Single Crystal Ti Nanowires Grown On Single Crystal NiTi Shape Memory Alloys

Single-crystal Ti nanowires were fabricated by electro-polishing single-crystal NiTi shape memory alloys. These self-assembled nanowires were aligned primarily along the [110] direction of the NiTi substrate, although some nanowires were observed along the [100] and [210] directions as well. The nanowires of this hexagonal-based material had a rectangular cross-section, of about 400X480 nm², and appeared smooth. The nanowire growth direction is along [0001] , and the nominal growth rate was about 0.2 microns per second. The resistivity of these nanowires was found to be 0.35 µW·m, which is comparable to the values for bulk materials and indicates sufficient removal of the oxide layer under our measurement conditions. This work is a significant advance in addressing the challenge of growing single-crystal Ti nanowires economically, which has been precluded by the reactivity of Ti combined with the inability of sputtering to produce single crystals.