XPS STUDY OF DOPING MECHANISM IN HEAVILY DOPED PbWO4:M3+(M = La, Nd, Gd) CRYSTALS

Lead tungstate (PbWO4) (PWO) crystals doped with high concentration trivalent rare earth ions have demonstrated to be a promising Cherenkov radiator material and also a potential material for optoelectronic application. In this paper, the doping mechanisms of the trivalent ions (La3+, Nd3+, and Gd3+) in the PWO host were studied using X-ray photoelectron spectroscopy (XPS), and the results were consistent with those of computer simulation. It was found that when heavily doped, La3+ may substitute for the W sites as well as the Pb sites for self-compensation by forming La dimers or small aggregates. However, the doping mechanism of heavily doped PWO:Nd3+ and PWO:Gd3+ might be different from that of heavily doped PWO:La3+ crystals.