Photoemission study on the growth and stability of Gd cluster films over Ni(110) surface

The growth of Gd films on a Ni(110) surface was studied by synchrotron radi ation photoemission spectroscopy (SRPES) and XPS techniques. The results sh owed that at a thickness below 0.20 nm Gd4f exhibited a single-peak feature indicating that the Gd film grows in layer-by-layer mode. When the Gd cove rage is larger than 0.20 nm, however, the Gd4f peak evolves into a double-p eak feature with 2.3 eV separation at 2.00 nm. A similar phenomenon was obs erved in the Gd4d XPS spectra. It is suggested that the double-peak structu re of Gd4f is attributed to Gd clusters which might exhibit different elect ronic states from Gd metal owing to their special structures. Anneal treatm ent induced the collapse of Gd clusters and uniform spread of Gd over the N i(110) surface, implying that Gd clusters are unstable thermodynamically. ( C) 2001 Elsevier Science B.V. All rights reserved.