Synthesis and characterization of hafnium carbide microcrystal chains with a carbon-rich shell via CVD

Novel hafnium carbide (HfC) microcrystal chains, with a periodically changing diameter and a nanoscale sharpening tip at the chain end, have been synthesized via a catalyst-assisted chemical vapor deposition (CVD) process. The as-synthesized chains with many octahedral microcrystals have diameters of between several hundreds of nm and 6 lm and lengths of ∼500 lm. TEM diffraction studies show that the chains are single-crystalline HfC and preferentially grow along a [001] crystal orientation. TEM/EELS/EDX analysis proves the chains are composed of a HfC core and a thin (several tens of nm to 100 nm) carbon-rich shell with the embedded HfC nanocrystallites (typically below 10 nm) surrounding the core. The growth mechanism model for the chains based on the vapor-liquid-solid process, the vapor-solid process, and the HfC crystal growth characteristics is discussed.