Mr Dmitry Fraimovitch (Tel Aviv University (IL))
The diamond crystals have several attractive properties for detector applications. The very wide bandgap enables high temperature operation with low leakage currents; the high carrier mobilities should enable fast and efficient charge collection; the material can be used for a combined conversion-detection of fast neutron (through 12C(n,α0)9 reaction creating a recoil atom and alpha particle); and the atomic number of diamond is similar to that of human body providing simple dose monitoring in medical applications. The main challenges for spectroscopy grade diamond are charge collection efficiency, polarization and long term stability. The choice of contact material, pre-treatment, and sputtering process details have shown to alter significantly the detector performance. We compared three diamond substrate grades: polycrystalline, optical grade single crystal, and electronic grade single crystal. We investigated the impact of plasma treatment on the surface properties. Characterization of diamond substrate permittivity and losses indicate grade and crystallinity related, characteristic differences for frequencies in 1 KHz-1 MHz range. Substantial grade related variations were also observed in surface electrostatic characterization performed by contact potential difference (CPD) mode of an atomic force microscope. Study of conductivity variations with temperature reveal that bulk trap energy levels are also dependent on the crystal grade.