Sio2 Reaction Lab Report

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Thermal decomposition Thermal decomposition of a compound to yield a deposit of the stable residue is called pyrolysis. In this a stable residue is deposited over a substrate by thermal decomposition and reaction of compounds. Organic-metallic compounds decompose at low temperature (< 600˚C) where as metal halides decomposes above 600˚ C to yield metallic deposits. Many of the organic silicates can be thermally decomposed to give substantially pure SiO2 films of dielectric properties close to those of silica. This is usually accomplished by passing an inert carrier gas carrying vapour from the silicates over heated substrates. For example
Si (OC2H5)4 decomposes to SiO2 + 4C2H4 + 2H2O -------------- (3.8) …show more content…

In some cases Oxygen is also introduced as a reactant carrier to control the characteristics of the film.
B. Vapour phase reaction Constituent species in the gaseous phase react in the presence of inert, oxidizing or even some reducing atmosphere to form the desired product. Thus SiO2 films can be produced by the reaction of SiCl4 vapour with carbon dioxide in the pressure of hydrogen gas and this is known as Philips process. The reaction goes in the following way
SiCl4 + CO2 + H2 SiO2 + CCl4 + H2 --------------- (3.9) SnO2 films often used as metal oxide resistors can be prepared from SnCl4 vapours in presence of water and HCl vapours at a temperature about 500˚C and the reaction can be represented by the equation
SnCl4 + 2H2O + HCl SnO2 + 4HCl + HCl ---------------

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