Decomposition of perchlorodisiloxane Original Research Article

The perchlorodisiloxane Si2OCl6 is studied ab initio with a series of basis sets and inclusion of electron correlation at the MP2 level. The molecular structure was investigated with special focus on the sensitive SiOSi angle and compared with experimental values as well as with the theoretically extensively surveyed Si2OH6. On the basis of 6-311+G(2d) geometries and MP2 energies the cleavage of SiCl bonds in dependence of the substitution of chlorine by oxygen on an Si center of model siloxanes was investigated. We deduce that reactions will start at SiCl3 and SiCl2 groups of chlorosiloxanes, because these groups lose Cl atoms most easily. The investigation of the structure and fragmentation of Si2OCl6 revealed that a split into SiOCl2 and SiCl4 is competitive to chlorine abstraction as an initial decomposition reaction. Our calculated reaction energies imply that particle growth in the chemical vapor deposition leading towards SiO2 will proceed uniformly with little variation in the oxygen content in agreement with experimental findings.