  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 {\deg}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.
