Growth Mechanism of SmB Nanowires Synthesized by Chemical Vapor Deposition: Catalyst-Assisted and Catalyst-Free.

SmB nanowires, as a prototype of nanostructured topological Kondo insulator, have shown rich novel physical phenomena relating to their surface. Catalyst-assisted chemical vapor deposition (CVD) is a common approach to prepare SmB nanowires and Ni is the most popular catalyst used to initiate the growth of SmB nanowires. Here, we study the effect of growth mechanism on the surface of SmB nanowires synthesized by CVD. Two types of SmB nanowires are obtained when using Ni as the catalyst. In addition to pure SmB nanowires without Ni impurity, a small amount of Ni is detected on the surface of some SmB nanowires by element analysis with transmission electron microscopy. In order to eliminate the possible distribution of Ni on nanowire surface, we synthesize single crystalline SmB nanowires by CVD without using catalyst. The difference between catalyst-assisted and catalyst-free growth mechanism is discussed.