Abstract
This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation.
Highlights
Free-standing heterostructure nanowire arrays have been widely investigated for their applications in nano gas sensors [1], nano photocatalysts [2,3,4], and field emission devices [5]
Covering the semiconductor nanowire arrays with metal particles can improve their sensitivity as gas sensors because metal particles on the surfaces of nanowires induce the formation of Schottky barrier junctions
The Schottky junction at the semiconductor/metal interface can enhance the separation of photoexcited electron–hole pairs to improve the efficiency of photocatalytic degradation of organic pollutant [2,3,4]
Summary
Free-standing heterostructure nanowire arrays have been widely investigated for their applications in nano gas sensors [1], nano photocatalysts [2,3,4], and field emission devices [5]. Covering the semiconductor nanowire arrays with metal particles can improve their sensitivity as gas sensors because metal particles on the surfaces of nanowires induce the formation of Schottky barrier junctions. The Schottky junction at the semiconductor/metal interface can enhance the separation of photoexcited electron–hole pairs to improve the efficiency of photocatalytic degradation of organic pollutant [2,3,4]. Metal silicides have been widely applied in Si technology as ohmic contacts, low-resistivity interconnects, and Schottky barrier, and they have been introduced into Si nanowires. The most common method for forming silicide/Si nano-heterojunctions is to drive thermally silicidation of Ni [6,7,8,9,10,11,12], Co [13], Pt [14], and Mn [15]
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