Growth and characterization of chloronitroaniline crystals for optical parametric oscillators I. XPS study of Mo-based compounds

The surface electronic structures and compositions of Mo-based compounds (oxides and nitrides) have been elucidated using X-ray photoelectron spectroscopy (XPS). The Mo nitride samples were synthesized using the temperature-programmed nitridation of a low surface area MoO3 with NH3. The Mo oxides were also used to compare XPS results. No significant change was observed in the surface electronic structure of core levels of Mo 3d, Mo 3p, N Is, and O Is for Mo nitrides after the hydrogen reduction. A species with a Mo 3d(5/2) binding energy of 228.4 +/- 0.2 eV from Mo nitrides was newly observed and was calculated to be Mo1.3+. This value indicates that the absolute magnitude of charge transfer from Mo 4d states to N 2p states is 1.3 electrons per molybdenum in Mo nitrides. The binding energies of Mo 3d(5/2) were shifted to lower ones (232.5 --> 230.0 --> 228.4 eV) as the oxides were transformed to nitride during nitridation (Mo6+ --> Mo4+ --> Modelta+). There are two different regions (nitride and oxide regions) present on the Mo nitride surface as shown from the deconvoluted Mo 3d peaks. For the Mo nitrides prepared in this study the nitride fraction was observed to be a majority on the surface. (C) 1999 Elsevier Science B.V. All rights reserved.