Detectors sensitive to ionizing radiations were assembled from high-purity single-crystal diamond plates with Ti/Au
injecting contacts. Spectrally resolved photoconductivity measurements in the range 2-6 eV were used to infer the defect
density in the diamond bulk material using silver contacts. The electrical behavior of annealed Ti/Au contacts was
analyzed in the dark through current-voltage measurements in the range ±500V (104 V/cm). Although contacts appear to
be ohmic in the dark, two different transport regimes were found under x-ray irradiation as a function of the applied bias
voltage. Recombinative regime at low bias and space charge limited injection regime at high bias were evidenced. The
analysis of the photocurrent's module and phase under x-ray modulated irradiation allowed us to highlight
photoconductive gain phenomena mitigated by a Poole-Frenkel field-assisted detrapping process. Through the analysis
of device's impedance under irradiation, a lumped-elements electrical circuit is proposed to explain the detector's
dynamic behavior.
Laser beam profiling technology in the UV spectrum of light is evolving with the increase of excimer lasers and lamps
applications, that span from lithography for VLSI circuits to eye surgery. The development of a beam-profiler, able to
capture the excimer laser single pulse and process the acquired pixel current signals in the time period between each
pulse, is mandatory for such applications. 1D and 2D array detectors have been realized on polycrystalline CVD
diamond specimens. The fast diamond photoresponse, in the ns time regime, suggests the suitability of such devices for
fine tuning feedback of high-power pulsed-laser cavities, whereas solar-blindness guarantees high performance in UV
beam diagnostics, also under high intensity background illumination. Offering unique properties in terms of thermal
conductivity and visible-light transparency, diamond represents one of the most suitable candidate for the detection of
high-power UV laser emission. The relatively high resistivity of diamond in the dark has allowed the fabrication of
photoconductive vertical pixel-detectors. A semitransparent light-receiving back-side contact has been used for detector
biasing. Each pixel signal has been conditioned by a multi-channel read-out electronics made up of a high-sensitive
integrator and a Σ-Δ A/D converter. The 500 μs conversion time has allowed a data acquisition rate up to 2 kSPS
(Sample Per Second).
Polycrystalline diamond detector prototypes suitable for x-ray spectroscopy were realized and tested. Thick diamond specimens, mechanically polished to reduce the surface roughness, were selected for prototypes development. Noble metal contacts were deposited on both faces, whereas multistrip structures were defined by photolithography on the growth face only with the aim of reducing the coupling capacitances and to allow characterization tests either in
planar or sandwich configuration. Leakage currents as low as 20 pA at 500 V were measured on a 270μm thick device. The x-ray sensitivity was tested monitoring the photocurrent as a function of the applied voltage under continuous 8.05 keV Cu Kα irradiation. Studies in pulsed mode were also performed by using a commercial miniature x-ray source. Pulse height distributions were carried out with a system composed of a charge-sensitive preamplifier and a digital pulse processor multi-channel analyzer. Analysis was carried out around Ta Lα and Cu Kα characteristic lines. Realized prototypes were able to resolve such two characteristic lines only 90 eV apart. Energy resolutions better than 3% have been evaluated for one of the prototype at 8.14 keV. Such features address very good energy resolving capabilities and the suitability of polished polycrystalline diamond in x-ray spectroscopy.
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