Development of single‐crystal CVD‐diamond detectors for spectroscopy and timing

Charge‐transport parameters measured for several single‐crystal CVD‐diamond films are discussed as well as the consequences for the energy‐ and the time resolution of charged‐particle detectors made of these samples. Applying a transient‐current technique, where 241 Am α‐particles are used for e–h pair creation, low‐field electron mobility values varying in the range 1300 < µ 0–e [cm 2 /Vs] < 3100 are obtained, and a common saturation velocity around v sat–e ≈ 1.9 × 10 7 [cm/s]. Hole data show impressive uniformity with µ 0–h ≈ 2330 [cm 2 /Vs] and v sat–h ≈ 1.4 × 10 7 [cm/s]. At detector operation bias (0.3 V/μm < E D < 3 V/μm) the holes drift systematically faster than the electrons. The lifetime of the charge carriers in best samples amounts to τ h ≈ 1 µs for holes and to τ e ∼ 320 ns for electrons. Comparable to the energy resolution of commercial silicon detectors, a Δ E = 17 keV (FWHM) is measured for 5.5 MeV α‐particles and Δ E / E ∼ 1% for heavy ions. Tests of single‐ and polycrystalline detectors with relativistic 27 Al ions of 2 AGeV reveal the same intrinsic time resolution of σ (Δ t ) = 28 ps indicating limitations due to electronic noise. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)