Auger spectra induced by Ne+ and Ar+ impact on Mg, Al, and Si

Abstract

Impact of Ne⁺ and Ar⁺ at energies of 20–200 keV on targets of Mg, Al, and Si gives rise to an electron spectrum that has sharp atomiclike features superimposed on a continuous background. The continuum is similar to the spectrum observed during electron impact and is generally ascribed to decay of L‐shell vacancies in the matrix. We show, however, that this is not completely correct, that the apparent continuum induced by ion impact extends to higher energies than for electron impact and that this is due to the presence of some hitherto unidentified atomiclike lines. We identify the atomiclike transitions as due to particles sputtered with L‐shell vacancies. A complete modelling of the spectra is performed which accounts quantitatively for all Auger peaks. We conclude that the major features are due to sputtered neutral atoms with a single inner shell vacancy. The electron configurations and energies are Mg⁰ 2p⁵3s²3p (50.6 eV), Al⁰ 2p⁵3s²3p² (73.8 eV), and Si⁰ 2p⁵3s²3p³ (101.1 eV). These are states where one electron has been removed from the L shell but an electron added to the 3p shell to maintain neutrality. Other weaker lines are identified as due to sputtered Mg⁺, Al⁺, and Si⁺ with single L‐shell vacancies. For the case of silicon we identify an additional feature that we tentatively ascribe to sputtered atoms decaying while still within the field of the surface. A detailed modelling of the spectrum with all these components provides a complete explanation of all features of the spectrum lending confidence to the line identifications. Line intensities provide relative transition probabilities for competing decay processes.