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

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) over bar4] axis (double slip orientation), were submitted to load cycles in tension and compression (tau = 10-20 MPa) at high temperature (650-750 degreesC). Dislocations were created at surfaces by Vickers indents. They were observed using a monochromatic beam (lambda = 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. (C) 2002 Elsevier Science B.V. All rights reserved.