Precursor of copper nitride films: laser photoionization of Cu(NH3)n clusters in a supersonic beam

The results of spectroscopic studies of Cu(NH3)(n) clusters formed in a sup ersonic beam from the laser ablated metal in gaseous ammonia are reported h ere. The ionization potentials (IP) of clusters with n = 2-9 have been meas ured. The observed IPs are shifted to lower energies with respect to the ba re Cu atom IP. They appear to decrease monotonically with increasing cluste r size. This trend is consistent with a model in which the unpaired valence electron of the ground electronic state is delocalized in a well bound sur face state. The data are confirmed by energetics and structure calculations performed by the density functional method. (C) 2000 Elsevier Science B.V. All rights reserved.