Comparison of fluctuation electron microscopy theories and experimental methods

Fluctuation electron microscopy (FEM) experiments to measure nanoscale structural order in amorphous materials come in two types: variable coherence and variable resolution. Either type can be implemented experimentally using either dark-field transmission electron microscope (TEM) imaging or nanodiffraction in a scanning TEM (STEM). We propose that the discrepancy in the magnitude between FEM signals measured with TEM and STEM is caused by a difference in coherence in the two methods. We also compare the nanoscale order length scales extracted from variable-resolution FEM data using the correlation length method proposed by Gibson et al and a method we recently proposed based on an explicit cluster model for nanoscale structural order in amorphous materials.