Diamond-based alpha particle detectors with coplanar geometry

In this paper, we report the results concerning significant improvement of charge collection efficiency for chemical vapor deposition (CVD) diamond-based alpha particle detectors with coplanar geometry by reducing the inter-electrode spacing from 100 to 25 μm. CVD diamond films used were prepared employing hot-filament CVD technique. Electrical contacts of the detectors were only patterned on the growth surface of the polished free-standing 300 μm thick diamond film using lift-off technology. The performance of the fabricated diamond-based detectors was tested using a²⁴¹Am alpha particle source with a characteristic energy of 5.5 MeV. Average charge collection efficiency of 52% for detector with narrow inter-electrode spacing of 25 μm and of 32% for detector with wide inter-electrode spacing of 100 μm was obtained, indicating that the detector with narrow inter-electrode has a higher charge collection efficiency than the detector with wide inter-electrode spacing. This should be attributed to fewer boundary trap and recombination centers between electrodes in detector with narrow inter-electrode spacing than that with wide inter-electrode spacing.