Charge State Dependent Energy Deposition by Ion Impact

We report on a measurement of craters in thin dielectric films formed by XeQ+ (26 <= Q <= 44) projectiles. Tunnel junction devices with ion-irradiated barriers were used to amplify the effect of charge-dependent cratering through the exponential dependence of tunneling conductance on barrier thickness. Electrical conductance of a crater sigma(c)(Q) increased by 4 orders of magnitude (7.9 x 10(-4) mu S to 6.1 mu S) as Q increased, corresponding to crater depths ranging from 2 to 11 angstrom. By employing a heated spike model, we determine that the energy required to produce the craters spans from 8 to 25 keV over the investigated charge states. Considering energy from preequilibrium nuclear and electronic stopping as well as neutralization, we find that at least (27 +/- 2)% of available projectile neutralization energy is deposited into the thin film during impact.