Well-aligned NiSi/Si heterostructured nanowire arrays as field emitters

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Nickel silicides are promising candidates in modern semiconductor devices as contact metals, metal gate electrodes, and source/drains in field effect transistors. A multistep template replication process was utilized to fabricate highly periodic and well-aligned silicon nanowires (SiNWs), and the size could be further reduced via dry oxidation and post chemical treatment. NiSi/Si heterostructured nanowire arrays were fabricated by nickel film deposition on SiNWs and then rapid thermal annealing at 550 °C. Field emission (FE) measurements illustrated that the turn-on field and field enhancement factor β of NiSi/Si heterostructures were 1.3 V/μm and ∼9000, better than that of the SiNWs, which were about 1.9 V/μm and ∼3900. These results are superior to the FE properties of other silicon-based nanomaterials. The excellent FE characteristics are attributed to the uniformly distributed nanowires with high aspect ratio and large proximity, high conductivity of uniform NiSi coating, and favorable morphological features with sharp and rough tips as hot emission spots. The single-crystalline silicon nanowires shelled with polycrystalline NiSi provide substantial opportunities for integration with Si devices to form active field emitters, and for exploration of the nickel silicides on other electrical and optical properties.