Measurement of the Fermi potential of diamond-like carbon and other materials

The Fermi potential Vf of diamond-like carbon (DLC) coatings produced with laser-controlled vacuum arc deposition and that of diamond, Al, Si, Be, Cu, Fe and Ni was measured using two different methods, (i) transmission of slow neutrons through foils in a time-of-flight experiment and (ii) cold neutron reflectometry (CNR). For diamond-like carbon in transmission we obtain Vf = (249 ± 14) neV. This is approximately the same as for beryllium and consistent with the theoretical expectations for the measured diamond (sp3) content of 45%. For an sp3-content of 67%, we find Vf = (271 ± 13) neV from reflectometry, again in agreement with theory. These findings open new perspectives in using DLC as storage volume and neutron guide coatings for ultracold neutron sources.