PYROLYSIS BEHAVIOR OF TITANOCENE DICHLORIDE USED AS A PRECURSOR FOR THE CHEMICAL-VAPOR-DEPOSITION OF TITANIUM CARBIDE AT ATMOSPHERIC-PRESSURE

In an attempt to lower the temperature of depositing titanium carbide on steel by chemical vapor deposition, titanocene dichloride (Cp(2)TiC l(2)) was used as an organometallic precursor. The thermochemistry of the precursor was characterized by several techniques. Both isothermal and dynamic thermogravimetric analysis showed that congruent sublimat ion of the precursor occurs below 160 degrees C. Above this temperatur e, the precursor progressively decomposed to leave a solid residue and a volatile compound which was observed by gas chromatography. Accordi ng to mass spectroscopy results, the lower temperature decomposition m echanism was interpreted as the loss of a Cp group. Melting of Cp(2)Ti Cl(2) was observed to occur at 264 degrees C, and the transformation p reviously reported at 290 degrees C corresponds to the total decomposi tion of the molecule rather than melting. This conclusion was supporte d by the detection of HCl by mass spectroscopy and gas-phase infrared spectroscopy. Chemical vapor deposition of TiC was then performed by t hree different experimental procedures. The composition of the layers measured by electron probe microanalysis with wavelength-dispersive sp ectroscopy indicated an excess of carbon in the film (18 at. % < carbo n in excess < 34 at. %). The amounts of both chlorine and oxygen conta ined in the films as well as the deposition rate was strongly dependen t on the vaporization temperature of Cp(2)TiCl(2).