The Structure of Atomic Nitrogen Adsorbed On

Nitrogen atoms adsorbed on a Fe(100) surface cause the formation of an ordered ~(2x2) overlayer with coverage 0.5. A structure analysis was performed by comparing experimental LEED I-V spectra with the results of multiple scattering Todel calculations. The N atoms were found to occupy fourfold hollow sites, with their plane 0.27 A above the plane of the surface Fe atoms. In addition, nitrogen adsorption causes an expansion of the two topmost Fe layers by 10% ( = 0.14 A). The minimum r-factor for this structure analysis is about 0.2 for a total of 16 beams. The resulting atomic arrangement is similar to that in the (002) plane of bulk Fe,N, thus supporting the view of a “surface nitride” and providing a consistent picture of the structural and bonding properties of this surface phase.