Three-dimensional diamond planar spiral detectors

Diamond's superior carrier transport properties and unparalleled radiation tolerance make it an ideal material for alpha/neutron detection. High performing diamond detectors are already commercially available. However, even high quality single crystal diamond can degrade after high doses of radiation, resulting in a reduction in carrier mean free path. It is well known that reducing the carrier collection distance, by decreasing the detector electrode spacing, makes radiation detectors more tolerant of mean free path reduction, and therefore more resilient to high radiation doses. One approach for thin device fabrication involves using thin diamond substrates, which can be fragile. In this work, a thin detector has been fabricated using a thick, highly resilient 300 μm diamond substrate by utilising a 3D network of laser-written nano-carbon network electrodes. An optimised femto-second laser write process, utilising specialised optical arrangements, is used to realise planar configured diamond detectors, comprising two Ti/Pt/Au spiral electrodes, connected to internal spiral nano-carbon network 'wall' electrodes, which extend 20 μm below the surface and have a 50 μm separation. It was found that introducing the nano-carbon network electrodes greatly improved the detector resolution and Charge Collection Efficiency. With close to 100% charge collection efficiency and ns rise times demonstrated, achieving "thin" detector performance, in "thick", structural substrates.