F and F-aggregates colour centres in lithium flouridefor high spatial resolution x-ray imaging

Stable formation of primary F and aggregate F2 and F 3+ colour centres in LiF crystals irradiated with a X-ray table-top source was investigated by optical absorption and photoluminescence measurements as a function of the irradiation dose. The F absorption band intensity follows a power law behaviour as a function of dose with a single exponent equal to 0.77, a value in excellent agreement with the predictions of a unified model for colour centres formation. The aggregate defects photoluminescence response appears suitable for applications in high dynamic range imaging plate X-ray detectors based on photoluminescence of coloured LiF. The choice of polycrystalline LiF thin films grown on different substrates allows one to obtain high resolved images even when more penetrating X-rays are used, as the colour centres formation is limited in depth by the film total thickness.