Release of nitrogen from SiOxNy films during RBS measurement

We have found that nitrogen atoms are released very rapidly from ultrathin SiO_xN_y films (2.6 nm) during RBS measurement with 500 keV He⁺ ions. The release behavior strongly depends on the preparation technique of the SiO_xN_y films. There is no release from the film prepared by thermal nitridation of SiO₂, while 80% of the nitrogen atoms are released from the film prepared by plasma nitridation at a fluence of 1×10¹⁶ cm^?2. The release cross-section for plasma SiO_xN_y films is of the order of 10^?16 cm². This large cross-section cannot be explained by a simple recoil mechanism. The nitrogen release is also observed under irradiation with 5–10 keV electrons though the cross-section is of the order of 10^?19 cm². These findings suggest that the observed nitrogen release is an electronic excitation induced process.