ATOMIC AND MOLECULAR PHYSICS SEMINAR Title: Surface and Lattice Vibrational modes in Hydrogenated and Deuterated Polycrystalline Diamond Speaker: Roger Azria, Université Paris-Sud, Orsay Time: Thursday 18th June at 3:15 pm Place: Phys.Aud. 3rd Floor Physics and Astronomy Abstract: Diamond surfaces are of great interest due to their special properties of hardness, thermal and chemical stability, electronic properties and biocompatibility. Hydrogenated diamond surfaces may exhibit negative electron affinity making these surfaces good candidates for the realization of detectors. I will report electron energy-loss spectra displaying elastic and inelastic excitation functions of lattice and surface vibrational modes for hydrogenated surfaces. These have been measured by high-resolution electron energy-loss (HREELS) spectroscopy for hydrogenated and deuterated polycrystalline diamond films. Data show in particular that (i) vibrational excitation functions are strongly influenced by the density of states characterizing the local environment of the CHx species for surface modes, with regard to stretching modes of sp2- and sp3- hybridised species and (ii) that for a given local environment the effect of an existing band gap - located above the vacuum level - on excitation functions associated with lattice modes depends on the number and depth of the layers involved in the vibrational spectra. An unambiguous attribution of the different peaks which appear in the HREELS spectra will also be given. Coffee, tea and cake will be served at 3 pm David Field