Hydrothermal Growth of Double-Layer ZnO:Sc for X-ray Imaging Application

The development of high-speed imaging technology requires ultrafast scintillators. ZnO is an excellent scintillator whose near-band-edge (NBE) radiation attenuation can reach subnanosecond levels. Homogeneous and unique double-layered ZnO:Sc microcrystals (1% doping) were prepared by adding polyvinylpyrrolidone during a hydrothermal reaction. The growth process of double-layer ZnO:Sc microcrystals and the effects of Sc doping concentration on the morphology of ZnO:Sc microcrystals were studied. ZnO:Sc tended to nucleate into twins in weakly basic hexamethylenetetramine. The c-axis growth of ZnO was inhibited by Sc doping, and the growth pyramid of ZnO:Sc was in accordance with the Burton–Cabrera–Frank growth model in the (002) plane, according to the spiral dislocation. Sheet ZnO:Sc microcrystals were obtained under high-concentration Sc doping. After hydrogen annealing, the NBE intensity of 0.5%-doped ZnO:Sc microcrystals was higher than that of ZnO, mainly owing to inhibition of defect luminescence and sheet morphology, which reduced the self-absorption of ZnO:Sc. The decay time of the ZnO:Sc microcrystals after hydrogen annealing under ultraviolet excitation was less than 1 ns. Combining the annealed microcrystals with polydimethylsiloxane to form a flexible composite film enables the scintillation screen to be used for ultrafast X-ray detection with a spatial resolution of up to 16 lp/mm.