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, semicondu ctor or oxide surfaces can be transformed into a nitrided compound via inte ractions of nitrogen species issued from a plasma or an ion beam. The therm al activation is a key factor in both cases to ensure chemical reactions an d short/long-range diffusion necessary to allow the growth of stable or met astable structures. In this work, we focus our attention on zirconium nitri des prepared under controlled temperature through reaction and diffusion, i n Zr films, of low energy NHx species produced in NH3 plasma and through th e implantation-diffusion of energetic N-2(+) ions during Zr deposition by u sing double ion beam sputtering. Zirconium nitrides show optical and electr ical properties that depend on the conditions and on kinetics of the nitrog en take-up: the material exhibits a transition from the stable metallic ZrN to a metastable phase Zr3N4 that appears transparent and insulating. The i nfluence of the energy of the nitriding species and of the temperature on n itride compositions and phases are addressed. A model using coupled implant ation and thermal diffusion mechanisms is proposed to explain the phases pr oduced. 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 . (C) 2000 Published by Elsevier Science S.A. All rights reserved.