Enhancement of electron correlation in Co thin clusters grown on S/GaAs (001)

An enhancement of the electron correlation effect by electron confinement is revealed in Co clusters formed on a sulfur passivated GaAs(001) surface. A satellite peak due to the strong electron correlation is observed at a binding energy of 5 eV in the valence band spectrum of Co photoemission spectroscopy. The photon energy dependences of the intensity and the spin polarization of the satellite are essentially the same to those of the well-known Ni 6 eV satellite. This suggests that the satellite is caused by the relatively strong 3d-3d electron correlation effect of the Co cluster and less hybridization effect at the interface.