PHOTOEMISSION-STUDY OF THE GROWTH OF THE LAF3 SI (111) INTERFACE

Photoemission spectroscopy with synchrotron radiation was used to stud y the LaF3/Si (111) interface as a function of annealing temperature f or LaF3 films. These films range in thickness from 0.7-11 monolayers a nd have been deposited at room temperature. The La/Si photoemission in tensity ratio at surface sensitive and bulk sensitive experimental con ditions shows that island formation occurs at 420-degrees-C. The stoic hiometry of the LaF3 films is conserved until desorption begins at app roximately 580-degrees-C, where fluorine desorbs from the surface comp letely and lanthanum remains on the silicon substrate. From a line sha pe analysis of the Si 2p and La 4d core levels it is apparent that the interface is dominated by La-Si bonds. Changes in the surface Fermi l evel are induced by the penetration of lanthanum into the surface laye rs of the silicon substrate upon annealing.