ON THE NECESSARY EXPERIMENTAL CONDITIONS TO GROW TITANIUM FILMS ON HOT TUNGSTEN FILAMENTS USING TITANIUM TETRAIODIDE

An experimental system has been built to grow titanium films on hot tungsten filaments by the pyrolytic decomposition of titanium tetraiodide. Different procedures are examined in this system to establish the necessary experimental conditions to promote titanium deposition. The experimental results are analyzed considering the thermodynamics of the deposition reaction. It has been found that the iodine partial pressure around the hot filament is the more relevant parameter to dictate the deposition feasibility and must always be kept lower than 10(-2) atm for typical TiI4 partial pressures. This statement applies to the dynamic experiments performed in our laboratory using titanium tetraiodide and also to the cyclic experiments performed by other authors using crude titanium and iodine. The morphology of the deposited films is also discussed.