Comparison of fluctuation electron microscopy theories and experimental methods

Abstract

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