THE STRUCTURE OF THE MON SURFACE COMPOUND ON FE-3.5-PERCENT-MO-N(100)STUDIED BY X-RAY PHOTOELECTRON DIFFRACTION - FIRST RESULTS FROM ELETTRA

Angle-resolved photoemission is used to determine the structure of two -dimensional surface compounds formed upon cosegregation of the consti tuent components on ferritic alloy single crystals. Polar angle intens ity distributions of photoelectrons (X-ray photo-electron diffraction) are recorded in the high symmetry [001] and [011] azimuths. The exper iments have been performed at the SuperESCA beamline of ELETTRA, the t hird generation synchrotron radiation source in Trieste. The formation of the two-dimensional surface compound MoN is found on Fe-3.5%, Mo-N (100) single crystal surfaces. From the observed (1 x 1) LEED pattern it is inferred that the surface compound is epitaxed to the bcc(100) s urface. X-ray photoelectron diffraction of Mo 3d(5/2,) Fe 3p and N 1s core level photoelectrons is used to determine the MoN structure. It i s found that the MoN surface compound consists of a double Mo and a si ngle N layer. The interlayer distances are determined according to d(M o-->Mo) = 1.71 +/- 0.07 Angstrom and d(N-->Mo) = 0.65 +/- 0.1 Angstrom . (C) 1997 Elsevier Science Ltd.