Effects of strain field in nitrogen-mediated Co film growth on Cu(0Â 0Â 1): Segregation and electronic structure change

Growth modes of Co thin films on the both N-saturated and partially N-adsorbed Cu(0 0 1) surfaces are studied in detail. From results of the STM and XPS measurements, segregation of N atoms depending on the Co island size is concluded. This new type of atom segregation is explained by means of a lattice strain of the substrate due to the small Co island formation. A novel core-level shift of N 1s during the Co film growth is also reported. A possible influence of the lattice strain to the electronic structure of the surfactant is discussed.