In-depth structural characterisation of the bct-hcp phase transition in Co epitaxial films
Istituto Nazionale per la Fisica della Materia and Dipartimento di Fisica
via Campi 213/a, 41100 Modena, Italy
Accepted: 3 December 1998
In-depth structural evolution of Co layers grown on Fe(001) has been investigated by modulated electron emission measurements during both film growth, by thermal evaporation, and erosion by mild ion sputtering. Co growth results in an epitaxial body-centered tetragonal (bct) phase which progressively turns to hexagonal close packed (hcp) in the 10–35 monolayers (ML) range. Erosion of a 40 ML thick film, performed under sputtering conditions such as to preserve structural order, shows that the bct/hcp interface is located significantly deeper than expected from measurements during growth. It is concluded that the transition to the hcp phase in the growing film begins on top of the bct layer and afterwards extends both upward and downward, reducing the thickness of the underlying bct layer.
PACS: 68.55.-a – Thin film structure and morphology / 68.35.Rh – Phase transitions and critical phenomena / 61.14.Rq – Other electron diffraction and scattering techniques for structure analysis
© EDP Sciences, 1999