Composition and Structure of Zirconium Nitride Films Produced by Ion Assisted Deposition
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ABSTRACT
The growth mechanism of ZrN1 films produced by reactive ion beam sputtering with or without concurrent low energy ion bombardment of argon or nitrogen has been investigated. The effect of substrate temperature in the range of 300-680K, partial pressure of nitrogen and ion/atom arrival rate on the composition and microstructure of the films have been studied. RBS analysis has confirmed that the nitrogen content varies over wide range 0-60 at. %, depending on the nitrogen/zirconium arrival rate, and the ion assist flux but it is independent of the ion assist energy. TEM analysis shows that the films are non-columnar and polycrystalline with grain sizes 1-15nm which depend on the nitrogen content and the deposition temperature. INTRODUCTION
The refractory transition-metal nitrides have attracted considerable interest owing to their wide range of applications which include wear resistant, hard coating2 and diffusion barrier3 layers. These mononitrides are exellent metallic conductors and superconductors with a Tc as high as 10 to 18 K. They are an attractive golden colour and crystallize in a NaCl type structure (B1 Type)4. The overstoichiometric nitride phase M 3N4 first reported by Juza et aP in 1964 and more
recently synthesised by various method6-9 , crystallizes in an ordered defect NaC1 structure which
is transparent and insulating. The combination of the two phases has offered favourable conditions for producing Josephson junctions4 . Although in recent years there have been numerous publications on the synthesis and properties of ZrNX, due to the diversity of the production techniques (such as reactive magnetron sputtering, sputter-ion plating and arc-evaporation) a systematic study has not been done. The individual processes which take place in all these methods are theoretically well established, however their combined effect becomes complicated and it often becomes impossible to clarify the relationship between the individual processes and hence determine the sputtering conditions for desired film properties. Among all the current techniques, reactive ion sputtering offers the most controllable compound thin film deposition. It offers a much better control over the ion impact energy, as well as independent control over the ion energy and current density. Furthermore, the mean free path of the particles is larger due to lower deposition pressures and sputtering by an inert gas ion beam extracted from an ion source is possible hence simplifying the sputtering mechanisms. In this paper we report on the role played by deposition parameters ( such as zirconium arrival rate for various nitrogen partial pressures, the ion assisted species as well ion energy and flux, and substrate temperature ) in
determining the composition, crystal orientation and
microstructure of the resulting films. 81 Mat. Res. Soc. Symp. Proc. Vol. 354 01995 Materials Research Society
EXPERIMENTAL
The apparatus used for this study comprises a stai
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