Correlation between Magnetron Discharge and Characteristics of Alloy (Ti,Cu)N Nano-Structure Thin Films

Abstract

Reactive magnetron sputtering using an alloy TiCu target and nitrogen as working gas was utilized to deposit ternary (Ti,Cu)N thin films. The aim of present work is to provide insight into the significance of nitrogen pressure, Ti addition, reflected neutral particles and energy flux on the characteristic of (Ti,Cu)N films. The ion induced secondary electron emission and surface poisoning of TiCu target were studied using I- V characteristic of magnetron discharge. The dependence of sputtering yield of Cu, Ti and TiCu target on incident angle of ions was simulated. Elemental titanium to copper (Ti:Cu) ratio in (Ti,Cu)N films was estimated using a model based on sputtering and mass transport. An estimation of energy flux due to reflected N neutrals toward substrate was presented. The structural analysis was identified using X- ray diffraction (XRD) technique. Phase identity is strongly depending on nitrogen pressure. Ti accommodation to Cu3N structure results in lattice constant expansion and (100) preferential orientation (texture growth). The Bonding environment of pure and Ti inserted Cu3N thin films were obtained from Raman spectroscopy. The Surface morphology and chemical composition of the films were studied by scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX), respectively. Ti addition deforms pyramidal- like grains to spherical ones. The optical study was performed by UV- Vis- near IR transmittance spectroscopy. Ti addition to Cu3N structure kills indirect semiconducting transition and governs the direct bandgap around 2.75 eV. Ti entrance results in interstitial N excess (N-richness) which acts as acceptor centers cause to hole injection to valence band (excited semiconductor) and bandgap widening. Electrical resistance of (Ti,Cu)N thin films shows quasi-metallic behavior. Grain boundary sliding causes to decrease in hardness of (Ti,Cu)N thin films.