Evidence for a strain-stabilized bct phase of cobalt deposited on Pd(100): An x-ray photoelectron diffraction study

The structure of cobalt layers grown on a Pd{100} single-crystal surface has been studied by scanned angle x-ray photoelectron diffraction. At room temperature the cobalt layers grow in a structure related to the bulk cobalt fee phase characterized by a large expansion of the in-plane lattice parameters and a corresponding contraction of the interlayer spacing (similar to 10%). This structure persists to coverages greater than 30-layer equivalents, and can be interpreted as a metastable body-centered-tetragonal (bct) phase.