STABILIZATION OF A H.C.P. CU PHASE BY THIN-FILM EPITAXY ON CO(1010)

A low energy electron diffraction (LEED)/Auger electron spectroscopy (AES) study indicates that Cu films grow in a layer-by-layer fashion adopting the lattice parameters of the underlying Co(1 0 1 0) substrate within the surface ( c a ratio 1.62) for at least the first four monolayers with films remaining of good single crystal quality upto at least 10 ML thickness. Comparison of polar intensity plots (PIPs) or the Cu2p 3 2 core level intensity for films of thickness > 3 ML with corresponding plots from face centered cubic (f.c.c.) Cu(1 1 0) and the Co(1 0 ovbar|1 0) substrate demonstrate that the film structure is hexagonal-close-packed (h.c.p.). Angle-resolved-ultraviolet photoemission spectroscopy (ARUPS) has been utilized to follow the development of the Cu valence band electronic structure. Comparison of the experimental ARUPS data from thick Cu films (> 6 ML) with a linear muffin-tin orbital (LMTO) band structure calculation of the ground state electronic structure for a hypothetical h.c.p. Cu lattice yields satisfactory agreement for experimentally observed spectral structure and the polarization dependence of peak intensities. We conclude that a meta-stable h.c.p. phase of Cu( c a = 16.2) may be prepared by thin films epitaxy on Co(1 0 1 0). © 1990.