Investigation On Preparation And Characteristics Of Metal-Doped Cu3N Films Deposited By Reactive Magnetron Sputtering

Copper nitride (Cu3N) thin films have been widely applied to optical storage, high-speed integrated circuits and solar cells, because of their high electrical resistivity, low thermal decomposition temperature and an obviously different reflectivity with elemental Cu in the infrared and visible light wave band. As Cu atoms do not occupy the "close-packing sites" in the (111) plane for Cu3N thin films, if other atoms can be filled in the body center of the cubic unit cell, the significant changes in the optical and electrical properties will be induced.First, Cu3N thin films are deposited on Si (100) and ITO glass substrates by means of direct current (DC) reactive magnetron sputtering method and the optimal film sample is obtained by changing deposition parameters in this thesis. It is indicated from X-ray diffraction spectrum that the Cu3N thin film demonstrate (111) preferred orientation. The film preferred orientation will change from (111) to (100) with the increase of nitrogen content, the decrease of sputtering pressure and the increase of substrate temperature. The surface morphology of Cu3N thin films is characterized by scanning electronic microscope (SEM). It is found that the Cu3N thin film has a compact surface microstructure composed with about60-120nm-sized pyramidal crystal grains. The resistivity of films is measured by using four-probe method. It is found that the resistivity of films sharply increases with the increase of the nitrogen content and the maximal resistivity of1170Ω·cm. cm is obtained when the nitrogen content increases to75%. The reflectivity of the film is measured by UV-VIS-NIR spectrophotometer. It is shown that the low reflectivity is found in the ultraviolet visible (UV-VIS) light range and the high reflectivity of86.8%at the wavelength of1000nm is attained when the substrate temperature is150℃. Secondly, Ti-doped copper nitride films are prepared by radio frequency (RF) and DC reaction co-sputtering. The Ti doping makes the diffraction peak intensity of the films decrease, and the other diffraction peaks of the films deposited on ITO glass substrates were easily observed with the increase of doping time. The SEM shows that the surface roughness of films increases, the grain size become uniform and the lattice constant is close to the theoretical value with the increase of the Ti content. Micro hardness of the film is increased from4.19GPa to5.04GPa due to Ti doping. The resistivity of the film decreases from5730Ω·cm to1210Ω·cm with the Ti content increase. The reflectivity of films is very low in the UV-VIS light range, and gets bigger due to Ti doping. The optical transmittance of the films deposited on ITO glass substrates is almost zero below the wavelength of700nm, and the Ti highly doping let the transmittance decrease. The band gap of the films is calculated by Tauc formula. It is found that the band gap decreases from1.39to1.18eV after Ti doping.Finally, Co-doped copper nitride films are prepared by DC magnetron sputtering. XRD indicates that it is similar to the Ti doping results. The other diffraction peaks of Co-doped films deposited on ITO glass substrates appear. The SEM shows that surface roughness increases with the increase of Co content, the grain size gradually becomes smaller and the grain appears ball shape. The resistivity of the films significantly decreases from5730Ω·cm to225Ω·cm due to Co doping. The reflectance of thin film decreases with the increase of Co concentration in the UV-VIS range. It is almost constant in the visible light range and optical transmittance is very low below the wavelength of700nm. The room-temperature ferromagnetism is observed by vibrating sample magnetometer for Co-doped thin films, it is indicated that the right Co doping content benefits to improve the magnetism of films.