CVD DIAMOND DETECTORS FOR RADIATION PULSE CHARACTERIZATION

Polycrystalline diamond films deposited by microwave plasma-enhanced c hemical vapour deposition (MPCVD) have been used for the fabrication o f resistive photoconductors. Such detectors can be used to measure the intensity and the temporal shape of pulsed radiation such as IR, visi ble, UV and X-rays. The photodetector response times were characterise d under fast Nd:Yag laser pulses (lambda = 266 nm, tau(L) = 30 ps at F WHM). The detector sensitivities were measured under both pulsed UV la ser and steady-state X-ray excitations (40 keV). The detector response time strongly depends on the CVD diamond film structural and physical properties, i.e., the film growth conditions. They exhibit a response signal presenting full widths at half maximum down to about 100 ps an d decay times down to about 130 ps. The diamond detector responses are compared to the responses measured on typical ultrafast photoconducto rs made from gallium arsenide pre-irradiated at 3x10(15) neutrons/cm(2 ) as well as from natural type IIa bulk diamond.