In situ compression of micropillars under coherent X‐ray diffraction: a case study of experimental and data‐analysis constraints. Issue 2 (28th February 2023)

• Record Type: Journal Article
• Authors: Godard, Pierre; Verezhak, Mariana; Sadat, Tarik; Mignerot, Florent; Jacques, Vincent L. R.; Le Bolloc'h, David; Richter, Carsten; Berenguer, Felisa; Diaz, Ana; Van Petegem, Steven; Renault, Pierre-Olivier; Thilly, Ludovic
• Is Part Of: Journal of applied crystallography. Volume 56:Issue 2(2023)
• Page Start: 381
• Page End: 390
• Publication Date: 2023-02-28
• Subjects: coherent X‐ray Bragg diffraction -- micropillars -- compression -- in situ -- InSb; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576723000493
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : The possibilities offered by three coherent X‐ray diffraction experimental setups applied to micropillar compression are discussed here. The yield stress was precisely determined with a collimated beam. Methods to deconvolve the signal coming from the pillar from that coming from the pedestal and to estimate in situ the curvature radius of the micropillar are also proposed here. Abstract : Micropillar compression is a method of choice to understand mechanics at small scale. It is mainly studied with electron microscopy or white‐beam micro‐Laue X‐ray diffraction. The aim of the present article is to show the possibilities of the use of diffraction with a coherent X‐ray beam. InSb micropillars in epitaxy with their pedestals ( i.e. their support) are studied in situ during compression. Firstly, an experiment using a collimated beam matching the pillar size allows determination of when the sample enters the plastic regime, independently of small defects induced by experimental artefacts. A second experiment deals with scanning X‐ray diffraction maps with a nano‐focused beam; despite the coherence of the beam, the contributions from the pedestal and from the micropillar in the diffraction patterns can be separated, making possible a spatially resolved study of the plastic strain fields. A quantitative measurement of the elastic strain field is nevertheless hampered by the fact that the pillar diffracts at the same angles as the pedestal. Finally, no image reconstructions were possible in these experiments, either in situ due to a blurring of the fringes during loading or post‐mortem because the defect density after yielding was too high. However, it is shown how to determine the elastic bending of the pillar in the elastic regime. Bending angles of around 0.3° are found, and a method to estimate the sample's radius of curvature is suggested.