Zero-bias operation and beam energy dependence of diamond sensors

Synthetic epitaxial diamond is considered one of the most promising materials to monitor high energy and high flux photon beams like synchrotron radiation and radiotherapy LINAC facilities. Literature data show that the sensors manufactured in the past with chemical vapor deposited (CVD) diamond, in addition of requiring high doses of pre-irradiation, aimed to obtain a stable and reproducible response, were characterized by long rise-time and fall-down transients, in the order of few seconds. This has been considered for a long time the bottle neck of such sensors and the research efforts focused on the metal contact to improve the device response. In recent years, CVD technology made available epitaxial single crystal diamond that has allowed improved performance of diamond detectors. In this paper we present sensors based on commercially available high quality mono-crystalline CVD diamond with two symmetric Schottky junctions who are able to work at zero-bias in electron and photon beams. Devices have shown a high reproducibility of response and sensitivity of 25 nC•Gy-1•mm-3 independent of the beam energy for 8keV, 6MV and 15MV x-ray photons as well as from 5 to 14 MeV electron energies. In addition to very low current in the dark (3.2×10-14 A), linearity of the response with the dose over more than five orders of magnitude has been observed as well as very fast off-on and on-off transients