PHOTOEMISSION-STUDY OF SOLID-STATE REACTION AND INITIAL OXIDATION OF THE CE AL(111) SYSTEM

High resolution photoemission spectroscopy has been used to study interface formation and initial oxidation of the Ce/Al(111) system at room temperature and at approximately 100 K. Both the evolution of the interface layer and the initial oxide growth have been investigated in detail. Evaporated Ce overlayers in the range 1-8 angstrom were found to interdiffuse with Al(111) to form a mixed interface with at least three different Ce-Al coordinations. At room temperature, one of the Ce-Al coordinations predominates as the mixed layer grows. At 100 K a wide variation of Ce-Al coordinations is observed, but none of these is preferred during growth. An enhancement in the initial rate of Al(111) substrate oxide growth is observed in the presence of a approximately 2 angstrom Ce overlayer at both temperatures. Decomposition of the Al 2p emission spectrum shows the presence of three suboxide peaks, which are similar to peaks previously observed in the pure oxygen/Al(111) system.