Simultaneous X-ray radiography and diffraction topography imaging applied to silicon for defect analysis during melting and crystallization

International audienceSynopsis A setup for simultaneous, time-resolved X-ray radiography and diffraction topography imaging is presented. It is used to study defect generation and growth mechanisms during heating, solidification and cooling of a silicon crystal. Abstract One of the key issues to be resolved to improve the performance of silicon solar cells is to reduce crystalline defect formation and propagation during the growth process fabrication step. For this purpose, the generation of structural defects such as grain boundaries and dislocations in silicon must be understood and characterised. We combine in situ X-ray diffraction imaging, historically named topography, with radiography imaging to analyse the development of crystal defects before, during and after crystallisation. Two individual indirect detector systems are implemented to record simultaneously the crystal structure (topographs) and the solid-liquid morphology evolution (radiographs) at high temperature. This allows for a complete synchronisation of the images and for an increased image acquisition rate compared to previous studies that used X-ray sensitive films to record the topographs. The experiments are performed with X-ray synchrotron radiation at beamline ID19 at the European Synchrotron Radiation Facility (ESRF). We present in situ observations of the heating, melting, solidification and holding stages of silicon samples to demonstrate that with the upgraded setup detailed investigations of time-dependent phenomena are now possible. The motion of dislocations is recorded during the entire experiment, so that their interaction with grain boundaries and their multiplication through the activation of Frank-Read sources can be observed. Moreover, the capability to record with two camera-based detectors allows for the study of the relationship between strain distribution, twinning and nucleation events. In conclusion, the simultaneous recording of topographs and radiographs has great potential for further detailed investigations of the interaction and generation of grains and defects that influence the growth process and the final crystalline structure in silicon and other crystalline materials