Effect of the oxidation temperature on microstructure and conductivity of ZnxNy thin films and their conversion into p-type ZnO:N films

Abstract

Transparent p-type ZnO:N thin films have been fabricated by the oxidation of n-type ZnxNy films. The ZnxNy thin films on glass substrate were deposited by pulsed filtered cathodic vacuum arc deposition using metallic zinc (99.999%) as a cathode target in pure nitrogen plasma. The properties of the films were examined after oxidation between 350 and 550°C in air atmosphere. The atomic force microscopy (AFM) analysis revealed that the surface morphology was smooth. As-deposited ZnxNy films were opaque and conductive (ρ=4.36×10−3Ωcm,ND=7.70×1021cm2/Vs) due to excess of Zn in the structure. After oxidation between 350 and 500°C, p-type ZnO:N thin films were obtained. The lowest resistivity of 44.50Ωcm with a hole concentration and Hall mobility of 2.08×1017cm−3 and 0.673cm2/Vs, respectively, was obtained after oxidation at 450°C. However, when the oxidation temperature reached to 550°C, the conduction type of the ZnO:N film was changed from p-type to n-type. X-ray photoemission spectroscopy (XPS) analysis confirmed the formation of ZnN bonds and substitution incorporation of oxygen for nitrogen on the surface of the film. Besides, with a further increase of oxidation temperature to 550°C, the decrease of N concentration in the sample was also confirmed by XPS analysis.