gets below 5 nm
Melting Point

16. Band gap
The band gap is increases with reducing the
size of the particles

17. Surface Area
The total surface area (or) the number of surface
atom increases with reducing size of the particles

18. • For semiconductors such as ZnO, CdS, and Si, the bandgap
changes with size
- Bandgap is the energy needed to promote an electron
from the valence band to the conduction band
- When the bandgaps lie in the visible spectrum, changing
bandgap with size means a change in color
• For magnetic materials such as Fe, Co, Ni, Fe3O4, etc., magnetic
properties are size dependent
- The ‘coercive force’ (or magnetic memory) needed to
reverse an internal magnetic field within the particle is
size dependent
- The strength of a particle’s internal magnetic field can be
size dependent