Surface extended X-ray absorption fine structure investigation of Fe islands grown on c(2 x 2) N/Cu(100) surface

We present the results of a surface extended X-lay absorption fine structure (SEXAFS) investigation of the growth of Fe islands on the c(2 x 2) N/Cu(100) surface for different N doses. It is known from scanning tunnelling microscopy (STM) experiments that at subsaturation coverage adsorbed N atoms on Cu(100) form square islands of c(2 x 2) periodicity and about 5 nm x 5 nm in size. These islands can self-organize in regular patterns. From the persistence of the c(2 x 2) low energy electron diffraction patterns obtained for any Fe and N coverage we deduce (in agreement with previous STM results) that Fe islands grow on surface areas which are not passivated by N atoms. In this study we estimate that we were able to produce Fe islands thicker than 10 atomic layers, a value higher than that observed using STM. The first shell analysis of SEXAFS data shows that Fe atoms are arranged in an fee lattice with tetragonal distortion, as observed in Fe/Cu(100) films, with the formation of bilayers and/or coalescence in small islands at the lowest coverage studied (one monolayer). (C) 1999 Elsevier Science B.V. All rights reserved.