Above and below surface interactions of highly charged ions on metals, insulators or semiconductors

We summarize in this paper recent experiments which demonstrate, for the first time, that different kinds of hollow atoms are formed during the interaction of slow highly charged ions above and below metal, insulator and semiconductor surfaces. These results show that, in both cases, the conduction or valence character of the most weakly bound target electrons plays an essential role in the interaction. The ions are accelerated above metal surfaces (contact) and backscattered on insulators by the holes formed during the capture of valence electrons. Below the surface the feeding of the hollow atoms strongly depends on the metal or insulator character of the target and is found to be much faster in metals than in insulators.