Electrical transport properties of oxygen vacancies-rich Re₂Zr₂O₇/SrTiO₃ (Re = la, ce, pr, gd) heterostructure in wide range of temperature

Oxygen vacancy is an important factor affecting various physical properties of oxide materials. In this work, oxygen vacancies-rich Re₂Zr₂O₇(Re = La, Ce, Pr, Gd) films were prepared on SrTiO₃(STO) substrate under the condition of high-temperature and high-vacuum annealing. Oxygen vacancies result the generation of impurity energy levels with different position in band-gap, which significantly increases the conductivity of the Re₂Zr₂O₇ films. The sample conductance conforms to the carrier thermal excitation model between 320 and 720 K, and follows the three-dimensional Mott variable range hopping conduction mechanism between 30 and 300 K. Below 30 K, the carrier transport is significantly affected by the scattering of ionized impurities. The Gd₂Zr₂O₇ film exhibits a notably higher hopping energy, which can be attributed to the fact that the ionization potential of the lanthanide element increases with its relative molecular mass, consequently resulting in enhanced electron localization. Meanwhile, as the oxygen vacancy concentration decreases, the average hopping energy gradually increases. This work has revealed the detailed energy band structure of Re₂Zr₂O₇ film through the study of electrical transport properties in wide range of temperature which paves the way for the future investigation based on this material.