Comparison of convergent-beam electron diffraction methods for determination of foil thickness

Abstract

The methods of determining foil thickness from convergent-beam diffraction patterns, the Kelly method and the Ackermann method, have been compared in experiments using silicon and iron foils. It was necessary to use the Kelly method to determine the effective extinction distances experimentally. However, tests showed that the thickness determined by the Ackermann method is less sensitive to both systematic and random variations in the data, particularly to variations in the value of the first intensity maxima, for which the percentage errors are largest. The precision in thickness measurement achieved in the study was of the order of 5%. The deviation in thickness determinations by both methods was less than 2%. The two methods are roughly equivalent unless errors can be reduced below this level.