An electron beam spectrometer for the measurement of the angular distribution of plasma losses in thin films

Details are given of an electron beam spectrometer using a magnetic deflection prism as a momentum analyser. The spectrometer is designed for the measurement, as a function of scattering angle, of the discrete energy losses of 10 keV electrons transmitted through thin solid films. The energy resolution is 0·7 eV and the angular resolution before unfolding is 0·8 mrad. The spectrometer has been used to verify the intensity dependence on scattering angle of the volume and surface plasma loss lines of aluminium to a high accuracy and also to obtain an accurate value for the volume loss, namely 15·19±0·03 eV. A folding technique used to analyse the intensity against angular scattering results is described together with a least-squares method for fitting the experimental data to the folded intensity-angle distribution.