Photoemission study of the growth and modification of the Al/Ta(110) interface

The Al/Ta(110) interface is studied as a function of Al coverage and temperature (300T1400 K) using photoemission. Valence-band and core-level data suggest that little or no atomic intermixing occurs at room temperature. An electronic state related to the hybridization of Ta 5d and Al 3sp states at the interface is seen at -1.3 eV binding energy. At about 4.6-monolayer-Al coverage, this interface state shifts {}0.7 eV to higher binding energy. A change in the rate of attenuation of the Ta 4f core-level intensity at this Al coverage suggests that the Al overlayer grows in a different mode at higher coverage. Heating to 1010 K results in a reacted overlayer at temperatures consistent with the formation of TaAl₃, and a careful examination of the photoemission data indicates that an aluminum-rich surface compound is formed. Further interdiffusion to form Ta-rich surface compounds occurs at higher temperatures.