~.l~ace science ELSEVIER Applied Surface Science 116 (1997) 318-323 Background-free Auger line shape of Ag N2,3VV measured with positron annihilation induced Auger electron spectroscopy E. Jung *, H.Q. Zhou, J.H. Kim, S. Starnes, R. Venkataraman, A.H. Weiss Department of Physics, University of Texas at Arlington, P.O. Box 19059, Arlington, TX 76019, USA Received 2 June 1996; accepted 2 June 1996 Abstract Auger spectra for the Ag(100) N2.3VV transition obtained utilizing positron annihilation induced Auger electron spectroscopy (PAES) are presented. This low energy transition of Ag is difficult to separate from the large secondary background which is present using electron induced Auger electron spectroscopy (EAES) and has not been studied extensively. In our measurements, the secondary electron background is eliminated by utilizing a positron beam whose energy is below the energy range of the of the Auger electrons. Measurements of the temperature dependence of PAES intensity, IpAES, and positronium fraction, fes, indicate that IpAES is proportional to the quantity (1 -fps)- Electron energy spectra taken at high temperature (fPs = 1) clearly demonstrate that the prominent low energy tail (LET) present in the PAES spectra is associated with Auger transitions and is not due to secondary electrons induced by collisions with the primary positron beam. The Auger line shape of the N2.3VV transition of Ag(100) is accounted for in terms of the convolution of the density of states of the N2,3 core levels and the density of states of the correlated two-hole final states estimated from the N2.3 XPS core level spectra and the Auger line shape of the MnVV transition. In addition, possible mechanisms leading to the production of the LET including a N2N3V transition followed by a N3V-VVV transition and/or electron energy loss during the escape from the topmost layer are discussed. Keywords: PAES; Surface; Ag; Auger line shape; N2.3VV transition; Low energy tail 1. Introduction The quasi-atomic-like Auger spectra correspond- ing to the M4,sVV transition in metallic silver has been the subject of a number of detailed studies [1-3]. The fact that these spectra are substantially narrower than the self convolution of the valence band has been ascribed to correlation effects in the two-hole final state [1-3]. The N2,3VV Auger transi- * Corresponding author. Tel.: + 1-817-2762511; fax: + 1-817- 2763637; e-mail: exj5091@utadg.uta.edu. tion shares the same VV final state as the M4.5VV transition, however, using conventional electron in- duced Auger electron spectroscopy (EAES), the broad peak at about 40 eV which results from this transition is difficult to separate from a large sec- ondary electron background. Perhaps as a conse- quence, this transition has not been extensively stud- ied. Previous studies [4] have indicated that by using a positron beam whose energy is below the energy range of the Auger electrons, PAES can be used to eliminate the background associated with secondary electrons which result directly from energy exchange 0169-4332/97/$17.00 Copyright © 1997 Elsevier Science B.V. All rights reserved. PII S0169-4332(96)01 076-8