SPATIALLY-RESOLVED IMAGING OF CHARGE COLLECTION EFFICIENCY IN POLYCRYSTALLINE CVD DIAMOND BY THE USE OF ION-BEAM-INDUCED CURRENT

Diamond based detectors have potential applications in high energy phy sics experiments. These detectors can be fabricated from synthetic Che mical Vapour Deposited (CVD) polycrystalline diamond films. Previously it has been shown by the Turin group and their coworkers in Zagreb th at it is possible to investigate the electrical characteristics of hig h quality polycrystalline CVD diamond films by Ion Beam Induced Curren t (IBIC). The present work describes IBIC images obtained using 2 MeV He+ irradiation of 250 mu m thick polycrystalline diamond films throug h a thin gold surface contact layer biased positively relative to the grounded rear surface of the film. In contrast to previous experiments the present spectra of collected charge display a clearly defined pea k from the induced charge. Images obtained by separating these spectra into different regions of interest allow the identification of region s in the sample of different charge collection efficiency. In particul ar the presence of some grains in which no charge collection appears p ossible and the reduction in charge collection efficiency at the grain boundaries is evident. (C) 1997 Elsevier Science B.V.