Influences of nitrogen partial pressure on the optical properties of copper nitride films

Abstract

Copper nitride (Cu₃N) films are made under different nitrogen pressures via radio frequency reactions and magnetron sputtering techniques. Scanning electron microscopy, X-ray diffraction, UV-visible spectrophotometry, and fluorescence spectrophotometry are conducted to test and analyze the structures and optical properties of the films. The films produced under distinct nitrogen pressures possess compact surfaces and even similar particle sizes. In addition, the Cu₃N (111) crystal faces are mainly formed at low nitrogen pressures, whereas the Cu₃N (100) crystal faces are mainly generated at high nitrogen pressures. The photo-induced luminous band of the Cu₃N films is concentrated in the blue-violet area. Moreover, the optical band gap (E_g) of the films varies within the range of 1.23–1.91 eV and increases along with R. This variation is caused by the change of vacancy centers inside the film crystal and the concentration of elementary copper atoms that causes a distinct defect energy level.