New Informations Obtained by Energy Filtered RHEED

Abstract

Reflection high-energy electron diffraction (RHEED) patterns, so far observed, are mixtures of those due to elastically and inelastically scattered electrons from the specimen surface. The background of the RHEED pattern, which consists of the signals attributed to inelastic electrons, sometimes disturbs the observation of detail diffraction features. In order to exclude these inelastic electrons, a retarding field analyzer was used as the energy filter. By using this energy filtered RHEED (EF-RHEED) apparatus, new RHEED patterns and rocking curves were obtained. In the EF-RHEED pattern of Si (001) 2 × 1 surface, a line pattern due to the disordering of the c (4 × 2) surface structure was clearly extracted from the background. In the EF-RHEED pattern of Si (111) 7 × 7 surface, some additional diffuse patterns were observed. Energy filtered rocking curves of diffraction spots are presented, which are different from conventional ones in their relative intensities. Especially, there is a serious difference when a diffraction spot goes through an intense Kikuchi line. Energy loss spectra of diffraction spots can be measured by this apparatus. It was found that the diffraction beams with very grazing take-off angle suffers a great probability of inelastic scattering from surface plasmon excitation.