A Review of (e,2e) Studies in Thin Films and Some Recent Results

Abstract

The form of the (e, Ze) cross section applicable to high energy symmetric transmission measurements in thin films is given in the plane wave impulse approximation. The difference expected for single crystal, non-single crystal and amorphous films is discussed. For certain kinematics, the measured (e, Ze) coincidence intensity can be related directly to the energy-momentum distribution of the target electron and a map of the occupied electron states can be obtained in principle. Recent experimental work in the authors' laboratory using about 100 A thin films of aluminium/aluminium oxide is discussed. Two peaks in the valence binding energy are seen at 13 and 31 eV whose angular correlations indicate that both are dispersionless and resemble P and S type atomic orbitals of oxygen. Neither peak resembles the free electron structure of aluminium. Improving the electron energy resolution from 4·5 to 1·5 eV while maintaining the momentum resolution constant at about 0·9 A-I did not significantly change the data which indicates the dominant effects of mUltiple scattering.