Orientation dependence of nickel silicide formation in contacts to silicon nanowires

The orientation dependence of Ni silicide phase formation in the silicidation of silicon nanowires (SiNWs) by Ni has been studied. SiNWs with a [112] growth direction contacted by Ni pads form θ -Ni 2 Si for annealing conditions from 350 to 700 ° C for 2 min. The θ -Ni 2 Si has an epitaxial orientation of θ -Ni 2 Si [ 001 ] ∥ Si [ 11 1 ¯ ] and θ -Ni 2 Si ( 100 ) ∥ Si ( 112 ) with the SiNW. On the other hand, SiNWs with a [111] growth direction react with Ni pads to form NiSi 2 with an epitaxial orientation of NiSi 2 [ 1 1 ¯ 0 ] ∥ Si [ 1 1 ¯ 0 ] and NiSi 2 ( 111 ) ∥ Si ( 111 ) after annealing at 450 ° C for 2 min. The [111] SiNWs were also silicided at 700 ° C for 2 min, forming the low-resistivity NiSi phase. The epitaxial phases identified in the reactions of Ni films with SiNWs suggest that lattice matching at both the silicide/Si growth front and the surface of the original SiNW may play a significant role in determining the first silicide segment to grow.