Nitrification of Reactively Magnetron Sputter Deposited Ti-Cu Nano-Composite Thin Films

Abstract

A metalloid Ti13Cu87 target was sputtered by reactive DC magnetron sputtering at various substrate temperatures in an Ar-N2 mixture ambient. The sputtered species were condensed on Si (111), glass slide and Potsssium bromide (KBr) substrates. The as-deposited films were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), optical spectrophotometry and four point probe technique. The as-deposited films present composite structure of nano-crystallite cubic anti-ReO3 structure of Ti inserted Cu3N (Ti:Cu3N) and nano-crystallite face centre cubic (fcc) structure of Cu. The titanium atoms and sequential nitrogen excess form a solid solution within the Cu3N crystal structure and accommodate in crystal lattice and vacant interstitial site, respectively. Depending on substrate temperature, unreacted N atoms interdiffuse between crystallites and their (and grain) boundaries. The films have agglomerated structure with atomic Ti:Cu ratio less than that of the original targets. A theoretical model has been developed, based on sputtering yield, to predict the atomic Ti:Cu ratio for the as-deposited films. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance spectra. The films’ resistivity is strongly depending on its microstructural features and substrate temperature.