Solvent Vapor Growth of Axial Heterostructure Nanowires with Multiple Alternating Segments of Silicon and Germanium

Abstract

Herein, we report the formation of multisegment Si-Ge axial heterostructure nanowires in a wet chemical synthetic approach. These nanowires are grown by the liquid injection of the respective silicon and germanium precursors into the vapor phase of an organic solvent in which a tin-coated stainless steel substrate is placed. The Si-Ge transition is obtained by sequential injection with the more difficult Ge-Si transition enabled by inclusion of a quench sequence in the reaction. This approach allows for alternating between pure Si and pure Ge segments along the entire nanowire length with good control of the respective segment dimensions. The multisegment heterostructure nanowires presented are Ge-Si, Si-Ge-Si, Ge-Si-Ge, Si-Ge-Si-Ge, and Si-Ge-Si-Ge-Si-Ge. The interfacial abruptness of the Ge to Si interface is also determined through the use of aberration corrected scanning transmission electron microscopy and electron energy loss spectroscopy.

Direct Growth of Si, Ge, and Si–Ge Heterostructure Nanowires Using Electroplated Zn: An Inexpensive Seeding Technique for Li‐Ion Alloying Anodes

“…[40,41] In this work, we demonstrate an efficient route for electrodepositing nanosized Zn seeds on stainless steel (SS) as a catalyst to facilitate the growth of Si, Ge, and Si-Ge axial heterostructure NWs within a high boiling point solvent (HBS) system. [14,32,42] The formation of a Zn-oxide layer was eliminated by injecting the reducing agent LiBH 4 and removing it in situ. To achieve the layer thickness and morphology necessary to effectively catalyze NW growth, a flash deposition technique was employed, whereby a high current density and short deposition time lead to the formation of Zn nuclei that uniformly deposit across the substrate surface.…”

Direct Synthesis of Alloyed Si1–xGex Nanowires for Performance-Tunable Lithium Ion Battery Anodes

“…Here, we report the direct synthesis of Sn seeded Si 1– x Ge x alloy NWs, in high densities from stainless steel current collectors, in a single step wet chemical reaction, using a high boiling point solvent system. − Different Si to Ge atomic ratios (Si 0.20 Ge 0.80 to Si 0.67 Ge 0.33 ) can be obtained by balancing the ratios and reactivities of the precursors that are simultaneously introduced into the flask in a single injection. The electrochemical performance of the Si 1– x Ge x NWs were studied in both half-cell and full-cell configurations with the most Si rich anodes displaying the highest capacities and the more Ge-rich anodes showing the best capacity retention at faster charge and discharge rates.…”

Nanodroplet Hydrodynamic Transformation of Uniform Amorphous Bilayer into Highly Modulated Ge/Si Island-Chains

“…The ability to modulate the compositional profile in germanium (Ge) and silicon (Si) superlattice structures has been the key to achieve artificially designed electronic, photonic, and phononic properties and functionalities. − The band profile engineering becomes more prominent in quasi one-dimensional (1D) Ge/Si superlattice nanowires (NWs), − where both a stronger lateral confinement and a periodic diameter variation can contribute to an enhanced band profile and transport modulation in the 1D channels. So far, periodic diameter modulations in Ge or Si NWs are usually accomplished by top-down electron beam lithography , and selective etching. , While compositional modulations in hetero Ge/Si NWs are mostly fabricated by vertical etching into a planar Ge/Si superlattice, , self-assembly growth led by nanometal droplets represents a straightforward, economic, and versatile bottom-up approach − to engineer the composition in Ge/Si NWs, − ,− where the precursor supplies are alternated periodically during a vapor–liquid–solid (VLS) − ,, or a solution–liquid–solid − growth process. In these precursor-alternating approaches, the chamber or solution environment has to be evacuated completely twice to complete a single period of Ge/Si segments to guarantee a thoroughly compositional transition and minimize the reservoir effects (for VLS growth, in the catalyst metal droplets). ,, This leads to a rather slow sequential multistep control to engineer the superlattice-like Ge/Si hetero NWs.…”