Investigation of the structure of ultra-thin films of Fe on Cu(1 1 1) using medium-energy ion scattering

The structure of a 12 ML ultra-thin film of Fe on Cu(1 1 1) has been investigated using medium-energy ion scattering. The as-deposited film was found to be poorly ordered with a mean square static displacement of 0.23 Å However, the order was improved by post-deposition annealing using temperatures up to 250 °C, which reduced the mean square static displacement to 0.15 Å. The structure of the as-deposited film was consistent with a poorly ordered Kurjumov–Sachs coincidence—(1 1 1)fcc∥(1 1 0)bcc, [ 1 ¯ 1 0 ] fcc ∥ [ 1 ¯ 1 1 ] bcc , [ 1 1 2 ¯ ] fcc ∥ [ 1 ¯ 1 2 ¯ ] bcc —as reported by other workers, but with some evidence of coexistence of other orientations. Upon annealing the more-ordered film structure was dominated by the Greninger–Troiano orientation—(1 1 1)fcc ∼ 1° from (1 1 0)bcc, 〈1 1 2〉fcc ∼ 2° from [ 1 1 ¯ 0 ] bcc —with coexistence of both Kurjumov–Sachs and Nishiyama–Wassermann—(1 1 1)fcc∥(1 1 0)bcc, [ 1 ¯ 0 1 ] fcc ∥ [ 0 0 1 ] bcc , [ 1 ¯ 2 1 ¯ ] fcc ∥ [ 1 ¯ 1 0 ] bcc —coincidences.