Organometallic route to the chemical vapor deposition of titanium carbide films at exceptionally low temperatures

Abstract

Titanium carbide, TiC, is one of the hardest materials known (9-10 Mohs), possesses remarkable thermal stability (mp 3067/sup 0/C), and is essentially unaffected by acids and aqueous alkali. These properties make TiC a very useful material for such applications as first-wall coatings for fusion reactors. Unfortunately, crystalline TiC is also brittle, and this limits its structural applications at low temperatures. With present industrial technology, only crystalline TiC coatings can be deposited on complex shapes; the commercial process involves chemical vapor deposition from hydrogen, methane, and titanium tetrachloride at 1000/sup 0/C. More recently, plasma-assisted chemical vapor deposition techniques have been applied to the synthesis of TiC coatings, but these methods also require high temperatures, in excess of 1200/sup 0/C. They now report a simple and powerful chemical vapor deposition (CVD) method for preparing thin films of TiC using an organometallic precursor at exceptionally low temperatures (approx. 150/sup 0/C). Tetraneopentyltitanium, Ti(CH/sub 2/C(CH/sub 3/)/sub 3/)/sub 4/ was chosen for metal-organic chemical vapor deposition (MOCVD) studies since it volatilizes easily and has been reported to thermolyze at low temperature. They have devised an improved synthesis of Ti(CH/sub 2/C(CH/sub 3/)/sub 3/)/sub 4/: interaction of Ti(OCH/sub 2/CH/sub 3/)/sub 4/ with 4 equi of LiCH/sub 2/C(CH/sub 3/)/submore » 3/ in pentane followed by sublimation at 50/sup 0/C (10/sup -3/ torr) gives yellow crystals of the titanium alkyl.« less