Zigzag configurations of hafnium carbide nanowires synthesised by chemical vapour deposition below the eutectic temperature

Abstract

Hafnium carbide nanowires were synthesised by a Ni-catalysed vacuum chemical vapour deposition method below the eutectic temperature of the Ni–C–Hf alloy. The zigzag growth behaviour of the hafnium carbide nanowires resulting from metastable growth was investigated by transmission electron microscopy in order to understand the sub-eutectic growth. Three typical zigzag configurations at joint angles of ∼125°, 45°, and 90° can be observed from the synthesised nanowires, where the structure with an angle of ∼125° is the most common, formed via a change in the growth direction from [ 2 ¯ 1 1 ¯ ] to [ 01 1 ¯ ] , or vice versa. The 45° zigzag structure is the second most common and is formed by alternating the axial direction three times between 〈011〉 and 〈001〉. The number of the zigzag structures with a 90° angle is the most rare among the three types and is formed by the change in growth direction between two energy-equal directions, from [ 1 ¯ 1 ¯ 0 ] to [ 1 1 ¯ 0 ] . Although alternating the growth direction brings about the zigzag geometry, the zigzag structured hafnium carbide nanowires have a single-crystal structure. In addition, the surface energies of the crystal planes play an important role in the growth of the hafnium carbide zigzag nanowires.