Preparation and imaging performance of nanoparticulated LuPO4:Eu semitransparent films under x-ray radiation

Abstract

The aim of the present work was to demonstrate the fabrication technique for semitransparent layers of nanoparticulated (~50 nm) LuPO4:15%Eu phosphors. Furthermore, to present their basic luminescent properties and provide results regarding their performance in a planar imaging system incorporating a CMOS photodetector. Parameters such as the Detective Quantum Efficiency (DQE), the Normalized Noise Power Spectrum (NNPS) and the Modulation Transfer Function (MTF), were investigated. The NNPS was found to present significantly higher values near the zero frequency for the 67 μm, 100 μm films, pointing on their higher non uniformities compared to the 220 and 460 μm films For the two thickest films (460 μm and 220 μm) the MTF curves practically do not differ, while MTFs for the thinner layers of 100 μm and 67 μm are higher as the layer’s thickness decreases. The higher DQE values observed for the 220 μm and 460 μm films up to medium frequencies, while at high frequencies the DQE values are comparable. Although the MTF values of these films are much lower than the thinner screens, the capability of the higher x-ray absorption, in conjunction with the low noise properties, lead to higher DQE values. The LuPO4:Eu semitransparent films seems to be a very promising scintillator for stationary x-ray imaging. The acquired data allow to predict that high-temperature sintering of our films under pressure may help to improve their imaging quality, since such a processing should increase the luminescence efficiency without significant growth of the grains, and thus without sacrificing their translucent character.