TEOS slowly hydrolyzes into silicon dioxide and ethanol when in contact with ambient moisture, but its flammability and toxicity are similar to that of an alcohol. To produce the vapor for use in processing, one may use a bubbler or a liquid injection system. However, addition of oxygen increases the deposition rate, presumably through providing an alternative path for removal of the ethyl groups from the surface. Relatively little gas phase reaction gives smooth films.
Films are thus dense and fairly stable as deposited with modest compressive stress.