Transformation of the semi-transparent into the metallic phase of zirconium nitride compounds by implantation at controlled temperature: the evolution of the optical properties

Zirconium nitrides reveal interesting optical and electrical properties, wh ich strongly depend on the nitrogen stoichiometry. When preparing these com pounds using dual-ion-beam sputtering, very contrasting optical film proper ties can be obtained: a stable ZrN metallic phase with gold-like colour and a Zr3N4 metastable phase with an insulating semi-transparent behaviour. In this paper, optical properties (complex index of refraction and colorimetr ic data) of these two zirconium nitride phases are presented. A colorimetri c comparison between the colour of gold and that of ZrN is also reported. T he Zr3N4 phase is thermodynamically unstable: this metastable character per mits us to foresee a transition to the stable phase ZrN on providing an ene rgy supply. Compared with other ways of providing energy, ion implantation is well suited because of its directional aspect. This work deals with the optical property evolution of Zr3N4 phase irradiated at 600 degrees C by 34 0 keV Ar2+ ions with different fluences. Ellipsometric measurements reveal a gradual evolution of the optical properties, starting from an insulating behaviour (Zr3N4 sample) and ending with a conductor-like behaviour. It is shown that a fluence of 5 x 10(16) ions cm(-2) is sufficient to transform t he semi-transparent Zr3N4 film into metallic film. A study of the electrica l properties of the most highly implanted samples and of ZrN films is also reported.