Decomposition of perchlorodisiloxane

Abstract

The perchlorodisiloxane Si 2OCl 6 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 Si 2OH 6. 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 SiCl 3 and SiCl 2 groups of chlorosiloxanes, because these groups lose Cl atoms most easily. The investigation of the structure and fragmentation of Si 2OCl 6 revealed that a split into SiOCl 2 and SiCl 4 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 SiO 2 will proceed uniformly with little variation in the oxygen content in agreement with experimental findings.