NONLINEAR SPUTTERING EFFECTS INDUCED BY MEV ENERGY GOLD CLUSTERS

Gold clusters Au(n)+ with 1 < n less-than-or-equal-to 4, accelerated to MeV energies at the Orsay tandem accelerator, have been used to induce secondary ion emission from the surface of thin organic and inorganic films. A non-linear enhancement of the secondary ion yields is observed when cluster impacts are compared to single atom impacts at the same velocity. It has been shown that the collective effects propagate in the solid over a depth larger than 2000 angstrom. The equilibrium charge state of cluster constituents after their passage through a thin carbon foil (1000 angstrom) has been measured. The mean value for the cluster constituents is the same as for single atoms at the same velocity.