Surface processes occurring under reactive ion bombardment studied by secondary electron emission

Abstract

In order to obtain information about the surface processes occurring under low energy ion bombardment, we have performed energy analysis of secondary electrons, mass and energy analysis of secondary ions as well as in situ AES and EELS measurements of Al, Si and transition metals under bombardment of various ions(H, He, N, O, Ne and Ar) with incident energy of 3–30 keV. In the high energy tail of secondary electron energy spectra of clean Al and Si surfaces, characteristic atomic like LMM Auger electron emission which is independent of ion species and energy of primary beam, was observed. It appears to be due to L shell vacancy formation via an electron promotion mechanism during symmetric collisions in the cascade process. Oxidized surfaces, however, were found to give somewhat different spectra perhaps resulting from asymmetric collisions between O atoms and recoil Al or Si atoms. In transition metals such an atomic like Auger transition was not observed, but bulk like MVV spectra similar to electron induced ones were observed. Surface modification by ion bombardment is revealed by in situ AES and EELS, and the chemical effect of energetic ion bombardment on metal surface is discussed.