Preparation And Characterization Of Doped Cu₃N Thin Films By Magnetron Sputtering

Copper nitride thin film (Cu₃N) is a metastable semiconducting material,which is formed through the covalent bonding between Cu and N atoms. With the low decomposition temperature, high resistivity and reflectance of infrared and visible band, Cu₃N has been attracting considerable attention as a new material applicable in optical storage and microelectronics. Moreover, Cu₃N is also an excellent host structure since it has the cubic anti-ReO₃ structure in which Cu atoms do not occupy the body center of the cubic unit cell, such that an additional atom can be inserted into the body center. This will cause remarkable changes in optical and electrical properties of this material.In this paper, Cu₃N films were deposited by reactive DC magnetron sputtering at various N₂-gas flow rates, Cu₃NixN films were prepared by co-sputtering of Ni and Cu targets. The films were characterized by XRD, EDS, SEM, UV-VIS, Profilometer, Four-probe and Microhardness Tester. From the experimental values, we studied the effects of doping Ni and N₂-gas flow rates on the structure and properties of Cu₃N films, the conclusions which have been made are as follows:(1) The N₂-gas flow rate affects the crystal structure and the preferred orientation of Cu₃N films. The deposited films prefer to being (111)-oriented at low N₂-gas flow rate but (100)-oriented at high one. The deposition rate of the films got a maximum when the N₂-gas flow rate was 15sccm. With the increasing of N₂-gas flow rate, the resistivity increased and then decreased, the microhardness was also affected. The optimum N₂-gas flow rate for producing high-quality and well-oriented Cu₃N films are 5～10sccm in this system.(2) The addition of Ni to Cu₃N films does not modify the film crystal structure and the preferred orientation, but the intensity of diffraction peak (111) reduced, and the position shifted a little angle with the contents of Ni to Cu₃N films increased, as also as the larger of the lattice constant. The Cu₃N phase disappeared when the contents of Ni excess. Furthermore, of infrared and visible, the alloy film of Cu and Ni obtained by the thermal decomposition showed a large difference in reflectance, which is applicable to the optical recording media. The electrical resistivity decreased greatly when the contents of Ni to Cu₃N films increased, which have made the films changed from semiconductor to conductor.