Effects of V and Gd doping on novel positive colossal electroresistance and quantum transport in PbPdO2 thin films with (002) preferred orientation†

In this work, PbPd_0.9V_0.1O₂ and PbPd_0.9Gd_0.1O₂ thin films with (002) preferred orientation were prepared using a pulsed laser deposition technique. The temperature dependence of resistivities ρ_I(T) was investigated under various applied DC currents. Colossal electroresistance (CER) effects were found in PbPd_0.9V_0.1O₂ and PbPd_0.9Gd_0.1O₂. It was found that the positive CER values of PbPd_0.9V_0.1O₂ and PbPd_0.9Gd_0.1O₂ reach 3816% and 154% for I = 1.00 μA at 10 K, respectively. In addition, the ρ_I(T) cycle curves of PbPd_0.9V_0.1O₂ and PbPd_0.9Gd_0.1O₂ thin films showed a critical temperature similar to that of PbPdO₂ (T_c = 260 K). Particularly, charge transfer between O¹⁻ and O²⁻ was confirmed by in situ XPS. Additionally, based on first-principles calculations and internal electric field models, the CER and magnetic sources in PbPd_0.9V_0.1O₂ and PbPd_0.9Gd_0.1O₂ can be well explained. Finally, it was found that thin film samples doped with V and G ions exhibit weak localization (WL) and weak anti-localization (WAL) quantum transport properties. Ion doping leads to a transition from WAL to WL. The study results indicate that PbPdO₂, one of the few oxide topological insulators, can exhibit novel quantum transport behavior after ion doping.