Dynamic response of CVD monocrystalline diamond to low-energy x-ray beam

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. © 2011 SPIE.