Improving Diamond Device Performances for Pulsed Mode Detection
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0956-J06-05
Improving Diamond Device Performances for Pulsed Mode Detection Hassen Hamrita, Dominique Tromson, Caroline Descamps, Christine Mer, Milos Nesladek, and Philippe Bergonzo LIST (CEA-Recherche Technologique)/DETECS/SSTM, CEA/Saclay, Gif-sur-Yvette, 91191, France ABSTRACT CVD diamond combines attractive properties for the fabrication of detection devices operating in specific environments. One inherent problem however with diamond is the presence of defect levels that are altering the detection characteristics. They result in unstable responses and carrier losses. One of the issues can be to operate the devices in the pulsed mode regime, when transitory effects are less impacted by defective levels evolution than for steady state currents. This therefore implies the use of materials that are faster, but also of lower carrier lifetime, and therefore generally agreed to be of poorer quality. This has therefore to be compromised with respect to the desired performances.
INTRODUCTION CVD diamond combines attractive properties for the fabrication of detection devices operating in specific environments. One inherent problem however with diamond is the presence of defect levels that are altering the detection characteristics. These are observed in most CVD materials just like they were observed before in very high quality natural diamonds. They result in unstable responses and carrier losses. Also, it is known that unstable observed sensitivities may result of the progressive filling of trapping levels (including e.g. pumping and polarisation effects) [1,2], with a detrimental effect on stability and response time. Several studies have aimed at identifying the origin of defect levels but the question remains open: impurities, dislocations, and grain boundaries are often associated with the presence of electrical defects. Here we propose to look at the temporal photoresponses to pulsed excitation, and to show the effect of the temporal progressive evolution of defects. The cases of high energy X-rays (14 MV electrons on W target), as well as of VUV (above diamond gap) photon pulses from a pulsed Xenon arc lamp are discussed. One application addressed is the case of the measurement of high energy neutrons (in the energy range of few MeV up to 30 MeV). This is needed e.g., for the study of inertial confinement plasma at fusion conditions. Here, the detection of the neutrons remains a challenge as the γ and scattered neutrons induced by neutrons interactions on the experimental hardware can blind the detectors. New neutron diagnostics based on CVD-Diamonds have been designed to achieve high energy neutron measurements in large γ background. We propose to compare diamond devices in the current or event-by-event modes and from several materials grown with controlled impurity levels. DEFECT POPULATIONS The relative non stability of the device sensitivity with respect to the device history has often been recorded. Studies have commented on the co-existence of deep trap level populations that require to be filled in orde
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