Segregation of Cu on annealed ultrathin Cr films deposited on Cu(001)

Thin Cr films (∼20 A) deposited in vacuum at 300 K on a Cu(001) single crystal have been annealed at various temperatures and analyzed by angle resolved ultraviolet photoemission, X-ray photoemission, X-ray photoelectron diffraction and low energy electron diffraction. The data show that Cu segregation occurs above 425 K, resulting in an atomic monolayer wetting the whole Cr film. At 775 K, the Cr overlayer collapses and the Cu(001) substrate surface becomes partly uncovered.