The Microstructure of Nanocrystalline TiB₂ Films Prepared by Chemical Vapor Deposition.

Nanocrystalline titanium diboride (TiB₂) ceramics films were prepared on a high purity graphite substrate via chemical vapor deposition (CVD). The substrate was synthesized by a gas mixture of TiCl₄, BCl₃, and H₂ under 1000 °C and 10 Pa. Properties and microstructures of TiB₂ films were also examined. The as-deposited TiB₂ films had a nano-sized grain structure and the grain size was around 60 nm, which was determined by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Further research found that a gas flow ratio of TiCl₄/BCl₃ had an influence on the film properties and microstructures. The analyzed results illustrated that the grain size of the TiB₂ film obtained with a TiCl₄/BCl₃ gas flow ratio of 1, was larger than the grain size of the as-prepared TiB₂ film prepared with a stoichiometric TiCl₄/BCl₃ gas flow ratio of 0.5. In addition, the films deposited faster at excessive TiCl₄. However, under the condition of different TiCl₄/BCl₃ gas flow ratios, all of the as-prepared TiB₂ films have a preferential orientation growth in the (100) direction.