A Molecular Route to Dip-coated Transition Metal Nitride Thin Films.
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2004 MRS Fall Meeting A Molecular Route to Dip-coated Transition Metal Nitride Thin Films. Andrew W. Jackson*, Andrew L. Hector School of Chemistry, University of Southampton, UK, SO17 1BJ ABSTRACT There is an increasing interest in sol-gel synthesis of nitrides. The ability to deposit films of these materials by dip- or spin-coating will increase the range of applications in which they are viable and is an important step toward general sol-gel processing of nitride materials. With transition metals, the ammono based analogue of the well established alkoxy route to gels is inherently difficult to control. Due to the basicity of the system, the overwhelming tendency is of the starting materials to favour particle growth which results in a precipitate rather than a stable emulsion, unless both environment and synthetic pathway are carefully controlled. Hence reports to date of sol-gel routes to nitrides describe production of powders. We report work on a sol-gel route to titanium nitride with the ammonolysis of titanium amides controlled by temperature and chemical moderators, resulting in stable emulsions useful for dip-coating. INTRODUCTION Transition metal nitrides (TMNs) form a class of materials with unique physical and electrical properties [1]. These properties range from high temperature resistance and hardness to superconductivity [2]. Therefore thin films of TMNs are ideal for use in high performance applications where the properties of these materials as a coating can be of great benefit, such as hard coatings on bearings or diffusion barriers in electronics. These coatings are primarily achieved by chemical vapour deposition (CVD). The development of a versatile and cost effective alternative method of depositing these ceramics would undoubtedly lead to new applications of TMN materials. Work on the transition metal amides was pioneered in the 1960s by Bradley et al. [3,4]. The ammonolysis of these materials was investigated by Brown and Maya [2] and then by Chisholm [5] demonstrating their use as precursors to TMN materials. As well as investigation into the ceramic precursors, extensive research into CVD of transition metal nitrides has been well catalogued with the likes of Gordon [6] and Dubois [7] furthering development of the technique, and incorporating the use of ammonia (NH3) into the successful deposition of these materials. The ammono based analogue of the well established alkoxy route to gels is inherently difficult to control [8] and reported sol-gel routes to nitrides have produced solid products in the form of powders [9,10]. We report the deposition of thin titanium nitride films produced by coating sols from the reaction of tetrakis(dimethylamino)titanium (TDMAT) with propylamine (H2NnPr) or ammonia (NH3). These reactions resulted in stable emulsions useful for application in dip-coating which can be aged with NH3(g), and can be confirmed by electron microscopy and powder diffraction. To our knowledge, this is the first example of the use of sol-gel methods to deposit films of nit
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