A study of the metal to nonmetal transition in Bi-doped ss-PbO(2) by high resolution x-ray photoemission

The influence of Bi doping on the electronic structure of Β-Pb O2 has been studied by high resolution x-ray photoemission spectroscopy. Doped films were prepared on Pt substrates by electrochemical deposition from solutions of Pb (N O3) 2 and Bi (N O3) 3 in HN O3. Bi doping was found to lead to a lowering of the density of states at the Fermi energy in valence region x-ray photoemission and to suppression of final state screening by mobile conduction electrons in Pb 4f core level photoemission. A metal to nonmetal transition was found to occur for bulk doping levels around 5 at. % Bi. There is evidence of pronounced surface segregation of Bi. In contrast to host Pb ions, core holes on surface Bi ions do not couple to the mobile conduction electrons in the metallic state. It is concluded that Bi acts as a p -type acceptor in Β-Pb O2 and traps charge carriers introduced by oxygen deficiency in Pb O2-x. © 2007 American Institute of Physics