Nano-scale imaging of the full strain tensor of specific dislocations extracted from a bulk sample

TL;DR

This paper introduces a novel method combining focused ion beam machining and a new analysis technique to measure the full 3D lattice strain tensor of specific dislocations in bulk materials using Bragg Coherent Diffraction Imaging.

Contribution

It develops a new approach to prepare BCDI samples from bulk materials and a displacement-gradient-based analysis for accurate strain tensor recovery.

Findings

Successfully extracted micron-sized BCDI samples from bulk tungsten

Achieved accurate measurement of the full strain tensor in dislocations

Enabled BCDI to be used on complex real-world materials

Abstract

Lattice defects play a key role in determining the properties of crystalline materials. Probing the 3D lattice strains that govern their interactions remains a challenge. Bragg Coherent Diffraction Imaging (BCDI) allows strain to be measured with nano-scale 3D resolution. However, it is currently limited to materials that form micro-crystals. Here we introduce a new technique that allows the manufacture of BCDI samples from bulk materials. Using tungsten as an example, we show that focussed ion beam (FIB) machining can be used to extract, from macroscopic crystals, micron-sized BCDI samples containing specific pre-selected defects. To interpret the experimental data, we develop a new displacement-gradient-based analysis for multi-reflection BCDI. This allows accurate recovery of the full lattice strain tensor from samples containing multiple dislocations. These new capabilities open the door to BCDI as a microscopy tool for studying complex real-world materials.