MODELS OF ENERGY-DEPENDENCE OF THE SECONDARY-ION YIELD COMPARED WITH EXPERIMENTAL RESULTS

The energy dependence of secondary ion yield is determined both by the (Sigmund-Thompson or Boltzmann type) energy distribution function of the secondary (neutral) particles and by the (exponential or power law ) ionization probability. The combination of these functions results i n four possible mathematical models of secondary ion emission. The ene rgy distributions of monoatomic singly charged positive ions emitted f rom pure metals and from amorphous alloys were studied experimentally. The parameters of the secondary ion emission models were calculated b y fitting the equations. The binding energies obtained were compared w ith independent experimental data taken from the literature (dissociat ion energy, enthalpy of formation). Correlation between these values s uggests that there are different possible emission pathways for differ ent ion species emitted from solid targets. (C) 1997 by John Wiley & S ons, Ltd.