The effect of post-oxidation of the silicon-on-insulator structure produced by implantation of oxygen (SIMOX) upon neutral oxygen vacancies (O3=Si-Si=O3, “=” denotes bonds with three separate oxygens) in the buried oxide has been investigated. It is observed that the photoluminescence intensity from the vacancies and the thickness of buried oxide increase after the post-oxidation. An Ar plasma was used to expose the buried oxide in order to convert the vacancies to E'r (O3=Si, “” denotes an unpaired electron) centers which are detectable by electron-spin-resonance. The total number of E’
centers was found to increase, which should suggest a similar increase in the number of the vacancies in the buried oxide. Similar measurements repeatedly done on the buried oxide by changing its thickness by etching revealed that the increased part of oxide by the post-oxidation contains the vacancies with a similar density to the original part of oxide, and that the post-oxidation scarcely affects the oxygen deficiency of the original part.