Plasma assisted deposition of thin films using molecular titanium alkoxide and amido precursors
Metal-containing polymer thin films are known to possess interesting electrical, magnetic, optical or barrier properties. Such coatings can be deposited by plasma assisted chemical vapour deposition (PACVD). This technique comprises the fragmentation and rearrangement of metallorganic precursors within a low pressure non-equilibrium electrical discharge. In this work, the deposition of titanium containing species embedded into a polymeric network from titanium tetraisopropoxide (TiTP), Ti[OCH(CH(_3))(_2)](_4), and tetrakis (dimethylamido) titanium (TMT), Ti[N(CH(_3))(_2)](_4), precursors has been investigated as a function of glow discharge power and substrate location. In addition these precursors have been mixed with hydrogen and ammonia gases during PACVD. These metal-containing plasma polymers layers have been characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM).It has been demonstrated that Ti02/polymer composite layers can be produced using the TiTP precursor with a wide range of stoichiometries. The mixing of hydrogen gas with TiTP create films which are stable towards oxidation and aging. TiTP/ammonia mixtures produced Ti(0,N)/polymer films which contained Ti-N bonds. Injection of TMT into a glow discharge has been found to result in a non-thermally assisted intramolecular alkyl (3-hydrogen activation mechanism to produce Ti(0,C,N)/polymer composite films. The film composition is found to be independent of glow discharge power beyond 5 W. Mixing with hydrogen gas lowers the carbon content due to recombination reactions competing with plasma polymerization. TMT/ammonia mixtures result in a gas phase transamination reaction prior to and during plasma activation causing a drop in the total carbon content due to replacement of the -N(CH(_3))(_2) ligand by –NH(_x).