Angular distribution of surface excitations for electrons backscattered from Al and Si surfaces

Spectra of electrons reflected from non crystalline Aluminum and Silicon su rfaces have been measured for energies between 300 and 3400 eV. Angular dis tributions of the elastic peak as well as multiple surface and bulk excitat ions were recorded for two geometrical arrangements, being each others mirr or image with respect to the trajectory of each detected electron. These ge ometries allow to distinguish between incoming and outgoing electrons in th e case such a difference depends on the direction of the electrons with res pect to the surface normal. Theoretical calculations [Surf. Interf, Anal. 2 6 (1998) 682] suggest that such a difference exists in the ratio of the ela stic peak and the intensity of the first surface plasmon. The present paper compares experimental results on this quantity that is closely related to the so-called surface excitation parameter far Aluminum and Silicon with th eory. The angular distribution of the elastic peak was found to closely fol low the single deflection model. Within the experimental accuracy of simila r to 5% no difference regarding the surface excitation parameter for incomi ng and outgoing electron trajectories was observed. (C) 2001 Elsevier Scien ce B.V, All rights reserved.