Influence of high fluence heavy ion irradiation on the performance of single crystal diamond detectors

Abstract

Radiation detectors based on diamond are highly favored for particle physics research due to their superior radiation hardness. In this work, the performance of single crystal diamond detectors under high fluence heavy ion radiation has been investigated. After irradiation by Fe13+ and Xe20+ ion beams with a high particle fluence of 1.2 × 1015 cm-2, the properties of unirradiated and irradiated intrinsic single crystal chemical vapor deposition (CVD) diamond detectors are compared by means of the spectroscopic energy resolution, charge collection efficiency (CCE), mobility-lifetime (μτ) product and time response using a 241Am alpha (α) particle source. The experimental results of the unirradiated sample with respect to I-V dark current levels, showed an ohmic behaviour of the Al and Cr/Au contact, CCE of 100%, fast response with a rise time of 750 ps and a fall time of 600 ps as well as drift velocities of 6.67 × 104 m/s and 4.72 × 104 m/s for holes and electrons respectively. In the case of the irradiated samples, the CCE, μτ product and time response pulse amplitude of holes and electrons were all degraded, indicating that high density trappings for both kinds of carriers were created under the diamond crystal surface and the trapping probability of holes and electrons was equal, which was different from the previous reports in the literature where only higher trapping probability of holes were observed under heavy ions irradiation. In particular, the spectroscopic performance as well as μτ product of holes and electrons in Fe13+ irradiated sample decreased more than those in Xe20+ irradiated sample, which implied that the recombination of electrons and holes increased in Fe13+ irradiated sample with greater penetration depth than that in Xe20+ irradiated sample when radiation fluence was up to 1015 cm-2, despite the lower density of lattice vacancies in Fe13+ irradiated sample. Moreover, the rise time of holes was slightly different, but the drift velocity was basically the same as that of the unirradiated sample, and so was that of the electrons. Anyway, the presented results showed that the diamond detectors irradiated by heavy ions at a high fluence of 1015 cm-2 still retained their good spectroscopic and very fast time response properties.