PRECISE AND ACCURATE REFINEMENTS OF THE 220 STRUCTURE FACTOR FOR SILICON BY THE SYSTEMATIC-ROW CBED METHOD

The 220 structure factor for silicon has been refined by matching rock ing curves extracted from energy filtered convergent beam electron dif fraction patterns to those calculated from a Bloch-wave formulation of the dynamical theory of electron diffraction. There is an excellent a greement between the refined results that are obtained from rocking cu rves recorded from different crystal thicknesses and published results . Purpose-written computer codes have been used to perform the fitting . Three efficient criteria for automatic beam selection have been inco rporated in these computer programs to guarantee the convergence of a calculation. The importance of minimization criteria and treatment of anomalous absorption on the convergence of the calculations have been tested. It is demonstrated that the refined structure factors are inde pendent of minimization criteria and that the computationally less int ensive perturbation treatment of absorption can be used to refine a st ructure factor with high precision (less than 0.1%) as well as high re lative accuracy.