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

Abstract

The structure of cobalt layers grown on a Pd͕100͖ 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 fcc phase characterized by a large expansion of the in-plane lattice parameters and a corresponding contraction of the interlayer spacing ͑ϳ10%͒. This structure persists to coverages greater than 30-layer equivalents, and can be interpreted as a metastable body-centered-tetragonal ͑bct͒ phase. ͓S0163-1829͑96͒06339-4͔

Structure and atomic interactions at theCo∕Pd(001)interface: Surface x-ray diffraction and atomic-scale simulations

“…27 For the topmost Co-interlayer spacing ͑d 12 ͒ we determine 1.61͑10͒ Å, which is 10% less than the fcc-bulk spacing of 1.77 Å. In agreement with elasticity theory considerations, 9 the contraction can be related to the 10% in-plane expansion of the Co structure to adapt to the Pd lattice ͑lattice constants: 2.50 Å for Co vs 2.75 Å for Pd͒.…”

“…Thus, a number of studies on the growth of Co on Pd͑001͒ were carried out in the past. [8][9][10][11] For preparation of ultrathin films it is a common approach to deposit films by thermal deposition ͑TD͒, where the metal is evaporated from a heated rod. In contrast, only a few studies have been carried out using pulsed laser deposition ͑PLD͒ to prepare ultrathin films.…”

Structural analysis of Co thin films grown on Ge(111) at room temperature by x‐ray photoelectron diffraction

“…In addition, for 0.7 and 1.5 ML, the broadening and vagueness of the observed forward-scattering peaks may be attributed predominantly to the partial epitaxial growth of CoGe 2 and the presence of partially disordered Co, 18 as well as to the photoelectrons not experiencing so many orders of multiple scattering at these low Co coverages.…”

Reconstructed bcc Co films on the surface

“…The growth of tetragonally distorted ð1 0 0Þ-oriented Co films has been reported for Co on Ptð1 0 0Þ [9], GaAsð1 0 0Þ [10], Geð1 0 0Þ [11], Feð1 0 0Þ [2,[12][13][14], FeAlð1 0 0Þ [15], Pdð1 0 0Þ [16,17], Wð1 0 0Þ [18,19] and Auð1 0 0Þ [20]. On Crð1 0 0Þ, Co grows pseudomorphically in a bcc structure for the first few monolayers followed by continuous relaxation towards hcp structure [21,22].…”