ANALYTICAL FILTERING OF LOW-ANGLE INELASTIC-SCATTERING CONTRIBUTIONS TO CBED CONTRAST

A theory which includes the multiple low-angle inelastic scattering co ntributions to convergent beam electron diffraction contrast is presen ted. It is based on a slice model where many-beam Bragg scattering may take place in the upper part, z, of the crystal. The inelastic electr on scattering takes place in a slice dz at crystal thickness z, and th ese electrons are then Bragg scattered in the lower part, (t - z), of the crystal. The total intensity is obtained through an integration ov er thickness and an addition of the separate contributions due to mult iple inelastic scattering. Theoretical profiles for the individual pla smon scattering contributions to the intensity have been calculated ac ross the (220) CBED disk in Si for the systematic (220) case. The theo retical calculations are compared to the corresponding experimental in tensities obtained by an energy filtering system. The experimental res ults are semi-quantitatively in good agreement with the calculations. The main features after elastic as well as after one to four times pla smon scattering are well reproduced by the theory.