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Amorphous p-Type Conducting Zn-x Ir Oxide (x > 0.13) Thin Films Deposited by Reactive Magnetron Cosputtering

Zinc-iridium oxide (Zn-Ir-O) thin films have been demonstrated as a p-type conducting material. However, the stability of p-type conductivity with respect to chemical composition or temperature is still unclear. In this study we discuss the local atomic structure and the electrical properties of Zn-Ir-O films in the large Ir concentration range. The films are deposited by reactive DC magnetron co-sputtering at two different substrate temperatures-without intentional heating and at 300 °C. Extended X-ray absorption fine structure (EXAFS) analysis reveals that strongly disordered ZnO4 tetrahedra are the main Zn complexes in Zn-Ir-O films with up to 67.4 at% Ir. As the Ir concentration increases, an effective increase of Ir oxidation state is observed. Reverse Monte Carlo analysis of EXAFS at Zn K-edge shows that the average Zn-O interatomic distance and disorder factor increase with the Ir concentration. We observed that the nano-crystalline w-ZnO structure is preserved in a wider Ir concentration range if the substrate is heated during deposition. At low Ir concentration, the transition from n- to p-type conductivity is observed regardless of the temperature of the substrates. Electrical resistivity decreases exponentially with the Ir concentration in the Zn-Ir-O films.