Effects of under- and overlayers on particle and photon emission from solid argon induced by 2 MeV protons

We studied electron emission, luminescence, and sputtering of thin condensed gas films by 2 MeV protons. For thin Ar films, an external electric field causes nearly complete extraction of excited electrons, hindering hole recombination. This leads to a reduction in luminescence and sputtering. We have observed that overlayers of Nz annul the effects of external electric fields and also that they decrease ion-induced luminescence from the bulk of the Ar films. In related experiments, 20 nm Krypton layers were grown between the metal substrate and the Ar films. We found that these underlayers change the dependence of particle and photon emission on Ar film thickness and dramatically increase electron emission. We discuss these new effects in terms of internal electric fields produced by unbalanced holes and of changed reactions of excitons and holes at the interfaces. (C) 2000 Elsevier Science B.V. All rights reserved.