Production of stable and metastable phases of zirconium nitrides by NH3 plasma nitridation and by double ion beam sputtering of zirconium films

Nitrided surfaces and nitrogen composition gradients in thin films exhibit interesting mechanical, electrical and optical properties. Metal, semiconductor or oxide surfaces can be transformed into a nitrided compound via interactions of nitrogen species issued from a plasma or an ion beam. The thermal activation is a key factor in both cases to ensure chemical reactions and short/long-range diffusion necessary to allow the growth of stable or metastable structures. In this work, we focus our attention on zirconium nitrides prepared under controlled temperature through reaction and diffusion, in Zr films, of low energy NHx species produced in NH3 plasma and through the implantation–diffusion of energetic N+2 ions during Zr deposition by using double ion beam sputtering. Zirconium nitrides show optical and electrical properties that depend on the conditions and on kinetics of the nitrogen take-up; the material exhibits a transition from the stable metallic ZrN to a metastable phase Zr3N4 that appears transparent and insulating. The influence of the energy of the nitriding species and of the temperature on nitride compositions and phases are addressed. A model using coupled implantation and thermal diffusion mechanisms is proposed to explain the phases produced. In relation with the described phenomena, a temperature-controlled plasma-immersion ion-implantation system is proposed for tailoring in-depth stable/metastable ceramic structures such as nitrides, oxides and carbides.