Imaging of the sensitivity in detector grade polycrystalline diamonds using micro-focused X-ray beams

We have used a micrometer size X-ray beam generated from a synchrotron light source to measure the map of sensitivity in polycrystalline diamond films. Devices probed consist of sandwich structures in order to maintain the electric field uniform in the device. This study focuses on high-grade (detector) commercially available CVD material, with high charge transport properties and big grain size. As the X-ray beam is scanned over the device surface, the response current is measured and plotted on 2D images. The sensitivity exhibits very strong variations that are associated with the grain boundaries within the material. By varying, the electric field, it appears that the signal does not increase linearly with the bias, revealing that carrier velocity saturation can be locally reached in some grains. Also, by varying the X-ray energy, the penetration depth could be varied in order to probe the material preferentially either in the volume or in the near-surface regions. (C) 2002 Elsevier Science B.V. All rights reserved.