Fabrication and properties of well-ordered arrays of single-crystalline NiSi2 nanowires and epitaxial NiSi2/Si heterostructures

In this study, we reported the design, fabrication, and characterization of wellordered arrays of vertically-aligned, epitaxial NiSi2/Si heterostructures and single-crystalline NiSi2 nanowires on (001)Si substrates. The epitaxial NiSi2 with facets was found to be the first and the only silicide phase formed inside the Si nanowires after annealing at a temperature as low as 300 A degrees C. Upon annealing at 500 A degrees C for 4 h, the residual parts of Si nanowires were completely consumed and the NiSi2/Si heterostructured nanowires were transformed to fully silicided NiSi2 nanowires. XRD, TEM and SAED analyses indicated that all the NiSi2 nanowires were single crystalline and their axial orientations were parallel to the [001] direction. The obtained vertically-aligned NiSi2 nanowires, owing to their well-ordered arrangement, single-crystalline structure, and low effective work function, exhibit excellent field-emission properties with a very low turn-on field of 1.1 V/m. The surface wettability of the nanowires was found to switch from hydrophobic to hydrophilic after the formation of NiSi2 phase and the measured water contact angle decreased with increasing extent of Ni silicidation. The increased hydrophilicity can be explained by the Wenzel model. The obtained results present the exciting prospect that the new approach proposed here will provide the capability to fabricate other highly-ordered, vertically-aligned fully silicided nanowire arrays and may offer potential applications in constructing vertical silicide-based nanodevices.