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

Cheng Sun,Dagmar Gerthsen,Erich Müller,Matthias Meffert

doi:10.1186/s40679-019-0065-1

Abstract

Dislocations and stacking faults are 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 vector b of dislocations or displacement vector R of stacking faults can 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 faults in 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-device camera 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.

Highlights

Dislocations and stacking faults are crystal defects which determine the mechanical properties of materials
We present systematic analyses of dislocation Burgers vectors and displacement vectors of stacking faults performed by low-keV scanning transmission electron microscopy (STEM) in a scanning electron microscope
Exploiting the g·R = n and g·b = n criterion, respectively, we have shown in this work that dislocation Burgers vectors b and displacement vectors R of stacking faults in GaN can be determined by low-keV STEM in a scanning electron microscope

Summary

Introduction

Dislocations and stacking faults are crystal defects which determine the mechanical properties of materials. They may strongly influence the electronic properties of semiconductors, because they act as scattering centers for charge carriers or as nonradiative recombination centers in light-emitting devices and solar cells. The direction (but not the length) of the Burgers vector b of dislocations can be determined by exploiting the g·b = n criterion [1, 2]. For this purpose, the sample must be oriented in a two-beam diffraction

Methods

Results

Conclusion