Effect of Annealing on the X-ray Detection Properties of Nano-sized Polycrystalline Lead Oxide Films

Polycrystalline lead oxide (PbO) film is an excellent candidate material for a direct conversion X-ray detector. However, the thick-bulky film tends to significantly reduce the charge collection efficiency for recombination process, and the effective number of electron-hole pairs is lower than that of thin film, because it is difficult to fabricate high-dense and thick PbO films. In this paper, we first synthesized nano-sized PbO particles that could be used in a novel high-efficiency flat panel X-ray detector using a simple solution/combustion method. Energy dispersive X-ray spectrometry, X-ray diffraction, and field emission scanning electron microscopy were used to analyze the component ratio and morphology of the PbO particles as a function of annealing temperature. Then, 150-µm-thick PbO films were deposited on glass substrates using a particle-in-binder method at room temperature. The influences of annealing before deposition on the X-ray detection characteristics of the PbO films were investigated in detail. The key parameters–the dark current, X-ray sensitivity, signal-to-noise ratio, and signal decay–were measured. The annealing conditions strongly affected the electrical properties of the PbO films. The X-ray sensitivity of films annealed in oxygen gas increased dramatically with increasing annealing temperatures up to 500 °C.