Growth of vapor-deposited cobalt films on Pt(111) studied by scanning tunneling microscopy

The initial nucleation and subsequent growth of vapor-deposited Co on Pt(111) has been studied by scanning tunneling microscopy and Auger-electron spectroscopy. When deposited at room temperature, Co nucleates spatially in a homogeneous manner and then grows quasi-layer-by-layer up to a coverage of FTHETA=3 monolayers. For FTHETA>3 monolayers, a three-dimensional island growth mode is observed. From a detailed analysis of the observed island shapes we present direct evidence that Co grows in a hcp pattern on Pt(111) after the third layer. The nucleation of Co at a deposition temperature above 300 K is strongly influenced by the appearance of a Co-induced surface reconstruction of Pt(111). This reconstruction leads to a dendritic growth of Co deposited at 400 K. Fingers of Co 3–5 nm wide and up to 250 nm long can be observed. The influence of the Pt reconstruction on the growth becomes smaller at higher deposition temperatures, leading to compact, triangular Co islands at 600 K