Texture formation in chemical vapor deposition of Ti(C,N).

Highlights • Reaction order is close to 1 with regards to CH 3 CN. • Reaction order is close to 0 with regards to TiCl 4. • Coating composition unaffected by precursor partial pressure. • Texture forming mechanism for 〈2 1 1〉 growth. Abstract The growth mechanism of Ti(C,N) coatings produced by chemical vapor deposition was investigated as a function of the TiCl 4 /CH 3 CN molar ratio in excess of H 2. The depositions were carried out at a total pressure of 8 kPa, using single crystalline (0 0 l) α-Al 2 O 3 substrates. The Ti(C,N) coatings were characterized by X–ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The investigated coatings were between 6 and 13 µm thick. The reaction orders of TiCl 4 and CH 3 CN were determined to 0 and 1, respectively, showing that CH 3 CN is the rate-determining reactant. The preferred orientation of the deposited Ti(C,N) was investigated, showing that molar ratios TiCl 4 /CH 3 CN higher than 2.5 lead to 〈2 1 1〉/〈3 1 1〉 oriented coatings. A formation mechanism for the 〈2 1 1〉/〈3 1 1〉 orientation s is suggested. Such high ratios lead to the formation of Ti {1 1 1} twinning planes, which provide surface sites that can facilitate fast dissociation of the strong cyanide bond, and thereby cause faster growth in the 〈2 1 1〉/〈3 1 1〉 directions. Coatings deposited at lower molar ratios show a pronounced 〈1 1 1〉 out-of-plane orientation, characterized by a {1 1 1} rocking curve yielding values for full width at half maximum (FWHM) below 0.5°. [ABSTRACT FROM AUTHOR]