Controlled growth of Si-based heterostructure nanowires and their structural and electrical properties

Abstract

Ni-catalyzed Si-based heterostructure nanowires grown on crystal Si substrates by hot-wire chemical vapor deposition (HWCVD) were studied. The nanowires which included NiSi nanowires, NiSi/Si core-shell nanowires, and NiSi/SiC core-shell nanowires were grown by varying the filament temperature Tf from 1150 to 1850 °C. At a Tf of 1450 °C, the heterostructure nanowires were formed by crystalline NiSi and crystalline Si that were attributed to the core and shell of the nanowires, respectively. The morphology of the nanowires showed significant changes with the increase in the filament temperature to 1850 °C. Moreover, the effect of hydrogen heat transfer from the filament temperature demonstrated significant phase changes from NiSi to Ni2Si with increase in the filament temperature. The increased filament temperature also enhanced reactions in the gas phase thus generating more SiC clusters and consequently formed the NiSi/SiC heterostructure core-shell nanowires at Tf of 1850 °C. This paper discusses the role of filament temperatures on the growth and constituted phase change of the nanowires as well as their electrical characteristics.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0980-6) contains supplementary material, which is available to authorized users.

Solid-State Limited Nucleation of NiSi/SiC Core-Shell Nanowires by Hot-Wire Chemical Vapor Deposition

“…The amorphous structure of the shell nanowire is depicted by the HRTEM image collected at the sidewall as shown in Figure 7 d. The shell nanowire clearly presents that the amorphous structure consisting of nano-crystallites embedded with its amorphous matrix. These nano-crystallites form as elongated crystallites contributing to the columnar structures as observed in the previous reports [ 25 , 35 ]. The estimated lattice spacing is approximately 0.25 nm corresponding to 3C-SiC (111) crystallographic plane (JCPDS card no.…”

“…This can be clearly shown on the formation of bumps along their lengths and the number of bump increases with increase in Ni thickness. The formation of these bumps is generally deduced by the out-diffusion of NiSi core [ 25 ]. These bumps were reported to potentially grow nanowire branches for electrochemical electrode and sensing applications [ 26 ].…”

“…The out-diffusion of the metal catalysts in the growth of the nanowires was also observed by Hannon et al and occurred during the mediation of the axial growth of the core nanowire [ 28 ]. The lateral expansion of the NiSi core is happened to release the stress applied by the axial growth of the shell nanowire [ 25 ]. This leads to the out-diffusion and thus results in the secondary growth of the nanowire branches at the out-diffusion points.…”