Direct current mode neutron detection, investigation of polarization effect on 500 μm single crystal CVD diamond detector, and depolarization techniques

Abstract

Electronic grade diamond such as single crystal (SC) chemical vapor deposition (CVD) diamond has excellent optoelectronic properties, which enables it to be used as a detector material for high energy detector applications. However, SC CVD diamond suffers from loss of signal contrast and performance over a period of continuous use due to polarization of the detector. When a SC CVD diamond is continuously exposed to radiation, trapped charge carriers build up at defect sites, resulting in the creation of a secondary electric field opposite to the bias field. The emergence of the secondary electric field causes charge collection efficiency loss and reduces the overall performance of the detector. In this work, the effect of polarization on the direct current (DC) neutron response of a 500 µm SC CVD diamond detector was investigated by irradiating the detector with 14.1 MeV neutrons produced from a deuterium-tritium neutron generator. Depolarization techniques were employed to de-trap charge carriers and decrease the strength of the secondary electric field. This was primarily through reverse biasing the applied field yet included scenarios with and without short-lived neutron irradiation. The results indicated that both without and with neutron irradiation techniques improved the stability of the detector response. The latter showed a superior stability at higher bias fields.