PARTICLE-INDUCED AUGER EMISSION FROM SI MONOLAYERS

We studied the Auger electron emission induced by Si atom bombardment in grazing incidence near the ionization threshold (800 eV) in Si film s on a Ge substrate, from submonolayer to 4 monolayers (ML) coverage. Atomic-like and bulk-like contributions to the particle induced Si Aug er emission were separately determined. We found that the atomic-to-bu lk yield ratio is strongly dependent on the coverage in the 0-2 ML ran ge. At low coverage, atomic emission originating in prompt, projectile -target collisions largely prevails. At increasing coverage, the casca de collisional regime (target-target collisions) leads to a predominan ce of bulk emission. A very large fraction (greater than or equal to 6 0%) of this bulk emission has been found to originate in the outermost Si layer.