Studies on energy distributions of species ejected from solid surfaces by means of multiphoton resonance ionization spectroscopy

Abstract

This paper reviews the energy distributions of neutral atoms ejected from a polycrystalline Cu target, the Si(1 1 1)-7×7 surface, the Si(1 1 1)-5×5-Cu surface and positive Cu ions ejected from the Si(1 1 1)-“5×5”–Cu surface by 5 keV Ar + ion bombardment. These energy distributions have been measured with very high efficiency by means of multi-photon resonance ionization spectroscopy, in order to obtain the surface binding energies. The energy distributions for Cu from the polycrystalline Cu target, Si from the Si(1 1 1)-7×7 surface, and Cu from the Si(1 1 1)-“5×5”–Cu surface have been found to peak at energies of around 3.0, 5.0 and 1.5 eV, and the function shapes of high-energy tails have been found to be proportional to E −1.9, E −1.2 and E −1.3, respectively. Based on the linear collision cascade theory, the surface binding energies are determined to be 5.7, 6.0 and 2.0 eV. The obtained values of the surface binding energy and the energy distributions are discussed. The ionization probability of Cu atoms ejected from the Si(1 1 1)-“5×5”–Cu surface has been found from the ratio of positive and neutral energy distributions to be proportional to the exponential function of the inverse of velocity. The velocity dependence is also discussed in terms of bond breaking model.