IBIC characterization of an ion-beam-micromachined multi-electrode diamond detector

Deep Ion Beam Lithography (DIBL) has been used for the direct writing of buried graphitic regions in monocrystalline diamond with micrometric resolution. As part of the development and the characterization of a fully ion-beam-micromachined solid-state ionization chamber, a device with interdigitated electrodes was fabricated by using a 1.8 MeV He+ ion microbeam, which scanned a 40 mu m thick homoepitaxial detector grade diamond sample grown by chemical vapor deposition (CVD). In order to evaluate the ionizing-radiation-detection performance of the device, charge collection efficiency (CCE) maps were extracted from Ion Beam Induced Charge (IBIC) measurements carried out by probing different arrangements of buried micro-electrodes. The analysis of the CCE maps allowed an exhaustive evaluation of the detector features, in particular the individuation of the different role played by electrons and holes in the formation of the induced charge pulses. Finally, a comparison of the performances of the detector with buried graphitic electrodes with those relevant to conventional metallic surface electrodes evidenced the formation of a dead layer overlying the buried electrodes as a result of the fabrication process.