Strain fields around dislocation arrays in a Σ9 silicon bicrystal measured by scanning transmission electron microscopy

Abstract

Strain fields around grain boundary dislocations are measured by applying geometric phase analysis on atomic resolution images obtained from multiple fast acquisitions in scanning transmission electron microscopy. Maps of lattice distortions in silicon introduced by an array of pure edge dislocations located at a Σ9(122) grain boundary are compared with the predictions from isotropic elastic theory, and the atomic structure of dislocation cores is deduced from images displaying all the atomic columns. For strain measurements, reducing the acquisition time is found to significantly decrease the effects of instabilities on the high-resolution images. Contributions from scanning artefacts are also diminished by summing multiple images following a cross-correlation alignment procedure. Combined with the sub-Ångström resolution obtained with an aberration corrector, and the stable dedicated microscope’s environment, therapid acquisition method provides the measurements of atomic displacements with accuracy below 10 pm. Finally, the advantages of combining strain measurements with the collection of various analytical signals in a scanning transmission electron microscope are discussed.

Keywords:

• aberration correction
• ADF
• Si
• silicon
• STEM
• stress–strain measurements
• dislocations
• grain boundaries

Acknowledgements

Electron microscopy was carried out at the Canadian Centre for Electron Microscopy, a facility supported by NSERC (Canada) and McMaster University. G.R. and G.A.B. acknowledge the Fonds France–Canada pour la Recherche for partial support of this collaboration. We also are indebted to Jany Thibault-Pénisson for the early ideas of a collaboration, the interest in comparing HRTEM and HAADF images of grain boundaries and providing the bicrystals used in this work. Jany enjoyed teaching electron microscopy and educating a young generation of electron microscopists. We were fortunate to have her as instructor at the 2009 Summer School in Electron Microscopy at McMaster University, full of motivation and very delighted to be in contact with students.

Notes

This paper is dedicated to the memory of Jany Thibault-Pénisson who pioneered the topic of quantitative high-resolution electron microscopy. When Jany lectured at the Summer Microscopy School organized at McMaster University in 2009, we discussed this topic, the HAADF capabilities of aberration-corrected STEM and possible areas of collaboration. Following the school and the collaboration between Marseille and McMaster under the “Fonds France Canada pour la Recherche”, the work developed under the form presented here.