Ion-induced Auger-electron emission from aluminum

Abstract

We have observed $\mathrm{Al} L_{2,3}$ Auger electrons from clean aluminum surfaces bombarded by mass-analyzed beams of noble-gas ions at 45° incidence, and in the energy range 600 eV - 15 keV. The electron energy spectra show a wide structure similar, though not identical, to that observed under electron impact, and sharp lines. These lines are identified as resulting from the Auger decay of $2p$-excited Al and ${\mathrm{Al}}^{+}$. The decay occurs in vacuum from sputtered particles, as suggested by the asymmetric Doppler broadening of the Auger lines. The Auger yields can be scaled when plotted against the maximum energy transfer in a projectile-Al collision, indicating that the excitation occurs mainly in symmetric collisions between target atoms. Exceptions are the cases of impact with ${\mathrm{He}}^{+}$ and low-energy ${\mathrm{Ne}}^{+}$ ions where projectile-Al collisions are responsible for the excitation, possibly by two-electron transitions.