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 rocking curves extracted from energy filtered convergent beam electron diffraction patterns to those calculated from a Bloch-wave formulation of the dynamical theory of electron diffraction. There is an excellent agreement between the refined results that are obtained from rocking curves 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 incorporated 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 independent of minimization criteria and that the computationally less intensive perturbation treatment of absorption can be used to refine a structure factor with high precision (less than 0.1%) as well as high relative accuracy.