Morphology of chemical vapor deposited titanium diboride

Titanium diboride has been chemical vapor deposited from TiCl₄, BCl₃, and H₃ gases on a heated graphite substrate. The morphologies of the deposits were correlated with the deposition parameters of substrate temperature, total pressure, B: Ti atomic ratio, Cl: H atomic ratio, and total flow rate. The diboride deposits exhibited a variety of morphologies which include coherent coatings with nodular or faceted surfaces, plate-like crystallites, dendritic crystallites, and irregularly shaped, faceted crystallites. The deposit morphology was found to be most sensitive to deposition temperature, B: Ti atomic ratio, and Cl: H atomic ratio. Variations in both the total pressure and total flow rate did not significantly affect the diboride morphology. All the TiB₂ deposits except those produced under a large excess of H₂ had a preferred orientation such that the hexagonal c-direction was parallel to the substrate surface.