Oxygen rich SIMOX?

¹⁸O(200 keV, 2.0*10¹⁷ cm^-2) has been implanted at 6 K into an 'as implanted' SIMOX wafer (silicon implanted with ¹⁶O at 200 keV, 1.8*10¹⁸ cm^-2 and 500 degrees C). In situ Rutherford backscattering measurements at 6 K, 77 K and room temperature indicate approximately 15% excess oxygen above the stoichiometric value for SiO₂ in the buried-oxide layer. Additional room-temperature measurements were carried out off-line by infrared and secondary ion mass spectrometries. A comparison of the original SIMOX material with the sample implanted with ¹⁸O at 6 K leads to the conclusion that during warm up the ¹⁸O concentration depth profile remains essentially unchanged with the maximum total concentration remaining above the original ¹⁶O value. The infrared measurements indicate that all of the oxygen atoms are bound to silicon atoms.