Atomic-scale observation of the deformation and failure of diamonds by in-situ double-tilt mechanical testing transmissi
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Published online 3 July 2020 | https://doi.org/10.1007/s40843-020-1373-3
Atomic-scale observation of the deformation and failure of diamonds by in-situ double-tilt mechanical testing transmission electron microscope holder 1,2†
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Yizhi Zhang , Yeqiang Bu , Junquan Huang , Tianye Jin , Anmin Nie , Hongtao Wang 3* Yongjun Tian ABSTRACT In-situ transmission electron microscopy (TEM) has been demonstrated to be a powerful method in resolving challenging problems such as interactions among various defects. To take advantage of the atomic resolution of advanced TEMs, a compact five-degree-of-freedom nanomanipulator was integrated with an indenter that was made of nanotwinned diamonds, for both the in-situ mechanical testing and double tilting of TEM samples. As a demonstration, in-situ bending tests were performed on the 〈111〉, 〈110〉 and 〈100〉 single-crystal diamond needles. The tests revealed the {111} cleavage to be the dominant failure mode. The in-situ indentation on a diamond nanoplate led to curved cracks consisting of nanometer-scale steps, which were identified to be atomic flat {111} facets. The atomic-scale observation of the deformation and failure of diamonds demonstrated the stability of the entire system and the durability of the indenter. We expect that more delicate research can be carried out by means of this holder in the near future, including in-situ stimulation, atomic characterization, and tomography. Keywords: mechanical testing holder, double tilt, diamond, in situ TEM, tomography
INTRODUCTION The most advanced transmission electron microscopes (TEMs) have pushed their spatial resolution to ~0.5 Å since their invention [1–3]. Such unparalleled resolution renders a TEM a unique tool in characterizing the atomic structures of crystalline materials in great depth [4]. More attention has been paid to in-situ TEM that provides
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detailed information about microstructural evolution instead of still post-mortem images [5–8]. The dynamic pictures enrich the understanding of the interactions among various defects, which are important in unveiling the mechanisms of macroscopic phenomena [7–10]. Currently, it is still a challenge to combine an atomicscale observation with an in-situ stimulus, especially under great mechanical loads [11]. The reasons for this are twofold. For the operation side, mechanical loading always leads to the displacements of atoms, lowering the imaging resolution. As a compromise, a TEM sample can be deformed incrementally in a step-wise manner. Then atomic resolution images can be taken in each step when the load is held still. This requires that the testing system has high stiffness and excellent mechanical stability. For the hardware side, atomic resolution TEM imaging requires the crystal orientation of a TEM sample to be aligned to the electron beam direction. To satisfy this condition, tilting samples in two orthogonal directions must be used. One tilting function is built-in with TEM, and it involves rotating a sample around the holder axis, i.e., α-ti
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