Structure and Thermal Stability of Copper Nitride Thin Films

Copper nitride (Cu3N) thin films were deposited on glass via DC reactive magnetron sputtering at various N2 flow rates and partial pressures with 150°C substrate temperature. X-ray diffraction and scanning electron microscopy were used to characterize the microstructure and morphology. The results show that the films are composed of Cu3N crystallites with anti-ReO3 structure. The microstructure and morphology of the Cu3N film strongly depend on the N2 flow rate and partial pressure. The cross-sectional micrograph of the film shows typical columnar, compact structure. The thermal stabilities of the films were investigated using vacuum annealing under different temperature. The results show that the introducing of argon in the sputtering process decreases the thermal stability of the films. 1. Introduction Transition metal nitrides show a wide variety of properties and have lots of applications, and some of them have acquired a large number of industrial application. Among them, copper nitrides have attracted considerable attention as a new material for optical storage devices and high speed integrated circuits, based on its unique properties, such as rather low thermal decomposition temperature, excellent electrical properties, and optical qualities [1, 2]. All of these properties are due to its special cubic anti-ReO3 structure. A number of nonequilibrium techniques, such as RF reactive sputtering [1, 3–7], DC magnetron sputtering [8], ion assisted vapor deposition [9], reactive pulsed laser deposition [10], and other methods [11], are currently used for the preparation of Cu3N films. In recent years, Terada et al. [3] prepared oriented epitaxial films by the reactive rf magnetron sputtering method on the Pt/MgO and substrates. They also reported that copper nitride films were amorphous on glass, MgO, and substrates. Maruyama and Morishita [12] have studied the electrical and optical characteristics of the films prepared by rf reactive sputtering. And the electrical and optical properties of the copper nitride films critically depended on the sputter process parameters such as nitrogen partial pressure, sputtering pressure, substrate temperature, and substrate bias voltage. The electrical resistivity of the films varied from ？Ω？cm to about 103？Ω？cm, and the optical band gap of the films increased from 0.8？eV to 1.9？eV with the various sputtering process parameters [12–15]. Liu et al. [5] and Ji et al. [16] have studied thermal stability of the films. Yue et al. [1, 17] have studied the structure, thermal properties, optical properties, and Hall effects