title: Origin of n- and p-type conductivity in undoped α-PbO: role of defects.
abstract: First-principles calculations have been applied to study the crystallographic defects in α-PbO in order to understand an origin of n- and p-type conductivity in otherwise undoped α-PbO. It was found that deposition in an oxygen-deficient environment defined in our simulations by the Pb-rich/O-poor limit stimulates a formation of O vacancies and Pb interstitials both characterized by quite low formation energies ∼1.0 eV. The O vacancy, being occupied by two electrons, shifts the balance of electrons and holes between these two defects to an excess of electrons (four electrons against two holes) that causes n-type doping. For the Pb-poor/O-rich limit, an excess of oxygen triggers the formation of the O interstitials characterized by such a low formation energy that a spontaneous appearance of this defect is predicted. It is shown that the concentration of O interstitials is able to reach an extreme magnitude equal to the number of possible defect sites (∼10(22) cm(-3)). The localized state formed by the O interstitial is occupied by two holes and because there are no other defects in reasonable concentration to balance the hole redundancy, p-type doping is induced.
authors.affiliation: Thunder Bay Regional Research Institute, 290 Munro Street, Thunder Bay, ON, P7A 7T1, Canada. Department of Physics, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Berashevich
authors.forename: J A
authors.initials: JA
authors.lastname: Rowlands
authors.forename: A
authors.initials: A
authors.lastname: Reznik