Normal incidence X-ray standing wave study of Fe on Cu(1 1 1)

The structure of annealed ultra-thin Fe films on Cu(1 1 1) has been investigated using normal incidence X-ray standing wave (NIXSW). Films of between 0.5 and 5.3 monolayer equivalence (MLE) have been deposited in situ and briefly annealed to 513 K. NIXSW measurements of the (1 1 1) and (1̄ 1 1) reflections using 2p3/2 photoemission show that the film is pseudomorphic up to 2 MLE, with near complete occupation of the fcc hollow sites. For this regime, the value of the (1 1 1) coherent position is equivalent to a film spacing relative to the lattice of 2.00±0.03 Å. For the 5.3 MLE film, there is a drastic reduction in the (1̄ 1 1) coherent fraction and shift in the (1̄ 1 1) coherent position that is consistent with the transformation of the entire film to a Kurjumov-Sachs oriented bcc(1 1 0) structure.