Strain state in bcc Fe films grown on Si(1 1 1)

The strain state of Fe films grown on Si(1 1 1) has been investigated by X-ray diffraction (XRD) in the thickness range between 11 and 304 monolayers. Fe grows tetragonally distorted with the orientation relationship Fe(1 1 1) 〈12¯1〉 // Si(1 1 1) 〈1¯21¯〉. At low coverage, the films grow pseudomorphic. Above 15 monolayers the films are characterized by the coexistence of a pseudomorphic phase with another one which relaxes with the Fe thickness. This relaxation proceeds rapidly in the earlier stages then slowly with the film thickness. The XRD characterization allows one to obtain quantitative information on the in-plane and out-of-plane strains.