Observations of specimen morphology effects on near-zone-axis convergent-beam electron diffraction patterns

Xiaofen Tan; Laure Bourgeois; Philip N H Nakashima

doi:10.1107/S1600576724001614

Observations of specimen morphology effects on near-zone-axis convergent-beam electron diffraction patterns

J Appl Crystallogr. 2024 Mar 21;57(Pt 2):351-357. doi: 10.1107/S1600576724001614. eCollection 2024 Apr 1.

Authors

Xiaofen Tan^{1

2}, Laure Bourgeois^{1

3}, Philip N H Nakashima¹

Affiliations

¹ Department of Materials Science and Engineering, Monash University, Victoria 3800, Australia.
² School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063, People's Republic of China.
³ Monash Centre for Electron Microscopy, Monash University, Victoria 3800, Australia.

Abstract

This work presents observations of symmetry breakages in the intensity distributions of near-zone-axis convergent-beam electron diffraction (CBED) patterns that can only be explained by the symmetry of the specimen and not the symmetry of the unit cell describing the atomic structure of the material. The specimen is an aluminium-copper-tin alloy containing voids many tens of nanometres in size within continuous single crystals of the aluminium host matrix. Several CBED patterns where the incident beam enters and exits parallel void facets without the incident beam being perpendicular to these facets are examined. The symmetries in their intensity distributions are explained by the specimen morphology alone using a geometric argument based on the multislice theory. This work shows that it is possible to deduce nanoscale morphological information about the specimen in the direction of the electron beam - the elusive third dimension in transmission electron microscopy - from the inspection of CBED patterns.

Keywords: convergent-beam electron diffraction; electron crystallography; multislice theory; nano-structured materials; specimen symmetry.

Grants and funding

XT is grateful for a Monash Graduate Scholarship, a Monash International Postgraduate Research Scholarship, an Alexander Moodie Scholarship, a Graduate Research Completion Award and a Faculty Postgraduate Publication Award. We thank the Australian Research Council for funding this work through Discovery Projects (grant Nos. DP150100558 awarded to LB; DP210100308 awarded to PN and LB). This research used equipment funded by Australian Research Council LIEF grants (grant No. LE110100223 awarded to the Monash Centre for Electron Microscopy).