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 degrees 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 (rho = 4.36 x 10(-3) Omega cm, N-D = 7.70 x 1021 cm(2)/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 44.50 Omega cm with a hole concentration and Hall mobility of 2.08 x 10(17) cm(-3) and 0.673 cm(2)/Vs, respectively, was obtained after oxidation at 450 degrees C. However, when the oxidation temperature reached to 550 degrees 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 Zn-N bonds and substitution incorporation of oxygen for nitrogen on the surface of the film. Besides, with a further increase of oxidation temperature to 550 degrees C, the decrease of N concentration in the sample was also confirmed by XPS analysis. (C) 2013 Elsevier B.V. All rights reserved.