Article pubs.acs.org/cm
High Density Growth of Indium seeded Silicon Nanowires in the Vapor phase of a High Boiling Point Solvent Hugh Geaney,† Tadhg Kennedy,† Calum Dickinson,† Emma Mullane,† Ajay Singh,†,‡ Fathima Laffir,† and Kevin M. Ryan†,‡,* †
Materials and Surface Science Institute and Department of Chemical and Environmental Sciences, University of Limerick, Limerick, Ireland ‡ SFI-Strategic Research Cluster in Solar Energy Research, University of Limerick, Limerick, Ireland S Supporting Information *
ABSTRACT: Herein, we describe the growth of Si nanowires (NWs) in the vapor phase of an organic solvent medium on various substrates (Si, glass, and stainless steel) upon which an indium layer was evaporated. Variation of the reaction time allowed NW length and density to be controlled. The NWs grew via a predominantly root-seeded mechanism with discrete In catalyst seeds formed from the evaporated layer. The NWs and substrates were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Xray diffraction (XRD), scanning transmission electron microscopy (STEM), energydispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The suitability of the indium seeded wires as anode components in Li batteries was probed using cyclic voltammetric (CV) measurements. The route represents a versatile, glassware-based method for the formation of Si NWs directly on a variety of substrates. KEYWORDS: silicon nanowires, indium, Li ion anode material
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catalyst for Si NW growth as its melting point, of just 156.6 °C, facilitates low reaction temperatures, while the incorporation of In atoms into the NW lattice can also be used to impart p-type doping.17−19 The incorporation of dopants also increase the electrical conductivity of the NWs, which can improve their suitability for Li ion cells due to enhanced charge/discharge rates versus their undoped analogues.20 While vacuum based CVD processes allow precise tuning of dimensions21 and composition22 and doping of the nanostructures,23 more recently developed organic solvent based syntheses have gained attention for their potential to produce high density NWs at low cost.24−26 The challenge is that the boiling point of conventional solvents provides for a very narrow temperature window (typically 10%) and include Ag,8 Al,9 and the archetypal NW catalyst, Au.10,11 Type B catalysts (e.g., In, Ga)12−15 also show one dominant eutectic point; however, the composition is typically
