Microvoids at the SiO2/Si interface

A variable-energy positron beam was used to study device-quality SiO2 (50-nm thick) grown thermally on the Si(100) surface. The unusual observation of ortho-positronium 3 decay at the interface demonstrates that microvoids >1 nm in size are present, most likely as a consequence of the thermal oxidation process. Other interfacial defects were also observed, illustrating the sensitivity of positron studies for studying interfacial properties. © 1989 The American Physical Society.