Three-dimensional analysis of dislocation networks in GaN using weak-beam dark-field electron tomography

Abstract

We have developed a new method of tomographically reconstructing extended three-dimensional dislocation networks using weak-beam dark-field (WBDF) imaging in a TEM. A series of WBDF images is recorded every few degrees over a large tilt range, while ensuring that the dark-field reflection used for imaging maintains a constant deviation parameter. With suitable filtering of the WBDF images prior to tomographic reconstruction, the three-dimensional distribution of dislocations is reproduced with high fidelity and high spatial resolution. The success of this approach is demonstrated for heteroepitaxial Mg-doped GaN films. The fidelity of the tomographic reconstruction varies with the dislocation line-vector and elastic anisotropy of the material.

Acknowledgements

We acknowledge Dr Menno Kappers and Professor Colin Humphreys for the provision of the GaN sample. JS acknowledges Newnham College, Cambridge for financial support.

Notes

¹ See accompanying movies at http://www-hrem.msm.cam.ac.uk/research/CETP/electron_tomography.html