Temperature-dependent structure and phase variation of nickel silicide nanowire arrays prepared by in situ silicidation

In this paper, we report an in situ silicidizing method to prepare nickel silicide nanowire arrays with varied structures and phases. The in situ reaction (silicidation) between Si and NiCl2 led to conversion of Si nanowires to nickel silicide nanowires. Structures and phases of the obtained nickel silicides could be varied by changing the reaction temperature. At a relatively lower temperature of 700 °C, the products are Si/NiSi core/shell nanowires or NiSi nanowires, depending on the concentration of NiCl2 solution. At a higher temperature (800 °C and 900 °C), other phases of the nickel silicides, including Ni2Si, Ni31Si12, and NiSi2, were obtained. It is proposed that the different diffusion rates of Ni and Si atoms at different temperatures played a critical role in the formation of nickel silicide nanowires with different phases.