1. Chemical Vapour Deposition (CVD)
David Xiulei Ji
Definition of typical CVD:
The vaporized precursors are introduced into a CVD reactor and adsorb onto a substance held at an elevated temperature.
Either happens:
1. Precursors decomposition (synthesis of CNT)
2. Precursors reaction with other gases or vapour to form crystal (synthesis of Metal Nitride)
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2. Typical Reactor and Process:
Precursors,
Carrier gases
CVD process:
mass transport of reactants to the growth surface
(b) chemical reactions on the growth surface
(c) removal of undesired composition in the product.
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3. Growth Mechanism: Substrate Different growth mode decided by
Physical Review Letters (1990)
Different growth mode decided by
Strain Energy
Interfacial free energy terms and lattice dismatch
Thin film, Nano particles and Thin film&Nano particles
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4. Conditions That Matter in CVD
Reactants flow rate and different reactants
Reaction Temperature
Pressure of the system
Reacting Time: thickness of film or length of nano stuffs
Carrier gas: Argon, H2, Water…. to achieve slow homogeneous growth
Substrate: different types (Si, SiO2, Ni, quartz etc.) differently terminated ect.
Position of substrate in terms of gas flow
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5. More CVD Methods:
a) LP PECVD: low pressured plasma enhanced CVD------utilized in industry
Limitations: Not good for deposition of materials in a large scale.
b) AP PECVD: Atmospheric pressured plasma enhanced CVD
c) MO CVD: Metal organo CVD. Organic ligands as reducing agent.
d) Catalytic CVD (Ni, Co, Fe nano particles)
e) Template based CVD such as employ Aluminium Membrane
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6. One Successful Case: Carbon Nanotube (CNT):
Initially synthesized under arc discharge method, one of CVD method.
Ref: Nature, (1990), 347, 354 (C60)
Nature, (1991), 354, 56 (First CNT)
Chemical Reviews, 2005, Vol. 105, No
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7. Thank you Want to know more?
Please go to the journal named Chemical Vapour Deposition
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