Secondary ion emission processes of sputtered alkali ions from alkali/Si(100) and Si(111)

The secondary alkali ion yield vs. the work function change (Delta phi) of Na, K and Cs/Si(100) and Si(111) was measured to discuss the details of sec ondary ion emission processes. In the case of alkali/metal systems, the sec ondary ion emission is explained by the electron tunneling model. In this m odel, the ionization of the ejected atom occurs as a result of electron res onant tunneling through the potential barrier separating an atom and a meta l, and the secondary ion yield depends on exponentially the work function c hange of metal surface. For alkali/Si(100) systems, the secondary ion emiss ion processes are explained in terms of the electron tunneling model since the secondary alkali ion yield vs. the work function change (Delta phi) fol lows the exponential manner. However, it is not easy to apply the simple el ectron tunneling model to our experimental results for alkali/Si(111) syste ms. There is the essential difference in surface structures between Si(100) and Si(111). Therefore, it is suggested that the local electronic environm ent around the adsorbates might be taken into consideration for alkali/Si(1 11) systems. (C) 2000 Elsevier Science B.V. All rights reserved.