Analysis of crystal defects by scanning transmission electron microscopy (STEM) in a modern scanning electron microscope

Dislocations and stacking faultsare important crystal defects, because they strongly influence material properties. As of now, transmission electron microscopy(TEM) is the most frequently used technique to study the properties of single dislocations and stacking faults. Specifically, the Burgers vectorb of dislocations or displacement vectorR of stacking faultscan be determined on the basis of the g·b = n (g·R = n) criterion by setting up different two-beam diffraction conditions with an imaging vector g. Based on the reciprocity theorem, scanning transmission electron microscopy(STEM) can also be applied for defect characterization, but has been less frequently used up to now. In this work, we demonstrate g·b = n (g·R = n) analyses of dislocations and stacking faultsin GaN by STEM imaging in a scanning electron microscope. The instrument is equipped with a STEM detector, double-tilt TEM specimen holder, and a charge-coupled-devicecamera for the acquisition of on-axis diffraction patterns. The latter two accessories are mandatory to control the specimen orientation, which has not been possible before in a scanning electron microscope.