PHOTOEMISSION-STUDY OF THE GROWTH OF THE NDF3/SI(111) INTERFACE

Photoemission spectroscopy with synchrotron radiation was used to study the NdF3/Si(111) interface as a function of annealing temperature for NdF3 films. These films range in thickness from 1-20 monolayers and were deposited at room temperature. Without annealing, both F-Si and Nd-Si bonding is observed, indicating that the planar triangular NdF3 molecules lie flat on the Si(111) substrate. At annealing temperatures between 400 and 500-degrees-C, the NdF3/Si(111) interface is dominated by Nd-Si bonding as evidenced from a line-shape analysis of the Si 2 p and Nd 4 f core levels. By resonant excitation of the giant 4 d-4 f absorption resonance, the photoemission signal from the partially occupied 4 f orbitals is enhanced and can be distinguished from the photoemission signal of the overlapping F 2 p valence band. At higher temperatures F is completely lost due to the decomposition of NdF3.