Influence of applied bias on direct conversion X-ray sensing capability of nanocrystalline Ca9Ag(PO4)6(OH)2

Silver (Ag) doping in hydroxyapatite (HAP) can enhance the attenuation coefficient (μ) 0.65 cm2/g at photon energy 70 keV as compared with pure hydroxyapatite (μ = 0.31 cm2/g). In this study, direct conversion X-ray sensors were fabricated using pure HAP (Ca10(PO4)6(OH)2) and Ag-doped HAP (Ca9Ag(PO4)6(OH)2) to realize superior X-ray sensing capability. Thick films of wet-chemical route derived nanocrystalline samples were deposited on interdigitated electrodes by glass rod sliding technique and its X-ray instigated photocurrent characteristics at 2 V biased condition were recorded for different low doses (mGy). The observed sensitivity at 7.97 mGy dose reveals ten folds enhancement from 0.19 nC/mGy cm3 to 1.00 nC/mGy cm3. According to the “Grain boundary double Schottky potential barrier height model”, the formation of potential barrier height (φb) at the interface of grain and grain boundaries of nanocrystalline samples is identical to the Schottky barrier. By increasing the applied bias, the conduction band starts to bend and suppresses the potential barrier height (φb). In higher biased conditions, φb does not exist. Hence, the influence of applied bias on direct conversion X-ray sensing capability of Ca9Ag(PO4)6(OH)2 was investigated and discussed in detail. [Display omitted] •Nanocrystalline HAP and Ag-doped HAP were synthesized and fabricated into a thick film sensor.•The effect of lattice substitution, Voltage bias, and Dose-dependent linear sensitivity was investigated using an intra-oral X-ray machine.•The X-ray instigated photocurrent measurement was carried out for both the sensors at different low doses (mGy) and applied bias.•Ag-doped HAP showed improved sensitivity than pure HAP and it can be used for direct X-ray imaging sensor development.