A 3-dimensional interdigitated electrode geometry for the enhancement of charge collection in diamond detectors

Chemical vapor deposition (CVD) diamond has considerable potential for use as a radiation detector, particularly for particles and photons. Various authors have reported investigations and performances of coplanar CVD diamond detectors with superficial interdigitated contacts (see Fig.1 (a)). In this work, single crystal CVD diamond film with a novel 3D interdigitated electrodes (see Fig.1 (b)) for ionizing radiation detection has been fabricated in order to increase the charge collection efficiency (CCE) and the time response. Finite Element Method (FEM) simulations of such device highlight the enhancement of the CCE in the inter-electrode region of the device with respect to that obtained by standard superficial electrodes. The straight field lines due to the 3D patterning of the electrodes result in a shorter travel path for the generated electron-hole cloud and in a higher drift velocity with respect to standard surface electrodes, thus contributing to a faster and more efficient charge collection mechanism. In order to evaluate the ionizing-radiation-detection performance of the devices, CCE maps and time- resolved measurements were extracted from an Ion Beam Induced Charge (IBIC) characterization carried out at the micro-beam facility of the Italian National Laboratories of Legnaro by raster-scanning a rarefied 1 MeV proton micro-beam over the active area of the diamond detectors. The experimental results, in good agreement with the numerical predictions, show a significant increase in the 3D-detector performance if compared with the results obtained by standard surface metallic electrodes.