Interactions of Pd(110) with (N 2+N)-EELS, AES and LEED studies

Abstract

The interactions of a Pd(110) surface with (N2+N) have been studied by means of high-resolution vibrational electron energy loss spectroscopy (EELS), Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). At 300 K, double- and triple-bonded N2 admolecules and N adatoms (located most probably in the long-bridge, short-bridge and on-top sites of the unreconstructed Pd(110) surface) are formed; some N atoms penetrate into the “bulk”. The double- and triple-bonded N2 admolecules are identified by the N-N stretching energies of 199 and 265 meV, respectively; the N adatoms in the long-bridge, short-bridge and on-top sites are identified by the Pd-N stretching energies of 55, 90 and ∼130 meV, respectively. By heating at ∼500 K, the triple-bonded N2 and most of the double-bonded N2 admolecules are desorbed. The Pd clean surface is recovered by heating at ∼900 K. The (2×3)-N structure is formed by a large (N2+N) exposure followed by heating at ∼500–800 K or by a large N2 exposure at ∼700 K. It is proposed that N atoms located in the long-bridge sites of the “distorted” Pd(110) surface form the (2×3)-N structure. Molecular nitrogen is not adsorbed on the (2×3)-N surface at 300 K.