Upon impact on a solid surface, the potential energy stored in slow highly charged ions is primarily deposited into the electronic system of the target. By decelerating the projectile ions to kinetic energies as low as 150 x q eV, we find first unambiguous experimental evidence that potential energy alone is sufficient to cause permanent nanosized hillocks on the (111) surface of a CaF(2) single crystal. Our investigations reveal a surprisingly sharp and well-defined threshold of potential energy for hillock formation which can be linked to a solid-liquid phase transition.
We compare reported compositions of a-C:H films in a ternary phase diagram. It is assumed that the films comprised three phases: sp3 hybridized carbon, sp2 hybridized carbon and hydrogen. The data are found to split into two well-separated groups. This separation depends on the method used to measure the sp3/sp2 ratio. We conclude from the comparison of NMR and infrared data that infrared analysis does not provide a quantitative measure of the sp3/sp2 ratio.
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