Mechanical testing device for in situ experiments on reversibility of dislocation motion in silicon

Abstract

We present a general-purpose mechanical testing device built and tested for in situ experiments using synchrotron radiation. A new setup was used in order to investigate the reversibility of dislocation motion under stress reversal. The observations were done by in situ transmission X-ray topography, at the ID 19 beamline of the ESRF. Specimens of FZ silicon single crystals, with a [ 1 1 ̄ 4 ] axis (double slip orientation), were submitted to load cycles in tension and compression ( τ=10–20 MPa) at high temperature (650–750 °C). Dislocations were created at surfaces by Vickers indents. They were observed using a monochromatic beam ( λ=0.035 nm) and a 220 diffraction vector. The images were recorded both on X-ray films and using the FRELON X-ray camera. The first observations show that dislocations may behave in different ways within the same specimen, and that their motion can be partially reversible.