Illustrate the chemical vapour deposition method in brief.
Chemical vapour deposition method (CVD):
A number of vapour phase deposition process have been developed for producing fibers along with minimal impurity content. The most popular techniques are the modified chemical vapour deposition (MCVD) method.
Commercial production of fibers is completed by using this method. In this method, upon the inner surface of a pure silica tube the doped silica layer is deposited.
The chemical reaction gets place between the vapour constituents which are being passed down the tube and deposition arises.
Characteristic vapours used are SiCl4, GeCl4 and O2. The reaction is illustrated as:
SiCl4 + O2 → SiCl4 +2Cl2
GeCl4 + O2 → GeO2 + 2Cl2