Diamond-graphite Pixel Array for Particles Detection

The response of graphite-diamond pixel detectors to 90Sr β-particles is reported. Laser induced graphitization was used to realize 200 μm × 200 μm square conductive graphite pads on one detector side whereas a large area graphite contact was realized on the other face for biasing. A board with nine hybrid charge sensitive pre-amplifier channels was used to test homogeneity of response of nine pixels at a time. In the dark the current is Ohmic up to 100 V where the current increases with a power law. While the bulk pixel resistance is 2.5 × 1012 Ω, the resistance between adjacent pixels depends on voltage following a power law. Under irradiation a resolved β-spectrum well separated from the noise contribution was observed on each pixel. The most probable value of the collected charge distribution is voltage dependent and saturates around ±300 V (0.6 V/μm) with a value of 0.70±0.05 fC (4300±300 equivalent electrons charge).