Reactive DC Magnetron Sputter Deposited Titanium-Copper-Nitrogen Nano-Composite Thin Films with an Argon/Nitrogen Gas Mixture

Abstract

A sintered Ti13Cu87 target was sputtered by reactive direct current (DC) magnetron sputtering with a gas mixture of argon/nitrogen for different sputtering powers. Titanium-copper-nitrogen thin films were deposited on Si (111), glass slide and potassium bromide (KBr) substrates. Phase analysis and structural properties of titanium-copper-nitrogen thin films were studied by X-ray diffraction (XRD). The chemical bonding was characterized by Fourier transform infrared (FTIR) spectroscopy. The results from XRD show that the observed phases are nano-crystallite cubic anti rhenium oxide (anti ReO3) structures of titanium doped Cu3N (Ti:Cu3N) and nano-crystallite face centered cubic (fcc) structures of copper. Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX) were used to determine the film morphology and atomic titanium/copper ratio, respectively. The films possess continuous and agglomerated structure with an atomic titanium/copper ratio (∼ 0.07) below that of the original target (∼ 0.15). The transmittance spectra of the composite films were measured in the range of 360 nm to 1100 nm. Film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using a reverse engineering method. In the visible range, the higher absorption coefficient of the films prepared at lower sputtering power indicates more nitrification in comparison to those prepared at higher sputtering power. This is consistent with the formation of larger Ti:Cu3N crystallites at lower sputtering power. The deposition rate vs. sputtering power shows an abrupt transition from metallic mode to poisoned mode. A complicated behavior of the films' resistivity upon sputtering power is shown.