CCDs for X-ray topography at synchrotrons

An X-ray sensitive CCD camera has been evaluated at the Daresbury Synchrotron Radiation Source (SRS) for use in X-ray topographic (XRT) studies of epitaxially grown, strain-layered semiconductors (InGaAs/GaAs). Current topographic images obtained with photographic emulsion plates require considerable exposure and processing times of up to an hour so that real-time XRT cannot be realised. However, results from the X-ray sensitive CCD camera have shown that misfit dislocation features in the sample wafer topograph can be revealed in exposure times of less than 15 min. Results obtained from the CCD are presented. Finally, a number of further improvements to the camera system are possible using recent developments in CCD technology which will improve the resolution and sensitivity and allow higher resolution topographs to be obtained in around 30 s, close to the goal for real-time imaging of layer growth by molecular beam epitaxy (MBE). These further developments and the implications on the performance of a new camera system for X-ray topography are discussed.